The growth reduction of wheat (Triticum aestivum L.) during and after waterlogging stress depends on the depth of water from the soil surface. In a pot experiment with 3-week-old plants, soil was waterlogged for 14 d at the surface, or at 100 or 200 mm below the surface, and pots were then drained to assess recovery. A fully drained treatment kept at field capacity served as control. During waterlogging, the relative growth rate of roots decreased more than that of shoots (by 6-27% for shoots, by 15-74% for roots), and plant growth was reduced proportionally as the water level was increased. Light-saturated net photosynthesis was reduced by 70-80% for the two most severe waterlogging treatments, but was little affected for plants in soil waterlogged at 200 mm below the surface. The number of adventitious roots formed per stem in plants grown in waterlogged soil increased up to 1.5 times, but the number of tillers per plant was reduced by 24-62%. The adventitious roots only penetrated 85-116 mm below the water level in all waterlogging treatments. Adventitious root porosity was enhanced up to 10-fold for plants grown in waterlogged soil, depending on water level and position along the roots. Porosity also increased in basal zones of roots above the water level when the younger tissues had penetrated the waterlogged zone. Fourteen days after draining the pots, growth rates of plants where the soil had been waterlogged at 200 mm below the surface had recovered, while those of plants in the more severely waterlogged treatments had only partially recovered. These findings show that the depth of waterlogging has a large impact on the response of wheat both during and after a waterlogging event so that assessment of recovery is essential in evaluating waterlogging tolerance in crops.
{"title":"Changes in physiological and morphological traits of roots and shoots of wheat in response to different depths of waterlogging","authors":"A. Malik, T. Colmer, H. Lambers, M. Schortemeyer","doi":"10.1071/PP01089","DOIUrl":"https://doi.org/10.1071/PP01089","url":null,"abstract":"The growth reduction of wheat (Triticum aestivum L.) during and after waterlogging stress depends on the depth of water from the soil surface. In a pot experiment with 3-week-old plants, soil was waterlogged for 14 d at the surface, or at 100 or 200 mm below the surface, and pots were then drained to assess recovery. A fully drained treatment kept at field capacity served as control. During waterlogging, the relative growth rate of roots decreased more than that of shoots (by 6-27% for shoots, by 15-74% for roots), and plant growth was reduced proportionally as the water level was increased. Light-saturated net photosynthesis was reduced by 70-80% for the two most severe waterlogging treatments, but was little affected for plants in soil waterlogged at 200 mm below the surface. The number of adventitious roots formed per stem in plants grown in waterlogged soil increased up to 1.5 times, but the number of tillers per plant was reduced by 24-62%. The adventitious roots only penetrated 85-116 mm below the water level in all waterlogging treatments. Adventitious root porosity was enhanced up to 10-fold for plants grown in waterlogged soil, depending on water level and position along the roots. Porosity also increased in basal zones of roots above the water level when the younger tissues had penetrated the waterlogged zone. Fourteen days after draining the pots, growth rates of plants where the soil had been waterlogged at 200 mm below the surface had recovered, while those of plants in the more severely waterlogged treatments had only partially recovered. These findings show that the depth of waterlogging has a large impact on the response of wheat both during and after a waterlogging event so that assessment of recovery is essential in evaluating waterlogging tolerance in crops.","PeriodicalId":8650,"journal":{"name":"Australian Journal of Plant Physiology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88407452","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tricia M. Denton, S. Schmidt, C. Critchley, G. Stewart
Stable carbon and nitrogen isotope signatures (delta C-13 and delta N-15) of Cannabis sativa were assessed for their usefulness to trace seized Cannabis leaves to the country of origin and to source crops by determining how isotope signatures relate to plant growth conditions. The isotopic composition of Cannabis examined here covered nearly the entire range of values reported for terrestrial C-3 plants. The delta C-13 values of Cannabis from Australia, Papua New Guinea and Thailand ranged from -36 to -25 parts per thousand, and delta N-15 values ranged from -1.0 to 15.8 parts per thousand. The stable isotope content did not allow differentiation between Cannabis originating from the three countries, but delta C-13 values of plantation-grown Cannabis differed