Aspectos fisiológicos e da produção do arroz em resposta ao silício / Physiological and productive aspects of rice plants according to silicon supplying

Kelly da Silva Coutinho Detmann

The objective of this study was to analyze the role of supplemental silicon (Si) in the biomass accumulation and grain yield of rice (Oryza sativa L.). Different experiments were carried out in which wild rice plants (japonica subsp. Oochikara - WT) and mutant defective for the absorption of Si - lsi1 (Low silicon rice 1) were raised under hydroponics conditions with different Si supplementation (0 or Si 2 mmol Si L-1). In the first experiment, it was performed an allometric analysis to evaluate the pattern of biomass allocation in different phenological stages according to Si supplying. In this study, regardless of genotype, it was shown that Si does not change the allocation of biomass in the first two phenological stages, but it increased grain yield in both genotypes (34% in WT and 24% in lsi1). In the second experiment, plants were allowed to grow with or without supplemental Si during the growing season. After that, when the early reproductive stage was reached, half of plants in each treatment (-Si and +Si) was crossed over with regard Si supplementation totalizing four treatments (-Si/-Si, -Si/+Si, +Si/-Si, and +Si/+Si). The Si was found to be more effective to increase productivity in the reproductive stage compared to vegetative stage. The addition of Si in the reproductive stage caused a prominent increase in grain production (number of grains per panicle). It was also observed an increase in photosynthetic rate but no changes in leaf angle was caused by Si supplying. Different ratios of grains number to leaf area were established to evaluate the effects of Si on the growth, production and photosynthesis. Such analyses were performed by linking advance gas exchange and chlorophyll a fluorescence measurements with carbon isotope labeling and metabolic profiling. Considering this, the third experiment consisted of WT and lsi plants with and without panicle, and raised with or without supplemental Si totalizing four treatments. Addition of Si increased the number and mass of individual grains. As a consequence, it seemed to cause some modifications on the source-sink relations. Such changes in the sink stimulated the photosynthetic activity in the leaf. That effect was primarily associated with an increased mesophilic conductance. However, the actual cause of that alteration still remains to be explained. In addition, supplemental Si changed the primary metabolism by stimulating the remobilization of amino acids.

Aspectos fisiológicos e da produção do arroz em resposta ao silício / Physiological and productive aspects of rice plants according to silicon supplying

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