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

Abstract

Mesophyll conductance (gm) has been shown to vary between genotypes of a number of species and with growth environments, including nitrogen availability, but understanding of gm variability in legumes is limited. We might expect gm in legumes to respond differently to limited nitrogen availability, due to their ability to fix atmospheric N2. Using online stable carbon isotope discrimination method, we quantified genetic variability in gm under ideal conditions, investigated gm response to N source (N2-fixation or inorganic N) and determined the effects of N source and water availability on the rapid response of gm to photosynthetic photon flux density (PPFD) and radiation wavelength in three genotypes of chickpea (Cicer arietinum). Genotypes varied 2-fold in gm under non-limiting environments. N-fed plants had higher gm than N2-fixing plants in one genotype, while gm in the other two genotypes was unaffected. gm response to PPFD was altered by N source in one of three genotypes, in which the gm response to PPFD was statistically significant in N-fed plants but not in N2-fixing plants. There was no clear effect of moderate water stress on the gm response to PPFD and radiation wavelength. Genotypes of a single legume species differ in the sensitivity of gm to both long- and short-term environmental conditions, precluding utility in crop breeding programmes.