Plant Nutrition — Physiology and Applications, 1990
Non-nodulated chickpea plants of a Fe-efficient variety were grown in a computer-controlled hydro... more Non-nodulated chickpea plants of a Fe-efficient variety were grown in a computer-controlled hydroponic system capable of measuring uptake rates of NO3 −, K+, H2PO4 −, Ca++, Mg ++ and Na+ from a nutrient solution and replenishing those ions taken up. Plants were subjected to two regimes of Fe supply (A: 0–20.5 days, 5.6 ppm Fe; 20.5–35.5 days, 0 ppm Fe. B: the reverse of A). Plants were harvested at intervals over the experimental period and their growth and nutrient contents were measured.
... Auteur(s) / Author(s). LE BOT J. ; ALLOUSH GA ; KIRKBY EA ; SANDERS FE ; Affiliation(s) du ou... more ... Auteur(s) / Author(s). LE BOT J. ; ALLOUSH GA ; KIRKBY EA ; SANDERS FE ; Affiliation(s) du ou des auteurs / Author(s) Affiliation(s). Univ. ... Revue / Journal Title. Journal of plant nutrition ISSN 0190-4167 CODEN JPNUDS Source / Source. 1990, vol. 13, n o 12, pp. ...
Grain growth in wheat depends on current photosynthesis and stem water-soluble carbohydrates (WSC... more Grain growth in wheat depends on current photosynthesis and stem water-soluble carbohydrates (WSC). In semiarid regions with terminal drought, grain filling in wheat crops may depend more on stem WSC content than on current assimilates. Reduction in grain yield under drought is attributed to shorter duration of linear grain growth despite increased contribution of stem reserves to grain yield. The amount of stem reserves is measured either by changes in stem dry weight (indirect method) or by stem WSC content (direct method). Genotypic variation in the rate and duration of linear grain growth and in percent contribution of stem reserves to grain yield has not been evaluated in wheat. The objectives of this study were: (i) to quantify the relationship between the direct and indirect measurement of stem reserves during and across the grain-filling period and (ii) to measure the extent of genotypic variation in rate and duration of linear grain growth and in percent contribution of stem reserves to grain yield. Dry weight, WSC content and grain yield of the main stem were measured at 10-day intervals in 11 diverse wheat genotypes under wellwatered and droughted-field conditions across 2 years. Drought reduced stem WSC content from 413 to 281 mg and grain yield from 4.6 to 2.5 t ha À1. Stem WSC content and dry weight were positively correlated. Genotypic differences in linear rate of grain growth were significant in well-watered (ranging from 48.9 to 72.4 mg spike À1 day À1) and in droughted-field (ranging from 33.2 to 59.9 mg spike À1 day À1) conditions. Drought, on average, reduced the linear rate and duration of grain growth by 20 and 50%, respectively. Reduction in linear rate ranged from 13 to 43%. The amount of current assimilates and stem reserves contributed to grain yield was reduced, respectively, by 54 and 11% under drought. Genotypic differences in percent contribution of stem reserves to grain yield were significant in well-watered (ranging from 19.1 to 53.6%) and in droughted-field (ranging from 36.6 to 65.4%) conditions. The wheat genotypes responded differently to drought. Main spike grain yield was reduced by 43% under drought due to 26 and 11% reduction in grain weight and number of grains, respectively. Grain yield was correlated with linear grain growth under well-watered (r = 0.96) and droughted (r = 0.83) conditions. The genotypic variation observed indicates that breeding for a higher rate of linear grain growth and greater contribution of stem reserves to grain yield should be possible in wheat to stabilize grain yield in stressful environments.
Wheat crops grown in dryland areas may depend more on stem reserves for grain filling than on cur... more Wheat crops grown in dryland areas may depend more on stem reserves for grain filling than on current photosynthesis. We evaluated the hypothesis that internode length, weight, and specific weight of genotypes affect accumulation and mobilization of stem reserves. This knowledge might complement selection in stressful environments. Genotypic variation for internode characteristics and their effects on dry matter accumulation and mobilization were measured at 10-d intervals in 11 diverse wheat cultivars grown under well-watered and droughted field conditions across 2 yr. Relationships among internode characteristics and accumulation and mobilization of stem reserves were determined. The main effect of year, irrigation, genotype, and harvest date and genotype 3 harvest date interaction were significant. Internode length, weight, and specific weight were reduced under drought. Mobilized dry matter from peduncle, penultimate, and the lower internodes ranged from 43 to 171, 81 to 272, and from 198 to 474 mg, respectively. Mobilized dry matter was less in well-watered than in droughted conditions for peduncle (93 vs. 110 mg) but not for penultimate (173 vs. 143 mg) and the lower internodes (331 vs. 304 mg). Drought increased mobilization efficiency, expressed as percentage of maximum dry mater mobilized, in the peduncle, penultimate, and the lower internodes by 65, 11, and 5%, respectively. Stem maximum specific weight was correlated (r 5 0.64) with stem mobilized dry matter. Balanced partitioning of stem length into upper and lower internodes and internode maximum specific weight are important in genotypic accumulation and mobilization of stem reserves in wheat.
... AMF-root colonization and/or decreased growth of mycorrhizal plants (Antunes and Cordoso, 199... more ... AMF-root colonization and/or decreased growth of mycorrhizal plants (Antunes and Cordoso, 1991; Howler et al., 1987; Manjunath et al., 1989; Ryan et al., 1994; Sieverding and Galvez, 1988). Information on acquisition of the macronutrients K, Ca, Mg, and S by mycorrhizal ...
A pot experiment was conducted in a greenhouse at Tishreen University location. The experiment in... more A pot experiment was conducted in a greenhouse at Tishreen University location. The experiment included three soils differ in their chemical properties: 1) heavy clay red soil rich in iron oxides; 2) a silt loam basiltic soil rich in manganese oxides; 3) clay red soil rich in calcium carbonate (34.8 %). Treatments included application of different levels of triple super phosphate (TSP, 46 % P 2 O 5 ) ranged from 0, 20, 40, 60, 80, to 100, mg P/kg soil were added to 0.5 kg soil. Pots were randomized in a green house, watered regularly to maintained 75% of the water holding capacity. Sub-samples were taken from each pot at times (0-30-60-90-120-150-180-210-240 Day). Soil P fractionation was only preformed for samples withdrawn at times 0 and 240 days.أسفل النموذج The incubation of the native soils led to an increase in available P in all soils after 240 day of incubation. The increase in extracted soil Pi differed mainly in phosphorus extracted with 0.5M NaOH and 1M HCl...
The impact on water quality by agricultural activity in karst terrain is an important considerati... more The impact on water quality by agricultural activity in karst terrain is an important consideration for resource management within the Appalachian region. Karst areas comprise about 18% of the region’s land area. An estimated one-third of the region’s farms, cattle, and agricultural market value are located on karst terrain. Mean nitrate concentrations in several karst springs in southeastern West Virginia exhibit a strong linear relationship with the percentage of agriculture land cover. Development of best management practices for efficient nitrogen (N) use and reduction of outflow of N to water from karst areas requires knowledge about N dynamics on those landscapes. Water extractable NO3-N and NH4-N were measured along transects at four soil depths in two grazed sinkholes and one wooded sinkhole. Distribution of soil NO3-N and NH4-N were related to frequency of animal presence and to topographic and hydrologic redistribution of soil and fecal matter in the grazed sinkholes. Kars...
