The Metabolism of the Germinating Oil Palm (Elaeis guineensis) Seedling : In Vivo Studies

Abstract

The metabolism of (14)C-labeled fatty acids and triacylglycerols was followed in intact germinating oil palm seedlings as well as in tissue slices. In the germinating seedling, the shoot contained a normal pattern of membrane fatty acids (mainly C(16), C(18:1), C(18:2)) but the kernel contained about 68% C(12) and C(14) fatty acids. Haustorium fatty acids were intermediate between the two. [(14)C]Acetate was actively metabolized by shoot and haustorium slices but not so actively by the kernel. Approximately 9% to 17% was converted to water-soluble substances, 4% to 6% to CO(2), and 0.5% to 5.9% to lipids. The fatty acids synthesized in the shoot and haustorium were mainly C(16), C(18), and C(18:1) fatty acids but in the kernel about 18% to 32% of the (14)C-fatty acids were C(12) fatty acids.[(14)C]Lauric acid was absorbed and metabolized by haustorium slices and by the haustorium in intact seedlings; it was partly esterified to triacylglycerols and also converted to water-soluble substances and insoluble tissue material. In contrast, tri-[(14)C]laurin was absorbed but not metabolized. The haustorium also absorbed other fatty acids but the longer chain (C(16) and C(18)) fatty acids were not esterified or metabolized further. Preincubation of the haustorium with plant hormones or in the presence of kernel tissue did not alter its inactivity towards tri-[(14)C]laurin.When tri-[(14)C]laurin or [(14)C]lauric acid were injected into the seed or the shoot, there was no movement or radioactivity to other parts of the seedling. When injected into the shoot, but not into the seed, tri-[(14)C] laurin was hydrolyzed and partly metabolized to water-soluble substances.