Changes in macroelement content in the pith of sago palm (Metroxylon sagu Rottb.) with palm age

Abstract The contents of N,P,K Ca, and Mg in the pith of sago palm trees differing in age (estimated years after sucker planting or emergence), growing in shallow peat soil (SPS) and mineral soil (MS) at Mukah, Sarawak, Malaysia, were determined to analyze the changes in macroelement contents with agiug. The average content (g kg sup(-l)) in the pith of trunk was in the order of K > Ca > N=> Mg > p, regardless of the soil types in which the trees grew and palm ages. The contents of all the elements except for P were higher in the younger palms and decreased until the trees were 8-10 years old (4-6 years after trunk formation) and hardly changed afterwards. P content in the pith was remarkably lower than that of other elements and minimal changes were observed with aging. The content gradient of each element except for K was observed from the basal low content) to top part (high content) of the pith for the longitudinal distribution in the trunk, while the K content was almost the same content along the longitudinal direction in the trunk, regardless of the palm ages. The N and Mg contents were higher in the peripheral part than in the central part, while no appreciable differences were observed for P,in terms of content gradient of each macroelement along the radial direction in the pith. The Ca content was higher in the central part than in the peripheral part at the palm age of 4-6 years old, but the content tended to be higher in reverse after the palm age of 8 years old. The K contents were higher in the peripheral part than in the central part as in the case of the N and Mg contents at the palm age of 4-6 years old, but thereafter, the highest content was observed in the central, middle and peripheral parts of the pith in the basal, central and top parts of the trunk, respectively. Accumulation of the macroelements in the pith which was in the order of K > CA > N > Mg > P, followed a S-shaped pattern as well as the increase of pith dry weight, regardless of the soil types, although the amount of K accumulated was higher in the sago palms growing in MS than in those growing in SPS at the same palm age. Based on the results obtained, the K content and accumulation among the macroelements in the pith of sago pallm were not only highest but also the distribution pattern of the content differed from that of other elements, and it was suggested that the relation between the K content and starch synthesis in the pith should be clarified.