EFFECTS OF SOME ROOTSTOCKS ON PHOTOSYNTHETIC PERFORMANCE OF YOUNG ‘VALENCIA’ ORANGE TREES IN CALCAREOUS SOIL

Iron deficiency is a major problem for many fruit crops grown on calcareous soils. Citrus orchards in the Mediterranean basin are often affected by high pH calcareous soils leading to tree nutrient imbalances promoted by iron deficiency. In this study ‘Valencia’ orange (Citrus sinensis Osb.) budded on five different rootstocks (‘Carrizo’ citrange, ‘Swingle’ citrumelo, ‘Rangpur’ lime, ‘Antalya Cleopatra’ mandarin, ‘Tuzcu 31 31’ sour orange) were evaluated in terms of their photosynthetic performances in calcareous soil. The experiment was conducted at the experimental plot of Cukurova University Faculty of Agriculture Department of Horticulture in 2011. Thus, leaf chlorophyll concentration, chlorophyll fluorescence parameters in light-adapted (QY: FV’ /FM’: Photosystem II quantum yield) and leaf gas exchange parameters were measured. ‘Valencia’ scion which was grown grafted onto ‘Rangpur lime’ and ‘Antalya Cleopatra’ mandarin rootstocks had the highest chlorophyll content while ‘Swingle’ citrumelo had the lowest. However, leaves of ‘Valencia’ scion did not change in term of transpiration rate whatever the rootstock. However, leaves of ‘Valencia’ scion grafted on ‘Swingle’ citrumelo rootstock displayed a significant reduction in photosynthetic rate, stomatal conductance and quantum yield of photosystem II. The highest photosynthetic rate and leaf water use efficiency were obtained for the leaves of ‘Valencia’ scion grafted on sour orange.