Animal manure and urine deposition can cause localized patches of high ionic strength (IS) soil i... more Animal manure and urine deposition can cause localized patches of high ionic strength (IS) soil in pastures, influencing plant production, nutritive value and sward composition. Chicory (Cichorium intybus L.) appears to thrive in high-nutrient input situations, but no information is available on chicory response to increasing IS. In a greenhouse experiment, we evaluated the effect of rhizosphere ionic strength (0.9, 4.0, 8.0 and 12.0 dS m)1) on productivity and nutritive value of chicory. Dry matter production decreased linearly as IS increased. Shoot concentrations for Ca, Na and Cl increased as IS increased. All mineral concentrations, except Cu, were substantially higher than or equal to the highest concentrations reported for forages. At all IS, nitrate-N and K exceeded maximum recommendation for ruminant diets. The sodium level could be high enough to reduce dry matter intake at the highest IS level. Crude protein and energy estimates indicate chicory would support production levels equivalent to those of other high-quality forages. In vitro organic matter disappearance increased as IS increased. Chicory as a component of a forage mixture could help stabilize forage yield in pastures and also shows promise for use as a nutrient mop in feedlot areas, where excess soil nutrients are a problem.
Grazing livestock create localized nutrient patches that increase soil ionic strength (IS) and in... more Grazing livestock create localized nutrient patches that increase soil ionic strength (IS) and influence plant productivity. The ability of plant root systems to control ion absorption and flux to xylem, and to sequester ions reaching leaf tissue in bound, nontoxic forms are means of minimizing IS. A greenhouse experiment was conducted to determine the growth and mineral acquisition responses of forage chicory (Cichorium intybus L. cv. Grasslands Puna) to increasing (0.9, 4, 8, and 12 dS m)1) IS in the rhizosphere obtained by additions of NaCl ⁄ CaCl 2 (1 : 1 m ratio). Plants were harvested four times after planting (20, 27, 34 and 41 d) to identify responses as a function of time. Increased accumulation and localization of Na in roots in comparison to shoots suggested that chicory restricted Na transport to shoots, and that insoluble Na in tissues increased with increasing IS. Soluble cations in shoots were about 50 % of total cations, irrespective of rhizosphere IS and Na uptake. Differences in the cation:anion ratio could not be accounted for by organic acid concentrations in chicory, but substantial accumulation of nonstructural carbohydrates as fructans in roots could contribute to charge balance. Our results demonstrate that forage chicory has moderate tolerance to IS, suggesting that it might be a useful species for sites with potential for IS. Chicory growth would probably be sustained under IS conditions, and the resultant vigorous growth and accumulation of mineral nutrients in shoots would contribute to acceptable nutritive value for grazing livestock. Plants capable of growing in and acquiring nutrients from nutrient-laden patches in the sward would help minimize erosion and nutrient transport, with positive benefits for water and soil quality.
Forage chicory is a productive forage resource for eastern North America; however, many soils in ... more Forage chicory is a productive forage resource for eastern North America; however, many soils in the region are acidic and deficient in P and might restrict the widespread use of forage chicory. There is no published information on response of forage chicory to P, or P acquisition strategies for morphologically different chicory cultivars. The literature suggests the following null hypothesis: "specific root length (SRL) will increase with P deficiency". We conducted controlled environment experiments using nutrient culture to determine plant mass, mineral composition, and root morphology of three forage chicory cultivars (Grasslands Puna (GP), LaCerta (LC) and Forage Feast (FF)) as a function of P supply, and test the null hypothesis with chicory. Phosphorus increased chicory growth irrespective of cultivar. Root morphology differed among cultivars independent of P supply with FF producing about twice the taproot mass of GP or LC. Root morphology was also impacted by P supply and the specific interactions between P and cultivar. Total root length and surface area of GP increased, and did not change in LC or FF under −P conditions. Thus, the null hypothesis must be rejected. Results suggest at least two different plant responses to −P conditions in chicory that seem to be attributes of specific cultivars: (a) increase in root length of the 0.28 mm root class (GP); (b) decrease in non-taproot mass density with −P and no change in root length or ratios between diameter classes (LC). The change in root length of small diameter class roots, as observed for GP, is typical of the responses to −P described in the literature. The decrease in root density seen with LC is probably an anatomical response that is not coupled with any observable morphological response. We conclude that use of the above null hypothesis as a paradigm for plant root response to P deficiency must be rejected. The routine use of specific root length as an indicator of environmentally induced changes in root system function is precluded by the presence of anatomical and physiological changes (adaptations) that have no concomitant gross morphological changes.
Phosphate rock (PR) and organic manure (OM) are promising amendments to acidic soils to correct P... more Phosphate rock (PR) and organic manure (OM) are promising amendments to acidic soils to correct P deficiency and Al/Mn toxicities. The interaction between PR and OM and consequent effects in acidic soil are not fully understood. The effects of OM on the dissolution of two types of PR (NCPR, North Carolina PR; SYPR, Syrian PR) and dry matter production and nutrient uptake efficiency in an acidic Lily loamy soil from West Virginia were examined in an incubation and plant pot studies. NCPR and SYPR were supplied at a rate of 500 mg P kg −1 and organic manure at a rate of 30 g kg −1. Observations were made over 126 days at 21-day intervals. The dissolution of applied NCPR and SYPR was calculated based on the estimation of ?Pi and ?TP-NaOH method. Dissolution of NCPR and SYPR calculated by TP-NaOH was quick during the initial 21 day (∼20%), and thereafter increased slowly reaching 42 and 40% at 126 day for NCPR and SYPR, respectively. On the other hand, percent dissolution calculated based on Pi-NaOH, while fluctuating within ±5% between intervals, were less by 10 and 15% at 126 day for NCPR and SYPR compared to dissolutions estimated based on-TP-NaOH. OM generally reduced PR dissolution, and to a 11-14% lesser extend in the presence of plant roots, presumably due to plant roots depleting P and Ca from the dissolution zone. OM increased dry matter production (DM) of switch grass, increased specific accumulation rates (SAcR, mg or µg g −1 DM) of P and Mg in shoots, decreased SAcRs of Al and Mn in shoots DM, and increased use of P from NCPR and SYPR. Approximately 29% of dissolved P from applied NCPR or SYPR was Bray-1 extractable-Pi and increasing to 45% when OM was also amended to the soil. This increase in dissolved P probably explains the enhanced growth and P concentration in switch grass DM.
Wheat crops grown in dryland areas may depend more on stem reserves for grain filling than on cur... more Wheat crops grown in dryland areas may depend more on stem reserves for grain filling than on current photosynthesis. We evaluated the hypothesis that internode length, weight, and specific weight of genotypes affect accumulation and mobilization of stem reserves. This knowledge might complement selection in stressful environments. Genotypic variation for internode characteristics and their effects on dry matter accumulation and mobilization were measured at 10-d intervals in 11 diverse wheat cultivars grown under well-watered and droughted field conditions across 2 yr. Relationships among internode characteristics and accumulation and mobilization of stem reserves were determined. The main effect of year, irrigation, genotype, and harvest date and genotype 3 harvest date interaction were significant. Internode length, weight, and specific weight were reduced under drought. Mobilized dry matter from peduncle, penultimate, and the lower internodes ranged from 43 to 171, 81 to 272, and from 198 to 474 mg, respectively. Mobilized dry matter was less in well-watered than in droughted conditions for peduncle (93 vs. 110 mg) but not for penultimate (173 vs. 143 mg) and the lower internodes (331 vs. 304 mg). Drought increased mobilization efficiency, expressed as percentage of maximum dry mater mobilized, in the peduncle, penultimate, and the lower internodes by 65, 11, and 5%, respectively. Stem maximum specific weight was correlated (r 5 0.64) with stem mobilized dry matter. Balanced partitioning of stem length into upper and lower internodes and internode maximum specific weight are important in genotypic accumulation and mobilization of stem reserves in wheat.
