Sucrose synthase （Sus） is a key enzyme in the breakdown of sucrose and is considered a biochemical marker for sink strength, especially in crop species, based on mutational and gene suppression studies. It remains e...Sucrose synthase （Sus） is a key enzyme in the breakdown of sucrose and is considered a biochemical marker for sink strength, especially in crop species, based on mutational and gene suppression studies. It remains elusive, however, whether, or to what extent, increase in Sus activity may enhance sink development. We aimed to address this question by expressing a potato Sus gene in cotton where Sus expression has been previously shown to be critical for normal seed and fiber development. Segregation analyses at T1 generation followed by studies in homozygous progeny lines revealed that increased Sus activity in cotton （1） enhanced leaf expansion with the effect evident from young leaves emerging from shoot apex; （2） improved early seed development, which reduced seed abortion, hence enhanced seed set, and （3） promoted fiber elongation. In young leaves of Sus overexpressing lines, fructose concentrations were significantly increased whereas, in elongating fibers, both fructose and glucose levels were increased. Since hexoses contribute little to osmolality in leaves, in contrast to developing fibers, it is concluded that high Sus activity promotes leaf development independently of osmotic regulation, probably through sugar signaling. The analyses also showed that doubling the Sus activity in 0-d cotton seeds increased their fresh weight by about 30%. However, further increase in Sus activity did not lead to any further increase in seed weight, indicating an upper limit for the Sus overexpression effect. Finally, based on the observed additive effect on fiber yield from increased fiber length and seed number, a new strategy is proposed to increase cotton fiber yield by improving seed development as a whole, rather than solely focusing on manipulating fiber growth.展开更多
Polar transport of the phytohormone auxin and the establishment of localized auxin maxima regulate em- bryonic development, stem cell maintenance, root and shoot architecture, and tropic growth responses. The past dec...Polar transport of the phytohormone auxin and the establishment of localized auxin maxima regulate em- bryonic development, stem cell maintenance, root and shoot architecture, and tropic growth responses. The past decade has been marked by dramatic progress in efforts to elucidate the complex mechanisms by which auxin transport regulates plant growth. As the understanding of auxin transport regulation has been increasingly elaborated, it has become clear that this process is involved in almost all plant growth and environmental responses in some way. However, we still lack information about some basic aspects of this fundamental regulatory mechanism. In this review, we present what we know （or what we think we know） and what we do not know about seven auxin-regulated processes. We discuss the role of auxin transport in gravitropism in primary and lateral roots, phototropism, shoot branching, leaf expansion, and venation. We also discuss the auxin reflux/fountain model at the root tip, flavonoid modulation of auxin transport processes, and outstanding aspects of post-translational regulation of auxin transporters. This discussion is not meant to be exhaustive, but highlights areas in which generally held assumptions require more substantive validation.展开更多
Gas exchange,chlorophyll a fluorescence kinetics,chloroplast pigments and spectral reflectance were investigated to explore the variations of photosynthetic capacity,primary photochemical reactions and development of ...Gas exchange,chlorophyll a fluorescence kinetics,chloroplast pigments and spectral reflectance were investigated to explore the variations of photosynthetic capacity,primary photochemical reactions and development of photo-protective mechanisms in chestnut leaves from emergence to full expansion under field conditions.The results showed that during leaf development,net photosynthetic rate(P_n)gradually increased.Although the maximum quantum yield of PSII photochemistry(φ_ Po)was quite high at the initial stages of leaf development,P_F was markedly lower than that in fully expanded leaves.When the relative leaf area(RLA)was about 10%,φ_ Po and