Secamento parcial do sistema radicular em laranjeira doce sob diferentes porta-enxertos

Abstract

Water deficit significantly limits citrus cultivation, affecting productivity and fruit quality due to droughts and high temperatures. Strategies such as Partial Rootzone Drying (PRD) in irrigated crops are essential to optimize water use and address water scarcity. Understanding the morphophysiological responses of plants under different irrigation conditions is crucial for the success of these techniques. This study aimed to investigate the physiological responses of sweet orange trees grafted onto two distinct rootstocks under PRD application. The greenhouse experiment evaluated 'Valencia' orange trees grafted onto 'Cravo' lemon and Sunki 'Tropical' mandarin, with roots divided into two PVC tubes filled with soil. A completely randomized 2x2 design was used, testing two rootstocks and two irrigation regimes: control (100% evapotranspiration) and partial rootzone deficit (PRD, 50% evapotranspiration), with six repetitions per treatment. Water extraction was monitored using Time Domain Reflectometry (TDR), and after 30 days, gas exchange, water use efficiency, and carboxylation were evaluated. The data were statistically analyzed (ANOVA) and the means compared by the F-test at 5% significance. The study revealed that orange trees grafted onto 'Cravo' lemon rootstock extracted more water from the soil than those grafted onto Sunki 'Tropical', which adopted a more conservative water use and carbon assimilation strategy during drought periods. Although 'Cravo' showed superior water use efficiency in one of the tests, the physiological differences between the rootstocks were not significant. The research indicates variations in genotype responses to controlled deficit irrigation, suggesting the need for more in-depth studies, both in greenhouse conditions and in field irrigation management practices.