Infection of tall fescue (Festuca arundinacea Schreb.) with its endemic Neotyphodium coenophialum... more Infection of tall fescue (Festuca arundinacea Schreb.) with its endemic Neotyphodium coenophialum-endophyte (Morgan-Jones and Gams) Glenn, Bacon and Hanlin appears to reduce copper (Cu) concentrations in forage and serum of grazing animals, contributing to a range of immune-related disorders. A greenhouse experiment was conducted to identify effects of novel endophyte strains on Cu acquisition by tall fescue (Festuca arundinacea Schreb.) varieties Grasslands Flecha and Jesup infected with a novel, non ergot producing endophyte strain AR542, and two perennial ryegrass (Lolium perenne L.) varieties Aries and Quartet infected with a novel, non lolitrem B producing strain AR1, and their noninfected (E−) forms. Individual endophyte/grass associations were cultivated in nutrient solutions at 1.0 (P+) and 0.0 mM (P−) phosphorus concentrations. The Cu 2+-binding activity of extracellular root exudates, and concentrations of Cu and other heavy metals in roots and shoots were measured. Extracellular root exudates of AR542-infected vs. E− tall fescue had higher Cu 2+-binding activity only in P− nutrient solution as shown by lower concentration of free Cu 2+ (0.096 vs. 0.188 mmol Cu 2+ g −1 root DM, respectively). The Cu 2+binding activity by root exudates of perennial ryegrass was not affected by endophyte infection, but was higher (i.e., lower concentration of free Cu 2+) in P− vs. P+ nutrient solution (0.068 vs. 0.114 mmol Cu 2+ g −1 root DM). In this hydroponic experiment, Cu concentrations in shoots of both grasses were not a function of Cu 2+-binding activity and endophyte effects on heavy metal concentrations in shoots and roots were specific for each variety. The Cu 2+binding activity of extracellular root exudates may affect Cu accumulation by field-grown, endophyte-infected tall fescue under P-limiting growth conditions and warrants verification by more specific methods.
Endophyte-infected (E+) tall fescue (Festuca arundinacea Schreb.) plants grown in phosphorus (P) ... more Endophyte-infected (E+) tall fescue (Festuca arundinacea Schreb.) plants grown in phosphorus (P) deficient soils accumulate more P in roots and shoots than noninfected isolines. In a growth chamber experiment, four tall fescue genotypes DN2, DN4, DN7, and DN11, infected with their naturally occurring strains of Neotyphodium coenophialum (Morgan-Jones & Gams) Glenn, Bacon & Hanlin, and their noninfected isolines (E-), were cultivated in nutrient solution at two P levels: 31 ppm (P+) and 0 ppm (P-) for 4 wk. The Fe 3+ reducing activity of extracellular reductants and intact root tissues, and total phenolic concentration in roots and shoots were measured. Endophyte infection significantly increased Fe 3+ reducing activity rate of extracellular reductants (9.6 × 10 −3 µmol Fe 3+ h −1 g −1 root FW) when compared to E-plants (3.9 × 10 −3) and Fe 3+ reduction rate of intact root tissues (6.16 and 4.48 µmol Fe 3+ h −1 g −1 root FW, respectively for E+ and E-plants). In response to P deficiency, Fe 3+ reduction rate of intact root tissues increased in E+ plants by 375% when compared to E-plants, whereas no significant differences were observed when P was provided. Total phenolic concentration was 20% greater in shoots of E+ plants than in E-plants. In response to P deficiency, total phenolic concentration significantly increased in roots of E+ plants by 7%, and decreased in roots of E-plants by 10%. The most active Fe 3+ reducing zones were located along branching of secondary and tertiary roots. The Fe 3+ reducing activity on the root surface and total phenolic concentration in roots and shoots increased dramatically in response to endophyte infection, especially under P limiting conditions.
Neotyphodium coenophialum (Morgan-Jones and Gams) Glenn, Bacon and Hanlin, a fungal endophyte fou... more Neotyphodium coenophialum (Morgan-Jones and Gams) Glenn, Bacon and Hanlin, a fungal endophyte found primarily in shoots of tall fescue (Festuca arundinacea Shreb.), can modify rhizosphere activity in response to phosphorus (P) deficiency. In a controlled environment experiment, two cloned tall fescue genotypes (DN2 and DN4) free (E-) and infected (E+) with their naturally occurring endophyte strains were grown in nutrient solutions at low P (3.1 ppm) or high P (31 ppm) concentrations for 21 d. Endophyte infection increased root dry matter (DM) of DN4 by 21% but did not affect root DM of DN2. Under P deficiency, shoot and total DM were not affected by endophyte but relative growth rate was greater in E+ than E-plants. In high P nutrient solution, E+ plants produced 13% less (DN2) or 29% more (DN4) shoot DM than E-plants. Endophyte affected mineral concentrations in roots more than in shoots. Regardless of P concentration in nutrient solution, E+ DN2 accumulated more P, Ca, Zn and Cu but less K in roots than E-plants. When grown in high P nutrient solution, concentrations of Fe and B in roots of E+ DN2 plants were reduced compared with those of E-plants. Concentrations of P, Ca and Cu in roots of DN4 were less, but K was greater in E+ than E-plants. In shoots, E+ DN2 had greater concentrations of Fe and Cu than E-DN2, regardless of P concentration in nutrient solution. Genotype DN4 responded to endophyte infection by reducing B concentration in shoots. Nutrient uptake rates were affected by endophyte infection in plants grown in low P nutrient solution. A greater uptake rate of most nutrients and their transport to shoots was observed in DN2, but responses of DN4 were not consistent. Results suggest that endophyte may elicit different modes of tall fescue adaptation to P deficiency.
