As known from literature lateral buds from pea (Pisum sativum) plants are released from apical do... more As known from literature lateral buds from pea (Pisum sativum) plants are released from apical dominance when repeatedly treated with exogenous cytokinins. Little is known, however, about the endogenous role of cytokinins in this process and whether they interact with basipolar transported IAA, generally regarded as the main signal controlling apical dominance. This paper presents evidence that such an interaction exists.The excision of the apex of pea plants resulted in the release of inhibited lateral buds from apical dominance (AD). This could be entirely prevented by applying 1-naphthylacetic acid (NAA) to the cut end of the shoot. Removal of the apex also resulted in a rapid and rather large increase in the endogenous concentrations of zeatin riboside (ZR), isopentenyladenosine (iAdo) and an as yet unidentified polar zeatin derivative in the node and internode below the point of decapitation. This accumulation of ZR and iAdo, was strongly reduced by the application of NAA. The observed increase in cytokinin concentration preceded the elongation of the lateral buds, suggesting that endogenous cytokinins play a significant role in the release of lateral buds from AD. However, the effect of NAA on the concentration of cytokinins clearly demonstrated the dominant role of the polar basipetally transported auxin in AD. The results suggest a mutual interaction between the basipolar IAA transport system and cytokinins obviously produced in the roots and transported via the xylem into the stem of the pea plants.
Hydrogen cyanamide (HC) has been used to break bud and seed dormancy and to improve rooting in se... more Hydrogen cyanamide (HC) has been used to break bud and seed dormancy and to improve rooting in several species, responses usually associated with the action of plant hormones. However, very few studies have measured endogenous hormones after HC treatment. Therefore, pea (Pisum sativum L.) seedlings with two fully developed internodes above the first leaf were sprayed with 0, 0.1 and 0.3% (v/v) HC. Endogenous concentration of indole-3-acetic acid (IAA), abscisic acid (ABA), zeatin/zeatin riboside and N6(Δ2-isopentenyl) adenine/ N6(Δ2-isopentenyl) adenosine were measured by radioimmunoassay 31 and 80 h after HC treatment. A significant increase in ABA and cytokinin (CK) levels was observed 31 h after treating the plants with 0.3% HC. Small necrotic spots were also noticed in this treatment, thus revealing a toxic effect of this treatment. Additionally, at 80 h, a significant increase in IAA was found for both HC concentrations applied. The action of HC upon ABA, CKs and IAA endogenous levels is discussed.
Embryogenic nucellar callus cultures of different Citrus species and cultivars growing in hormon... more Embryogenic nucellar callus cultures of different Citrus species and cultivars growing in hormone-free medium were transferred to medium containing either sucrose or glycerol as the only carbohydrate source. Glycerol has been reported to induce further development of Citrus somatic embryos, while in the presence of sucrose they continue to proliferate in an 'undifferentiated' manner. The endogenous hormone levels of the cultures were evaluated after 2 and 5 days to characterise the initial steps of embryo development. In most cases, differences among treatments were observed only after 5 days of culture. Higher cytokinin levels were found in most of the cultures transferred to the glycerol-containing medium. The effect of ageing sweet orange cultures on their endogenous hormone levels was determined by leaving them in the original culture medium without subculturing for 60 days. While no changes were observed in the free indoleacetic acid and gibberellin contents, lower levels of abscisic acid and cytokinins were found in the aged cultures than in those transferred at the normal interval, every 30 days. The endogenous hormone contents of Citrus callus of different genotypes were compared. Significant differences were observed in the levels of all hormones evaluated, even when the in vitro ontogeny of the different genotypes was very similar.
