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

TLDR: In this paper, the responses of full sun-light exposed (FSE) leaves, leaves at intermediate position (IP) and shaded leaves (S) of three Passiflora genotypes [P. edulis f. flavicarpa (M); P. giberti (G) and P. cincinnata (C)].

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