Plants grown in highly weathered or high alkaline soils often experience P stress, but never a P ... more Plants grown in highly weathered or high alkaline soils often experience P stress, but never a P free environment. Thus, applications of mineral P fertilizers are often required to achieve maximum yield. Responses of different plant species or cultivars were the subject of numerous investigations in which P was withheld from the growth media. In this study, chickpea plants (Cicer arietinum L.) grown hydroponically in complete nutrient solution for 17 days (1 mM P) were then maintained at low-P supply for 14 days (0.01 mM). Measurements included dry matter (DM) 1 , production of shoots and roots, PEP carboxylase, organic acid anion (Org A-), and root morphological responses. Dry matter of shoots and roots were reduced equally in plants subjected to Low-P supply. The uptake rates of all mineral nutrients were reduced soon after low-P was imposed within 1-2 days for Ca 2+ , Mg 2+ , and SO 4 2and within 3-4 days in case of K + and NO 3-. High and low P plants continued to alkalize the nutrient solution, but the rate of OHreleased from the roots was considerably reduced in low-P plants. Cumulative values of OHreleased from the roots after low P treatment was imposed linearly correlated with the difference of anion-cation uptakes in high-P (R 2 = 0.9989) and in low-P plants (R 2 = 0.9947). Physiological responses to low-P include an enhanced activity of PEPcase in shoots and to a greater extent in roots, which could explain the higher concentrations of Org Ain shoots and roots of low-P plants. Root image analyses showed an enhanced branching density in low-P plants resulting in shorter but slender roots than those in high-P plants. These responses could probably explain the greater inflow rates and SAcR rates of micronutrient cations (Zn, Cu, Mn, and Fe) into the shoots of P-limited plants. chickpea / phosphorus / stress / nutrient uptake / roots morphology Résumé-Réponses du pois chiche en culture hydroponique à une faible alimentation en phosphore : changement de pH, taux d'absorption des minéraux et modifications morphologiques des racines. Les plantes poussant sur des sols fortement altérés ou très alcalins souffrent souvent d'un déficit de phosphore (P), mais ne se trouvent jamais dans un environnement sans P. Les applications d'engrais minéraux phosphoriques sont donc souvent nécessaires pour obtenir un rendement maximum. Les réponses des diverses espèces ou variétés de plantes ont fait l'objet de nombreuses recherches dans lesquelles le P a été enlevé des milieux de culture. Dans cette étude, les plants de pois chiche (Cicer arietinum L.) cultivés hydroponiquement dans une solution nutritive complète pendant 17 jours (1 mM de P), furent ensuite maintenus avec une faible alimentation en P pendant 14 jours (0,01 mM). Les mesures comprenaient la matière sèche des parties aériennes et des racines, la carboxylase PEP, l'anion acide organique (Org A-), et les réponses morphologiques des racines. La matière sèche des parties aériennes et des racines fut réduite de manière égale pour les plantes carencées. Les taux de prélèvement de tous les minéraux furent réduits rapidement après l'imposition d'une faible alimentation en P, en 1-2 jours pour le Ca 2+ , le Mg 2+ et le SO 4 2et en 3-4 jours dans le cas du K + et du NO 3-. Les plantes, cultivées avec un fort ou un faible taux de P, ont continué d'alcaliniser la solution nutritive, mais le taux de OHrelâché par les racines a été considérablement réduit pour les plantes carencées. Les valeurs cumulatives de OHlibérés par les racines après que les deux doses de P aient été imposées, sont corrélées linéairement avec la différence « anion-cation » absorbés dans les plantes pour la forte (R 2 = 0,9989) et la faible (R 2 = 0,9947) concentration en P. Les réponses physiologiques à une faible concentration en P comportent un accroissement d'activité de la carboxylase PEP dans les parties aériennes et dans une plus grande mesure dans les racines, ce qui peut expliquer les fortes concentrations de Org Adans les parties aériennes et les racines des plantes carencées en P. Les analyses d'images de racines ont montré, de plus, un accroissement de la densité de ramification pour les plantes carencées en P, induisant des racines plus courtes et plus fines que celles des plantes non carencées. Ces réponses pourraient probablement expliquer les plus grands taux d'absorption et d'accumulation spécifique pour les macro et les micronutriments (Zn, Cu, Mn et Fe) dans les parties aériennes des plantes stressées. pois chiche / carence / phosphore / absorption racinaire / morphologie des racines
The spatial distribution and partitioning of water dissolved phosphorus fractions in the soil pro... more The spatial distribution and partitioning of water dissolved phosphorus fractions in the soil profile of a grazed karst sinkhole landscape were investigated. We also measured P fractions in surface runoff entering a sinkhole drain and in karst spring flow draining the study area. Grazing increased total N, C, and all forms of P of soil. Dissolved inorganic orthophosphate (DPi) was the highest in the surface soil layer and diminished significantly with depth. The proportion of dissolved unreactive phosphorus (DPu) increased with soil depth. Changes in DPu with landscape position and depth were closely correlated with changes in dissolved organic carbon (DOC) suggesting that the mobility and transport of DPu was mediated by DOC. Landscape position sampling showed molybdate reactive phosphorus (MRP) and DPu increased toward the bottom and center of sinkholes. The distribution of DPi and DPu in surface runoff and that occurring in underground watercourses confirms the significance of DPu transported into karst groundwater. phosphorus transport / dissolved unreactive phosphorus / molybdate reactive phosphorus / karst / grazing impacts Résumé-Mobilité du phosphore dans une zone karstique paturée. La distribution spatiale et la partition des fractions de phosphore dissoutes dans le profil de sol d'un paysage pâturé de dolines karstiques ont été étudiées. Nous avons également mesuré les fractions de P dans les eaux de surface entrant dans un drain de doline et dans l'écoulement ressortant du karst drainant le secteur d'étude. Le pâturage a augmenté N total, C, et toutes les formes de P de sol. L'orthophosphore inorganique dissous (DPi) était le plus élevé dans la couche de surface du sol et réduit significativement avec la profondeur. La proportion de phosphore non réactif dissous (DPu) a augmenté avec la profondeur de sol. Des changements de DPu en fonction de la position dans le paysage et de la profondeur ont été étroitement corrélés avec des changements du carbone organique dissous (DOC) suggérant que la mobilité et le transport du DPu ont été facilités par le DOC. Un échantillonnage dans le paysage a montré une augmentation de phosphore réactif au molybdate (MRP) et de DPu vers le fond et le centre des dolines. La distribution de DPi et DPu dans l'écoulement de surface et ce qui se produit lors du transit de l'eau sous terre confirme la valeur significative du DPu transporté dans les eaux souterraines du karst. transport de phosphore / phosphore dissous non réactif / phosphore réactif au molybdate / karst / impacts du pâturage
Communications in Soil Science and Plant Analysis, 2001
Plants grown in acidic soils often have reduced productivity because of limited mineral nutrients... more Plants grown in acidic soils often have reduced productivity because of limited mineral nutrients. For plants to obtain adequate nutrients under these conditions, some source of fertilizer is commonly added or a method to make nutrients more available to plants, such as mycorrhiza, is needed. Maize (Zea mays L.) was grown in acidic soil (pHW 4.7, soilwater, 1:1) with added phosphate rock (PR) and the arbuscular mycorrhizal fungus (AMF) Glomus clarum to determine the effectiveness of AMF and PR for supplying nutrients, especially P. Plants were grown in a growth chamber and harvested when plants had grown in treated soil 15, 22, 29, and 36 d. Plant dry matter (DM) was greatly enhanced by PR, and even more at each harvest when roots were colonized with AMF (AMF+PR). Shoot DM increased more than root DM with PR (PR and AMF+PR) treatments. Total root length (RL) was greater for plants grown with PR and AMF+PR compared to the Control (no added P or AMF) and AMF plants. Colonization of roots by AMF was higher for AMF+PR than for AMF plants. Acquisition of P followed the sequence of AMF+PR > PR >> AMF > Control. Other nutrients commonly limiting in acidic soil [e.g., calcium (Ca), magnesium (Mg), and potassium (K)] were greatly enhanced in AMF compared to nonmycorrhizal (nonAMF) plants. The AMF plants had 2-3-fold greater inflow rates [inflow = μg nutrient m−1 RL day−1] of Ca, Mg, copper (Cu), zinc (Zn), and boron (B) than nonAMF plants. The application of PR and/or AMF colonization decreased the concentrations of iron (Fe), manganese (Mn), and aluminum (Al) in the shoots. The lower specific accumulation rate [SAcR = μg nutrient g−1 shoot DM day−1] of Fe, Mn, and Al in the shoots indicated a possible precipitation or/and formation of metal-organic complexes in the roots. Application of PR to this acidic soil did not inhibit maize response to AMF, and both PR and AMF were important for optimal growth of maize in this acidic soil.
