STUDIES ON THE GERMINATION MECHANISM OF CATHARANTHUS-ROSEUS (L) DON,G. CV ALBA SEEDS - EFFECT OF TEMPERATURE AND PROMOTERS

Freshly harvested seeds of the white flowered periwinkle cultivar [Cat haranthus roseus (L.) G.Don cl. alba] after sundrying, exhibited 40% g ermination in the dark at 25 degrees C while only 9% at 15 degrees C, 20% at 20 degrees C and 9% at 30 degrees C. In continuous light at 25 degrees C, the same inhibition was noted. Pretreatment with GA(3) of 2 .886 mM for 6h and 12h produced 84% and 100% germination respectively in the dark while KNO3 of 100 mM for 24h also produced 90% germination . GA(3) pretreatment partially negated light induced inhibition of ger mination where 52% germination was noted as against 10% in the control . KNO3 pretreatment, however, produced only 24% germination in continu ous light. Thiourea altogether failed to increase germination in the d ark. Both low and high temperature inhibition was significantly reduce d by GA, and KNO,. Again pretreatment only for lh at 30 degrees C foll owed by a lower concentration of GA(3) i.e., 1.443 mM for 24h produced 80% germination and a 6h pretreatment similarly produced 93% germinat ion. In the case of KNO3, the lower concentration of 10 m.M produced 7 4% and 81% germination with the same hours of pretreatment. At 30 degr ees C leakage oi electrolyte, soluble carbohydrate and amino acid was more compared with 25 degrees C and 20 degrees C.