Dormancy in Lolium rigidum (annual ryegrass) seeds can be alleviated by warm stratification in th... more Dormancy in Lolium rigidum (annual ryegrass) seeds can be alleviated by warm stratification in the dark or by application of fluridone, an inhibitor of plant abscisic acid (ABA) biosynthesis via phytoene desaturase. However, germination and absolute ABA concentration are not particularly strongly correlated. The aim of this study was to determine if cytokinins of both plant and bacterial origin are involved in mediating dormancy status and in the response to fluridone. Seeds with normal or greatly decreased (by dry heat pre-treatment) bacterial populations were stratified in the light or dark and in the presence or absence of fluridone in order to modify their dormancy status. Germination was assessed and seed cytokinin concentration and composition were measured in embryo-containing or embryo-free seed portions. Seeds lacking bacteria were no longer able to lose dormancy in the dark unless supplied with exogenous gibberellin or fluridone. Although these seeds showed a dramatic swit...
ABSTRACT Yield and harvest index of narrow-leafed lupin (Lupinus angustifolius L.) are variable, ... more ABSTRACT Yield and harvest index of narrow-leafed lupin (Lupinus angustifolius L.) are variable, and factors affecting their reliability have not been clearly identified. In this study, plants were grown in sand culture and were non-nodulated and supplied with mineral nitrogen (N) or acquired N through symbiotic N-2 fixation. Transient N deficiency was imposed a number of times during development in nodulated plants by hushing pure O-2 to the roots to suppress N-2 fixation and in non-nodulated plants by changing the rate of N addition. Low N supply (0.4 mM) before floral initiation or for 2 weeks during floral initiation caused a reduction in seed yield. Transient N deficiency induced by O-2 flush during early growth (Weeks 6 and 7 after sowing) had a marked effect on vegetative growth, the number of main stem flowers, pod set, and seed yield. The early N deficiency also affected shoot and root N concentrations and total cytokinin concentrations in root exudate. Compared with N-2-fixing plants, those supplied with adequate mineral N had a greater flower number and greater branch growth and biomass, but not higher pod set and seed yield, resulting in lower harvest index. Seed N concentrations were also decreased by transient N deficiencies at early (floral initiation), mid (flowering), and late (grain,filling) stages. These findings indicate that any field conditions which transiently reduce N-2 fixation (e.g. temporary waterlogging or drought) are likely to result in lower grain yield and quality of lupin crops.
... quality, rather than quantity, have been found to alter branches was associated with a reduct... more ... quality, rather than quantity, have been found to alter branches was associated with a reduction in the length tiller growth in barley (Davis and Simmons, 1994). Even ... Downloaded from Page 2. 548 Miguel et al. excised from lupins (Lupinus angustifolius L. cv. Merrit) grown ...
... Stewart K. Field 1 , Jason P. Smith 2 ,* , Bruno P. Holzapfel 3 , W. James Hardie 4 and RJ Ne... more ... Stewart K. Field 1 , Jason P. Smith 2 ,* , Bruno P. Holzapfel 3 , W. James Hardie 4 and RJ Neil Emery 5 ... The authors also acknowledge the past and ongoing support of Dennis Greer in the project. * Corresponding author (email: jasmith{at}csu.edu.au). Abstract. ...
Trans-isomers of cytokinins (CK) are thought to predominate and have greater biological activity ... more Trans-isomers of cytokinins (CK) are thought to predominate and have greater biological activity than corresponding cis-isomers in higher plants. However, this study demonstrates a system within which the predominant CK are cis-isomers. CK were measured at four developmental stages in developing chickpea (Cicer arietinum L. cultivar Kaniva) seeds by gas chromatography-mass spectrome- try. Concentrations were highest at an early endospermic
In legumes, the formation of rhizobial and mycorrhizal root symbioses is a highly regulated proce... more In legumes, the formation of rhizobial and mycorrhizal root symbioses is a highly regulated process which requires close communication between plant and microorganism. Plant mutants that have difficulties establishing symbioses are valuable tools for unravelling the mechanisms by which these symbioses are formed and regulated. Here E151, a mutant of Pisum sativum cv. Sparkle, was examined to characterize its root growth and symbiotic defects. The symbioses in terms of colonization intensity, functionality of micro-symbionts, and organ dominance were compared between the mutant and wild type. The endogenous cytokinin (CK) and abscisic acid (ABA) levels and the effect of the exogenous application of these two hormones were determined. E151 was found to be a low and delayed nodulator, exhibiting defects in both the epidermal and cortical programmes though a few mature and functional nodules develop. Mycorrhizal colonization of E151 was intensified, although the fungal functionality was...