We used a scanning electron microscope to study the ultrastructure of vegetative and floral parts... more We used a scanning electron microscope to study the ultrastructure of vegetative and floral parts of Guadua amplexifolia from Costa Rica, a bamboo characterized by a solid culm in the base and a small lumen in the distal part. The most evident characteristics were: epidermic cells with operculated-oblique papillae in the palea, the great amount of ceric papillae forming rosettes
... librarian. You can purchase online access to this Article for a 24-hour period (price varies ... more ... librarian. You can purchase online access to this Article for a 24-hour period (price varies by title): If you already have a Wiley Online Library or Wiley InterScience user account: login above and proceed to purchase the article. ...
... Mayra Montiel1,2, Víctor M. Jiménez3 & Eric Guevara3 1 Facultad de Ciencias Agroalimentar... more ... Mayra Montiel1,2, Víctor M. Jiménez3 & Eric Guevara3 1 Facultad de Ciencias Agroalimentarias, Escuela de Zootecnia, Universidad de Costa Rica. ... B. Sección ampliada de la zona abaxial con los estomas, células cortas, de sílice, células largas con paredes muy onduladas y ...
Guadua angustifolia Kunth was successfully propagated in vitro from axillary buds. Culture initia... more Guadua angustifolia Kunth was successfully propagated in vitro from axillary buds. Culture initiation, bud sprouting, shoot and plant multiplication, rooting and acclimatization, were evaluated. Best results were obtained using explants from greenhouse-cultivated plants, following a disinfection procedure that comprised the sequential use of an alkaline detergent, a mixture of the fungicide Benomyl and the bactericide Agri-mycin, followed by immersion in sodium hypochlorite (1.5% w/v) for 10 min, and culturing on Murashige and Skoog medium containing 2 ml l−1 of Plant Preservative Mixture®. Highest bud sprouting in original explants was observed when 3 mg l−1 N6-benzylaminopurine (BAP) was incorporated into the culture medium. Production of lateral shoots in in vitro growing plants increased with BAP concentration in culture medium, up to 5 mg l−1, the highest concentration assessed. After six subcultures, clumps of 8–12 axes were obtained, and their division in groups of 3–5 axes allowed multiplication of the plants. Rooting occurred in vitro spontaneously in 100% of the explants that produced lateral shoots. Successful acclimatization of well-rooted clumps of 5–6 axes was achieved in the greenhouse under mist watering in a mixture of soil, sand and rice hulls (1:1:1).
... Mayra Montiel 1,2 , Eric Guevara 3 & Víctor M. Jiménez 3. ... una zona costal con el ... more ... Mayra Montiel 1,2 , Eric Guevara 3 & Víctor M. Jiménez 3. ... una zona costal con el haz vascular con los dos vasos de metaxilema y uno de protoxilema, la agrupación de células floemáticas, la vaina de esclerénquima que lo rodea, cuyas células presentan paredes gruesas, el ...
Embryogenic callus and suspension cultures of carrot (Daucus carota L., cv. Nantaise), growing on... more Embryogenic callus and suspension cultures of carrot (Daucus carota L., cv. Nantaise), growing on/in medium including 1 mg/l 2,4-dichlorophenoxy acetic acid (2,4-D), were transferred to medium with or without this plant growth regulator, to impair or induce, respectively, further development of somatic embryos. The endogenous hormone levels of the cultures were determined over 7 days by means of radio-immunoassay, to characterize their evolution in the initial stages of embryo development. In general, levels of indoleacetic acid (IAA) and abscisic acid (ABA) showed only short-lived differences among treatments during this time in both types of tissue analyzed (i.e., a peak of IAA in callus cultures in the absence of 2,4-D, 48 h after medium change, and higher ABA contents 144 h after subculture of suspension cultures in the presence of 2,4-D). Gibberellins (1, 3 and 20) were detected only in suspension cultures devoid of 2,4-D, starting 24 h after subculture. Concerning the evaluated cytokinins—zeatin/zeatin riboside and N 6(Δ2-isopentenyl) adenine/N 6(Δ2-isopentenyl) adenosine—the most remarkable observation is that high levels of the former generally coincided with low concentrations of the latter, indicating a shift from precursor to the active form, and vice versa.
