FIRST OBSERVATIONS ON PHYSIOLOGICAL EFFECTS OF IRRIGATION IN PISTACHIO

A research aimed at focusing the effects of different amount of irrigation water supply on net CO₂ assimilation and related parameters has been undertaken on pistachio cv. Larnaka in Southern Italy. Four seasonal irrigation volumes restoring 0 – 25 – 50 and 75% ET_c (0 – 1,500 – 3,000 – 4,500 m³ ha^-1) were applied by drip irrigation. From first results, all the ecophysiological parameters were influenced by irrigation, but to a different extent. The stomatal conductance and transpiration rates were influenced by irrigation per se, while the assimilation rate and the related parameters were influenced by the irrigation level. Stomatal conductance and transpiration rates were found significantly lower in nonirrigated trees; no difference was found among the other treatments. The restoring of 50% ET_c would seem to match the best results in net CO₂ uptake per leaf area unit and per whole leaf, photosynthetic efficiency and water use efficiency. No difference was found as concerns the vegetative traits of the shoots and the transpiration rate per whole leaf at different irrigation levels.