Transitory Carbohydrate Reserves in Vegetative Organs of Coconut Under Different Growth Conditions and Its Relation with Reproductive and Vegetative Growth of The Palm

Abstract

The study evaluated the non structural carbohydrate reserves in vegetative organs and vegetative and reproductive growth rates of a 25 year old Tall x Tall coconut (Cocos nucifera L) during the peak season of coconut yield (May/June) under S 2 and S 4 Land Suitability Classes (LSC) in three Agro Ecological Regions (WL 3 , IL 1a and DL 3 ). Trunk (inner and outer), root (new roots and mature roots) and leaf samples (petiole, leaf blade and leaf ekel from 9 th , 14 th and 22 nd fronds) were collected, total soluble sugars (TSS) and starch concentrations were analyzed and TSS and starch reserves at palm level were estimated. Growth rate of trunk and leaves (vegetative) and developing nuts of all bunches of a palm (reproductive) were measured.The highest (3.86 kg month -1 ) and the lowest (0.81 kg month -1 ) reproductive growth rates and the highest (3.8 kg month -1 ) and the lowest (2.1 kg month -1 ) vegetative growth rates were found in the palms grown under S 2 and S 4 LSC in the DL 3 , respectively. There was a constant vegetative growth rate of 3.3 kg month -1 for the palms in WL 3 and IL 1a irrespective of the AER or LSC. The most dominant nonstructural reserve substance in the vegetative organs of coconut was soluble sugars (TSS) and the starch concentration was approximately half the TSS concentration in all vegetative parts irrespective of the AER or the LSC. TSS and starch showed a marked pattern of distribution, with highest concentration in trunk (114-134 mg g -1 TSS and 60-83 mg g -1 starch), intermediate in leaves (69-117 mg g -1 TSS and 33-69 mg g -1 starch) and lowest in roots (22-79 mg g -1 TSS and 17-33 mg g -1 starch). The highest TSS and starch reserves in leaf compartments (kg per palm) were found in the S 2 -grown palms of the DL 3 which had the highest reproductive and vegetative growth rates during May-June season.

Major determinants of fruit set and yield fluctuation in coconut (Cocos nucifera L.)

“…Therefore, it could be assumed that the variation in sink strength of a palm is more critical than the variation in source strength in determining the variation in fruit set. Sink strength of a palm is the total dry matter requirement for potential growth and respiration (Henson, 2007 (Ranasinghe et al, 2011). Therefore, the sink strength of vegetative organs can be assumed constant; hence the driving force of seasonal variation in fruit set could be associated with the sink strength of reproductive organs [assimilate requirement of reproductive organs (developing fruits in all bunches)].…”