Lipids of soybean and sunflower seedlings grown under drought conditions

Abstract

Abstract Soybean and sunflower seedlings were grown under field irrigation and water deficit conditions. One set of plants was submitted to water depletion 12 days after sowing and all seedlings were harvested 20 days after sowing. In comparison to controls, the decrease in the soil water potential to - 1.5 MPa produced in both of the stressed species a reduction in leaf water potential with a consequent increase in the water saturation deficit, which was higher in sunflower. Only sunflower suffered a reduction in height, fr. wt, dry wt and in the lipid extract and lipid phosphorus content. Phospholipids decreased by more than 50% in stressed sunflower seedlings while they remained constant in soybean. Diacylglycerol and triacylglycerol concentrations increased in both species under water stress. The free sterol/phospholipid molar ratio was higher in the stressed seedlings of both species. The glycolipid content increased in soybean but was reduced in sunflower plants, with the monogalactosyldiacilglycerol being present in the largest amounts. The degree of unsaturation of the fatty acids of the various lipid classes in general did not change in response to water stress, with the exception of the diacylglycerols where it decreased. In all the lipid classes examined, unsaturation was higher than 60% in both stressed and unstressed seedlings. The free sterols presented a contrasting behaviour, showing an increase in stressed soybean and a reduction in stressed sunflower. Under water deficit conditions there was no change in the ‘more planar’ to ‘less planar’ sterol ratio.