LEAF STOMATAL CONDUCTANCE AND STOMATAL MORPHOLOGY OF MUSA GERMPLASM

Drought tolerance combined with resistance to black sigatoka (BS) dise ase are two desirable traits for plantains in some parts of the tropic s. Field evaluation of leaf stomatal conductance, single leaf transpir ation rate, photochemical efficiency, and role of stomata in BS resist ance, was done for 18 genotypes of Musa spp., which included diploid a nd triploid banana and plantains and tetraploid plantain hybrids, at a sub-humid and a humid site. Conductances were significantly (P less t han or equal to 0.01) higher for leaf abaxial than adaxial surfaces (S ), while clonal (C) differences were significant (P less than or equal to 0.05). Interactions between sampling period (T: morning vs afterno on) and location (L), and clone and location (C x L) were significant for both conductance and transpiration; (C x T x L) interaction was si gnificant for conductance. Significant interactions for (C x L) and (C x T) suggested that conductance and transpiration of a specific clone need to be considered for a given environment. Total variation in con ductance was explained by the following variables: S, C, (C x L), (C x T), and(C x L x T). In general, ABB cooking banana had higher conduct ances than other Musa taxonomic groups (AAB, AA, AAA, and AAAB). Evalu ation of morphological and physiological traits of leaf stomata indica ted that the resistance to BS disease is due to non-stomatal mechanism s.