Agentes promotores da mitigação do déficit hídrico em mudas de Talisia esculenta (A. St. Hil) Radlk

Abstract

Drought is an increasingly frequent and worrying condition in the agricultural scenario, and therefore the search for strategies to mitigate the deleterious effects of this condition has increased, which can cause morphological and physiological changes in plants, which are decisive during the production and development of seedlings of several species. As an alternative to this problem, we have the use of substances and application of techniques that provide a reduction in the impact of water stress on plants. However, data on the action of these mitigators in forest species, especially in native Brazilian species, are scarce. Thus, we aimed to evaluate the potential of shading and the application of silicon and salicylic acid in mitigating the stressful effect of water deficit in seedlings of Talisia esculenta Radlk. In the first experiment, divided into two experimental trials arranged in a completely randomized design, the impact of shading on the development and photosynthetic metabolism of seedlings was evaluated, which were grown under 0, 30 and 70% shading for 30 days. In addition, the effect of shading in the face of water deficit on the development and metabolism of seedlings grown for 30 days under the following treatments was evaluated: 0% + irrigation; 0% + water suspension; 30% + irrigation; 30% + water suspension; 70% + irrigation; 70% + water suspension. When only the impact of shading was evaluated, it was observed that the 70% level was more beneficial to the development of T. esculenta seedlings, as it provided higher quality seedlings with greater photosynthetic performance. When shading was evaluated in view of the water deficit submitted to seedlings, it was observed that the deficit caused damage to the photochemical activities in photosystem II and gas exchange, resulting in seedlings with lower quality. The 70% shading alleviated the stressful effect of the water deficit, enabling better photosynthetic performance and seedling quality. In the second experiment, the potential of silicon (SI) and salicylic acid (SA) applications in mitigating the effects of water deficit on the metabolism of seedlings that were grown under the treatments: irrigation, irrigation suspension, irrigation suspension + SI 0.5 g L −1, irrigation suspension + SI 1.0 g L −1, irrigation suspension + SA 50 mg L −1 and irrigation suspension + SA 100 mg L −1 was evaluated. The lowest doses of SI and AS were efficient in mitigating the damage caused by water deficit, promoting a rapid recovery of the photosynthetic capacity of the seedlings after the return of irrigation, as well as providing higher quality seedlings after this period. The application of 0.5 g of Si also provided the highest plasticity indices of A, A/Ci and Fv/F m, which indicates a greater potential for ecological resilience. Therefore, the 70% condition presented the greatest potential for the initial development and establishment of the species, while the application of silicon and acid at low doses was able to mitigate the deleterious effects of water deficit.