Alterações metabólicas e nutricionais de pseudocereais submetidos ao elevado CO2 e alagamento

Abstract

Responsible for causing a series of extreme weather events, climate change can lead to droughts, floods, rising temperatures and increased emissions of greenhouse gases such as carbon dioxide (CO2). Since there is growing evidence that environmental changes and its impacts are leading to an understanding of potential pressures on the ability to ensure adequate food supplies for the human population, it is extremely important to comprehend how plants and natural ecosystems will respond to these changes. Thus, the present work aimed to investigate the potential effects of two different agents of climate change: CO2 and flooding. Therefore, amaranth plants cv. BRS Alegria and quinoa cv. BRS Piabiru were evaluated in the transitional stage between vegetative and reproductive, since this is considered the key event for the reproduction of cultivated plants. Three studies were carried out: in open top chambers (OTC's) with different levels of CO2 (400 and 700 ppm) evaluating the primary and secondary metabolism; in growth chambers where the seeds obtained in the previous experiment were evaluated for parental effects; and the third experiment involved submitting the plants to the condition of soil flooding. As a result, it was possible to observe that both cultures are capable of altering their primary and secondary metabolism due to elevated concentrations of CO2. Changes in gas exchange, saccharolytic enzymes and carbohydrate metabolism reflected in growth parameters and photosynthetic pigments when at elevated CO2 levels. These changes altered the nutritional dynamics of several nutrients, harming the productive potential of crops. In addition, evaluations related to secondary metabolism showed us there was an increase in antioxidant capacity, betalains and phenolic compounds. These results suggest that there was a generation of reactive oxygen species during the photosynthetic process. When evaluating amaranth and quinoa seeds and seedlings from plants grown in a CO2-enriched environment, a parental effect can be observed in seeds and seedlings. The first germination count and the germination speed index showed that although its germination potential was not altered, this initial process occurred in a more accelerated way. These results could be confirmed through the biochemical activity of α-amylase and acid phosphatase enzymes in different periods and CO2 concentrations. In another experiment, the plants were submitted to different periods of flooding, both species showed severe metabolic alterations when submitted to flooding in the periods of 48 and 96 hours. However, during recovery, photosynthetic pigments showed values close to the control, helping to maintain gas exchange in the fight against ROS only by amaranth and plants. On the other hand, analyzes of the invertases showed that sucrose synthase was not able to complete the cleavage process in its entirety. This suggests that compounds essential for metabolic pathways such as fructose and glucose were absent, in addition to a possible imbalance of sucrose between shoots and roots. The results of the present research show significant advances for the management of both crops in the face of climate change. However, studies aimed at the nutritional quality of these pseudocereals in the proposed scenario are still necessary.