The Experts below are selected from a list of 51 Experts worldwide ranked by ideXlab platform

Jianhua Zhang - One of the best experts on this subject based on the ideXlab platform.

  • grain filling of cereals under soil drying
    New Phytologist, 2006
    Co-Authors: Jianchang Yang, Jianhua Zhang
    Abstract:

    Monocarpic Plants require the initiation of whole-plant senescence to remobilize and transfer assimilates pre-stored in vegetative tissues to grains. Delayed whole-plant senescence caused by either heavy use of nitrogen fertilizer or adoption of lodging-resistant cultivars/hybrids that remain green when the grains are due to ripen results in a low harvest index with much nonstructural carbohydrate (NSC) left in the straw. Usually, water stress during the grain-filling period induces early senescence, reduces photosynthesis, and shortens the grain-filling period; however, it increases the remobilization of NSC from the vegetative tissues to the grain. If mild soil drying is properly controlled during the later grain-filling period in rice (Oryza sativa) and wheat (Triticum aestivum), it can enhance whole-plant senescence, lead to faster and better remobilization of carbon from vegetative tissues to grains, and accelerate the grain-filling rate. In cases where plant senescence is unfavorably delayed, such as by heavy use of nitrogen and the introduction of hybrids with strong heterosis, the gain from the enhanced remobilization and accelerated grain-filling rate can outweigh the loss of reduced photosynthesis and the shortened grain-filling period, leading to an increased grain yield, better harvest index and higher water-use efficiency.

  • grain filling of cereals under soil drying
    New Phytologist, 2006
    Co-Authors: Jianchang Yang, Jianhua Zhang
    Abstract:

    Contents Summary 223 I. Introduction 224 II. Problems in grain filling: unfavorably delayed whole-plant senescence 224 III. Controlled soil drying improves carbon remobilization and grain filling as a result of enhanced whole-plant senescence 225 IV. Hormonal regulation of whole-plant senescence and grain filling 229 V. Activities of key enzymes involved in carbon remobilization and grain filling 230 VI. Conclusions 232 Acknowledgements 232 References 232 Summary Monocarpic Plants require the initiation of whole-plant senescence to remobilize and transfer assimilates pre-stored in vegetative tissues to grains. Delayed whole-plant senescence caused by either heavy use of nitrogen fertilizer or adoption of lodging-resistant cultivars/hybrids that remain green when the grains are due to ripen results in a low harvest index with much nonstructural carbohydrate (NSC) left in the straw. Usually, water stress during the grain-filling period induces early senescence, reduces photosynthesis, and shortens the grain-filling period; however, it increases the remobilization of NSC from the vegetative tissues to the grain. If mild soil drying is properly controlled during the later grain-filling period in rice (Oryza sativa) and wheat (Triticum aestivum), it can enhance whole-plant senescence, lead to faster and better remobilization of carbon from vegetative tissues to grains, and accelerate the grain-filling rate. In cases where plant senescence is unfavorably delayed, such as by heavy use of nitrogen and the introduction of hybrids with strong heterosis, the gain from the enhanced remobilization and accelerated grain-filling rate can outweigh the loss of reduced photosynthesis and the shortened grain-filling period, leading to an increased grain yield, better harvest index and higher water-use efficiency.

  • water deficit induced senescence and its relationship to the remobilization of pre stored carbon in wheat during grain filling
    Agronomy Journal, 2001
    Co-Authors: Jianchang Yang, Jianhua Zhang, Zhiqing Wang, Qingsen Zhu, Lijun Liu
    Abstract:

    Remobilization and transfer of the pre-stored food in vegetative tissues to the grains in Monocarpic Plants require the initiation of whole plant senescence. However, mechanisms by which plant senescence promotes remobilization of assimilates are rather obscure. This study examined the relationship between the senescence induced by water deficits and C remobilization during grain fill. Two semi-winter wheat cultivars (Triticum aestivum L.),Yangmai 158 and Yangmai 931, were treated with two levels of nitrogen (normal [NN] or high [HN]) and three levels of soil moisture (well-watered, moderate water deficit, and severe water deficit). Results showed that water deficits enhanced the senescence by accelerating loss of leaf nitrogen and chlorophyll and increasing lipid peroxidation. At maturity, 75 to 92% of pre-anthesis C stored in the straw was reallocated to grains in water-deficit treatments, 50 to 80% higher than the amount in well-watered treatments, indicating that water deficits promoted remobilization. The peak values of abscisic acid (ABA) in both leaves and grains under water-defidt treatments were 63 to 144% higher than those under well-watered treatments. The elevated ABA level correlated with the degree of earlier leaf senescence, the 14 C partitioning into grains, and the carbon remobllization. The activites of both add invertase (INV) and sucrose synthase (SS) in grains were also enhanced by water deficits at the midstage of grain fill. Our results suggest that the senescence and remobilization promoted by water defidts during grain fill are coupled processes in wheat, and elevated ABA concentration may play a regulative role.

