Respostas morfofisiológicas e bioquímicas de uma espécie exótica e uma nativa da caatinga, sob diferentes condições de disponibilidade hídrica

Abstract

Plants of the Caatinga biome, in addition to going through water limitations, compete for resources with introduced exotic species, where these can cause changes in the phytophysiognomy of this environment. Thus, the present work aimed to evaluate the morphophysiological and biochemical behavior of an exotic species (Megathyrsus maximus) and a native species (Pavonia varians) from the Caatinga, under different water availability conditions. The seedlings of P. varians and M. maximus were collected in a regeneration area of the Catimbau National Park - PE. After collection, they were taken to a greenhouse belonging to the Biology department and transplanted into trays containing washed sand and topsoil, remaining under these conditions for 19 days for vegetative reestablishment. Then the plants were transferred to polyethylene bags for acclimatization for 15 days, and after this period they remained for 35 days under different conditions of water availability (10, 30 and 60% of the pot capacity). Biometric parameters (height, stem diameter, and number of leaves) were evaluated every 7 days. While biochemical analyzes (total soluble proteins, antioxidant enzymes, levels of hydrogen peroxide (H2O2), malondialdehyde (MDA), levels of pigments, sucrose, soluble carbohydrates, and proline content) and anatomical analysis were performed at the end of the experiment. Quantitative data were submitted to ANOVA and compared by Tukey's test at 5% probability. In both species, in the treatments with lower water availability, there was an increase and maintenance in the production of roots, reduction of the leaf area, proving to be important strategies to promote the absorption of water from the soil, seeking to maintain cellular turgidity. water availability, the carotenoid content was maintained in both species, protecting the plants against oxidative damage, as well as the sucrose and total soluble carbohydrates content and the increase in the proline content in M. maximus (51.70% and 83, 67%) as the maintenance of this amino acid in P. varians, acting as osmoregulatory molecules, promoting osmotic adjustment, protecting cells from dehydration. Anatomical analyzes in P. varians showed reduced mesophyll and epidermal cells and in M. maximus showed irregular bulliform cells under the lowest conditions of water availability. Therefore, it was possible to observe similarities in the strategies to tolerate drought in both species, and that the relationship between the osmoregulatory molecules can be one of the main defense strategies to overcome water scarcity in P. varians and M. maximus.