between well-watered plants (average delta C-13 of -30.0 parts per thousand) and plants that had received little irrigation (average delta C-13 of -26.4 parts per thousand). Cannabis grown under controlled conditions had delta C-13 values of -32.6 and -30.6 parts per thousand with high and low water supply, respectively. These results indicate that water availability determines leaf C-13 in plants grown under similar conditions of light, temperature and air humidity. The delta C-13 values also distinguished between indoor- and outdoor-grown Cannabis; indoor- grown plants had overall more negative delta C-13 values (average -31.8 parts per thousand) than outdoor-grown plants (average -27.9 parts per thousand). Contributing to the strong C-13-depletion of indoor- grown plants may be high relative humidity, poor ventilation and recycling of C-13-depleted respired CO2. Mineral fertilizers had mostly lower delta N-15 values (-0.2 to 2.2 parts per thousand) than manure-based fertilizers (7.6 to 22.7 parts per thousand). It was possible to link delta N-15 values of fertilizers associated with a crop site to soil and plant delta N-15 values. The strong relationship between soil, fertilizer, and plant delta N-15 suggests that Cannabis delta N-15 is determined by the isotopic composition of the nitrogen source. The distinct delta N-15 values measured in Cannabis crops make delta N-15 an excellent tool for matching seized Cannabis with a source crop. A case study is presented that demonstrates how delta C-13 and delta N-15 values can be used as a forensic tool.
{"title":"Natural abundance of stable carbon and nitrogen isotopes in Cannabis sativa reflects growth conditions","authors":"Tricia M. Denton, S. Schmidt, C. Critchley, G. Stewart","doi":"10.1071/PP01066","DOIUrl":"https://doi.org/10.1071/PP01066","url":null,"abstract":"Stable carbon and nitrogen isotope signatures (delta C-13 and delta N-15) of Cannabis sativa were assessed for their usefulness to trace seized Cannabis leaves to the country of origin and to source crops by determining how isotope signatures relate to plant growth conditions. The isotopic composition of Cannabis examined here covered nearly the entire range of values reported for terrestrial C-3 plants. The delta C-13 values of Cannabis from Australia, Papua New Guinea and Thailand ranged from -36 to -25 parts per thousand, and delta N-15 values ranged from -1.0 to 15.8 parts per thousand. The stable isotope content did not allow differentiation between Cannabis originating from the three countries, but delta C-13 values of plantation-grown Cannabis differed between well-watered plants (average delta C-13 of -30.0 parts per thousand) and plants that had received little irrigation (average delta C-13 of -26.4 parts per thousand). Cannabis grown under controlled conditions had delta C-13 values of -32.6 and -30.6 parts per thousand with high and low water supply, respectively. These results indicate that water availability determines leaf C-13 in plants grown under similar conditions of light, temperature and air humidity. The delta C-13 values also distinguished between indoor- and outdoor-grown Cannabis; indoor- grown plants had overall more negative delta C-13 values (average -31.8 parts per thousand) than outdoor-grown plants (average -27.9 parts per thousand). Contributing to the strong C-13-depletion of indoor- grown plants may be high relative humidity, poor ventilation and recycling of C-13-depleted respired CO2. Mineral fertilizers had mostly lower delta N-15 values (-0.2 to 2.2 parts per thousand) than manure-based fertilizers (7.6 to 22.7 parts per thousand). It was possible to link delta N-15 values of fertilizers associated with a crop site to soil and plant delta N-15 values. The strong relationship between soil, fertilizer, and plant delta N-15 suggests that Cannabis delta N-15 is determined by the isotopic composition of the nitrogen source. The distinct delta N-15 values measured in Cannabis crops make delta N-15 an excellent tool for matching seized Cannabis with a source crop. A case study is presented that demonstrates how delta C-13 and delta N-15 values can be used as a forensic tool.","PeriodicalId":8650,"journal":{"name":"Australian Journal of Plant Physiology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87551165","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Detailed studies in field experiments have shown repeatedly that the transfer of 15 N 2 fixed by diazotrophic bacteria to wheat tissue is minimal. Here, a simple and convenient laboratory co-culture model was designed to assess important features of the association between Azospirillum brasilense and wheat, such as the rate of nitrogen fixation (acetylene reduction), ammonia excretion from the bacterium and the transfer of newly fixed 15 N 2 from the associative diazotroph to the shoot tissue of wheat plants. After 70 h, in this