Phenotypic variation in photosynthetic traits in wheat grown under field versus glasshouse conditions:Mismatch between field versus glasshouse-grown plants

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 characterised 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. Detailed phenotyping of photosynthetic traits in the two lines using glasshouse-grown plants showed no difference in Vc,max,25/Narea determined directly via in vivo and in vitro methods. Detailed phenotyping of glasshouse-grown plants of the 80 wheat lines also showed no correlation between photosynthetic traits measured via high throughput phenotyping of field-grown plants. Our findings suggest that the complex interplay between traits determining crop productivity and the dynamic environments experienced by field-grown plants needs to be considered when designing strategies for effective wheat crop yield improvement when breeding for particular environment

Tree community variation in a tropical continental island according to slope aspect and human interference

ABSTRACT Associating description of unrecorded tropical tree community structure to sampling approaches that can help determine mechanisms behind floristic variation is important to further the comprehension of how plant species coexist at tropical forests. Thus, this study had the goals of (i) evaluating tree community structure on the continental island of Marambaia (23°4’37.09”S; 43°59’2.15”W) and (ii) testing the prediction that there are local scale changes in a tropical tree community structure between slopes facing different geographic orientation and with distinct human interference history. We established 60 (0.6 ha) sampling units in three different slope sites with distinct predominant geographic orientation and human interference. We sampled all woody trees with diameter at breast height (dbh) ≥ 5 cm. We found a total of 1.170 individuals representing 220 species, 120 genera and 50 families. The overall tree community structure and structural descriptors (abundance of individuals, basal area, species richness and diversity) varied extensively between the sites. The evidence presented here supports that local scale topography variations and human interference history can be important factors contributing to the known floristic heterogeneity of the Atlantic Rainforest. Future work on the study area should focus on disentangling effects from distinct causal factors over tree community variation and species occurrence

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 CO2 assimilation in fully illuminated leaves at the top of unstressed crop canopies.The CO2-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.Most of the assay components are available commercially and others can be produced by established protocols, making adoption of the assay achievable by most plant biochemistry laboratories.Its relative high-throughput capacity enables large-scale experiments aimed at screening germplasm for improved Rubisco function