Moléculas sinalizadoras em sementes de milho para tolerância a estresses abióticos

Abstract

Abiotic stress is a growing concern in maize production, with factors such as drought, salinity, and high temperatures challenging its productivity. These adverse conditions trigger the formation of reactive oxygen species (ROS), which can damage plant cells. However, plants possess a robust antioxidant system, composed of enzymes such as catalase, peroxidases, and superoxide dismutase, that act to neutralize ROS. This system can be activated using priming techniques, such as soaking seeds in solutions that activate defense mechanisms. This approach, therefore, represents a viable tool to increase agricultural productivity and ensure food security in the face of challenges imposed by climate change and other environmental stress factors. The objective of this study was to analyze the efficiency of seed physiological conditioning in the presence of signaling molecules for inducing tolerance to abiotic stresses during seed germination and maize seedling development, as well as to evaluate the physiological and biochemical aspects of seeds under these conditions during storage. Three experiments were conducted: one under water stress, saline, and control conditions; another under high-temperature and control conditions; and a third with five storage periods of pre-applied conditioning treatments on maize seeds under four germination conditions, with four replications. Therefore, the first experiment was conducted in a 6x3x3 factorial scheme, with six conditioning solutions, three stress conditions, and three cultivars; the second in a 6x2x3 factorial, with six conditioning solutions, two germination stress conditions, and three cultivars; and the third in a 5x4 factorial, with five storage periods and four germination conditions. The seeds were subjected to physiological conditioning in a B.O.D. at 24 °C for 24 hours in aerated solutions of indole-3-acetic acid, melatonin, sodium nitroprusside, hydrogen peroxide, and chitosan. Subsequently, the seeds were subjected to physiological tests under the proposed germination conditions. The following were determined: water content; germination; first germination count; abnormal seedlings; primary root length, shoot length, primary root width, total seedling length, and root-to-shoot length ratio; H2O2 extraction and lipid peroxidation; analysis of the enzymes superoxide dismutase, catalase, and ascorbate peroxidase. Means were subjected to analysis of variance, and when significant, mean tests were applied. Physiological conditioning improves the physiological quality of seeds, even under favorable conditions for plant development. The use of hydrogen peroxide and indole-3-acetic acid as conditioning solutions provides better quality for seeds of different Zea mays L. genetic materials under water and saline stress. Additionally, the use of indole-3-acetic acid and melatonin via conditioning was effective under high temperature stress. Under these conditions, generally, higher germination and vigor, lower percentage of abnormal seedlings, lower H2O2 concentration and lipid peroxidation, and higher enzymatic activity were observed. Prolonged storage of conditioned seeds can lead to deterioration of their germination capacity, a process influenced by various factors, including temperature, humidity, storage conditions, and chemicals used in conditioning.