VARIATIONS IN GROWTH AND PHOTOSYNTHETIC PARAMETERS OF SOME CLONAL SEMI-DWARFING AND VIGOROUS SEEDLING PEAR (Pyrus spp.) ROOTSTOCKS IN RESPONSE TO DEFICIT IRRIGATION

A greenhouse experiment was conducted to estimate the impacts of various deficit irrigation regimes (DIR) as 100 (control), 75 (medium DIR, MDIR) and 50% (severe DIR, SDIR) of field capacity (FC) on the growth and photosynthetic traits of five rootstocks (two vigorous seedling including Pyrus betulifolia and Dargazi seedling (P. communis L.) as well as three clonal semi-dwarfing rootstocks including OH×F69, OH×F87 and Pyrodwarf in 2016. Although in all studied rootstocks the growth and photosynthetic parameters negatively affected under MDIR and SDIR conditions, but P. betulifolia and Pyrodwarf rootstocks had the better growth rate, chlorophylls, total carbohydrates, relative water content, sub-stomatal CO2 (Ci), photosynthesis rate (PN) and instantaneous water use efficiency compared to others. Therefore, the use of P. betulifolia and Pyrodwarf (as drought tolerance rootstocks) could be more appropriate under various DIR conditions.