Fisiologia metabólica e sinalização no desenvolvimento reprodutivo da cana-de-açúcar sob a influência de piraclostrobina

Abstract

Sugarcane (Saccharum spp.) is one of the most important crops, being a source of worldwide industrial production in both the food and bioenergy sectors. Flowering directly affects its production, since this process consumes sucrose stored in the stem for the development of floral structures. One of the strategies in the creation of new technologies for production gains is the use of the fungicide pyraclostrobin, which has often been related to physiological effects on plants. Data still under analysis, support the hypothesis that pyraclostrobin can promote some type of signaling with the induction of flowering, supposedly, via sugar and nitrogen metabolism. In this sense, the objective of this work was to investigate the influence of pyraclostrobin on photosynthetic and respiratory responses, as well as on the production of nitric oxide (NO), in sugarcane. Additionally, the objective was to evaluate the consequences of these effects on growth, development, and flowering based on RNA-seq analyzes. For that, an experiment was carried out with plants grown in a pot and another experiment under field conditions. In the pot experiment, photosynthetic parameters, respiration, chlorophyll, and carotenoid contents, and nitric oxide production were evaluated. In the field experiment, a new management system was evaluated to optimize and validate the effects on growth and development, and flowering. Also, the data were investigated from the analysis of the plant transcriptome with and without the application of pyraclostrobin. The results showed that sugarcane plants, submitted to treatment with pyraclostrobin, showed faster responses to the increase in light radiation. There were increases both in respiration and in the levels of photosynthetic pigments. NO production was increased in the leaves of treated plants. The analyzed variables had different responses with treatment. In the field, the plants had an increase in the diameter and height of the stalk, showed a reduction in the pith process, an extension of the vegetative growth phase and an increase in the final productivity. Qualitative data from the visualization of the meristematic region showed that the model of 3 applications of pyraclostrobin has the potential to inhibit the flowering of sugar cane. RNA-seq analyzes suggest that pyraclostrobin is involved in stress regulation, in thermal tolerance mechanisms linked to plant production, in photosynthetic regulatory mechanisms, in impacts on source-drain relationships, chloroplast and mitochondrial signaling, and regulation in the flowering induction.