Leaf gas exchange and water potential (psil) were assessed daily and seasonaly in four varieties of dwarf coconut (Cocos nuficera L.) under field conditions: Cameroon Red Dwarf (CRD), Gramame Red Dwarf (GRD), Gramame yellow Dwarf (GYD) and Jiqui Green Dwarf (JGD). All varieties showed strong reduction of stomatal conductance (gs) values in the dry season. At this period, transpiration (E) and net photosynthesis (A) rates decreased largely in JGD and in GRD, when both genotypes presented greater values of intrinsic water use efficiency (A/gs) than in wet season, specially JGD. Taking in account all genotypes studied in wet season, the leaf gas exchange was conditioned by photosynthetic photon flux density (PFFD) and by gs values. On the other hand, during the dry season, leaf gas exchange was correlated only with gs values. The variety CRD did not restrict E in dry season, showing the lowest psil but holding the highest A values per day among genotypes under drought. Contrastingly, the genotype JGD could control efficiently E intensity, maintaining the highest A/gs ratio despite of reduced A values in dry season. In dwarf coconut plantations with high technical management such as in irrigated areas, the CRD could be the most suitable variety to achieve favorable carbon balance during the year.
Cocos nucifera L.; stomatal condutance; transpiration; net photosynthesis
