Biometric, physiological and anatomical responses of Passiflora spp. to controlled water deficit

The species of passion fruit (Passiflora spp.) are cultivated commercially for food, medicinal and ornamental purposes, especially in tropical regions of the planet subject to intense seasonal drought. This study assessed biometric, physiological, and anatomical responses of P. edulis, P. gibertii, P. cincinnata, P. alata and P. setacea to controlled water deficit. Seedlings with five months of age were subjected to soil water deficit imposed by irrigation suspension until the complete stomatal closure. All assessed species were susceptible to water deficit, with 50-75% reduction in vegetative growth, even though distinct mechanisms of coexistence with this stress were demonstrated by the evaluated genotypes. P. gibertii and P. edulis showed vigorous growth, quick closing and stomatal opening in response to soil water content, the first being more efficient in extracting water from the substrate even with lowest soil water storage. The effects of water deficit were postponed in P. setacea and P. cincinnata, which showed reduced leaf area and stomatal conductance even under irrigation, particularly in P. setacea. P. alata showed large leaf area but lower stomatal conductance and decreased root system by irrigation suspension. P. alata was the species that showed the most anatomical changes resulting from water deficit, such as reductions in the thickness of the leaf blade, adaxial epidermis, palisade parenchyma, and spongy parenchyma. On the other hand, P. setacea was the species that showed greatest ability to survive under water restriction due to tolerate prolonged drought periods with minor anatomical changes when compared to the control.