model, insignificant amounts of newly fixed N 2 were transferred from an ammonia-excreting strain of A. brasilense to the shoot tissue of wheat. However, when malate was added to the co-culture the 15 N enrichment of the shoot tissue increased 48-fold, indicating that 20% of shoot N had been derived from N 2 fixation. Thus, the inability of the host plant to release carbon in the rhizosphere is a significant constraint in the development of associative N 2 -fixing systems. These specific results suggest that wheat plants with an increased release ofphotosynthate to the rhizosphere should be a priority for the future development of broad-acre agricultural systems that are more self-sufficient for nitrogen nutrition. The simplicity of the model for assessing the critical parameters of associative 15 N 2 fixation may allow large-scale surveys of plant-bacterial interactions to be conducted and a selection of improved associations for further study.
{"title":"A simplified model for assessing critical parameters during associative 15N2 fixation between Azospirillum and wheat","authors":"C. Wood, N. Islam, R. Ritchie, I. Kennedy","doi":"10.1071/PP01036","DOIUrl":"https://doi.org/10.1071/PP01036","url":null,"abstract":"Detailed studies in field experiments have shown repeatedly that the transfer of 15 N 2 fixed by diazotrophic bacteria to wheat tissue is minimal. Here, a simple and convenient laboratory co-culture model was designed to assess important features of the association between Azospirillum brasilense and wheat, such as the rate of nitrogen fixation (acetylene reduction), ammonia excretion from the bacterium and the transfer of newly fixed 15 N 2 from the associative diazotroph to the shoot tissue of wheat plants. After 70 h, in this model, insignificant amounts of newly fixed N 2 were transferred from an ammonia-excreting strain of A. brasilense to the shoot tissue of wheat. However, when malate was added to the co-culture the 15 N enrichment of the shoot tissue increased 48-fold, indicating that 20% of shoot N had been derived from N 2 fixation. Thus, the inability of the host plant to release carbon in the rhizosphere is a significant constraint in the development of associative N 2 -fixing systems. These specific results suggest that wheat plants with an increased release ofphotosynthate to the rhizosphere should be a priority for the future development of broad-acre agricultural systems that are more self-sufficient for nitrogen nutrition. The simplicity of the model for assessing the critical parameters of associative 15 N 2 fixation may allow large-scale surveys of plant-bacterial interactions to be conducted and a selection of improved associations for further study.","PeriodicalId":8650,"journal":{"name":"Australian Journal of Plant Physiology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72653991","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
V. Reis, Fábio Bueno dos Reis, D. Quesada, O. C. Oliveira, B. Alves, S. Urquiaga, R. Boddey
The semi-humid or humid tropics are ideal for the production of large quantities of biomass from fast-growing C 4 grasses, but high yields normally require large quantities of fertiliser, especially N, which has a very high input from fossil fuels (natural gas). A program has been started recently to use elephant grass (Pennisetum purpureum Schum.) to substitute firewood as a fuel and also to make charcoal for iron production. In this case, any large N fertiliser additions would mean that the yield of bio fuel per unit of fossil fuel invested would be detrimentally affected. In this study, we report on the potential for the selection of genotypes of fast-growing C 4 tropical grasses ofthe genera Pennisetum and Brachiaria for their capacity to obtain N inputs from plant-associated biological nitrogen fixation (BNF). Fourteen genotypes each of Brachiaria and Pennisetum were screened for BNF contributions by growing them in 15 N-labelled soil. In the case of the Pennisetum, after a suitable cutting height for the crop had been selected, there were large differences in dry matter production, N accumulation and 15 N enrichment. The differences in 15 N enrichment between genotypes were statistically significant and BNF inputs were estimated as high as 41% of accumulated N. In the study on Brachiaria genotypes, potential inputs of BNF seemed lower. Only one or two genotypes of B. brizantha and B. ruziziensis obtained more then 20% of their N from BNF. The N 2 -fixing bacteria that were most commonly associated with shoots and roots the Pennisetum genotypes were of the genus Herbaspirillum, but predominantly of a recently described new species. The Brachiaria spp. from three different sites (Rio de Janeiro, Goania, Bahia) were predominately colonised by Azospirillum spp., most of the isolates being of the species Azospirillum amazonense. Very few Herbaspirilla were isolated from these plants.
