ASSIMILATE STORAGE IN VEGETATIVE ORGANS OF COCONUT (Cocos nucifera)

Abstract

Assimilate storage in vegetative organs is an essential buffer for the source–sink imbalances that inevitably occur in perennial plants. In contrast to temperate trees, little information is available on such storage in tropical perennials, and almost none for Cocos nucifera. This paper describes the chemical nature, quantity and distribution of carbohydrate reserves in coconut plants grown in an environment favourable to production. The study was carried out on the island of Santo (Republic of Vanuatu, Southern Pacific) on twelve 17-year-old adult plants, representative of a large population, which were felled and characterized for root, trunk and crown dry matter, and contents of soluble sugars and starch. Roots were divided into three diameter classes and distal/proximal portions, the trunk into three axial and three or four radial zones, and the crown into petiole, rachis and leaflets for various leaf ages. The aggregate reserve pool size was compared with estimates of incremental demand for assimilates for growth and fruit production. Plants contained little starch but large quantities of sucrose were found, mainly located in the trunk. Less sucrose was present in roots and little in leaf blades. Large glucose and fructose pools were found in leaves, near the apex of the trunk and in the terminal portions of large roots. Aggregate soluble and non-soluble sugar pools were about equivalent to six months of copra production or 51 days of crop growth. More studies are needed on the dynamics of these sugars to evaluate their physiological role, particularly with regards to stress periods and fluctuating demand for fruit filling.

Photosynthetic Assimilation, Carbohydrates in Vegetative Organs and Carbon Removal in Nut-Producing and Sap-Producing Coconut Palms

“…Sucrose, the transport form of carbohydrates in many plants, was found to be the dominant sugar in the vegetative parts of coconut (Mialet-Serra et al, 2005). Under favourable environmental conditions, 17 year-old Vanuatu Red Dwarf (VRD) x Vanuatu Tall (VT) hybrid palms, contained little starch but had large quantities of sucrose, mainly located in the trunk.…”

“…Two leaflets from the middle portion of the selected leaf were taken for analysis. Trunk tissues were collected from just beneath the leaf canopy where the highest trunk-carbohydrate content is found (Mialet-Serra et al, 2005). Two core samples were drawn from opposite sides of the trunk, at a depth of 6.0 cm from the surface, using an electric drill with a 5 mm drill bit, causing minimum damage to the trunk.…”

Growth and leaf production in the tropical palm Euterpe edulis: Light conditions versus developmental constraints

“…By contrary, in Cocos nucifera, leaf production and stem growth were invariable when carbon availability changed (Mialet-Serra et al, 2008). It is important to note that palm stem functions as water and carbon storage compartments (Holbrook and Sinclair, 1992;Mialet-Serra et al, 2005), and that stem storage capacity increases with palm height (Holbrook and Sinclair, 1992). The studies of Legros et al (2009a,b) and Mialet-Serra et al (2008) were performed with adult palms, with stems large enough to help buffering imbalances between carbon sources and sinks.…”

Phenology and growth adjustments of oil palm (Elaeis guineensis) to photoperiod and climate variability

“…No model currently exists that captures the specificities of this plant shared in part with other members of the palm family such as coconut (Mialet-Serra, 2005;Mialet-Serra et al, 2008): regular successions of phytomers on a single axis that each potentially produces an inflorescence, a range of phenological adjustment processes to environmental events during specific sensitive stages of phytomer development along its multi-annual phenology, sink -source imbalances, to some extent, stored reserves and, to be confirmed by further studies, photoperiodic control of flowering resulting in latitude-specific, seasonal maxima of flowering and fruiting. Such a model would not only be of interest to oil palm agronomists and breeders but also encapsulate the physiological and developmental organization of a plant type that differs markedly from other cultivated plants such as cereals, legumes and dicotyledonous trees.…”