Dormancy in Lolium rigidum (annual ryegrass) seeds can be alleviated by warm stratification in th... more Dormancy in Lolium rigidum (annual ryegrass) seeds can be alleviated by warm stratification in the dark or by application of fluridone, an inhibitor of plant abscisic acid (ABA) biosynthesis via phytoene desaturase. However, germination and absolute ABA concentration are not particularly strongly correlated. The aim of this study was to determine if cytokinins of both plant and bacterial origin are involved in mediating dormancy status and in the response to fluridone. Seeds with normal or greatly decreased (by dry heat pre-treatment) bacterial populations were stratified in the light or dark and in the presence or absence of fluridone in order to modify their dormancy status. Germination was assessed and seed cytokinin concentration and composition were measured in embryo-containing or embryo-free seed portions. Seeds lacking bacteria were no longer able to lose dormancy in the dark unless supplied with exogenous gibberellin or fluridone. Although these seeds showed a dramatic swit...
Green kiwifruit (Actinidia deliciosa) retain high concentrations of chlorophyll in the fruit fles... more Green kiwifruit (Actinidia deliciosa) retain high concentrations of chlorophyll in the fruit flesh, whereas in gold-fleshed kiwifruit (A. chinensis) chlorophyll is degraded to colourless catabolites during fruit development, leaving yellow carotenoids visible. The plant hormone group the cytokinins has been implicated in the delay of senescence, and so the aim of this work was to investigate the link between cytokinin levels in ripening fruit and chlorophyll de-greening. The expression of genes related to cytokinin metabolism and signal transduction and the concentration of cytokinin metabolites were measured. The regulation of gene expression was assayed using transient activation of the promoter of STAY-GREEN2 (SGR2) by cytokinin response regulators. While the total amount of cytokinin increased in fruit of both species during maturation and ripening, a high level of expression of two cytokinin biosynthetic gene family members, adenylate isopentenyltransferases, was only detected ...
Dormancy in Lolium rigidum (annual ryegrass) seeds can be alleviated by warm stratification in th... more Dormancy in Lolium rigidum (annual ryegrass) seeds can be alleviated by warm stratification in the dark or by application of fluridone, an inhibitor of plant abscisic acid (ABA) biosynthesis via phytoene desaturase. However, germination and absolute ABA concentration are not particularly strongly correlated. The aim of this study was to determine if cytokinins of both plant and bacterial origin are involved in mediating dormancy status and in the response to fluridone. Seeds with normal or greatly decreased (by dry heat pre-treatment) bacterial populations were stratified in the light or dark and in the presence or absence of fluridone in order to modify their dormancy status. Germination was assessed and seed cytokinin concentration and composition were measured in embryo-containing or embryo-free seed portions. Seeds lacking bacteria were no longer able to lose dormancy in the dark unless supplied with exogenous gibberellin or fluridone. Although these seeds showed a dramatic swit...
ABSTRACT Yield and harvest index of narrow-leafed lupin (Lupinus angustifolius L.) are variable, ... more ABSTRACT Yield and harvest index of narrow-leafed lupin (Lupinus angustifolius L.) are variable, and factors affecting their reliability have not been clearly identified. In this study, plants were grown in sand culture and were non-nodulated and supplied with mineral nitrogen (N) or acquired N through symbiotic N-2 fixation. Transient N deficiency was imposed a number of times during development in nodulated plants by hushing pure O-2 to the roots to suppress N-2 fixation and in non-nodulated plants by changing the rate of N addition. Low N supply (0.4 mM) before floral initiation or for 2 weeks during floral initiation caused a reduction in seed yield. Transient N deficiency induced by O-2 flush during early growth (Weeks 6 and 7 after sowing) had a marked effect on vegetative growth, the number of main stem flowers, pod set, and seed yield. The early N deficiency also affected shoot and root N concentrations and total cytokinin concentrations in root exudate. Compared with N-2-fixing plants, those supplied with adequate mineral N had a greater flower number and greater branch growth and biomass, but not higher pod set and seed yield, resulting in lower harvest index. Seed N concentrations were also decreased by transient N deficiencies at early (floral initiation), mid (flowering), and late (grain,filling) stages. These findings indicate that any field conditions which transiently reduce N-2 fixation (e.g. temporary waterlogging or drought) are likely to result in lower grain yield and quality of lupin crops.
