This viewpoint devises recommendations for future studies utilizing 13C isotopically non-stationary metabolic flux analysis to characterize plant metabolism. Most importantly, it highlights the ...necessity for model validation.
The aims of this paper was to modify the photosynthesis model of Farquhar, von Caemmerer and Berry (FvCB) to be able to predict light dependency of the carboxylation capacity (Vc) and to improve the ...prediction of temperature dependency of the maximum carboxylation capacity (Vcmax) and the maximum electron transport rate (Jmax). The FvCB model was modified by adding a sub-model for Ribulose-1,5-bisphosphate carboxylase (Rubisco) activation and validating the parameters for temperature dependency of Vcmax and Jmax. Values of parameters for temperature dependency of Vcmax and Jmax were validated and adjusted based on data of the photosynthesis response to temperature. Parameter estimation was based on measurements under a wide range of environmental conditions, providing parameters with broad validity. The simultaneous estimation method and the nonlinear mixed effects model were applied to ensure the accuracy of the parameter estimation. The FvCB parameters, Vcmax, Jmax, I- (the efficiency of light energy conversion), I, (the curvature of light response of electron transport), and Rd (the non-photorespiratory CO2 release) were estimated and validated on a dataset from two other years. Observations and predictions matched well (R2 = 0.94). We conclude that incorporating a sub-model of Rubisco activation improved the FvCB model through predicting light dependency of carboxylation rate; and that estimating Vcmax, Jmax, I-, I,, and Rd requires data sets of both CO2 and light response curves.
By examining the collecting interests and protective practices of Cosimo III de' Medici, the study reveals the close ties between the arts and natural sciences in the early modern period. A number of ...previously unpublished sources of images and texts reveal a panorama of botanical splendor and scholarship during the era of the "last Medici" and examine the achievements and boundaries of grand-ducal patronage.
Comparisons among C4 maize, sorghum, and pearl millet show that soil type and source–sink balance affect transpiration efficiency under high vapor pressure deficit in a species-dependent manner.
...Abstract
We have previously reported that there is a tight link between high transpiration efficiency (TE; shoot biomass per unit water transpired) and restriction of transpiration under high vapor pressure deficit (VPD). In this study, we examine other factors affecting TE among major C4 cereals, namely species’ differences, soil type, and source–sink relationships. We found that TE in maize (10 genotypes) was higher overall than in pearl millet (10 genotypes), and somewhat higher than in sorghum (16 genotypes). Overall, transpiration efficiency was higher in high-clay than in sandy soil under high VPD, but the effect was species-dependent with maize showing large variations in TE and yield across different soil types whilst pearl millet showed no variation in TE. This suggested that species fitness was specific to soil type. Removal of cobs drastically decreased TE in maize under high VPD, but removal of panicles did not have the same effect in pearl millet, suggesting that source–sink balance also drove variations in TE. We interpret the differences in TE between species as being accounted for by differences in the capacity to restrict transpiration under high VPD, with breeding history possibly having favored the source–sink balance in maize. This suggests that there is also scope to increase TE in pearl millet and sorghum through breeding. With regards to soil conditions, our results indicate that it appears to be critical to consider hydraulic characteristics and the root system together in order to better understand stomatal regulation and restriction of transpiration under high VPD. Finally, our results highlight the importance of sink strength in regulating transpiration/photosynthesis, and hence in influencing TE.
The evolutionary success of plants relies to a large extent on their extraordinary ability to adapt to changes in their environment. These adaptations require that plants balance their growth with ...their stress responses. Plant hormones are crucial mediators orchestrating the underlying adaptive processes. However, whether and how the growth-related hormone auxin and the stress-related hormones jasmonic acid (JA), salicylic acid, and abscisic acid (ABA) are coordinated remains largely elusive. Here, we analyze the physiological role of AMIDASE 1 (AMI1) in plant growth and its possible connection to plant adaptations to abiotic stresses. AMI1 contributes to cellular auxin homeostasis by catalyzing the conversion of indole-acetamide into the major plant auxin indole-3-acetic acid. Functional impairment of AMI1 increases the plants' stress status rendering mutant plants more susceptible to abiotic stresses. Transcriptomic analysis of ami1 mutants disclosed the reprogramming of a considerable number of stress-related genes, including JA and ABA biosynthesis genes. The ami1 mutants exhibit only moderately repressed growth, but an enhanced ABA accumulation, which suggests a role for AMI1 in the crosstalk between auxin and ABA. Altogether, our results suggest that AMI1 is involved in coordinating the trade-off between plant growth and stress responses, balancing auxin with ABA homeostasis.
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