Panga-panga (Millettia stuhlmannii Taub.) responses to atmospheric demand and water availability

Abstract

Mozambique government plans to expand the national forestry planted area to 1 million ha in the next decades. However, the lack of information on how native trees respond to Mozambique main climate is an obstacle to forestry expansion. The limitation in water availability combined with adverse temperature are the main constraints to tree growth in the country. Thus the objective of this study was to characterize the effect of atmospheric demand combined with water availability levels on the morphological and physiological characteristics of Panga-panga (Millettia stuhlmannii). To do that, the seedlings were put in pots inside air-conditioned greenhouses under two atmospheric conditions: high demand (T = 21.2 and VPD = 0.29 kPa) and low demand (T = 26.9 and VPD = 1.49 kPa), and under four water availability conditions in the soil (100, 80, 60 and 40% of the water holding capacity in the substrate). In addition, growth, gas exchange and pigment analysis were performed after 86 days of experimentation. The highest values of photosynthesis, stomatal conductance and transpiration occurred under high atmospheric demand combined with 100% of water availability. Our results revealed that the magnitude of growth losses due to individual effects of water availability limitation or low atmospheric demand were similar, but worsen when Panga-panga seedlings were exposed to both conditions combined.