Plant Nutrition — Physiology and Applications, 1990
Non-nodulated chickpea plants of a Fe-efficient variety were grown in a computer-controlled hydro... more Non-nodulated chickpea plants of a Fe-efficient variety were grown in a computer-controlled hydroponic system capable of measuring uptake rates of NO3 −, K+, H2PO4 −, Ca++, Mg ++ and Na+ from a nutrient solution and replenishing those ions taken up. Plants were subjected to two regimes of Fe supply (A: 0–20.5 days, 5.6 ppm Fe; 20.5–35.5 days, 0 ppm Fe. B: the reverse of A). Plants were harvested at intervals over the experimental period and their growth and nutrient contents were measured.
... Auteur(s) / Author(s). LE BOT J. ; ALLOUSH GA ; KIRKBY EA ; SANDERS FE ; Affiliation(s) du ou... more ... Auteur(s) / Author(s). LE BOT J. ; ALLOUSH GA ; KIRKBY EA ; SANDERS FE ; Affiliation(s) du ou des auteurs / Author(s) Affiliation(s). Univ. ... Revue / Journal Title. Journal of plant nutrition ISSN 0190-4167 CODEN JPNUDS Source / Source. 1990, vol. 13, n o 12, pp. ...
Grain growth in wheat depends on current photosynthesis and stem water-soluble carbohydrates (WSC... more Grain growth in wheat depends on current photosynthesis and stem water-soluble carbohydrates (WSC). In semiarid regions with terminal drought, grain filling in wheat crops may depend more on stem WSC content than on current assimilates. Reduction in grain yield under drought is attributed to shorter duration of linear grain growth despite increased contribution of stem reserves to grain yield. The amount of stem reserves is measured either by changes in stem dry weight (indirect method) or by stem WSC content (direct method). Genotypic variation in the rate and duration of linear grain growth and in percent contribution of stem reserves to grain yield has not been evaluated in wheat. The objectives of this study were: (i) to quantify the relationship between the direct and indirect measurement of stem reserves during and across the grain-filling period and (ii) to measure the extent of genotypic variation in rate and duration of linear grain growth and in percent contribution of stem reserves to grain yield. Dry weight, WSC content and grain yield of the main stem were measured at 10-day intervals in 11 diverse wheat genotypes under wellwatered and droughted-field conditions across 2 years. Drought reduced stem WSC content from 413 to 281 mg and grain yield from 4.6 to 2.5 t ha À1. Stem WSC content and dry weight were positively correlated. Genotypic differences in linear rate of grain growth were significant in well-watered (ranging from 48.9 to 72.4 mg spike À1 day À1) and in droughted-field (ranging from 33.2 to 59.9 mg spike À1 day À1) conditions. Drought, on average, reduced the linear rate and duration of grain growth by 20 and 50%, respectively. Reduction in linear rate ranged from 13 to 43%. The amount of current assimilates and stem reserves contributed to grain yield was reduced, respectively, by 54 and 11% under drought. Genotypic differences in percent contribution of stem reserves to grain yield were significant in well-watered (ranging from 19.1 to 53.6%) and in droughted-field (ranging from 36.6 to 65.4%) conditions. The wheat genotypes responded differently to drought. Main spike grain yield was reduced by 43% under drought due to 26 and 11% reduction in grain weight and number of grains, respectively. Grain yield was correlated with linear grain growth under well-watered (r = 0.96) and droughted (r = 0.83) conditions. The genotypic variation observed indicates that breeding for a higher rate of linear grain growth and greater contribution of stem reserves to grain yield should be possible in wheat to stabilize grain yield in stressful environments.
Wheat crops grown in dryland areas may depend more on stem reserves for grain filling than on cur... more Wheat crops grown in dryland areas may depend more on stem reserves for grain filling than on current photosynthesis. We evaluated the hypothesis that internode length, weight, and specific weight of genotypes affect accumulation and mobilization of stem reserves. This knowledge might complement selection in stressful environments. Genotypic variation for internode characteristics and their effects on dry matter accumulation and mobilization were measured at 10-d intervals in 11 diverse wheat cultivars grown under well-watered and droughted field conditions across 2 yr. Relationships among internode characteristics and accumulation and mobilization of stem reserves were determined. The main effect of year, irrigation, genotype, and harvest date and genotype 3 harvest date interaction were significant. Internode length, weight, and specific weight were reduced under drought. Mobilized dry matter from peduncle, penultimate, and the lower internodes ranged from 43 to 171, 81 to 272, and from 198 to 474 mg, respectively. Mobilized dry matter was less in well-watered than in droughted conditions for peduncle (93 vs. 110 mg) but not for penultimate (173 vs. 143 mg) and the lower internodes (331 vs. 304 mg). Drought increased mobilization efficiency, expressed as percentage of maximum dry mater mobilized, in the peduncle, penultimate, and the lower internodes by 65, 11, and 5%, respectively. Stem maximum specific weight was correlated (r 5 0.64) with stem mobilized dry matter. Balanced partitioning of stem length into upper and lower internodes and internode maximum specific weight are important in genotypic accumulation and mobilization of stem reserves in wheat.
... AMF-root colonization and/or decreased growth of mycorrhizal plants (Antunes and Cordoso, 199... more ... AMF-root colonization and/or decreased growth of mycorrhizal plants (Antunes and Cordoso, 1991; Howler et al., 1987; Manjunath et al., 1989; Ryan et al., 1994; Sieverding and Galvez, 1988). Information on acquisition of the macronutrients K, Ca, Mg, and S by mycorrhizal ...
A pot experiment was conducted in a greenhouse at Tishreen University location. The experiment in... more A pot experiment was conducted in a greenhouse at Tishreen University location. The experiment included three soils differ in their chemical properties: 1) heavy clay red soil rich in iron oxides; 2) a silt loam basiltic soil rich in manganese oxides; 3) clay red soil rich in calcium carbonate (34.8 %). Treatments included application of different levels of triple super phosphate (TSP, 46 % P 2 O 5 ) ranged from 0, 20, 40, 60, 80, to 100, mg P/kg soil were added to 0.5 kg soil. Pots were randomized in a green house, watered regularly to maintained 75% of the water holding capacity. Sub-samples were taken from each pot at times (0-30-60-90-120-150-180-210-240 Day). Soil P fractionation was only preformed for samples withdrawn at times 0 and 240 days.أسفل النموذج The incubation of the native soils led to an increase in available P in all soils after 240 day of incubation. The increase in extracted soil Pi differed mainly in phosphorus extracted with 0.5M NaOH and 1M HCl...
The impact on water quality by agricultural activity in karst terrain is an important considerati... more The impact on water quality by agricultural activity in karst terrain is an important consideration for resource management within the Appalachian region. Karst areas comprise about 18% of the region’s land area. An estimated one-third of the region’s farms, cattle, and agricultural market value are located on karst terrain. Mean nitrate concentrations in several karst springs in southeastern West Virginia exhibit a strong linear relationship with the percentage of agriculture land cover. Development of best management practices for efficient nitrogen (N) use and reduction of outflow of N to water from karst areas requires knowledge about N dynamics on those landscapes. Water extractable NO3-N and NH4-N were measured along transects at four soil depths in two grazed sinkholes and one wooded sinkhole. Distribution of soil NO3-N and NH4-N were related to frequency of animal presence and to topographic and hydrologic redistribution of soil and fecal matter in the grazed sinkholes. Kars...
