A comparison of stomatal conductance responses to blue and red light between C3 and C4 photosynthetic species in three phylogenetically-controlled experiments.

Introduction: C photosynthesis is an adaptation that has independently evolved at least 66 times in angiosperms. C plants, unlike their C ancestral, have a carbon concentrating mechanism which suppresses photorespiration, often resulting in faster photosynthetic rates, higher yields, and enhanced water use efficiency. Moreover, the presence of C photosynthesis greatly alters the relation between CO assimilation and stomatal conductance.

Corrigendum: Activation of CO assimilation during photosynthetic induction is slower in C than in C photosynthesis in three phylogenetically controlled experiments.

[This corrects the article DOI: 10.3389/fpls.2022.

Activation of CO assimilation during photosynthetic induction is slower in C than in C photosynthesis in three phylogenetically controlled experiments.

Introduction: Despite their importance for the global carbon cycle and crop production, species with C photosynthesis are still somewhat understudied relative to C species. Although the benefits of the C carbon concentrating mechanism are readily observable under optimal steady state conditions, it is less clear how the presence of C affects activation of CO assimilation during photosynthetic induction.

Methods: In this study we aimed to characterise differences between C and C photosynthetic induction responses by analysing steady state photosynthesis and photosynthetic induction in three phylogenetically linked pairs of C and C species from , , and genera.

Phenotypic variation in photosynthetic traits in wheat grown under field versus glasshouse conditions.

Recognition of the untapped potential of photosynthesis to improve crop yields has spurred research to identify targets for breeding. The CO2-fixing enzyme Rubisco is characterized by a number of inefficiencies, and frequently limits carbon assimilation at the top of the canopy, representing a clear target for wheat improvement. Two bread wheat lines with similar genetic backgrounds and contrasting in vivo maximum carboxylation activity of Rubisco per unit leaf nitrogen (Vc,max,25/Narea) determined using high-throughput phenotyping methods were selected for detailed study from a panel of 80 spring wheat lines.

Improving C4 photosynthesis to increase productivity under optimal and suboptimal conditions.

Although improving photosynthetic efficiency is widely recognized as an underutilized strategy to increase crop yields, research in this area is strongly biased towards species with C3 photosynthesis relative to C4 species. Here, we outline potential strategies for improving C4 photosynthesis to increase yields in crops by reviewing the major bottlenecks limiting the C4 NADP-malic enzyme pathway under optimal and suboptimal conditions. Recent experimental results demonstrate that steady-state C4 photosynthesis under non-stressed conditions can be enhanced by increasing Rubisco content or electron transport capacity, both of which may also stimulate CO2 assimilation at supraoptimal temperatures.

Measuring Rubisco activity: challenges and opportunities of NADH-linked microtiter plate-based and 14C-based assays.

Rubisco is central to carbon assimilation, and efforts to improve the efficiency and sustainability of crop production have spurred interest in phenotyping Rubisco activity. We tested the hypothesis that microtiter plate-based methods provide comparable results to those obtained with the radiometric assay that measures the incorporation of 14CO2 into 3-phosphoglycerate (3-PGA). Three NADH-linked assays were tested that use alternative coupling enzymes: glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and glycerolphosphate dehydrogenase (GlyPDH); phosphoenolpyruvate carboxylase (PEPC) and malate dehydrogenase (MDH); and pyruvate kinase (PK) and lactate dehydrogenase (LDH).

Spectrophotometric Determination of RuBisCO Activity and Activation State in Leaf Extracts.

RuBisCO plays a central role in photosynthesis and, due to its catalytic inefficiencies, frequently limits CO assimilation in fully illuminated leaves at the top of unstressed crop canopies. The CO-fixing enzyme is heavily regulated and not all the enzyme present in the leaf is active at any given moment. In this chapter, a spectrophotometric assay is described for measuring RuBisCO activity and activation state in leaf extracts.

Quantification of Photosynthetic Enzymes in Leaf Extracts by Immunoblotting.

In this chapter, we describe a method to extract and quantify photosynthetic enzymes using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting. The method is particularly suitable for characterizing altered protein amounts in leaves of plants produced from genetic engineering or gene-editing approaches. We focus on RuBisCO and RuBisCO activase, a molecular chaperone required to sustain the activity of RuBisCO and CO fixation, yet the method can be easily adapted to investigate other leaf proteins of interest.

Physiological Plasticity Is Important for Maintaining Sugarcane Growth under Water Deficit.

The water availability at early phenological stages is critical for crop establishment and sugarcane varieties show differential performance under drought. Herein, we evaluated the relative importance of morphological and physiological plasticity of young sugarcane plants grown under water deficit, testing the hypothesis that high phenotypic plasticity is associated with drought tolerance. IACSP95-5000 is a high yielding genotype and IACSP94-2094 has good performance under water limiting environments.

Short-term physiological changes in roots and leaves of sugarcane varieties exposed to H2O2 in root medium.

The aim of this study was to evaluate the differential sensitivity of sugarcane genotypes to H2O2 in root medium. As a hypothesis, the drought tolerant genotype would be able to minimize the oxidative damage and maintain the water transport from roots to shoots, reducing the negative effects on photosynthesis. The sugarcane genotypes IACSP94-2094 (drought tolerant) and IACSP94-2101 (drought sensitive) were grown in a growth chamber and exposed to three levels of H2O2 in nutrient solution: control; 3 mmol L(-1) and 80 mmol L(-1).

Superoxide dismutase and ascorbate peroxidase improve the recovery of photosynthesis in sugarcane plants subjected to water deficit and low substrate temperature.

The physiological responses of C4 species to simultaneous water deficit and low substrate temperature are poorly understood, as well as the recovery capacity. This study investigated whether the effect of these abiotic stressors is cultivar-dependent. The differential responses of drought-resistant (IACSP94-2094) and drought-sensitive (IACSP97-7065) sugarcane cultivars were characterized to assess the relationship between photosynthesis and antioxidant protection by APX and SOD isoforms under stress conditions.