electron transport per active reaction centers(ET_O/RC)were just a little lower than that in fully expanded leaves,indicating that its primary photochemical capability had been nearly completed.Due to low chlorophyll concentration,absorption flux per excited cross-section(ABS/CS)in a young leaf was less,nevertheless the absorption flux per reaction center(ABS/RC)was more than that in a mature leaf because of lower density of reaction centers(RC/CS)in the young leaf.High ABS/RC as well as low P_n resulted in more heat dissipation per reaction center(DI_O/RC).The changes of chlorophyll were in opposition to the de-epoxidating degree of xanthophyll cycle pigments(ΔPRI)at various expanding stages of leaf.The content of chlorophyll per leaf area(ChlNDI)increased steadily with the progress of leaf expansion.When exposed to high irradiance at midday,the de-epoxidation of xanthophyll cycle pigments in newly developing leaves was considerably enhanced compared with fully expanded ones,which indicated that xanthophyll cycle might play a key role in excessive energy dissipation in young chestnut leaves.Anthocyanin accumulation was observed in newly emerging leaves of chestnut.The foliage was not photostable and was vulnearable to photo-damage because levels of light utilization and its capacity to dissipate excess energy were low.Above results implied that anthocyanins could protect展开更多
Plants acclimate to drought optimizing the trade-off between biomass production and water loss while ensuring their survival and reproduction. Plants also modify their growth or phenology as complementary strategies i...Plants acclimate to drought optimizing the trade-off between biomass production and water loss while ensuring their survival and reproduction. Plants also modify their growth or phenology as complementary strategies in response to stress. Despite evidence of an interaction between flowering time and plant growth response to environmental stresses, this interaction in response to drought is under debate. To contribute to the analysis of this interaction, leaf growth of 35 genetically modified lines of Arabidopsis thaliana and their common wild-type, Col-0 was analyzed by a quantitative multi-scale phenotyping approach from cellular to whole plant scale both in well-watered and soil moderate water deficit conditions. These genotypes were selected for the various physiological functions potentially altered by their genetic modification and that could interact with plant growth and/or their drought responses. In all genotypes, leaf expansion decreased in response to drought both at the whole rosette and the individual leaf levels. Additionally, epidermal cell area and/or epidermal cell number decreased in response to the drought treatment. In contrast, the number of rosette leaves was reduced in only half of the genotypes and leaf growth duration was only modified in 4 of them. Despite long photoperiod conditions, the duration of the vegetative phase, i.e. the time elapsed between germination and flowering stage, varied from 12 to 27 days among genotypes under well watered conditions. Our analyses revealed that the differences of flowering time observed in well-watered condition impacted the leaf area response to drought. Early-flowering genotypes slightly decreased their final leaf number, but strongly reduced their individual leaf area compared with the late-flowering ones. This result underlines the difficulty to analyze plant response to environmental stresses when genotypes with different flowering dates are compared.展开更多
The growth rate of any multilayered plant organ is limited by the cell layer with the least extensibility. The dicot leaf blade has two epidermal layers covering the mesophyll layers, in which the vascular network is ...The growth rate of any multilayered plant organ is limited by the cell layer with the least extensibility. The dicot leaf blade has two epidermal layers covering the mesophyll layers, in which the vascular network is embedded. There has been a lingering uncertainty about which layer limits the rate of blade expansion in dicot leaves. The current study made use of leaf strips cut from the argenteum variety of Pisum sativum L., in which the epidermal layers can easily be removed with minimal damage. After this procedure, the mesophyll showed accelerated growth in short-term and long-term