Carbon metabolism in coffee plants and its interaction with water and phosphorus availabilities

Abstract

The water deficiency and low phosphorus (Pi) availability are important limiting factors to crop growth and yield under tropical conditions. The aim of this project is to test the hypothesis that a high phosphorus availability will alleviate the negative effects of water stress on carbon metabolism of young coffee plants. Coffee plants cv. Catuaí (Coffea arabica L.) will be subjected to three phosphorus treatments: low availability (P-); recommended availability (PA); and high availability (P+). Plants will grown under such conditions until those plants of P- treatment show visual symptoms of P deficiency. At this time, we expect that all Pi reserve in plant tissues was used and depleted. So, physiological responses to subsequent water deficit will be driven only by the additional phosphorus supplying (PA and P+ treatments). In the experiment I, plants will be subjected to two water levels (80 or 30% of soil field capacity) for 90 days, being evaluated the long term response to water deficit in plants of treatments PA and P+. In the experiment II, plants will be subjected to water withholding or maintained with soil at 80% of field capacity, being evaluated the short term response to water deficit in PA and P+ plants. Leaf gas exchange, photochemistry, leaf water potential, whole-plant hydraulic conductance, leaf pigment content, leaf carbohydrate content, dry mass, plant morphological characteristics and chemical composition of plant tissues will be evaluated in both experiments. Both experiments will be in randomized blocks, following the splitsplitplot design. Data will be subjected to analysis of variance and the mean values (n= 5 to 10) compared by the Tukey test (a=0.05). (AU)