The study was conducted at the experimental farm of Mustafa Kemal University, Dörtyol, Turkey during the 2010 and 2011 growing seasons. The aim of this study was to investigate the effect of Troyer™ and Carrizo™ citranges (Poncirus trifoliata Raf. x Citrus sinensis Osb. var. Troyer™ and Carrizo™), and common sour orange (Citrus aurantium L. var. common), rootstocks on the seasonal variation of carbohydrate content in the leaves of cvs. Fremont™, Nova™, and Robinson™ mandarin. The seasonal variation of carbohydrate content of the three cultivars budded on different rootstocks was nearly same. Soluble carbohydrate concentration showed a continuous decrease from January to mid or late-summer, and then slowly began to increase after early autumn till winter. The sucrose was the dominant soluble carbohydrate in leaves. The seasonal evolution of starch content in leaves increased initially during January to March, and then decreased in April. The starch concentration showed a continuous decrease slowly until the mid-autumn, and then accumulation began during late-autumn and winter. The total carbohydrate content differences among the rootstocks were significant, but the content was changed among the cultivars and according to the season. The change in the total carbohydrate content of leaf tissues showed a strong similarity in cultivars budded on different rootstocks throughout the year. The total carbohydrate content reached their lowest levels in July for cv. Robinson™, in August for cv. Fremont™ and cv. Nova™. The total carbohydrate content in leaves increased from the mid- or late-summer to winter. It is suggested that the seasonal variation of carbohydrate content in plant tissues can be considered during fertilization program in mandarin trees.
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