Gas exchange of seedlings of taxi-branco submitted to leaf temperature variation and irrigation suspension/Trocas gasosas de plantas jovens de taxi-branco submetidas a variacao de temperatura foliar e suspensao da irrigacao

The study aimed to investigate the influence of leaf temperature variation associated with irrigation suspension on gas exchange of seedlings of Sclerolobium paniculatum Vogel. The study was carried out in a greenhouse at experimental area of Embrapa, Amazonia Ocidental. Plants were grown in a greenhouse and, after four months were subjected to three treatments (irrigated maintained until the field capacity, irrigation suspended for eight and 14 days). We evaluated the physiological parameters of gas exchange, net assimilation rate of C[O.sub.2] (A), leaf transpiration (E), stomatal conductance ([g.sub.s]) and water use efficiency (WUE) which were obtained through a photosynthesis portable meter (CI-340, CID, Inc). The results showed reduction of net assimilation rate of C[O.sub.2] depending on the elevation of the leaf temperature and without irrigation. After eight days without irrigation, decreased rates of photosynthetic assimilation of C[O.sub.2] in 62, 65, 75, 58, 50 and 64%, and after 14 days the reduction was 80, 85, 85, 84, 86 and 93% compared to plants irrigated maintained at temperatures of 25, 30, 35, 40, 45 and 50[degrees]C, respectively. The leaf transpiration was inversely proportional to rates of net photosynthetic assimilation of C[O.sub.2], which has increased with an increased leaf temperature. The physiological behavior of gas exchange of Sclerolobium paniculatum