Ecofisiologia de Schinus terebinthifolius Raddi (Anacardiaceae) sob estresse hídrico

Abstract

Some temporal variation regarding resources availability is observed in Brazilian Cerrado, especially when it comes to water resources, which are essential to plants physiology. Therefore, in order to occupy this kind of biome, plants show morphological or physiological adaptations that will assure them obtaining and efficient utilization of available resources in the area.The objective of this study was to evaluate seeds germination performance, initial growth and seedling quality of Schinus terebinthifolius Raddi (Anacardiaceae), as well as its water and photosynthetic metabolism, and then, verify the plant’s adaptive capacity or the plant’s water stress tolerance. In the experiment one, the tubes were irrigated in order to keep 25, 50, 75 and 100% of soil water holding capacity, and they were kept covered. Among all evaluated characteristics in the chapter one, the best soil water holding capacity was 75%. In the second experiment, the vases were distributed in two groups: 1 – Control, in which the plant’s hydration occurred periodically in order to keep 75% of soil water holding capacity. 2 – Water stress, in which irrigation was suspended until the rate of photosynthesis was at or near zero, and then they were irrigated again and for the following twelve days, keeping 75% of the soil water holding capacity followed by one more suspension and resuming irrigation cycle. In order to evaluate the effect of intermittent water deficit in the beginning of the experiment, during the suspension and resuming irrigation cycle, and when the rate of photosynthesis was near to zero, the plants were analyzed in four different periods (T0, 1º F0, 1º S/R, 2º F0). The water stress decreased the rate of photosynthesis, the stomatal conductance and transpiration, the rubisco carboxylation efficiency, the chlorophyll content, and the number of leaves. Consequently, it decreased the plant growth of the S. terebinthifolius species. Plants recovered their rubisco carboxylation efficiency, but they had not had their rate of photosynthesis increased. The Dickson Quality Index did not vary for water-stressed plants and it was higher for Control plants. The level of antioxidants enzymes increased both in the aerial part and in the roots. The water stress meaningfully reduces growth and quality of S. terebinthifolius Raddi seedlings, since they cannot recover after rehydration. There were no alteration in the number and layout of tissue layers; however, it was observed foliar tissue thickness reduction in respond to water deficit.