{"title":"Biological nitrogen fixation associated with tropical pasture grasses","authors":"V. Reis, Fábio Bueno dos Reis, D. Quesada, O. C. Oliveira, B. Alves, S. Urquiaga, R. Boddey","doi":"10.1071/PP01079","DOIUrl":"https://doi.org/10.1071/PP01079","url":null,"abstract":"The semi-humid or humid tropics are ideal for the production of large quantities of biomass from fast-growing C 4 grasses, but high yields normally require large quantities of fertiliser, especially N, which has a very high input from fossil fuels (natural gas). A program has been started recently to use elephant grass (Pennisetum purpureum Schum.) to substitute firewood as a fuel and also to make charcoal for iron production. In this case, any large N fertiliser additions would mean that the yield of bio fuel per unit of fossil fuel invested would be detrimentally affected. In this study, we report on the potential for the selection of genotypes of fast-growing C 4 tropical grasses ofthe genera Pennisetum and Brachiaria for their capacity to obtain N inputs from plant-associated biological nitrogen fixation (BNF). Fourteen genotypes each of Brachiaria and Pennisetum were screened for BNF contributions by growing them in 15 N-labelled soil. In the case of the Pennisetum, after a suitable cutting height for the crop had been selected, there were large differences in dry matter production, N accumulation and 15 N enrichment. The differences in 15 N enrichment between genotypes were statistically significant and BNF inputs were estimated as high as 41% of accumulated N. In the study on Brachiaria genotypes, potential inputs of BNF seemed lower. Only one or two genotypes of B. brizantha and B. ruziziensis obtained more then 20% of their N from BNF. The N 2 -fixing bacteria that were most commonly associated with shoots and roots the Pennisetum genotypes were of the genus Herbaspirillum, but predominantly of a recently described new species. The Brachiaria spp. from three different sites (Rio de Janeiro, Goania, Bahia) were predominately colonised by Azospirillum spp., most of the isolates being of the species Azospirillum amazonense. Very few Herbaspirilla were isolated from these plants.","PeriodicalId":8650,"journal":{"name":"Australian Journal of Plant Physiology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75898291","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Y. Yanni, R. Rizk, F. A. El-Fattah, A. Squartini, V. Corich, A. Giacomini, F. J. Bruijn, Jan LW Rademaker, Jaime Maya-Flores, P. Ostrom, M. Vega-Hernández, R. Hollingsworth, E. Martínez-Molina, P. Mateos, E. Velázquez, J. Wopereis, E. Triplett, M. Umali-Garcia, Julieta A. Anarna, B. Rolfe, J. K. Ladha, James H. Hill, R. Mujoo, P. Ng, F. Dazzo
his paper summarizes a multinational collaborative project to search for natural, intimate associations between rhizobia and rice (Oryza sativa L.), assess their impact on plant growth, and exploit those combinations that can enhance grain yield with less dependence on inputs of nitrogen (N) fertilizer. Diverse, indigenous populations of Rhizobium leguminosarum bv. trifolii (the clover root-nodule endosymbiont) intimately colonize rice roots in the Egyptian Nile delta where this cereal has been rotated successfully with berseem clover (Trifolium alexandrinum L.) since antiquity. Laboratory and greenhouse studies have shown with certain rhizobial strain-rice variety combinations that the association promotes root and shoot growth thereby significantly improving seedling vigour that carries over to significant increases in grain yield at maturity. Three field inoculation trials in the Nile delta indicated that a few strain-variety combinations significantly increased rice grain yield, agronomic fertilizer N-use efficiency and harvest index. The benefits of this association leading to greater production of vegetative and reproductive biomass more likely involve rhizobial modulation of the plant's root architecture for more efficient acquisition of certain soil nutrients [e.g. N, phosphorus (P), potassium (K), magnesium (Mg), calcium (Ca), zinc (Zn), sodium (Na) and molybdenum (Mo)] rather than biological N 2 fixation.
