Arquitetura radicular e relações hídricas de plantas cítricas

Abstract

Root architecture affects the growth of the plant and its agricultural production, although it is related to genetic factors, water and physical limitations of the soil can reduce the rooting volume and of soil explored, thus compromising the vegetal and productive development. With the objective of evaluating root architecture and water relations of citrus plants regarding drought tolerance and physical impediments in the soil, experiments were conducted in the field and in greenhouse, using management practices, which included direct seeding of the rootstock at the final site of the orchard, subsoiling, the diversification of rootstocks, and the most recent, the creation of artificial macropores, aiming to minimize these physical-water limitations. The plants were submitted to the continuous drying of the compacted soil in polyvinyl chloride (PVC) laminated columns under controlled conditions, and to the rainfed cultivation, under field conditions, in cohesive soils of Coastal Trails. The growth of the area, the root architecture and the water relations were evaluated through measurements of soil moisture and physiological measurements. In the field condition, the initial production of fruits was also evaluated. The results of the field studies (Chapter I and II) confirm that, independent of the management practices adopted, the root system distribution is characterized by the superficiality, imposed by the cohesive horizons, with a concentration of the first 0.40 m depth, on the projection of the crown, the initial responses being similar to those of the long term. Among the management practices adopted, planting of protected seedlings (PM) grown in a screened nursery, and 'Cravo' lime rootstock (LC), were more effective in the extraction of water from the soil to the greater root vigor and aerial part, being also attributed to this rootstock the greater initial production of fruits. Moisture in the first 0.40 m of the soil along with the upper roots should be the best indicator for vigor, productivity and water status of the plant, grown under rainfed conditions. The soil structure is preponderant for root development, and the use of artificial macropores (Chapter III) serve as channels of lower resistance for the root growth of 'Cravo Santa Cruz' lime in compacted soil columns, however their number and distribution did not influence the growth of the area and root volume, probably due to the exploitation of the soil in the upper layer, in the control condition.