Gas exchange activities and relative water content at different fruit growth and developmental stages of ON and OFF cultivated pistachio trees

The present research was carried out to study gas exchange activities at different stages of fruit growth and development in OFF and ON pistachio cultivars including Ohadi, Kalleh-Ghochi, Akbari, Ahmad-Aghaii, Rezaii Zoudras and Haratii. Thus, different OFF and ON shoots were chose at different stages of fruit growth and development and also postharvest stage as followed: 1- beginning of endocarp growth; 2- pith hardening; 3- beginning of endosperm rapid growth; 4- end of embryo development; 5- ripening and harvesting times and 6- post harvest. Data indicated that gas exchange activities and relative water content significantly affected by cultivar, fruit growth and development stages and ON and OFF bearing statuses. The highest amount of photosynthetic activity was shown by Rezaii Zoudras followed by Akbari, Ohadi, Ahmad-Aghaii, Kalleh- Ghochi and Haratii, respectively. The highest and lowest photosynthetic (Pn) and transpiration (E) rates were resulted from ʹRezaii Zoudrasʹ and ʹHaratiiʹ, respectively. The highest rates of stomatal conductance (gs) and relative water content (RWC) were obtained by ʹOhadiʹ, and ʹOhadiʹ and ʹKalleh-Ghochiʹ, respectively. Data showed the highest and lowest Pn at first (T1) and fifth (T5) stages of fruit growth and development. The highest and lowest rates of E were obtained at second and third stages and fifth stage, respectively. Our results illuminated that gas exchange activity studies are the main way choosing the best cultivar for a special condition.