{"title":"The beneficial plant growth-promoting association of Rhizobium leguminosarum bv. trifolii with rice roots","authors":"Y. Yanni, R. Rizk, F. A. El-Fattah, A. Squartini, V. Corich, A. Giacomini, F. J. Bruijn, Jan LW Rademaker, Jaime Maya-Flores, P. Ostrom, M. Vega-Hernández, R. Hollingsworth, E. Martínez-Molina, P. Mateos, E. Velázquez, J. Wopereis, E. Triplett, M. Umali-Garcia, Julieta A. Anarna, B. Rolfe, J. K. Ladha, James H. Hill, R. Mujoo, P. Ng, F. Dazzo","doi":"10.1071/PP01069","DOIUrl":"https://doi.org/10.1071/PP01069","url":null,"abstract":"his paper summarizes a multinational collaborative project to search for natural, intimate associations between rhizobia and rice (Oryza sativa L.), assess their impact on plant growth, and exploit those combinations that can enhance grain yield with less dependence on inputs of nitrogen (N) fertilizer. Diverse, indigenous populations of Rhizobium leguminosarum bv. trifolii (the clover root-nodule endosymbiont) intimately colonize rice roots in the Egyptian Nile delta where this cereal has been rotated successfully with berseem clover (Trifolium alexandrinum L.) since antiquity. Laboratory and greenhouse studies have shown with certain rhizobial strain-rice variety combinations that the association promotes root and shoot growth thereby significantly improving seedling vigour that carries over to significant increases in grain yield at maturity. Three field inoculation trials in the Nile delta indicated that a few strain-variety combinations significantly increased rice grain yield, agronomic fertilizer N-use efficiency and harvest index. The benefits of this association leading to greater production of vegetative and reproductive biomass more likely involve rhizobial modulation of the plant's root architecture for more efficient acquisition of certain soil nutrients [e.g. N, phosphorus (P), potassium (K), magnesium (Mg), calcium (Ca), zinc (Zn), sodium (Na) and molybdenum (Mo)] rather than biological N 2 fixation.","PeriodicalId":8650,"journal":{"name":"Australian Journal of Plant Physiology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90802329","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
F. M. Perrine, Joko Prayitno, J. Weinman, F. Dazzo, B. Rolfe
We examined growth responses of rice seedlings (Oryza sativa L. cv. Pelde) to specific Rhizobium strains and their mutants, to investigate the molecular basis of colonization and the stimulation or inhibition of rice growth and development by rhizobia. Inoculation experiments with rice seedlings showed that specific Rhizobium isolates of these rice-associated and legume-associated rhizobia could either promote, inhibit, or have no influence on rice plant growth. There are genes on certain plasmids of Rhizobium leguminosarum bv. trifolii and R. leguminosarum bv. viciae that affect the growth and development of rice root morphology. Additionally, we found that bacteria can intimately associate with, and enter into, rice seedling roots by alternative mechanisms to those encoded by the symbiotic (pSym) and the tumour-inducing (Ti) plasmids. Investigations suggest an involvement of the phytohormone auxin, and possibly nitrate, in this complex rice-Rhizobium interaction.
