Validação de um protótipo portátil para quantificar o teor de água foliar por método óptico

Abstract

Lack of water has become a serious problem in modern times, an increasingly scarce resource if there is no better management. Each crop needs a specific amount of water for better development and yield. Considering this aspect it is very important to study the best way of quantifying possible indicators for water surplus or deficit, thus improving water management. An alternative for optimize water resources in agriculture in a rational way is to obtain the value of the plants hydration level. In general, plant hydration level can be estimated by visual symptoms or measured quantitatively in terms of water content or plant energy status. Therefore, water conditions in the plant tissues can be evaluated both by the content as the water free energy. The water content is expressed in relative content and saturation deficit while free energy is expressed in total water potential in the plant. Some techniques aim the measurement of leaf water potential, which allows, among others, control the need and quantity of irrigation. However, most existing techniques for determining water potential involve water vapor pressure determinations in equilibrium or use pressure camera; with limitations on the high sampling number and the destructive analysis, as well as indirect measurements in the soil. Besides, the techniques for measuring leaf water content are indirect methods, such as leaf temperature. The measurements of potential and water leaf content need some care in order to observed if data reflect the true plant water status. The aim of this study was to validate a low cost portable device to analyze water activity in the field leaf, obtaining the water content in the plant leaf. The method uses the biospeckle laser phenomena (non destructive) and is divided in several stages, from the illumination and the capture of leaves images by the prototype to the images analysis by statistical methods.