Desempenho fotossintético e relações hídricas em duas variedades tradicionais de arroz do Pantanal Mato-Grossense cultivadas com e sem alagamento

Abstract

Rice is of paramount importance for food security as it is one of the most produced and consumed cereals in the world. However, the crop is extremely susceptible to water stress, especially during the reproductive stage, significantly affecting production. With the advancement of large-scale agriculture, more productive varieties replaced traditional varieties, often adapted to local growing conditions, quenching, over time, most of the genetic diversity of crops. In São Pedro de Joselândia, Pantanal Mato-Grossense, farmers cultivate two traditional varieties of rice with relevant characteristics for the preservation of the crop's biodiversity. The objective of this work was to evaluate the physiological changes on the photosynthetic and productive potential of two traditional varieties of rice, from Pantanal Mato-Grossense (Branquinho and Agulhinha Vermelho, compared to a commercial material (BRS-Esmeralda), grown in flooded condition or not. We evaluated the photosynthetic response curve of liquid at chloroplast CO2 concentration (PNxCc curve) and photosynthetically active flux density (PNxI curve), the fluorescence of chlorophyll, the photosynthetic pigment content, growth parameters and producing and water relations obtained from pressure-volume curves (PV curve). It was found that stomatal conductance (gs), the intercellular concentration of CO2 (Ci) and the relationship between Ci and the concentration of CO2 in the air (Ci/Ca) suffered a reduction when the species was cultivated in a nonflooded condition in relation to the flooded cultivation. However, the net photosynthetic rate (PN), as well as the variables associated with chlorophyll fluorescence, the content of photosynthetic pigments and the parameters derived from pressure-volume curves (PV curves) did not differ significantly between water availability conditions. It was found that the non-commercial varieties did not show significant physiological variation as to the parameters studied depending on the cultivation condition, apparently not being a problem cultivation in non-flooded condition; however, it is important that work is carried out to assess behaviour of these varieties under conditions of water deficit.