As known from literature lateral buds from pea (Pisum sativum) plants are released from apical do... more As known from literature lateral buds from pea (Pisum sativum) plants are released from apical dominance when repeatedly treated with exogenous cytokinins. Little is known, however, about the endogenous role of cytokinins in this process and whether they interact with basipolar transported IAA, generally regarded as the main signal controlling apical dominance. This paper presents evidence that such an interaction exists.The excision of the apex of pea plants resulted in the release of inhibited lateral buds from apical dominance (AD). This could be entirely prevented by applying 1-naphthylacetic acid (NAA) to the cut end of the shoot. Removal of the apex also resulted in a rapid and rather large increase in the endogenous concentrations of zeatin riboside (ZR), isopentenyladenosine (iAdo) and an as yet unidentified polar zeatin derivative in the node and internode below the point of decapitation. This accumulation of ZR and iAdo, was strongly reduced by the application of NAA. The observed increase in cytokinin concentration preceded the elongation of the lateral buds, suggesting that endogenous cytokinins play a significant role in the release of lateral buds from AD. However, the effect of NAA on the concentration of cytokinins clearly demonstrated the dominant role of the polar basipetally transported auxin in AD. The results suggest a mutual interaction between the basipolar IAA transport system and cytokinins obviously produced in the roots and transported via the xylem into the stem of the pea plants.
Hydrogen cyanamide (HC) has been used to break bud and seed dormancy and to improve rooting in se... more Hydrogen cyanamide (HC) has been used to break bud and seed dormancy and to improve rooting in several species, responses usually associated with the action of plant hormones. However, very few studies have measured endogenous hormones after HC treatment. Therefore, pea (Pisum sativum L.) seedlings with two fully developed internodes above the first leaf were sprayed with 0, 0.1 and 0.3% (v/v) HC. Endogenous concentration of indole-3-acetic acid (IAA), abscisic acid (ABA), zeatin/zeatin riboside and N6(Δ2-isopentenyl) adenine/ N6(Δ2-isopentenyl) adenosine were measured by radioimmunoassay 31 and 80 h after HC treatment. A significant increase in ABA and cytokinin (CK) levels was observed 31 h after treating the plants with 0.3% HC. Small necrotic spots were also noticed in this treatment, thus revealing a toxic effect of this treatment. Additionally, at 80 h, a significant increase in IAA was found for both HC concentrations applied. The action of HC upon ABA, CKs and IAA endogenous levels is discussed.
Embryogenic nucellar callus cultures of different Citrus species and cultivars growing in hormon... more Embryogenic nucellar callus cultures of different Citrus species and cultivars growing in hormone-free medium were transferred to medium containing either sucrose or glycerol as the only carbohydrate source. Glycerol has been reported to induce further development of Citrus somatic embryos, while in the presence of sucrose they continue to proliferate in an 'undifferentiated' manner. The endogenous hormone levels of the cultures were evaluated after 2 and 5 days to characterise the initial steps of embryo development. In most cases, differences among treatments were observed only after 5 days of culture. Higher cytokinin levels were found in most of the cultures transferred to the glycerol-containing medium. The effect of ageing sweet orange cultures on their endogenous hormone levels was determined by leaving them in the original culture medium without subculturing for 60 days. While no changes were observed in the free indoleacetic acid and gibberellin contents, lower levels of abscisic acid and cytokinins were found in the aged cultures than in those transferred at the normal interval, every 30 days. The endogenous hormone contents of Citrus callus of different genotypes were compared. Significant differences were observed in the levels of all hormones evaluated, even when the in vitro ontogeny of the different genotypes was very similar.
