Crescimento inicial e acumulação de osmólitos em duas espécies arbóreas que crescem na restinga, Schinus terebinthifolius Raddi (Anacardiaceae) e Terminalia catappa L. (Combretaceae), submetidas ao alagamento

Abstract

Soil flooding is an abiotic stress that results in consequences for plant growth and development, threatening the survival of non-tolerant species. Diverse natural environments face different adversities, such as high temperatures and floods, and these effects can be intensified by climate changes, which cause an increase in ocean temperatures and sea levels. Considering the impacts of flooding and the importance of species conservation in threatened ecosystems, the present study aimed to evaluate the initial growth and osmolytes accumulation in two Restinga tree species, Schinus terebinthifolius Raddi and Terminalia catappa L., subjected to flooding soil. After the germination and acclimatization, the experiment was conducted in a greenhouse, with sixteen plants of each species, distributed in two treatments, control and flooding, during sixteen days, with a randomized block design. The length of the stem and root, stem diameter, variation in the number of leaves, ratio of chlorotic and/or necrotic leaves, leaf area, specific leaf area, and biomass allocation were determined. Moreover, the relative water content, rate of electrolyte leakage, SPAD index, photosynthetic pigment content, and osmolyte accumulation in leaves and roots were evaluated. Flooding resulted in a reduction in stem growth, number of leaves and, consequently, leaf area and biomass allocation in leaves, with more significant impacts on T. catappa. There was an increase in biomass allocation in the stem for T. catappa. Flooding caused an increase in specific leaf areas, which may be related to the low investment in leaf biomass. The relative water content and rate of electrolyte leakage did not differ between treatments. Chlorophyll a and b content was lower only in T. catappa. The protein concentration in the leaves did not vary in response to flooding, but a reduction was observed in the roots. The concentration of soluble sugars was also lower in the roots, which could mean more significant use of solutes in the fermentation process and damage to the plants energy supply. We observed more significant amino acids and proline accumulation in the flooded treatment in both species, associated with a tolerance mechanism to damage to the cell membrane. However, the accumulation of osmolytes may not have protected T. catappa against stress, impairing the translocation of sugars from the leaves to the roots. The impact of flooding on a native and an exotic plant was different for the period evaluated. T. catappa was more sensitive to flooding, considering the reductions in growth, photosynthetic pigment content and energy supply, so S. terebinthifolius had greater tolerance to flooding of the root system, related to its biochemical characteristics compared to this species.