GA₃ and ABA mediated effect on maturation and germination of zygotic embryos in coconut (Cocos nucifera L.)

The effects of growth hormones, viz. GA₃ and ABA were studied on mature (11 months after fertilization) and immature (9 months after fertilization) zygotic embryos of coconut cv. West Coast Tall for maturation, germination and plant development. The GA₃ levels tried were 1.0 μM, 0.5 μM, 0.05 μM and 0.01 μM, and of ABA 10 μM, 20 μM and 30 μM. The germination percentage, weight gain (g), shoot length (cm) and root length (cm) were recorded both at incubation period (90 days) as well as in retrieval medium. Embryos germinated in all the levels of GA₃ irrespective of their maturity. The immature embryos showed maximum growth in medium supplemented with highest level of GA₃. The growth of mature embryos was relatively less and on a par between 0.5 and 1.0 μM. The weight gained for immature embryos was on a par among different levels of GA₃ except the lowest level. There was no significant difference for growth characters of retrieved embryos that were first inoculated in different levels of GA₃.

Significant effect of ABA on germination per cent was noted. The ABA (10 μM - 20 μM) improved germination of immature embryos. All the 3 levels were significantly superior to the control. Significant interaction between maturity of embryos and levels of ABA for initial shoot length (60 days) and root length (130 days) was observed. Interaction between maturity of embryos and levels of ABA was significant with regard to length of shoot and root in the retrieval medium. Irrespective of the maturity of embryos, supplementation of ABA contributed for gaining weight. The poor growth and germination of embryos at higher levels of ABA indicate that, for dormancy, higher levels of ABA may be tried.