Changes in Relative Proportions of Plant Growth Regulators in the Liquid Endosperm during Seed Development in Coconut Cultivars/Hybrids

Cocos nucifera L. is an important cash crop commercially planted for its diverse utilities. Coconut water (liquid endosperm) is widely used as a revitalizing health drink and is a cheaper source of many bioactive compounds especially plant growth regulators (PGRs). However, the dynamics of PGRs during liquid endosperm formation and the varietal difference have not been studied well. In the present investigation, two cultivars; tall (West coast tall) and dwarf (Gangabondam) and their reciprocal hybrids (T×D and D×T) were screened for the study of dynamics of PGRs during liquid endosperm formation. Fifteen hormones belonging to seven major classes of phytohormones, viz., IAA, IBA, SA, GA 3 , GA 4 , GA 7 , t Z, t ZR, BA, ABA, ACC, JA, cis J, meJA, and 24-epiBL, were simultaneously assayed by LC-MS/MS method. IAA, GA 4 , BA/ tZ , SA, JA/ cis J and 24-epiBL were the predominant forms in the liquid endosperm in all the cultivars/hybrids. Liquid endosperm of four month old nuts were found to be an excellent source for BA whereas t Z in mature nuts of all cultivars/hybrids. SA was found in extremely higher levels in in all stages of maturity. IAA and SA were found to be involved in solid endosperm formation and embryo differentiation while GA 4 was detected at a lower level initially and found to accumulate at maturity. Elevated level of GA 4 and the low level of ABA in the liquid endosperm of mature nuts indicate hormonal antagonism in this recalcitrant species in order to carry out quicker germination. JA and ci sJ were the predominant jasmonates in the liquid endosperm of all varieties. 24-epiBL was detected in the liquid endosperm of all cultivars while ACC was found in insignificant level. The hormonal dynamics was found to have a similar trend in all varieties except D×T hybrid. The work is relevant for the coconut growers to understand the right time for fruit harvesting to get optimal benefit and for the plant breeders to develop breeding strategies.