The growth and distribution of the root system affect the response of the plants to water deficit. This work aim at the to evaluation of 'Valencia' orange budded on 'Rangpur<FONT FACE=Symbol>¢</FONT> lime and Poncirus trifoliata ('Trifoliata') as to root growth, gas exchange (CO2 and H2O), leaf water potential and distribution of carbohydrates in several organs, in plants submitted to water deficit. Plants were transplanted to 32 rizotrons, which allowed root visualization of the roots. Sixteen plants in each rootstock were submitted to irrigation and the other 16 remained without irrigation. Water deficit was induced withholding the water supply. Stomatal conductance declined after the fourth day without irrigation, causing a reduction of the photosynthesis, the transpiration and the carboxilation efficiency. The total carbohydrate content (sucrose + reducing sugars + starch) in plants without water stress was greater in 'Trifoliata', and among the water deficit treatments it was always less. The dry phytomass of the plants without water deficit was greater in both rootstocks. Among the irrigated and non irrigated treatments, the length of the roots same of rootstocks was similar. However, the root lengths of plants on 'Rangpur' lime were significantly greater than that on 'Trifoliata'. Even under water deficit and great decrease of the photosynthetic production, the roots maintained growth, possibly at the expenses of mobilized substrates of other plant parts.
Carbohydrates; Citrus sinensis; vegetative growth; 'Rangpur' lime; 'Trifoliata'; gas exchange