We used a scanning electron microscope to study the ultrastructure of vegetative and floral parts... more We used a scanning electron microscope to study the ultrastructure of vegetative and floral parts of Guadua amplexifolia from Costa Rica, a bamboo characterized by a solid culm in the base and a small lumen in the distal part. The most evident characteristics were: epidermic cells with operculated-oblique papillae in the palea, the great amount of ceric papillae forming rosettes
... librarian. You can purchase online access to this Article for a 24-hour period (price varies ... more ... librarian. You can purchase online access to this Article for a 24-hour period (price varies by title): If you already have a Wiley Online Library or Wiley InterScience user account: login above and proceed to purchase the article. ...
... Mayra Montiel1,2, Víctor M. Jiménez3 & Eric Guevara3 1 Facultad de Ciencias Agroalimentar... more ... Mayra Montiel1,2, Víctor M. Jiménez3 & Eric Guevara3 1 Facultad de Ciencias Agroalimentarias, Escuela de Zootecnia, Universidad de Costa Rica. ... B. Sección ampliada de la zona abaxial con los estomas, células cortas, de sílice, células largas con paredes muy onduladas y ...
Guadua angustifolia Kunth was successfully propagated in vitro from axillary buds. Culture initia... more Guadua angustifolia Kunth was successfully propagated in vitro from axillary buds. Culture initiation, bud sprouting, shoot and plant multiplication, rooting and acclimatization, were evaluated. Best results were obtained using explants from greenhouse-cultivated plants, following a disinfection procedure that comprised the sequential use of an alkaline detergent, a mixture of the fungicide Benomyl and the bactericide Agri-mycin, followed by immersion in sodium hypochlorite (1.5% w/v) for 10 min, and culturing on Murashige and Skoog medium containing 2 ml l−1 of Plant Preservative Mixture®. Highest bud sprouting in original explants was observed when 3 mg l−1 N6-benzylaminopurine (BAP) was incorporated into the culture medium. Production of lateral shoots in in vitro growing plants increased with BAP concentration in culture medium, up to 5 mg l−1, the highest concentration assessed. After six subcultures, clumps of 8–12 axes were obtained, and their division in groups of 3–5 axes allowed multiplication of the plants. Rooting occurred in vitro spontaneously in 100% of the explants that produced lateral shoots. Successful acclimatization of well-rooted clumps of 5–6 axes was achieved in the greenhouse under mist watering in a mixture of soil, sand and rice hulls (1:1:1).
... Mayra Montiel 1,2 , Eric Guevara 3 & Víctor M. Jiménez 3. ... una zona costal con el ... more ... Mayra Montiel 1,2 , Eric Guevara 3 & Víctor M. Jiménez 3. ... una zona costal con el haz vascular con los dos vasos de metaxilema y uno de protoxilema, la agrupación de células floemáticas, la vaina de esclerénquima que lo rodea, cuyas células presentan paredes gruesas, el ...
Embryogenic callus and suspension cultures of carrot (Daucus carota L., cv. Nantaise), growing on... more Embryogenic callus and suspension cultures of carrot (Daucus carota L., cv. Nantaise), growing on/in medium including 1 mg/l 2,4-dichlorophenoxy acetic acid (2,4-D), were transferred to medium with or without this plant growth regulator, to impair or induce, respectively, further development of somatic embryos. The endogenous hormone levels of the cultures were determined over 7 days by means of radio-immunoassay, to characterize their evolution in the initial stages of embryo development. In general, levels of indoleacetic acid (IAA) and abscisic acid (ABA) showed only short-lived differences among treatments during this time in both types of tissue analyzed (i.e., a peak of IAA in callus cultures in the absence of 2,4-D, 48 h after medium change, and higher ABA contents 144 h after subculture of suspension cultures in the presence of 2,4-D). Gibberellins (1, 3 and 20) were detected only in suspension cultures devoid of 2,4-D, starting 24 h after subculture. Concerning the evaluated cytokinins—zeatin/zeatin riboside and N 6(Δ2-isopentenyl) adenine/N 6(Δ2-isopentenyl) adenosine—the most remarkable observation is that high levels of the former generally coincided with low concentrations of the latter, indicating a shift from precursor to the active form, and vice versa.
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