研究了水稻幼苗(Oryza sativa L. cv.)的生长响应。研究根瘤菌定植的分子基础，以及根瘤菌对水稻生长发育的促进或抑制作用。水稻幼苗接种试验表明，这些水稻相关根瘤菌和豆科相关根瘤菌的特异性分离株对水稻生长有促进、抑制或不影响作用。豆科根瘤菌的某些质粒上存在基因。三叶草和豆科植物。影响水稻根系形态生长发育的藤蔓。此外，我们发现细菌可以通过共生质粒(pSym)和肿瘤诱导质粒(Ti)编码的替代机制与水稻幼苗根系密切相关并进入水稻幼苗根系。研究表明植物激素生长素，可能还有硝酸盐，参与了这种复杂的水稻-根瘤菌相互作用。
{"title":"Rhizobium plasmids are involved in the inhibition or stimulation of rice growth and development","authors":"F. M. Perrine, Joko Prayitno, J. Weinman, F. Dazzo, B. Rolfe","doi":"10.1071/PP01046","DOIUrl":"https://doi.org/10.1071/PP01046","url":null,"abstract":"We examined growth responses of rice seedlings (Oryza sativa L. cv. Pelde) to specific Rhizobium strains and their mutants, to investigate the molecular basis of colonization and the stimulation or inhibition of rice growth and development by rhizobia. Inoculation experiments with rice seedlings showed that specific Rhizobium isolates of these rice-associated and legume-associated rhizobia could either promote, inhibit, or have no influence on rice plant growth. There are genes on certain plasmids of Rhizobium leguminosarum bv. trifolii and R. leguminosarum bv. viciae that affect the growth and development of rice root morphology. Additionally, we found that bacteria can intimately associate with, and enter into, rice seedling roots by alternative mechanisms to those encoded by the symbiotic (pSym) and the tumour-inducing (Ti) plasmids. Investigations suggest an involvement of the phytohormone auxin, and possibly nitrate, in this complex rice-Rhizobium interaction.","PeriodicalId":8650,"journal":{"name":"Australian Journal of Plant Physiology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83982137","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study investigated the chloroplast pigment content of the Australian mistletoe Amyema miquelii (Lehm. ex Miq.) Tiegh. over diurnal periods in sun- and shade-acclimated leaves. Amyema miquelii exhibited the typical higher plant complement of neoxanthin, the xanthophyll cycle pigments, lutein, chlorophylls a and b and β carotene. Substantial levels of lutein epoxide were also present. Interestingly, diurnal light exposure elicited a decrease in lutein epoxide that paralleled the decrease in violaxanthin. Compared with shade-acclimated leaves, sun leaves exhibited reduced lutein epoxide and violaxanthin levels and higher chlorophyll a/b ratios. It is clear that the pools of violaxanthin and lutein epoxide respond in parallel to both diurnal light changes and sun-shade acclimation, although there seemed to be some differences in the recovery characteristics. These results raise a question as to whether lutein and lutein epoxide cycling may provide an auxiliary means of energy dissipation for some species.
{"title":"Diurnal and acclimatory responses of violaxanthin and lutein epoxide in the Australian mistletoe Amyema miquelii","authors":"S. Matsubara, A. Gilmore, C. B. Osmond","doi":"10.1071/PP01031","DOIUrl":"https://doi.org/10.1071/PP01031","url":null,"abstract":"This study investigated the chloroplast pigment content of the Australian mistletoe Amyema miquelii (Lehm. ex Miq.) Tiegh. over diurnal periods in sun- and shade-acclimated leaves. Amyema miquelii exhibited the typical higher plant complement of neoxanthin, the xanthophyll cycle pigments, lutein, chlorophylls a and b and β carotene. Substantial levels of lutein epoxide were also present. Interestingly, diurnal light exposure elicited a decrease in lutein epoxide that paralleled the decrease in violaxanthin. Compared with shade-acclimated leaves, sun leaves exhibited reduced lutein epoxide and violaxanthin levels and higher chlorophyll a/b ratios. It is clear that the pools of violaxanthin and lutein epoxide respond in parallel to both diurnal light changes and sun-shade acclimation, although there seemed to be some differences in the recovery characteristics. These results raise a question as to whether lutein and lutein epoxide cycling may provide an auxiliary means of energy dissipation for some species.","PeriodicalId":8650,"journal":{"name":"Australian Journal of Plant Physiology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75289783","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Both the existing theory as well as the measurements that have traditionally been used to describe the water relations of plants in thermodynamic terms are not consistent with standard thermodynamic theory. In this article, three main errors are identified: (1) the assumption that the internal energy of a system includes the gravitational potential energy, when it does not; (2) the assumption that water spontaneously moves along gradients of chemical potential, when the Gibbs theory predicts that it would spontaneously move across phase boundaries, so that the chemical potential would be equal in adjacent phases; and (3) the assumption that plants and soil are single-phase systems, when they are in fact multi-phase systems. Examples are used to demonstrate the above errors. Measurements which can be used to separate plant and soil systems into bulk phases (i.e. solid, liquid and gas), which have long been used by wood and soil scientists, are shown to be ideal for the purpose of describing plant and soil systems using thermodynamic methods.
