Individual and combined effects of transient drought and heat stress on carbon assimilation and seed filling in chickpea

Abstract

High temperatures and decreased rainfall are detrimental to yield in chickpea (Cicer arietinum L.), particularly
during grain filling. This study aimed to (i) assess the individual and combined effects of drought and heat stress on
biochemical seed-filling processes, (ii) determine genotypic differences in heat and drought tolerance, and (iii) determine any
cross-tolerance. Plants were grown outdoors in the normal growing season when temperatures during seed filling were
32 20 C; heat stress). Half of the pots were kept adequately watered
throughout, but water was withheld from the others from the initiation of seed filling until the relative leaf water content
reached 50% of the irrigated plants (drought stress); all plants were rewatered thereafter until seed maturit. Water was
withheld for 13 days (normal sowing) and 7 days (late sowing), so soil moisture decreased by 54–57%. Tests on leaves and
seeds were performed after the stress. Individual and combined stress damaged membranes, and decreased cellular oxidising
ability, stomatal conductance, PSII function and leaf chlorophyll content; damage was greater under combined stress. Leaf
Rubisco activity increased with heat stress, decreased with drought stress and decreased severely with combined stress.
Sucrose and starch concentrations decreased in all seeds through reductions in biosynthetic enzymes; reductions were greater
under combined stress. These effects were more severe in heat- and drought-sensitive genotypes compared with droughttolerant
genotypes. Drought stress had a greater effect than heat stress on yield and the biochemical seed-filling mechanisms.
Drought- and heat-tolerant genotypes showed partial cross-tolerance