Leaf photosynthetic responses of passion fruit genotypes to varying sunlight exposure within the canopies

摘要: Passion fruit plants (Passiflora spp.) have very dense canopies so that leaves located at the top of them can shade the ones more internally located. This change physiological and morphological leaf traits. Here we used gas exchange chlorophyll a fluorescence parameters as tools to evaluate responses of full sun-light exposed (FSE) leaves, at intermediate position (IP) shaded (S) three Passiflora genotypes [P. edulis f. flavicarpa (Maguary selection—FB 100) (M); P. giberti (G) cincinnata (C)]. FSE presented greater net photosynthetic rates (A net ), what accounted for increasing both intrinsic water use efficiency efficiency. Otherwise, grown adapted environments tended always show low A values, although such values were increased 12:00, when light availability was improved. Leaves IP S leaves presented higher ratio internal ambient CO2 concentration (C i /C a ) likely due reduced carboxylation photoprotection mechanisms against high intensities, while leaves under lower intensities (IP S) showed variable responses of fluorescence, depending on genotype.