... quality, rather than quantity, have been found to alter branches was associated with a reduct... more ... quality, rather than quantity, have been found to alter branches was associated with a reduction in the length tiller growth in barley (Davis and Simmons, 1994). Even ... Downloaded from Page 2. 548 Miguel et al. excised from lupins (Lupinus angustifolius L. cv. Merrit) grown ...
... Stewart K. Field 1 , Jason P. Smith 2 ,* , Bruno P. Holzapfel 3 , W. James Hardie 4 and RJ Ne... more ... Stewart K. Field 1 , Jason P. Smith 2 ,* , Bruno P. Holzapfel 3 , W. James Hardie 4 and RJ Neil Emery 5 ... The authors also acknowledge the past and ongoing support of Dennis Greer in the project. * Corresponding author (email: jasmith{at}csu.edu.au). Abstract. ...
Trans-isomers of cytokinins (CK) are thought to predominate and have greater biological activity ... more Trans-isomers of cytokinins (CK) are thought to predominate and have greater biological activity than corresponding cis-isomers in higher plants. However, this study demonstrates a system within which the predominant CK are cis-isomers. CK were measured at four developmental stages in developing chickpea (Cicer arietinum L. cultivar Kaniva) seeds by gas chromatography-mass spectrome- try. Concentrations were highest at an early endospermic
In legumes, the formation of rhizobial and mycorrhizal root symbioses is a highly regulated proce... more In legumes, the formation of rhizobial and mycorrhizal root symbioses is a highly regulated process which requires close communication between plant and microorganism. Plant mutants that have difficulties establishing symbioses are valuable tools for unravelling the mechanisms by which these symbioses are formed and regulated. Here E151, a mutant of Pisum sativum cv. Sparkle, was examined to characterize its root growth and symbiotic defects. The symbioses in terms of colonization intensity, functionality of micro-symbionts, and organ dominance were compared between the mutant and wild type. The endogenous cytokinin (CK) and abscisic acid (ABA) levels and the effect of the exogenous application of these two hormones were determined. E151 was found to be a low and delayed nodulator, exhibiting defects in both the epidermal and cortical programmes though a few mature and functional nodules develop. Mycorrhizal colonization of E151 was intensified, although the fungal functionality was...
Dormancy in Lolium rigidum (annual ryegrass) seeds can be alleviated by warm stratification in th... more Dormancy in Lolium rigidum (annual ryegrass) seeds can be alleviated by warm stratification in the dark or by application of fluridone, an inhibitor of plant abscisic acid (ABA) biosynthesis via phytoene desaturase. However, germination and absolute ABA concentration are not particularly strongly correlated. The aim of this study was to determine if cytokinins of both plant and bacterial origin are involved in mediating dormancy status and in the response to fluridone. Seeds with normal or greatly decreased (by dry heat pre-treatment) bacterial populations were stratified in the light or dark and in the presence or absence of fluridone in order to modify their dormancy status. Germination was assessed and seed cytokinin concentration and composition were measured in embryo-containing or embryo-free seed portions. Seeds lacking bacteria were no longer able to lose dormancy in the dark unless supplied with exogenous gibberellin or fluridone. Although these seeds showed a dramatic swit...
Green kiwifruit (Actinidia deliciosa) retain high concentrations of chlorophyll in the fruit fles... more Green kiwifruit (Actinidia deliciosa) retain high concentrations of chlorophyll in the fruit flesh, whereas in gold-fleshed kiwifruit (A. chinensis) chlorophyll is degraded to colourless catabolites during fruit development, leaving yellow carotenoids visible. The plant hormone group the cytokinins has been implicated in the delay of senescence, and so the aim of this work was to investigate the link between cytokinin levels in ripening fruit and chlorophyll de-greening. The expression of genes related to cytokinin metabolism and signal transduction and the concentration of cytokinin metabolites were measured. The regulation of gene expression was assayed using transient activation of the promoter of STAY-GREEN2 (SGR2) by cytokinin response regulators. While the total amount of cytokinin increased in fruit of both species during maturation and ripening, a high level of expression of two cytokinin biosynthetic gene family members, adenylate isopentenyltransferases, was only detected ...
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