Condutância estomática em folhas de feijoeiro submetido a diferentes regimes de irrigação Stomatal conductance in leaves of bean plants submitted to different irrigation regimes

O controle estomático é importante propriedade fisiológica por meio da qual as plantas limitam a perda de água, ocasionando reduções na condutância estomática e, geralmente, reduzindo as trocas gasosas como forma de resposta das plantas a diversos fatores, incluindo o estresse hídrico. O objetivo deste trabalho foi determinar a condutância estomática em folhas de feijoeiro submetido a diferentes regimes de irrigação. O experimento foi conduzido no Departamento de Engenharia Rural da Faculdade de Ciências Agrárias e Veterinárias de Jaboticabal - SP. As irrigações nos tratamentos foram determinadas em função do esgotamento de água no solo: T1 - irrigado quando esse atingiu 40% da capacidade de água disponível (CAD); T2 - quando atingiu 60% da CAD; T3 - quando atingiu 80% da CAD, e T4 - não irrigado (irrigado somente para favorecer a emergência das plântulas). As medições de condutância estomática foram realizadas diariamente no campo, nas duas faces da folha, utilizando-se de um porômetro. Em todos os tratamentos, em diversas medições, foi observada redução da condutância estomática em resposta a baixos valores de potencial mátrico e a altos valores de déficit de pressão de vapor e vice-versa. As folhas das plantas do tratamento T4, que foram submetidas a menor disponibilidade hídrica no solo, apresentaram os menores valores de condutância estomática durante os estádios do florescimento e enchimento de grãos.<br>Stomatal control is an important physiological process for plants to reduce water loss. It causes reduction in stomatal conductance and generally in gas exchanges, as a response of several factors including water stress. The objective of this study was to determine the stomatal conductance of bean leaves submitted to different irrigation regimes. Field experiment was conducted at the São Paulo State University, in Jaboticabal, Brazil. Irrigation of the treatments occurred when available water capacity in the soil decreased to 40; 60 and 80% (respectively, treatments T1, T2 and T3), while irrigation in T4 occurred only to assure seedling emergence. Direct measurements of stomatal conductance were taken every day under field conditions in both adaxial and abaxial leaf surfaces using porometer. In all treatments, several measurements showed reduced stomatal conductance in response to low values of matric potential and high values of vapor pressure deficit (DPV) and vice-versa. The lowest values of stomatal conductance of T4 leaves, taken from plants under the most restrictive water supply regime tested in this study, were observed during the period of plant flowering and grain development

Estimating Foliar Pigment Concentration of Rice Crop Using Integrated Hyperspectral Index

Part 1: GIS, GPS, RS and Precision FarmingInternational audiencePhotosynthetic pigment concentration has strong relationship with nitrogen (N) concentration which is an essential element of plant growth and plays an important role in estimating the net primary productivity (NPP) in terrestrial ecosystem research and precision agriculture (PA). In this study, hyperspectral reflectance and pigment concentration of the upper three leaves of rice crop (Oryza sativa L.) with five N fertilization rates were measured in the laboratory. The results showed that there was no significant difference between the leaf hyperspectral reflectance and pigment concentrations in the visible and near-infrared (NIR) spectral regions at each leaf position. But in the shortwave infrared (SWIR) region, the difference of each two of the three leaf positions was obviously significant at level 0.05. The integrated hyperspectral index MCARI/OSAVI[670,800] had been proved to be better linear related with leaf pigment concentrations at different leave position. The result demonstrated that MCARI/OSAVI[670,800] was a reliable and stable hyperspectral index for estimating pigment concentration at leaf level