Photosynthetic response of umbu trees to vapor pressure deficit

Abstract

Abstract The objective of this work was to evaluate the photosynthetic response to vapor pressure deficit (VPD) in umbu (Spondias tuberosa) tree accessions. The experiment was carried out in a completely randomized design in a 5×7×2 factorial arrangement (five umbu accessions – BRS-68, EPAMIG-05, BGU-61, BGU-75, and BGU-50 –, seven evaluation times, and two reading times – at 8 a.m. and 2 p.m.) in split-split plots in time. Leaf temperature increased with air temperature. The variation of stomatal conductance and transpiration with the VPD was not significant. Net photosynthesis rate, carboxylation efficiency, and instantaneous water-use efficiency decreased with increasing VPD in all accessions, except in BRS-68, whose rates remained positive.

Keywords

• Spondias tuberosa
• carboxylation efficiency
• correlation
• ecophysiology
• giant umbu