experiments and light and darkness. Extension of both layers is strongly promoted by acidic solutions. Isolated mesophyll layers expand in response to light. This effect depends on turgor pressure, photosynthesis, and the plasma membrane H+-ATPase. The data allow concluding that expanding leaf blades share with axial stem organs a similar arrangement of tissue tension: an expanding core tissue pushing against a restrictive epidermal envelope. In complete leaves, partial removal of the epidermis from only one side of the blade causes a strong epinastic or hyponastic response. Removal of matching epidermis strips from both sides of complete blades causes the exposed mesophyll strip to elongate in excess of the neighboring tissue: it buckles.展开更多
观察哈尔滨70种观赏植物春季的展叶特征,分析植物展叶时序性、叶片色彩属性及两者与气温变化的相关性,研究哈尔滨春季设计中植物选择范围,为地域性植物色彩设计提供科学依据.结果表明,在70种观赏植物中,最早进入完全展叶期的是二月兰、...观察哈尔滨70种观赏植物春季的展叶特征,分析植物展叶时序性、叶片色彩属性及两者与气温变化的相关性,研究哈尔滨春季设计中植物选择范围,为地域性植物色彩设计提供科学依据.结果表明,在70种观赏植物中,最早进入完全展叶期的是二月兰、紫花地丁、华北茶镳子和稠李,当候温达到16℃、日温差在10～12℃时,有37种植物（占52.9％）全部展叶,可以达到较为明显的季相景观效果.植物叶色的NCS叶色值分布在NCS S 1070-G950Y至NCS S 6020-G70Y的26个标准颜色中,乔木、灌木、草本植物分别覆盖3、11、13种.其中NCS S 3060-G40Y和NCS S 4050-G40Y色值所占比例最大、分别为20％和17.1％.展开更多
文摘Sucrose synthase （Sus） is a key enzyme in the breakdown of sucrose and is considered a biochemical marker for sink strength, especially in crop species, based on mutational and gene suppression studies. It remains elusive, however, whether, or to what extent, increase in Sus activity may enhance sink development. We aimed to address this question by expressing a potato Sus gene in cotton where Sus expression has been previously shown to be critical for normal seed and fiber development. Segregation analyses at T1 generation followed by studies in homozygous progeny lines revealed that increased Sus activity in cotton （1） enhanced leaf expansion with the effect evident from young leaves emerging from shoot apex; （2） improved early seed development, which reduced seed abortion, hence enhanced seed set, and （3） promoted fiber elongation. In young leaves of Sus overexpressing lines, fructose concentrations were significantly increased whereas, in elongating fibers, both fructose and glucose levels were increased. Since hexoses contribute little to osmolality in leaves, in contrast to developing fibers, it is concluded that high Sus activity promotes leaf development independently of osmotic regulation, probably through sugar signaling. The analyses also showed that doubling the Sus activity in 0-d cotton seeds increased their fresh weight by about 30%. However, further increase in Sus activity did not lead to any further increase in seed weight, indicating an upper limit for the Sus overexpression effect. Finally, based on the observed additive effect on fiber yield from increased fiber length and seed number, a new strategy is proposed to increase cotton fiber yield by improving seed development as a whole, rather than solely focusing on manipulating fiber growth.
基金This work was funded by the National Science Foundation，A.S.M.and Purdue Agriculture Research Foundation grant to W.A.P
文摘Polar transport of the phytohormone auxin and the establishment of localized auxin maxima regulate em- bryonic development, stem cell maintenance, root and shoot architecture, and tropic growth responses. The past decade has been marked by dramatic progress in efforts to elucidate the complex mechanisms by which auxin transport regulates plant growth. As the understanding of auxin transport regulation has been increasingly elaborated, it has become clear that this process is involved in almost all plant growth and environmental responses in some way. However, we still lack information about some basic aspects of this fundamental regulatory mechanism. In this review, we present what we know （or what we think we know） and what we do not know about seven auxin-regulated processes. We discuss the role of auxin transport in gravitropism in primary and lateral roots, phototropism, shoot branching, leaf expansion, and venation. We also discuss the auxin reflux/fountain model at the root tip, flavonoid modulation of auxin transport processes, and outstanding aspects of post-translational regulation of auxin transporters. This discussion is not meant to be exhaustive, but highlights areas in which generally held assumptions require more substantive validation.
