EFFECT OF HORMONES AND SPERMIDINE ON THE TURNOVER OF INOSITOLPHOSPHOLIPIDS IN BRASSICA SEEDLINGS

The effect of hormones (NAA and BAP) and a polyamine (spermidine) on the turnover of inositol-phospholipids has been studied in Brassica oleracea seedlings. Incubation of hypocotyls for 4 hr with the hormones resulted in a significant decrease in the levels of labelled phosphatidylinositol 4,5-bisphosphate (PIP2), phosphatidylinositol 4-phosphate (PIP) and phosphatidylinositol (PI), whereas the inositol 1,4-bisphosphate (IP2) and inositol 1,4,5-trisphosphate (IP3) level increased by 26%. An increase in PIP and PIP2 accompanied by a decrease in PI, IP2 and IP3 level was observed when hypocotyls were treated with spermidine. Treatment with a combination of hormones and polyamine evoked a fast turnover of inositolphospholipids, showing an appreciable decrease in PIP2, PIP and PI with a corresponding increase in IP2 and IP3 level. It is suggested that hormones act mainly on PIP2 and induce its breakdown to produce IP2 and IP3 and 1,2-diacylglycerol (DAG), to induce various biological responses.