Moderate warm temperature improves shoot growth, affects carbohydrate status and stimulates photosynthesis of sweet orange plants

Citrus plants were grown under two thermal conditions for evaluating carbon metabolism acclimation to moderate warm temperature (30/20oC, day/night), and its likely impact on plant growth. As reference, plants were grown at 25/20oC, in which they were subjected to optimum temperature for photosynthesis during the diurnal period (25oC). Higher photosynthetic rates were found at 30/20oC as compared to 25/20oC in both mature and young leaves, being this response associated with higher stomatal conductance. After 30 days of thermal treatment, plants grown at 30/20oC presented higher shoot growth as compared to those at 25/20oC. The carbohydrate concentration decreased in stem and root tissues, while it increased in leaf tissues under moderate warm conditions. Both mature and young leaves showed higher photoassimilate consumption/exportation at 30/20oC than at 25/20oC. In this paper, we have proven that citrus plants present a positive balance in carbon metabolism as an acclimation mechanism to temperature changes, with plants presenting increased photosynthesis. Such photosynthetic acclimation was associated with improved vegetative growth, being both mature and young tissues sensitive to changes in thermal regimen.