Mark Rees - One of the best experts on this subject based on the ideXlab platform.

  • seed dormancy and delayed flowering in Monocarpic Plants selective interactions in a stochastic environment
    The American Naturalist, 2006
    Co-Authors: Mark Rees, Karen E Rose, Dylan Z Childs, Jessica C Metcalf, A W Sheppard, Peter J Grubb
    Abstract:

    We explore the effects of temporal variation in multiple demographic rates on the joint evolution of delayed reproduction and seed dormancy using integral projection models (IPMs). To do this, we extend the standard IPM to include a discrete state variable representing the number of seeds in the seed bank, density-dependent recruitment, and temporal variation in demography. Parameter es- timates for Carlina vulgaris and Carduus nutans are obtained from long-term studies. Carlina is relatively long lived and has a short- lived seed bank, whereas most Carduus Plants flower in their first year and the seed bank is long lived. Using the evolutionarily stable strategy (ESS) approach, we predict the observed flowering and ger- mination strategies. There is excellent agreement between the pre- dictions and the field observations. The effects of temporal variation on the joint ESS are partitioned into components arising from non- linear averaging (systematic changes in the mean resulting from the interaction between variability and nonlinearity) and nonequilibrium dynamics (fluctuations in fitness caused by temporal variation). This shows that temporal variation can have substantial effects on the observed flowering and germination strategies and that covariance between demographic processes is important. We extend the models

  • seed dormancy and delayed flowering in Monocarpic Plants selective interactions in a stochastic environment
    The American Naturalist, 2006
    Co-Authors: Mark Rees, Karen E Rose, Dylan Z Childs, Jessica C Metcalf, A W Sheppard, Peter J Grubb
    Abstract:

    Abstract: We explore the effects of temporal variation in multiple demographic rates on the joint evolution of delayed reproduction and seed dormancy using integral projection models (IPMs). To do this, we extend the standard IPM to include a discrete state variable representing the number of seeds in the seed bank, density‐dependent recruitment, and temporal variation in demography. Parameter estimates for Carlina vulgaris and Carduus nutans are obtained from long‐term studies. Carlina is relatively long lived and has a short‐lived seed bank, whereas most Carduus Plants flower in their first year and the seed bank is long lived. Using the evolutionarily stable strategy (ESS) approach, we predict the observed flowering and germination strategies. There is excellent agreement between the predictions and the field observations. The effects of temporal variation on the joint ESS are partitioned into components arising from nonlinear averaging (systematic changes in the mean resulting from the interaction bet...

  • evolutionary demography of Monocarpic perennials
    Trends in Ecology and Evolution, 2003
    Co-Authors: Jessica Metcalf, Karen E Rose, Mark Rees
    Abstract:

    Monocarpic Plants, which flower once then die, are ideal systems for testing evolutionary ideas because the cost of reproduction is easily quantified and the timing of flowering is a key determinant of darwinian fitness. Monocarps should flower at the size that maximizes fitness, enabling models of life-history evolution to be tested. These models are becoming increasingly sophisticated and accurate, making a review of the techniques and underlying theory timely. Here, we review the long-term demography of Monocarpic species, focusing on how demographic rates vary with size and age. We then examine the broad array of evolutionary models, and question what aspects of the demography are crucial for the successful prediction of the size and age at flowering, shedding light on both the important aspects of monocarp demography and current advances in life-history modelling.

Jianchang Yang - One of the best experts on this subject based on the ideXlab platform.

