Effects of kinetin on distribution and exudation of free sterols and free fatty acids in Arachis hypogaea L. 'Argentine' under axenic conditions

Abstract

The effect of kinetin concentrations (10⁻⁶M and 10⁻⁴M) on distribution of free fatty acids and sterols in plant parts and root exudates of 57-day-old peanut plants grown in nutrient solutions under gnotobiotic conditions was studied. Kinetin was applied to the roots in the culture medium five days before harvest. Upon harvesting root exudates were collected and plants divided into leaves, stems, and roots. The extracted lipid fraction was partitioned using silica gel thin-layer chromatography. Quantitation and identification of free fatty acids and sterols were accomplished by isothermal gas-liquid chromatography.

On the basis of ug fatty acid/mg tissue and ug fatty acid/mg lipid kinetin caused no significant changes in total fatty acid concentration. The only significant increase in total sterol concentration was observed in the 10⁻⁴M treatment (ug sterol/mg lipid) in the stems. Use of individual component concentrations, relative percentages, and ratios helped distinguish trends.

Shifts in quantity and quality of the free fatty acids and sterols may have been a result of one or a combination of effects attributed to kinetin. Decrease in root exudation in the 10⁻⁶M treatment may have been due to altered membrane integrity. Increase in the sitosterol/ stigmasterol ratio in stems of treated plants may have been a result of delayed senescence. Trends showed transport of free fatty acids and sterols to the roots in 10⁻⁶M treated plants. Kinetin may have effected sterol concentration through changes in HMGCoA reductase activity by unsaturated fatty acids.