{"title":"On the use of thermodynamic methods to describe water relations in plants and soil","authors":"M. Roderick","doi":"10.1071/PP01021","DOIUrl":"https://doi.org/10.1071/PP01021","url":null,"abstract":"Both the existing theory as well as the measurements that have traditionally been used to describe the water relations of plants in thermodynamic terms are not consistent with standard thermodynamic theory. In this article, three main errors are identified: (1) the assumption that the internal energy of a system includes the gravitational potential energy, when it does not; (2) the assumption that water spontaneously moves along gradients of chemical potential, when the Gibbs theory predicts that it would spontaneously move across phase boundaries, so that the chemical potential would be equal in adjacent phases; and (3) the assumption that plants and soil are single-phase systems, when they are in fact multi-phase systems. Examples are used to demonstrate the above errors. Measurements which can be used to separate plant and soil systems into bulk phases (i.e. solid, liquid and gas), which have long been used by wood and soil scientists, are shown to be ideal for the purpose of describing plant and soil systems using thermodynamic methods.","PeriodicalId":8650,"journal":{"name":"Australian Journal of Plant Physiology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76149122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Grapevines are considered well adapted to high irradiance during growth. It is still controversial, however, whether photoinactivation of photosystem II is completely avoided in high light-acclimated grapevines growing in the field. This study examines the functional stability of PSII in leaf discs (floated on water) of field-grown, high light-acclimated grapevines as a function of photon exposure. Measuring functional PSII units by flash-induced oxygen evolution, it was found that the susceptibility of PSII to photoinactivation was less in sun-exposed leaves than shade leaves of Vitis riparia Michaux, and enhanced by lincomycin, an inhibitor of chloroplast-encoded protein synthesis. Vitis vinifera L. cv. Chardonnay, grown in a glasshouse with slightly lower irradiance, exhibited an intermediate susceptibility. Significantly, the dark-relaxed quantum efficiency of PSII, measured as (Fm – Fo)/Fm, where Fm and Fo are the chlorophyll (Chl) fluorescence yields for closed and open reaction centres, respectively, declined much more slowly than did the number of functional PSII units in V. riparia. Thus, measurements of (Fm – Fo)/Fm may give an impression of little photoinactivation of PSII, even when nearly half of functional PSII units may be lost. By contrast, the parameter 1/Fo – 1/Fm is a more linear indicator of functional PSII units. The results indicate that grapevines may suffer photoinactivation of PSII, at least when leaf discs are floated on water.
