Aspectos ecofisiológicos e potencial de recuperação em mudas de Dipteryx alata Vogel sob alagamento e sombreamento

Abstract

Dipteryx alata Vogel is a tree widely found in the Brazilian Cerrado and its main importance is related to family farming with the commercialization of almond and its by-products, as income supplement, in addition this species is also promising for the recovery of degraded areas. The constant environmental and climatic changes, also considered abiotic stresses, affect plant development and growth, which may modify long-term biomes. As an example of this stress, we can highlight flooding, which occurs occasionally in that region where D. alata is found. Although, plant responses to water stress by flooding involve several metabolic changes that may assure vegetal adaptability and survival. Besides, the knowledge about luminosity of species can reduce stressful effects. Thus, the aim of this study was to evaluate the morphophysiological and biochemical changes in D. alata seedlings under shading levels and flooding times, as well as the potential for seedling recovery. In the first experiment, we evaluated the photosynthetic metabolism and seedling quality under three levels of shading (0% – full sunlight, 30% and 70%) with two water regimes (flooding and control), but also, the periods of evaluation which lasted 60 days of flooding and periods of recovery which consisted of 100 days after the end of flooding. We verified that flooding reduced gas exchanges, chlorophyll a fluorescence, plant height and seedling quality, however this species recovered or showed recovery trend for the most characteristics evaluated 100 days after the end of the stressful condition, showing the best results with the reduction of flooding under 30% of shading. The seedling quality and plant height did not show recovery or any tendency to recover from flooding, in addition the leaf area was also compromised by the stress. In the second experiment, we evaluated the effects of flooding on photosynthetic and antioxidant systems as well as the seedling quality of D. alata during four periods of evaluation (0, 20, 40 and 60 days) and also during the periods of recovery, in which consisted of 100 days after ending each period of evaluation (0 + 100, 20 + 100, 40 + 100, 60 + 100 days), allowing us to study the effects of post-flooding. Our results suggested that flooded seedlings were sensible to stress up to 60 days of evaluation showing the most visible damages in photosynthetic apparatus, however seedling quality was maintained up to 40 days of evaluation, but there was not the recovery for previously-flooded plants up to 60 days. Morphological changes, such as hypertrophied lenticels, associated with physiological changes and an efficient antioxidant enzyme system must have contributed to the recovery of these seedlings, then conferring tolerance to stress. Thus, we may suggest by these results the use of D. alata seedlings in projects with degraded areas where flooding occurs temporary, in which the establishment of these plants must occur in shading conditions, for example, by pioneer species already implanted.