Changes of leaf water potential and gas exchange during and after drought in triticale and maize genotypes differing in drought tolerance

Influence of drought (D) on changes of leaf water potential (psi) and parameters of gas exchange in D-resistant and D-sensitive genotypes of triticale and maize was compared. Soil D (from -0.01 to -2.45 MPa) was simulated by mannitol solutions. At -0.013 MPa significant differences in T, net photosynthetic rate (P-N), transpiration rate (E), stomatal conductance (g(s)), and internal CO2 concentration (C-i) of D-resistant and D-sensitive triticale and maize genotypes were not found. Together with the increase in concentration of the mannitol solution the impact of D on E and g(s) for D-sensitive genotypes (CHD-12, Ankora) became lower than for the D-resistant ones (CHD-247, Tina). Inversely, impact of D on psi was higher in D-sensitive than D-resistant genotypes. From 1 to 3 d of D, a higher decrease in P-N was observed in D-resistant genotypes than in the D-sensitive ones. Under prolonged D (5-14 d) and simultaneous more severe D the decrease in P-N was lower in D-resistant than in D-sensitive genotypes. Changes in psi, P-N, E, and g(s) caused by D in genotypes differing in the drought susceptibility were similar for triticale and maize. Compared to control plants, increase of C-i was different for triticale and maize genotypes. Hence one of the physiological reasons of different susceptibility to D between sensitive and resistant genotypes is more efficient protection of tissue water status in resistant genotypes reflected in higher decrease in g, and limiting E compared to the sensitive ones. Other reason, observed in D-resistant genotypes during the recovery from D-stress, was more efficient removal of detrimental effects of D.