Effects of water stress on the yield and photosynthesis of field-grown sweet pepper (Capsicum annuum L.)

This trial was carried out to understand: i) whether a rainfed pepper crop is subjected to photosynthesis and growth limitations in central Italy summer conditions; ii) the processes which are affected by the limitations; and iii) whether the limitations are relieved by irrigation and can therefore be attributed to transient water stress. Photosynthesis, stomatal conductance, LAD, and intercepted solar radiation of the rainfed crop were lower than in the irrigated control but the difference became significant only after the first fruit harvest. Rubisco activity and content and the quantum yield of CO2 fixation were similar over the entire season in control and rainfed pepper. Stomatal limitations were removed by maintaining detached leaves of rainfed pepper in water but photosynthesis recovered to only 75% of control photosynthesis. The incomplete recovery can be attributed to increased and unrecoverable limitations to CO2 diffusion in the mesophyll of rainfed pepper as shown by simultaneous measurements of fluorescence and gas-exchange.