Photosynthetic metabolism and growth of pineapple (Ananas comosus L. Merr.) cultivated ex vitro

Pineapple (Ananas comosus L.) is a bromeliad with constitutive CAM metabolism. However, facultative C3/CAM metabolism in the first 2 months of growth is a characteristic of this species. Thus, young pineapple plants can exhibit C3 photosynthesis when the environmental conditions, such as the diurnal temperature range and water supply, are favorable to growth. However, high temperature diurnal amplitude, soil/air moisture alterations and changes in light intensity in association with air humidity have caused facultative C3/CAM metabolism. The objective of the study was to assess the physiology and growth of ex vitro ‘Vitória’ and ‘IAC Fantástico’ pineapple genotypes during acclimatization from the in vitro environment. The research was carried out in a greenhouse using the split plot design used in the in vitro culture (Couto et al, Rev Bras Frutic 36(2):459–466, 2014). The explants were planted in trays with Vivatto® substrate. The net photosynthesis rate, growth and photochemical efficiency were measured at 60 and 75 days of acclimatization (DA). The greater growth (canopy diameter and height, shoot dry mass, total dry mass and leaf area) of ‘IAC Fantástico’ was associated with CAM metabolism. CAM metabolism was likely induced by the stressful environmental micrometeorological variables inside the greenhouse. In contrast, ‘Vitória’ exhibited C3 metabolism and reduced growth at 60 and 75 DA. ‘Vitoria’ had greater photosynthate partitioning to the root system and high photochemical efficiency 75 DA. We conclude that the stress imposed by the environmental conditions induced CAM metabolism in ‘IAC Fantástico’ and increased growth gain characteristics at 60–70 DA.