Photosynthetic Response of Wheat to Stress Induced by Puccinia Recondita and Post-Infection Drought

Abstract

To quantify photosynthetic response of wheat to the combination of a fungal brown rust infection and a post-infection drought, four treatments were compared: no stress (control), fungal stress (FS), water stress (WS), and twofold stress (WS×FS). Predawn leaf water potential (Ψwp) was similar in FS and WS treatments over a 3-week period. In the WS treatment, net photosynthetic rate (P N) and stomata CO2 conductance (g s) diminished concomitantly with a constant intercellular CO2 concentration (C i) close to 200 µmol mol−1. In the FS treatment, a reduction of P N occurred with an increase in respiration rate (doubling of the CO2 compensation concentration) and in C i but with no water loss modification. Healthy leaves of infected plants (FS) showed a reduction of P N as well, with constant g s and increased C i. In the twofold stress treatment (WS×FS), leaves showed reduced P N in relation to the lower Ψwp. Deleterious effects of both drought and fungal infection on the final area of leaves and dry matter were additive.