Irradiance availability and growth of leguminous trees of cerrado.

We evaluated photosynthetic performance, growth, and biomass partitioning in tree species Anadenanthera falcata and Stryphnodendron adstringens growing under full solar irradiance and in the shade equivalent to that found in understory of the Cerradão physiognomy. The study was conducted free of water stress by watering, in São Carlos, state of São Paulo, Brazil, until 1140 days after sowing (DAS). We obtained irradiance and leaf gas exchange data with a portable infrared gas analyzer. In the sunny area, both species presented higher respiration in the dark, light saturation point, regular and potential photosynthetic capacity and higher apparent carboxylation efficiency. Besides, under full solar irradiance, the total biomass, leaf area, height, stem diameter, and the total number of leaflets were significantly (p<0.05) higher at 240, 360, and 570 DAS. S. adstringens did not survive in the shade after 1140 DAS, while A. falcata showed a survival of 100% under both irradiance regimes. The irradiance attenuation in dense physiognomies of cerrado vegetation, as that found in Cerradão, affected several levels of plant organization since early growth. Our results highlighted how natural irradiance availability in Cerrado vegetation determined per se the carbon balance, the development and the survival of tree species.