Mitigation of High Temperatures with Ascophyllum nodosum Biostimulants in Papaya (Carica papaya L.) Seedlings
Elevated temperatures pose a significant threat to plant metabolism and physiological processes, ultimately reducing agricultural productivity. The application of bio-stimulants represents a potential strategy to mitigate the adverse effects of heatwaves on crop cultivation. This study investigated the effects of two commercially available products, Baltiko® and Acadian®, both containing extracts of the seaweed Ascophyllum nodosum, on ‘Aliança’ papaya seedlings.
Six different concentrations of each product (0, 1, 2, 3, 4, and 8 milliliters per liter) were applied weekly over a four-week period. These applications were conducted at two distinct times to simulate conditions of moderate and high temperatures. The findings of the study revealed that the bio-stimulant treatments had different impacts on gas exchange, seedling development, and the concentration of nutrients in both the leaves and roots of the papaya seedlings, depending on the temperature conditions.
During the period characterized by moderate temperatures, increasing the dosage of the bio-stimulants generally led to enhanced gas exchange and increased aerial development of the seedlings. Additionally, there were increases in the levels of potassium and boron in the leaves, while root growth tended to decrease with higher doses. Acadian® treatment resulted in higher concentrations of boron in both the leaves and the roots compared to treatment with Baltiko®.
In contrast, during the period of elevated temperatures, increases were observed in leaf area, root dry mass, and the leaf content of several essential nutrients, including phosphorus, potassium, sulfur, and zinc, as well as potassium in the roots. These positive changes were primarily attributed to the application of the bio-stimulant products. Based on the observed results, the study suggests that a lower dose of the bio-stimulants, specifically 3 milliliters per liter, is recommended for application during periods of mild temperatures, Debio 0123 while a higher dose, around 6 milliliters per liter, is more beneficial for mitigating the effects of elevated temperatures on ‘Aliança’ papaya seedlings.