文摘Gas exchange,chlorophyll a fluorescence kinetics,chloroplast pigments and spectral reflectance were investigated to explore the variations of photosynthetic capacity,primary photochemical reactions and development of photo-protective mechanisms in chestnut leaves from emergence to full expansion under field conditions.The results showed that during leaf development,net photosynthetic rate(P_n)gradually increased.Although the maximum quantum yield of PSII photochemistry(φ_ Po)was quite high at the initial stages of leaf development,P_F was markedly lower than that in fully expanded leaves.When the relative leaf area(RLA)was about 10%,φ_ Po and electron transport per active reaction centers(ET_O/RC)were just a little lower than that in fully expanded leaves,indicating that its primary photochemical capability had been nearly completed.Due to low chlorophyll concentration,absorption flux per excited cross-section(ABS/CS)in a young leaf was less,nevertheless the absorption flux per reaction center(ABS/RC)was more than that in a mature leaf because of lower density of reaction centers(RC/CS)in the young leaf.High ABS/RC as well as low P_n resulted in more heat dissipation per reaction center(DI_O/RC).The changes of chlorophyll were in opposition to the de-epoxidating degree of xanthophyll cycle pigments(ΔPRI)at various expanding stages of leaf.The content of chlorophyll per leaf area(ChlNDI)increased steadily with the progress of leaf expansion.When exposed to high irradiance at midday,the de-epoxidation of xanthophyll cycle pigments in newly developing leaves was considerably enhanced compared with fully expanded ones,which indicated that xanthophyll cycle might play a key role in excessive energy dissipation in young chestnut leaves.Anthocyanin accumulation was observed in newly emerging leaves of chestnut.The foliage was not photostable and was vulnearable to photo-damage because levels of light utilization and its capacity to dissipate excess energy were low.Above results implied that anthocyanins could protect
文摘Plants acclimate to drought optimizing the trade-off between biomass production and water loss while ensuring their survival and reproduction. Plants also modify their growth or phenology as complementary strategies in response to stress. Despite evidence of an interaction between flowering time and plant growth response to environmental stresses, this interaction in response to drought is under debate. To contribute to the analysis of this interaction, leaf growth of 35 genetically modified lines of Arabidopsis thaliana and their common wild-type, Col-0 was analyzed by a quantitative multi-scale phenotyping approach from cellular to whole plant scale both in well-watered and soil moderate water deficit conditions. These genotypes were selected for the various physiological functions potentially altered by their genetic modification and that could interact with plant growth and/or their drought responses. In all genotypes, leaf expansion decreased in response to drought both at the whole rosette and the individual leaf levels. Additionally, epidermal cell area and/or epidermal cell number decreased in response to the drought treatment. In contrast, the number of rosette leaves was reduced in only half of the genotypes and leaf growth duration was only modified in 4 of them. Despite long photoperiod conditions, the duration of the vegetative phase, i.e. the time elapsed between germination and flowering stage, varied from 12 to 27 days among genotypes under well watered conditions. Our analyses revealed that the differences of flowering time observed in well-watered condition impacted the leaf area response to drought. Early-flowering genotypes slightly decreased their final leaf number, but strongly reduced their individual leaf area compared with the late-flowering ones. This result underlines the difficulty to analyze plant response to environmental stresses when genotypes with different flowering dates are compared.
文摘The growth rate of any multilayered plant organ is limited by the cell layer with the least extensibility. The dicot leaf blade has two epidermal layers covering the mesophyll layers, in which the vascular network is embedded. There has been a lingering uncertainty about which layer limits the rate of blade expansion in dicot leaves. The current study made use of leaf strips cut from the argenteum variety of Pisum sativum L., in which the epidermal layers can easily be removed with minimal damage. After this procedure, the mesophyll showed accelerated growth in short-term and long-term experiments and light and darkness. Extension of both layers is strongly promoted by acidic solutions. Isolated mesophyll layers expand in response to light. This effect depends on turgor pressure, photosynthesis, and the plasma membrane H+-ATPase. The data allow concluding that expanding leaf blades share with axial stem organs a similar arrangement of tissue tension: an expanding core tissue pushing against a restrictive epidermal envelope. In complete leaves, partial removal of the epidermis from only one side of the blade causes a strong epinastic or hyponastic response. Removal of matching epidermis strips from both sides of complete blades causes the exposed mesophyll strip to elongate in excess of the neighboring tissue: it buckles.
文摘观察哈尔滨70种观赏植物春季的展叶特征,分析植物展叶时序性、叶片色彩属性及两者与气温变化的相关性,研究哈尔滨春季设计中植物选择范围,为地域性植物色彩设计提供科学依据.结果表明,在70种观赏植物中,最早进入完全展叶期的是二月兰、紫花地丁、华北茶镳子和稠李,当候温达到16℃、日温差在10～12℃时,有37种植物（占52.9％）全部展叶,可以达到较为明显的季相景观效果.植物叶色的NCS叶色值分布在NCS S 1070-G950Y至NCS S 6020-G70Y的26个标准颜色中,乔木、灌木、草本植物分别覆盖3、11、13种.其中NCS S 3060-G40Y和NCS S 4050-G40Y色值所占比例最大、分别为20％和17.1％.
