EFFECT OF N, K, CI ON PHOTOSYNTHESIS AND WATER RELATIONS OF OPEN POLLINATED TALL (typica) COCONUT SEEDLINGS

Abstract

CO2 assimilation and plant water status were measured in sand-culture-grown amputatedcoconut seedlings treated with three levels ofN, K, and CI and subjected to different soil waterdeficit conditions. Application of increased levels of N and K enhanced the assimilation of C02while individual and combined effects of N,K, and CI improved the water economy of coconutseedlings. Under the soil water deficit conditions, adequate supply o fN helped to maintain highleaf water potential by the accumulation of solutes like proline and sugars. Whereas, adequatesupply of K and Cl themselves acted as osmotica by increased accumulation of these nutrients inleaf tissues, although other solute concentrations such as those of sugars and proline were reduced.Our data show that maintenance of sufficient levels of N and K contribute to the growth of thecoconut seedling through improved gaseous exchange, CO2 assimilation and better partitioningof assimilated carbon into shoot and roots, potassium and C1 are further important for maintenanceof water status of coconut seedlings by improved stomatal regulation, water uptake and osmoticadjustment of tissues under water deficit conditions.