4‐Desmethylsterol composition of citrus rootstocks of different salt exclusion capacity

Abstract

Fibrous roots from seedlings of three citrus rootstocks (Rungpur lime, Kharna khatta and Etrog citron) grown hydroponically for 6 weeks in the presence or absence of 50 mM NaCl were analysed for their content of free, esterified, and glycosidic sterols. Leaf chloride analyses indicated that Rangpur lime was a good Cl‐ excluder and the other two rootstocks were Cl‐ accumulators.On a dry weight basis and in the absence of NaCI only the free 4‐desmethyIsterol levels showed significant rootstock differences. Kharna khatta had the highest, and Rangpur lime the lowest, free stcrol levels. Sitostcrol was the major component of all sterol fractions of Rangpur lime, the esterified fraction of the other rootstocks, and the glycosidic sterol fraction of Kharna khatta. The ratio of sitosterol to stigmasterol was highest in Rangpur lime and lowest in Etrog citron in all cases and the ratio of apos;more‐planar apos; to apos;less‐planar apos; free sterols was highest in Etrog citron and lowest in Rangpur lime.Treatment with 50 mM NaCI resulted in an increase in free sterol levels in Rangpur lime and a decrease in Kharna khatta. Steryl ester levels were unaffected in Rangpur lime but were significantly reduced in the other rootstocks. In all three sterol fractions the sitosterol/stigmasterol ratio was decreased. A decrease in the ratio of apos;more‐planarapos; to apos;less‐planarapos; free sterols was observed only in Kharna khatta and, more notably, Etrog citron. Salt‐induced changes in the apos;more‐planar apos; to apos;less‐planar apos; free sterol ratio correlated well with salt exclusion capacity.