Animal manure and urine deposition can cause localized patches of high ionic strength (IS) soil i... more Animal manure and urine deposition can cause localized patches of high ionic strength (IS) soil in pastures, influencing plant production, nutritive value and sward composition. Chicory (Cichorium intybus L.) appears to thrive in high-nutrient input situations, but no information is available on chicory response to increasing IS. In a greenhouse experiment, we evaluated the effect of rhizosphere ionic strength (0.9, 4.0, 8.0 and 12.0 dS m)1) on productivity and nutritive value of chicory. Dry matter production decreased linearly as IS increased. Shoot concentrations for Ca, Na and Cl increased as IS increased. All mineral concentrations, except Cu, were substantially higher than or equal to the highest concentrations reported for forages. At all IS, nitrate-N and K exceeded maximum recommendation for ruminant diets. The sodium level could be high enough to reduce dry matter intake at the highest IS level. Crude protein and energy estimates indicate chicory would support production levels equivalent to those of other high-quality forages. In vitro organic matter disappearance increased as IS increased. Chicory as a component of a forage mixture could help stabilize forage yield in pastures and also shows promise for use as a nutrient mop in feedlot areas, where excess soil nutrients are a problem.
Grazing livestock create localized nutrient patches that increase soil ionic strength (IS) and in... more Grazing livestock create localized nutrient patches that increase soil ionic strength (IS) and influence plant productivity. The ability of plant root systems to control ion absorption and flux to xylem, and to sequester ions reaching leaf tissue in bound, nontoxic forms are means of minimizing IS. A greenhouse experiment was conducted to determine the growth and mineral acquisition responses of forage chicory (Cichorium intybus L. cv. Grasslands Puna) to increasing (0.9, 4, 8, and 12 dS m)1) IS in the rhizosphere obtained by additions of NaCl ⁄ CaCl 2 (1 : 1 m ratio). Plants were harvested four times after planting (20, 27, 34 and 41 d) to identify responses as a function of time. Increased accumulation and localization of Na in roots in comparison to shoots suggested that chicory restricted Na transport to shoots, and that insoluble Na in tissues increased with increasing IS. Soluble cations in shoots were about 50 % of total cations, irrespective of rhizosphere IS and Na uptake. Differences in the cation:anion ratio could not be accounted for by organic acid concentrations in chicory, but substantial accumulation of nonstructural carbohydrates as fructans in roots could contribute to charge balance. Our results demonstrate that forage chicory has moderate tolerance to IS, suggesting that it might be a useful species for sites with potential for IS. Chicory growth would probably be sustained under IS conditions, and the resultant vigorous growth and accumulation of mineral nutrients in shoots would contribute to acceptable nutritive value for grazing livestock. Plants capable of growing in and acquiring nutrients from nutrient-laden patches in the sward would help minimize erosion and nutrient transport, with positive benefits for water and soil quality.
Forage chicory is a productive forage resource for eastern North America; however, many soils in ... more Forage chicory is a productive forage resource for eastern North America; however, many soils in the region are acidic and deficient in P and might restrict the widespread use of forage chicory. There is no published information on response of forage chicory to P, or P acquisition strategies for morphologically different chicory cultivars. The literature suggests the following null hypothesis: "specific root length (SRL) will increase with P deficiency". We conducted controlled environment experiments using nutrient culture to determine plant mass, mineral composition, and root morphology of three forage chicory cultivars (Grasslands Puna (GP), LaCerta (LC) and Forage Feast (FF)) as a function of P supply, and test the null hypothesis with chicory. Phosphorus increased chicory growth irrespective of cultivar. Root morphology differed among cultivars independent of P supply with FF producing about twice the taproot mass of GP or LC. Root morphology was also impacted by P supply and the specific interactions between P and cultivar. Total root length and surface area of GP increased, and did not change in LC or FF under −P conditions. Thus, the null hypothesis must be rejected. Results suggest at least two different plant responses to −P conditions in chicory that seem to be attributes of specific cultivars: (a) increase in root length of the 0.28 mm root class (GP); (b) decrease in non-taproot mass density with −P and no change in root length or ratios between diameter classes (LC). The change in root length of small diameter class roots, as observed for GP, is typical of the responses to −P described in the literature. The decrease in root density seen with LC is probably an anatomical response that is not coupled with any observable morphological response. We conclude that use of the above null hypothesis as a paradigm for plant root response to P deficiency must be rejected. The routine use of specific root length as an indicator of environmentally induced changes in root system function is precluded by the presence of anatomical and physiological changes (adaptations) that have no concomitant gross morphological changes.
Phosphate rock (PR) and organic manure (OM) are promising amendments to acidic soils to correct P... more Phosphate rock (PR) and organic manure (OM) are promising amendments to acidic soils to correct P deficiency and Al/Mn toxicities. The interaction between PR and OM and consequent effects in acidic soil are not fully understood. The effects of OM on the dissolution of two types of PR (NCPR, North Carolina PR; SYPR, Syrian PR) and dry matter production and nutrient uptake efficiency in an acidic Lily loamy soil from West Virginia were examined in an incubation and plant pot studies. NCPR and SYPR were supplied at a rate of 500 mg P kg −1 and organic manure at a rate of 30 g kg −1. Observations were made over 126 days at 21-day intervals. The dissolution of applied NCPR and SYPR was calculated based on the estimation of ?Pi and ?TP-NaOH method. Dissolution of NCPR and SYPR calculated by TP-NaOH was quick during the initial 21 day (∼20%), and thereafter increased slowly reaching 42 and 40% at 126 day for NCPR and SYPR, respectively. On the other hand, percent dissolution calculated based on Pi-NaOH, while fluctuating within ±5% between intervals, were less by 10 and 15% at 126 day for NCPR and SYPR compared to dissolutions estimated based on-TP-NaOH. OM generally reduced PR dissolution, and to a 11-14% lesser extend in the presence of plant roots, presumably due to plant roots depleting P and Ca from the dissolution zone. OM increased dry matter production (DM) of switch grass, increased specific accumulation rates (SAcR, mg or µg g −1 DM) of P and Mg in shoots, decreased SAcRs of Al and Mn in shoots DM, and increased use of P from NCPR and SYPR. Approximately 29% of dissolved P from applied NCPR or SYPR was Bray-1 extractable-Pi and increasing to 45% when OM was also amended to the soil. This increase in dissolved P probably explains the enhanced growth and P concentration in switch grass DM.
Wheat crops grown in dryland areas may depend more on stem reserves for grain filling than on cur... more Wheat crops grown in dryland areas may depend more on stem reserves for grain filling than on current photosynthesis. We evaluated the hypothesis that internode length, weight, and specific weight of genotypes affect accumulation and mobilization of stem reserves. This knowledge might complement selection in stressful environments. Genotypic variation for internode characteristics and their effects on dry matter accumulation and mobilization were measured at 10-d intervals in 11 diverse wheat cultivars grown under well-watered and droughted field conditions across 2 yr. Relationships among internode characteristics and accumulation and mobilization of stem reserves were determined. The main effect of year, irrigation, genotype, and harvest date and genotype 3 harvest date interaction were significant. Internode length, weight, and specific weight were reduced under drought. Mobilized dry matter from peduncle, penultimate, and the lower internodes ranged from 43 to 171, 81 to 272, and from 198 to 474 mg, respectively. Mobilized dry matter was less in well-watered than in droughted conditions for peduncle (93 vs. 110 mg) but not for penultimate (173 vs. 143 mg) and the lower internodes (331 vs. 304 mg). Drought increased mobilization efficiency, expressed as percentage of maximum dry mater mobilized, in the peduncle, penultimate, and the lower internodes by 65, 11, and 5%, respectively. Stem maximum specific weight was correlated (r 5 0.64) with stem mobilized dry matter. Balanced partitioning of stem length into upper and lower internodes and internode maximum specific weight are important in genotypic accumulation and mobilization of stem reserves in wheat.