{"title":"Photoinactivation of photosystem II in high light-acclimated grapevines","authors":"J. Flexas, L. Hendrickson, W. Chow","doi":"10.1071/PP99210","DOIUrl":"https://doi.org/10.1071/PP99210","url":null,"abstract":"Grapevines are considered well adapted to high irradiance during growth. It is still controversial, however, whether photoinactivation of photosystem II is completely avoided in high light-acclimated grapevines growing in the field. This study examines the functional stability of PSII in leaf discs (floated on water) of field-grown, high light-acclimated grapevines as a function of photon exposure. Measuring functional PSII units by flash-induced oxygen evolution, it was found that the susceptibility of PSII to photoinactivation was less in sun-exposed leaves than shade leaves of Vitis riparia Michaux, and enhanced by lincomycin, an inhibitor of chloroplast-encoded protein synthesis. Vitis vinifera L. cv. Chardonnay, grown in a glasshouse with slightly lower irradiance, exhibited an intermediate susceptibility. Significantly, the dark-relaxed quantum efficiency of PSII, measured as (Fm – Fo)/Fm, where Fm and Fo are the chlorophyll (Chl) fluorescence yields for closed and open reaction centres, respectively, declined much more slowly than did the number of functional PSII units in V. riparia. Thus, measurements of (Fm – Fo)/Fm may give an impression of little photoinactivation of PSII, even when nearly half of functional PSII units may be lost. By contrast, the parameter 1/Fo – 1/Fm is a more linear indicator of functional PSII units. The results indicate that grapevines may suffer photoinactivation of PSII, at least when leaf discs are floated on water.","PeriodicalId":8650,"journal":{"name":"Australian Journal of Plant Physiology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86472179","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Olga Babourina, B. Hawkins, R. Lew, I. Newman, S. Shabala
Mechanisms underlying changed K + uptake by plantsat low pH need to be deciphered. One possibility is that K+ acquisition is under the strict control of plasmamembrane potential (E m ), which,in turn, is affected by external pH. To test this hypothesis, we used themicroelectrode ion flux measurement (MIFE ) technique tostudy net K + and H +fluxes near Arabidopsis root hairs at different externalpH, KCl concentrations and clamped Em . Lowering the solution pH led to strong H+ influx, K + efflux andsignificant E m depolarisation.Addition of K + to the bathing media causedsignificant net K + uptake when external pH wasover the range 5.5–6.0. At external pH below 5.0, however, correlationbetween K + availability and net K+ uptake was negative. To explain this apparentparadox, measurements of net K + and H+ fluxes from the root hair surface were performedconcurrently with E m clamped at different values above and below the restingpotential (approx. –180 mV). Our data revealed a strong dependence ofnet K + flux on the clamping voltage. Clamping atvalues more negative than the resting potential caused a significant increasein K + uptake into the root hair; clamping at lessnegative values (–20 and 0 mV) caused significant net K+ efflux from the cell. Qualitatively similarresults were observed for net H + flux. Ourobservations indicate direct control of K + flux bychanging E m , and suggest thatE m depolarisation could be themain reason for the observed K + efflux at low pH.
{"title":"K^+ transport by Arabidopsis root hairs at low pH","authors":"Olga Babourina, B. Hawkins, R. Lew, I. Newman, S. Shabala","doi":"10.1071/PP01018","DOIUrl":"https://doi.org/10.1071/PP01018","url":null,"abstract":"Mechanisms underlying changed K + uptake by plantsat low pH need to be deciphered. One possibility is that K+ acquisition is under the strict control of plasmamembrane potential (E m ), which,in turn, is affected by external pH. To test this hypothesis, we used themicroelectrode ion flux measurement (MIFE ) technique tostudy net K + and H +fluxes near Arabidopsis root hairs at different externalpH, KCl concentrations and clamped Em . Lowering the solution pH led to strong H+ influx, K + efflux andsignificant E m depolarisation.Addition of K + to the bathing media causedsignificant net K + uptake when external pH wasover the range 5.5–6.0. At external pH below 5.0, however, correlationbetween K + availability and net K+ uptake was negative. To explain this apparentparadox, measurements of net K + and H+ fluxes from the root hair surface were performedconcurrently with E m clamped at different values above and below the restingpotential (approx. –180 mV). Our data revealed a strong dependence ofnet K + flux on the clamping voltage. Clamping atvalues more negative than the resting potential caused a significant increasein K + uptake into the root hair; clamping at lessnegative values (–20 and 0 mV) caused significant net K+ efflux from the cell. Qualitatively similarresults were observed for net H + flux. Ourobservations indicate direct control of K + flux bychanging E m , and suggest thatE m depolarisation could be themain reason for the observed K + efflux at low pH.","PeriodicalId":8650,"journal":{"name":"Australian Journal of Plant Physiology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2001-08-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86274778","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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