Algas marinhas e melatonina na indução da tolerância ao calor e déficit hídrico no mamoeiro e pimenteira-do-reino
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Data
2025-02-28
Autores
Ferreira, Thayanne Rangel
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Universidade Federal do Espírito Santo
Resumo
Abiotic stresses cause physiological and biochemical imbalances, such as stomatal closure, reduced photosynthesis, alterations in water balance, biomass allocation, and carbohydrate metabolism, ultimately compromising plant growth and productivity. One strategy to minimize the effects of these stresses in agriculture is the use of biostimulants. This study aimed to develop and validate sustainable strategies using seaweed extracts and melatonin to mitigate heat and water deficit in plants, promoting crop resilience and contributing to more sustainable and productive agriculture.Three experiments were conducted. The first evaluated two commercial products (Baltiko® and Acadian®), both containing extracts from the seaweed Ascophyllum nodosum, applied to ‘Aliança’ papaya (Carica papaya L.) seedlings. Six doses (0, 1, 2, 3, 4, and 8 mL L⁻¹) were applied weekly for four weeks during two distinct periods under moderate and high temperature conditions. The two following studies involved drought and recovery trials with ‘Aliança’ papaya seedlings and black pepper (Piper nigrum L.) v. Bragantina. Prior to the imposition of drought stress, foliar applications of melatonin and seaweed extracts (Ascophyllum nodosum and Lithothamnium calcareum) were carried out. The results showed that the effectiveness of the commercial products Baltiko® and Acadian® varied depending on the dose and climatic conditions. Baltiko® stood out in improving water use efficiency, while Acadian® enhanced gas exchange and boron uptake. Therefore, dose adjustment according to environmental conditions is recommended: 3 mL L⁻¹ under moderate temperatures and 6 mL L⁻¹ under high temperatures. Under heat stress, increased evaporation and vapor pressure deficit reduce product availability to the plant, requiring higher doses to ensure treatment efficacy. Foliar applications of melatonin, A. nodosum, and L. calcareum were effective in mitigating the effects of drought stress in both ‘Aliança’ papaya and Bragantina black pepper seedlings. These treatments promoted higher water retention by lowering leaf water potential and favored the recovery of leaf water potential after rehydration periods. In papaya, chlorophyll a fluorescence revealed that photosynthetic functionality was more affected during the second drought cycle, with inhibition of the photosynthetic apparatus at that stage. In contrast, in black pepper, the greatest impact on photosynthetic performance occurred during the first drought cycle. Water stress reduced chlorophyll content, possibly as a strategy to minimize photo-oxidative damage. Among the tested biostimulants, melatonin and L. calcareum stood out by enhancing vegetative growth, indicating better adaptation to water deficit conditions
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Bioestimulantes , Carica papaya , Ciclos de seca , Piper nigum , Mudas , Temperaturas elevadas , Bio-stimulants , Drought cycles , Seedlings , High temperatures