Infection of tall fescue (Festuca arundinacea Schreb.) with its endemic Neotyphodium coenophialum... more Infection of tall fescue (Festuca arundinacea Schreb.) with its endemic Neotyphodium coenophialum-endophyte (Morgan-Jones and Gams) Glenn, Bacon and Hanlin appears to reduce copper (Cu) concentrations in forage and serum of grazing animals, contributing to a range of immune-related disorders. A greenhouse experiment was conducted to identify effects of novel endophyte strains on Cu acquisition by tall fescue (Festuca arundinacea Schreb.) varieties Grasslands Flecha and Jesup infected with a novel, non ergot producing endophyte strain AR542, and two perennial ryegrass (Lolium perenne L.) varieties Aries and Quartet infected with a novel, non lolitrem B producing strain AR1, and their noninfected (E−) forms. Individual endophyte/grass associations were cultivated in nutrient solutions at 1.0 (P+) and 0.0 mM (P−) phosphorus concentrations. The Cu 2+-binding activity of extracellular root exudates, and concentrations of Cu and other heavy metals in roots and shoots were measured. Extracellular root exudates of AR542-infected vs. E− tall fescue had higher Cu 2+-binding activity only in P− nutrient solution as shown by lower concentration of free Cu 2+ (0.096 vs. 0.188 mmol Cu 2+ g −1 root DM, respectively). The Cu 2+binding activity by root exudates of perennial ryegrass was not affected by endophyte infection, but was higher (i.e., lower concentration of free Cu 2+) in P− vs. P+ nutrient solution (0.068 vs. 0.114 mmol Cu 2+ g −1 root DM). In this hydroponic experiment, Cu concentrations in shoots of both grasses were not a function of Cu 2+-binding activity and endophyte effects on heavy metal concentrations in shoots and roots were specific for each variety. The Cu 2+binding activity of extracellular root exudates may affect Cu accumulation by field-grown, endophyte-infected tall fescue under P-limiting growth conditions and warrants verification by more specific methods.
Endophyte-infected (E+) tall fescue (Festuca arundinacea Schreb.) plants grown in phosphorus (P) ... more Endophyte-infected (E+) tall fescue (Festuca arundinacea Schreb.) plants grown in phosphorus (P) deficient soils accumulate more P in roots and shoots than noninfected isolines. In a growth chamber experiment, four tall fescue genotypes DN2, DN4, DN7, and DN11, infected with their naturally occurring strains of Neotyphodium coenophialum (Morgan-Jones & Gams) Glenn, Bacon & Hanlin, and their noninfected isolines (E-), were cultivated in nutrient solution at two P levels: 31 ppm (P+) and 0 ppm (P-) for 4 wk. The Fe 3+ reducing activity of extracellular reductants and intact root tissues, and total phenolic concentration in roots and shoots were measured. Endophyte infection significantly increased Fe 3+ reducing activity rate of extracellular reductants (9.6 × 10 −3 µmol Fe 3+ h −1 g −1 root FW) when compared to E-plants (3.9 × 10 −3) and Fe 3+ reduction rate of intact root tissues (6.16 and 4.48 µmol Fe 3+ h −1 g −1 root FW, respectively for E+ and E-plants). In response to P deficiency, Fe 3+ reduction rate of intact root tissues increased in E+ plants by 375% when compared to E-plants, whereas no significant differences were observed when P was provided. Total phenolic concentration was 20% greater in shoots of E+ plants than in E-plants. In response to P deficiency, total phenolic concentration significantly increased in roots of E+ plants by 7%, and decreased in roots of E-plants by 10%. The most active Fe 3+ reducing zones were located along branching of secondary and tertiary roots. The Fe 3+ reducing activity on the root surface and total phenolic concentration in roots and shoots increased dramatically in response to endophyte infection, especially under P limiting conditions.
Neotyphodium coenophialum (Morgan-Jones and Gams) Glenn, Bacon and Hanlin, a fungal endophyte fou... more Neotyphodium coenophialum (Morgan-Jones and Gams) Glenn, Bacon and Hanlin, a fungal endophyte found primarily in shoots of tall fescue (Festuca arundinacea Shreb.), can modify rhizosphere activity in response to phosphorus (P) deficiency. In a controlled environment experiment, two cloned tall fescue genotypes (DN2 and DN4) free (E-) and infected (E+) with their naturally occurring endophyte strains were grown in nutrient solutions at low P (3.1 ppm) or high P (31 ppm) concentrations for 21 d. Endophyte infection increased root dry matter (DM) of DN4 by 21% but did not affect root DM of DN2. Under P deficiency, shoot and total DM were not affected by endophyte but relative growth rate was greater in E+ than E-plants. In high P nutrient solution, E+ plants produced 13% less (DN2) or 29% more (DN4) shoot DM than E-plants. Endophyte affected mineral concentrations in roots more than in shoots. Regardless of P concentration in nutrient solution, E+ DN2 accumulated more P, Ca, Zn and Cu but less K in roots than E-plants. When grown in high P nutrient solution, concentrations of Fe and B in roots of E+ DN2 plants were reduced compared with those of E-plants. Concentrations of P, Ca and Cu in roots of DN4 were less, but K was greater in E+ than E-plants. In shoots, E+ DN2 had greater concentrations of Fe and Cu than E-DN2, regardless of P concentration in nutrient solution. Genotype DN4 responded to endophyte infection by reducing B concentration in shoots. Nutrient uptake rates were affected by endophyte infection in plants grown in low P nutrient solution. A greater uptake rate of most nutrients and their transport to shoots was observed in DN2, but responses of DN4 were not consistent. Results suggest that endophyte may elicit different modes of tall fescue adaptation to P deficiency.
