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The response of mesophyll conductance to short- and long-term environmental conditions in chickpea genotypes

Mesophyll conductance to CO(gm), which regulates the diffusion of COfrom substomatal cavities to the sites of carboxylation, is now recognized as a significant and variable limitation to photosynthesis. It is a combination of gaseous diffusion through the intercellular airspaces and diffusion in the liquid phase through the mesophyll cell walls, plasma membrane, cytosol and chloroplast envelope to chloroplast stroma, the site of carboxylation. ghas been shown to vary between genotypes of a number of species and with growth environments, including nitrogen availability, but understanding of gvariability in legume species is limited.

Chickpea plant
Chickpea growing in the field. Image credit: Carl Davies, CSIRO (distributed under a CC license;

Given the growing interest in gas a breeding selection target for increased photosynthesis, and a lack of understanding of gregulation in legumes, a recent study by Shrestha et al. and published in AoBP investigated the effect of water availability and nitrogen source on gacross chickpea (Cicer arietinum) genotypes. The authors suspected gof legumes might respond differently to limited nitrogen availability than other crop species, due to their ability to fix atmospheric N2. Chickpea genotypes were found to vary in their gsensitivity to nitrogen source. Genotypes also differed in the effects of nitrogen source on the rapid response of gto light intensity. There was however no clear effect of reduced water availability on the gresponse to light intensity or quality. The significant variability in response of gto long- and short-term environmental conditions observed in these experiments indicates that inclusion of gas a selection trait is not straightforward. Future work should look to examine gresponses of a wide range of legumes and environments, and explore the underlying mechanisms of gin greater detail.

Researcher highlight

Arjina Shrestha

Arjina Shrestha received her BSc in Agriculture from Tribhuvan University, Nepal in 2005. After completing her undergraduate studies, she worked as a horticulture officer on an in situ biodiversity conservation project in Nepal for three years. She obtained an MSc in Horticulture from Oklahoma State University, USA in 2011, and a PhD in plant physiology from the University of Sydney, Australia in 2017, under the supervision of Professor Margaret M. Barbour. She currently holds a postdoctoral research associate position with Professor Barbour in the Legumes for Sustainable Agriculture Research Hub in the School of Life and Environmental Sciences at the University of Sydney.

Arjina is a plant physiologist with primary areas of interest in photosynthesis research (particularly the conductance to COdiffusion within leaves), plant water relations and abiotic stress phyiology. She has investigated leaf-level gas exchange processes under varying growth environments using stable carbon and oxygen isotopes.

Written by William Salter

William (Tam) Salter is a Postdoctoral Research Associate in the School of Life and Environmental Sciences and Sydney Institute of Agriculture at the University of Sydney. He has a bachelor degree in Ecological Science (Hons) from the University of Edinburgh and a PhD in plant ecophysiology from the University of Sydney. Tam is interested in the identification and elucidation of plant traits that could be useful for ecosystem resilience and future food security under global environmental change. He also has an active interest in effective scientific communication.

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