  • grain filling of cereals under soil drying
    New Phytologist, 2006
    Co-Authors: Jianchang Yang, Jianhua Zhang
    Abstract:

    Monocarpic Plants require the initiation of whole-plant senescence to remobilize and transfer assimilates pre-stored in vegetative tissues to grains. Delayed whole-plant senescence caused by either heavy use of nitrogen fertilizer or adoption of lodging-resistant cultivars/hybrids that remain green when the grains are due to ripen results in a low harvest index with much nonstructural carbohydrate (NSC) left in the straw. Usually, water stress during the grain-filling period induces early senescence, reduces photosynthesis, and shortens the grain-filling period; however, it increases the remobilization of NSC from the vegetative tissues to the grain. If mild soil drying is properly controlled during the later grain-filling period in rice (Oryza sativa) and wheat (Triticum aestivum), it can enhance whole-plant senescence, lead to faster and better remobilization of carbon from vegetative tissues to grains, and accelerate the grain-filling rate. In cases where plant senescence is unfavorably delayed, such as by heavy use of nitrogen and the introduction of hybrids with strong heterosis, the gain from the enhanced remobilization and accelerated grain-filling rate can outweigh the loss of reduced photosynthesis and the shortened grain-filling period, leading to an increased grain yield, better harvest index and higher water-use efficiency.

  • grain filling of cereals under soil drying
    New Phytologist, 2006
    Co-Authors: Jianchang Yang, Jianhua Zhang
    Abstract:

    Contents Summary 223 I. Introduction 224 II. Problems in grain filling: unfavorably delayed whole-plant senescence 224 III. Controlled soil drying improves carbon remobilization and grain filling as a result of enhanced whole-plant senescence 225 IV. Hormonal regulation of whole-plant senescence and grain filling 229 V. Activities of key enzymes involved in carbon remobilization and grain filling 230 VI. Conclusions 232 Acknowledgements 232 References 232 Summary Monocarpic Plants require the initiation of whole-plant senescence to remobilize and transfer assimilates pre-stored in vegetative tissues to grains. Delayed whole-plant senescence caused by either heavy use of nitrogen fertilizer or adoption of lodging-resistant cultivars/hybrids that remain green when the grains are due to ripen results in a low harvest index with much nonstructural carbohydrate (NSC) left in the straw. Usually, water stress during the grain-filling period induces early senescence, reduces photosynthesis, and shortens the grain-filling period; however, it increases the remobilization of NSC from the vegetative tissues to the grain. If mild soil drying is properly controlled during the later grain-filling period in rice (Oryza sativa) and wheat (Triticum aestivum), it can enhance whole-plant senescence, lead to faster and better remobilization of carbon from vegetative tissues to grains, and accelerate the grain-filling rate. In cases where plant senescence is unfavorably delayed, such as by heavy use of nitrogen and the introduction of hybrids with strong heterosis, the gain from the enhanced remobilization and accelerated grain-filling rate can outweigh the loss of reduced photosynthesis and the shortened grain-filling period, leading to an increased grain yield, better harvest index and higher water-use efficiency.

  • water deficit induced senescence and its relationship to the remobilization of pre stored carbon in wheat during grain filling
    Agronomy Journal, 2001
    Co-Authors: Jianchang Yang, Jianhua Zhang, Zhiqing Wang, Qingsen Zhu, Lijun Liu
    Abstract:

    Remobilization and transfer of the pre-stored food in vegetative tissues to the grains in Monocarpic Plants require the initiation of whole plant senescence. However, mechanisms by which plant senescence promotes remobilization of assimilates are rather obscure. This study examined the relationship between the senescence induced by water deficits and C remobilization during grain fill. Two semi-winter wheat cultivars (Triticum aestivum L.),Yangmai 158 and Yangmai 931, were treated with two levels of nitrogen (normal [NN] or high [HN]) and three levels of soil moisture (well-watered, moderate water deficit, and severe water deficit). Results showed that water deficits enhanced the senescence by accelerating loss of leaf nitrogen and chlorophyll and increasing lipid peroxidation. At maturity, 75 to 92% of pre-anthesis C stored in the straw was reallocated to grains in water-deficit treatments, 50 to 80% higher than the amount in well-watered treatments, indicating that water deficits promoted remobilization. The peak values of abscisic acid (ABA) in both leaves and grains under water-defidt treatments were 63 to 144% higher than those under well-watered treatments. The elevated ABA level correlated with the degree of earlier leaf senescence, the 14 C partitioning into grains, and the carbon remobllization. The activites of both add invertase (INV) and sucrose synthase (SS) in grains were also enhanced by water deficits at the midstage of grain fill. Our results suggest that the senescence and remobilization promoted by water defidts during grain fill are coupled processes in wheat, and elevated ABA concentration may play a regulative role.