Plants grown in highly weathered or high alkaline soils often experience P stress, but never a P ... more Plants grown in highly weathered or high alkaline soils often experience P stress, but never a P free environment. Thus, applications of mineral P fertilizers are often required to achieve maximum yield. Responses of different plant species or cultivars were the subject of numerous investigations in which P was withheld from the growth media. In this study, chickpea plants (Cicer arietinum L.) grown hydroponically in complete nutrient solution for 17 days (1 mM P) were then maintained at low-P supply for 14 days (0.01 mM). Measurements included dry matter (DM) 1 , production of shoots and roots, PEP carboxylase, organic acid anion (Org A-), and root morphological responses. Dry matter of shoots and roots were reduced equally in plants subjected to Low-P supply. The uptake rates of all mineral nutrients were reduced soon after low-P was imposed within 1-2 days for Ca 2+ , Mg 2+ , and SO 4 2and within 3-4 days in case of K + and NO 3-. High and low P plants continued to alkalize the nutrient solution, but the rate of OHreleased from the roots was considerably reduced in low-P plants. Cumulative values of OHreleased from the roots after low P treatment was imposed linearly correlated with the difference of anion-cation uptakes in high-P (R 2 = 0.9989) and in low-P plants (R 2 = 0.9947). Physiological responses to low-P include an enhanced activity of PEPcase in shoots and to a greater extent in roots, which could explain the higher concentrations of Org Ain shoots and roots of low-P plants. Root image analyses showed an enhanced branching density in low-P plants resulting in shorter but slender roots than those in high-P plants. These responses could probably explain the greater inflow rates and SAcR rates of micronutrient cations (Zn, Cu, Mn, and Fe) into the shoots of P-limited plants. chickpea / phosphorus / stress / nutrient uptake / roots morphology Résumé-Réponses du pois chiche en culture hydroponique à une faible alimentation en phosphore : changement de pH, taux d'absorption des minéraux et modifications morphologiques des racines. Les plantes poussant sur des sols fortement altérés ou très alcalins souffrent souvent d'un déficit de phosphore (P), mais ne se trouvent jamais dans un environnement sans P. Les applications d'engrais minéraux phosphoriques sont donc souvent nécessaires pour obtenir un rendement maximum. Les réponses des diverses espèces ou variétés de plantes ont fait l'objet de nombreuses recherches dans lesquelles le P a été enlevé des milieux de culture. Dans cette étude, les plants de pois chiche (Cicer arietinum L.) cultivés hydroponiquement dans une solution nutritive complète pendant 17 jours (1 mM de P), furent ensuite maintenus avec une faible alimentation en P pendant 14 jours (0,01 mM). Les mesures comprenaient la matière sèche des parties aériennes et des racines, la carboxylase PEP, l'anion acide organique (Org A-), et les réponses morphologiques des racines. La matière sèche des parties aériennes et des racines fut réduite de manière égale pour les plantes carencées. Les taux de prélèvement de tous les minéraux furent réduits rapidement après l'imposition d'une faible alimentation en P, en 1-2 jours pour le Ca 2+ , le Mg 2+ et le SO 4 2et en 3-4 jours dans le cas du K + et du NO 3-. Les plantes, cultivées avec un fort ou un faible taux de P, ont continué d'alcaliniser la solution nutritive, mais le taux de OHrelâché par les racines a été considérablement réduit pour les plantes carencées. Les valeurs cumulatives de OHlibérés par les racines après que les deux doses de P aient été imposées, sont corrélées linéairement avec la différence « anion-cation » absorbés dans les plantes pour la forte (R 2 = 0,9989) et la faible (R 2 = 0,9947) concentration en P. Les réponses physiologiques à une faible concentration en P comportent un accroissement d'activité de la carboxylase PEP dans les parties aériennes et dans une plus grande mesure dans les racines, ce qui peut expliquer les fortes concentrations de Org Adans les parties aériennes et les racines des plantes carencées en P. Les analyses d'images de racines ont montré, de plus, un accroissement de la densité de ramification pour les plantes carencées en P, induisant des racines plus courtes et plus fines que celles des plantes non carencées. Ces réponses pourraient probablement expliquer les plus grands taux d'absorption et d'accumulation spécifique pour les macro et les micronutriments (Zn, Cu, Mn et Fe) dans les parties aériennes des plantes stressées. pois chiche / carence / phosphore / absorption racinaire / morphologie des racines
The spatial distribution and partitioning of water dissolved phosphorus fractions in the soil pro... more The spatial distribution and partitioning of water dissolved phosphorus fractions in the soil profile of a grazed karst sinkhole landscape were investigated. We also measured P fractions in surface runoff entering a sinkhole drain and in karst spring flow draining the study area. Grazing increased total N, C, and all forms of P of soil. Dissolved inorganic orthophosphate (DPi) was the highest in the surface soil layer and diminished significantly with depth. The proportion of dissolved unreactive phosphorus (DPu) increased with soil depth. Changes in DPu with landscape position and depth were closely correlated with changes in dissolved organic carbon (DOC) suggesting that the mobility and transport of DPu was mediated by DOC. Landscape position sampling showed molybdate reactive phosphorus (MRP) and DPu increased toward the bottom and center of sinkholes. The distribution of DPi and DPu in surface runoff and that occurring in underground watercourses confirms the significance of DPu transported into karst groundwater. phosphorus transport / dissolved unreactive phosphorus / molybdate reactive phosphorus / karst / grazing impacts Résumé-Mobilité du phosphore dans une zone karstique paturée. La distribution spatiale et la partition des fractions de phosphore dissoutes dans le profil de sol d'un paysage pâturé de dolines karstiques ont été étudiées. Nous avons également mesuré les fractions de P dans les eaux de surface entrant dans un drain de doline et dans l'écoulement ressortant du karst drainant le secteur d'étude. Le pâturage a augmenté N total, C, et toutes les formes de P de sol. L'orthophosphore inorganique dissous (DPi) était le plus élevé dans la couche de surface du sol et réduit significativement avec la profondeur. La proportion de phosphore non réactif dissous (DPu) a augmenté avec la profondeur de sol. Des changements de DPu en fonction de la position dans le paysage et de la profondeur ont été étroitement corrélés avec des changements du carbone organique dissous (DOC) suggérant que la mobilité et le transport du DPu ont été facilités par le DOC. Un échantillonnage dans le paysage a montré une augmentation de phosphore réactif au molybdate (MRP) et de DPu vers le fond et le centre des dolines. La distribution de DPi et DPu dans l'écoulement de surface et ce qui se produit lors du transit de l'eau sous terre confirme la valeur significative du DPu transporté dans les eaux souterraines du karst. transport de phosphore / phosphore dissous non réactif / phosphore réactif au molybdate / karst / impacts du pâturage
Communications in Soil Science and Plant Analysis, 2001
Plants grown in acidic soils often have reduced productivity because of limited mineral nutrients... more Plants grown in acidic soils often have reduced productivity because of limited mineral nutrients. For plants to obtain adequate nutrients under these conditions, some source of fertilizer is commonly added or a method to make nutrients more available to plants, such as mycorrhiza, is needed. Maize (Zea mays L.) was grown in acidic soil (pHW 4.7, soilwater, 1:1) with added phosphate rock (PR) and the arbuscular mycorrhizal fungus (AMF) Glomus clarum to determine the effectiveness of AMF and PR for supplying nutrients, especially P. Plants were grown in a growth chamber and harvested when plants had grown in treated soil 15, 22, 29, and 36 d. Plant dry matter (DM) was greatly enhanced by PR, and even more at each harvest when roots were colonized with AMF (AMF+PR). Shoot DM increased more than root DM with PR (PR and AMF+PR) treatments. Total root length (RL) was greater for plants grown with PR and AMF+PR compared to the Control (no added P or AMF) and AMF plants. Colonization of roots by AMF was higher for AMF+PR than for AMF plants. Acquisition of P followed the sequence of AMF+PR > PR >> AMF > Control. Other nutrients commonly limiting in acidic soil [e.g., calcium (Ca), magnesium (Mg), and potassium (K)] were greatly enhanced in AMF compared to nonmycorrhizal (nonAMF) plants. The AMF plants had 2-3-fold greater inflow rates [inflow = μg nutrient m−1 RL day−1] of Ca, Mg, copper (Cu), zinc (Zn), and boron (B) than nonAMF plants. The application of PR and/or AMF colonization decreased the concentrations of iron (Fe), manganese (Mn), and aluminum (Al) in the shoots. The lower specific accumulation rate [SAcR = μg nutrient g−1 shoot DM day−1] of Fe, Mn, and Al in the shoots indicated a possible precipitation or/and formation of metal-organic complexes in the roots. Application of PR to this acidic soil did not inhibit maize response to AMF, and both PR and AMF were important for optimal growth of maize in this acidic soil.
Uploads
Papers by ghiath alloush