Alterações fisiológicas e anatômicas em plântulas de Annona muricata L. (graviola) e Annona squamosa L. (pinha) submetidas a estresse salino

Abstract

Annnonaceae family approximately 128 genus and 2300 species. (Judd, 1999), being the Annona muricata L.. andAnnona squamosa L. the most important species of this genus (Pinto e Silva, 1995). Salinity can affect some processes in the plant life cycle. Plant responses to salt exposure are complex and involve alterations in morphology, physiology, anatomy and primary and secondary metabolism. Therefore, salt stress effects can be studied by analyzing aspects related to anatomical, metabolic and growth alterations. The main objective of this work was to analyze the anatomical (through the light microscopy and scanning electron microscopy), metabolic (amino acid composition), growth and development alterations (roots length, shoots length, fresh weight, dry weight and leave surface) in A. muricata L. and A. squamosa L. seedling esposed to salinity (NaCl) in the Unidade Experimental Horto Florestal, Universidade Estadual de Feira de Santana. The experiments were performed in a 12:12 h light/dark cycle at 26º C/ 20º Cin a hydroponic system and the salt trataments were carrid out five different concentrations of NaCl (0, 3, 100, 300 and 500 mM ) for periods of 1, 2 and 3 days for 2 weeks old seedlings. Similar experiment was carrid ourt two months old seedlings which were exposed to 0, 100 and300 mM NaCl for periods 1, 2, 3 and 7 days. The growth of A. squamosa seedlings was more affected by NaCl than A, muricata seedlings. Root length and leaf area for both species were inhibited by the hightest NaCl concentrations test. However, for A. muricata the fresh weight and shoots length remained at the levels of the control plants. Te analyses of fresh and dry wight suggested that the reduction in growth observed was due to water uptake reduction, but not a decrease in the rate of photosynthesis. The Annona muricata L. exhibited a better control of stomata opening under salt stress. Anatomic alterations such as chloroplast size (increased volume) were cleary observed under NaCl treatment in both species whereas the leaves of A. muricata exiibited an increased number of trichomes, including in control plants which suggest to salinity. The presence of Cl - in the different tissues of both the species showed that this ion was almost equally distribuited within the plant system since it was not observed any accumulation in the roots. It was also present in the leaves. The amino acid analysis allowed to demonstrated the presence of prolina in leaves of both the species when exposed to the highest concentrations oh NaCl indicating the salt stress has been established in the seedlings.