Uso de protetor solar para minimizar os efeitos do excesso de luminosidade e aumento na temperatura do ar sobre a fotossíntese e pegamento de frutos em citros

Abstract

The foliar application of products that act similar to a sunscreen, of the kaolin type, can prevent oxidative damage, by reducing the leaf temperature, maintaining the stomatal opening and improving the assimilation of CO2. This study aimed to evaluate the use of this sunscreen to minimize the effects of climatic stresses on photosynthesis, fruit setting, productivity and fruit quality in citrus. The experiment was conducted in an experimental orchard, of Hamlin sweet orange [Citrus sinensis (L.) Osbeck], grafted on Swingle citrumelo [C. paradisi Macf x Poncirus trifoliata (L.) Raf.], at the Sylvio Moreira Citriculture Center (IAC), municipality of Cordeirópolis, SP. The treatments were T1- control and T2- kaolin (30 g L-1). The number of buds, flowers and fruits calculated for each 100 nodes were evaluated weekly, defining the percentage of plant fruit taking, in addition to the fruit diameter after the physiological fall that occurred around 16/01/2019, in addition to fruits fixed on the east and west sides of the plant. The average leaf temperature throughout the experiment and productivity in kg of fruits were also evaluated. By measuring gas exchanges made on 8/25/2018, at two times, at 9:00 am and 1:00 pm with the help of IRGA, Li-6800, Inc. Lincoln, USA, it was defined as stomatal conductance, transpiration and assimilation of CO₂ for old leaves and new leaves, both for the east side and for the west side. At the end, the fruits were submitted to juice quality analysis. The application of kaolin during the flowering and fruit setting period did not affect the flowering intensity and the number of fixed fruits. There was no effect on leaf temperature. During the harvest of the fruits there was no effect on the final production and quality of the fruits. However, it is necessary to highlight that during the fruitful period in the 2018/19 harvest, no limiting conditions were registered for production in the state of São Paulo.