Phenotyping stomatal closure by thermal imaging for GWAS and TWAS of water use efficiency-related genes.

Stomata allow CO2 uptake by leaves for photosynthetic assimilation at the cost of water vapor loss to the atmosphere. The opening and closing of stomata in response to fluctuations in light intensity regulate CO2 and water fluxes and are essential for maintaining water-use efficiency (WUE). However, a little is known about the genetic basis for natural variation in stomatal movement, especially in C4 crops.

Drivers of Natural Variation in Water-Use Efficiency Under Fluctuating Light Are Promising Targets for Improvement in Sorghum.

Improving leaf intrinsic water-use efficiency (), the ratio of photosynthetic CO assimilation to stomatal conductance, could decrease crop freshwater consumption. has primarily been studied under steady-state light, but light in crop stands rapidly fluctuates. Leaf responses to these fluctuations substantially affect overall plant performance.

Transgenic insertion of the cyanobacterial membrane protein ictB increases grain yield in Zea mays through increased photosynthesis and carbohydrate production.

The C4 crop maize (Zea mays) is the most widely grown cereal crop worldwide and is an essential feedstock for food and bioenergy. Improving maize yield is important to achieve food security and agricultural sustainability in the 21st century. One potential means to improve crop productivity is to enhance photosynthesis.

Retrospective analysis of biochemical limitations to photosynthesis in 49 species: C crops appear still adapted to pre-industrial atmospheric [CO ].

Leaf CO uptake (A) in C photosynthesis is limited by the maximum apparent rate of PEPc carboxylation (V ) at low intercellular [CO ] (c ) with a sharp transition to a c -saturated rate (V ) due to co-limitation by ribulose-1:5-bisphosphate carboxylase/oxygenase (Rubisco) and regeneration of PEP. The response of A to c has been widely used to determine these two parameters. V and V depend on different enzymes but draw on a shared pool of leaf resources, such that resource distribution is optimized, and A maximized, when V and V are co-limiting.

Light, Not Age, Underlies the Maladaptation of Maize and Miscanthus Photosynthesis to Self-Shading.

and use NADP-ME subtype C photosynthesis and are important food and biomass crops, respectively. Both crops are grown in dense stands where shaded leaves can contribute a significant proportion of overall canopy productivity. This is because shaded leaves, despite intercepting little light, typically process light energy very efficiently for photosynthesis, when compared to light-saturated leaves at the top of the canopy.

Water Use Efficiency as a Constraint and Target for Improving the Resilience and Productivity of C and C Crops.

The ratio of plant carbon gain to water use, known as water use efficiency (WUE), has long been recognized as a key constraint on crop production and an important target for crop improvement. WUE is a physiologically and genetically complex trait that can be defined at a range of scales. Many component traits directly influence WUE, including photosynthesis, stomatal and mesophyll conductances, and canopy structure.

Bundle sheath chloroplast volume can house sufficient Rubisco to avoid limiting C4 photosynthesis during chilling.

C4 leaves confine Rubisco to bundle sheath cells. Thus, the size of bundle sheath compartments and the total volume of chloroplasts within them limit the space available for Rubisco. Rubisco activity limits photosynthesis at low temperatures.

Loss of photosynthetic efficiency in the shade. An Achilles heel for the dense modern stands of our most productive C4 crops?

The wild progenitors of major C crops grew as individuals subjected to little shading. Today they are grown in dense stands where most leaves are shaded. Do they maintain photosynthetic efficiency in these low light conditions produced by modern cultivation? The apparent maximum quantum yield of CO assimilation (ΦCO2max,app), a key determinant of light-limited photosynthesis, has not been systematically studied in field stands of C crops.