Toshihiko Sato - One of the best experts on this subject based on the ideXlab platform.

  • effects of phenological constraints on sex allocation in cosexual Monocarpic Plants
    Oikos, 2000
    Co-Authors: Toshihiko Sato
    Abstract:

    The effects of two phenological constraints in resource investment to reproduction – resource limitation at the flowering stage and unpredictability of resources gained after flowering – on the resource allocation between male and female functions in Monocarpic Plants are considered using the ESS (evolutionarily stable strategy) approach. The model predicts that the sex allocation including the seed maturation stage has a female bias, when the quantity of reproductive resources available at flowering is small compared with that which is obtained after flowering, or when the cost of seed maturation relative to ovule production is low. The fluctuation of the quantity of resources available for seed maturation favors overproduction of ovules. As a result, more resources are allocated to female function and less to male function at flowering. The ESS allocation depends on the variability of resources and the cost of seed maturation relative to ovule production. The probability that total resource allocation has a female bias becomes higher than 0.5, and it depends on the cost of seed maturation relative to ovule production rather than resource variability. On the other hand, the probability that resource allocation has a female bias decreases with resource variability if we assume that the floral sex ratio is fixed. Future studies of plant sex allocation would profit by taking account of the phenological process of reproduction such as ovule production or seed maturation.

Peter J Grubb - One of the best experts on this subject based on the ideXlab platform.

  • seed dormancy and delayed flowering in Monocarpic Plants selective interactions in a stochastic environment
    The American Naturalist, 2006
    Co-Authors: Mark Rees, Karen E Rose, Dylan Z Childs, Jessica C Metcalf, A W Sheppard, Peter J Grubb
    Abstract:

    Abstract: We explore the effects of temporal variation in multiple demographic rates on the joint evolution of delayed reproduction and seed dormancy using integral projection models (IPMs). To do this, we extend the standard IPM to include a discrete state variable representing the number of seeds in the seed bank, density‐dependent recruitment, and temporal variation in demography. Parameter estimates for Carlina vulgaris and Carduus nutans are obtained from long‐term studies. Carlina is relatively long lived and has a short‐lived seed bank, whereas most Carduus Plants flower in their first year and the seed bank is long lived. Using the evolutionarily stable strategy (ESS) approach, we predict the observed flowering and germination strategies. There is excellent agreement between the predictions and the field observations. The effects of temporal variation on the joint ESS are partitioned into components arising from nonlinear averaging (systematic changes in the mean resulting from the interaction bet...

  • seed dormancy and delayed flowering in Monocarpic Plants selective interactions in a stochastic environment
    The American Naturalist, 2006
    Co-Authors: Mark Rees, Karen E Rose, Dylan Z Childs, Jessica C Metcalf, A W Sheppard, Peter J Grubb
    Abstract:

    We explore the effects of temporal variation in multiple demographic rates on the joint evolution of delayed reproduction and seed dormancy using integral projection models (IPMs). To do this, we extend the standard IPM to include a discrete state variable representing the number of seeds in the seed bank, density-dependent recruitment, and temporal variation in demography. Parameter es- timates for Carlina vulgaris and Carduus nutans are obtained from long-term studies. Carlina is relatively long lived and has a short- lived seed bank, whereas most Carduus Plants flower in their first year and the seed bank is long lived. Using the evolutionarily stable strategy (ESS) approach, we predict the observed flowering and ger- mination strategies. There is excellent agreement between the pre- dictions and the field observations. The effects of temporal variation on the joint ESS are partitioned into components arising from non- linear averaging (systematic changes in the mean resulting from the interaction between variability and nonlinearity) and nonequilibrium dynamics (fluctuations in fitness caused by temporal variation). This shows that temporal variation can have substantial effects on the observed flowering and germination strategies and that covariance between demographic processes is important. We extend the models