Root hydraulic properties of eucalyptus in response to nitrate and phosphorus deficiency and sudden changes in their availability

CORINA GRACIANO; ANNA ZWIENIECKA; MACIEJ ZWIENIECKI

LA PLATA

Congreso; XXVIII Reunión Argentina de Fisiología Vegetal; 2010

ASAFV

Nitrate and phosphorus are two important nutrients and they differ in mobility in soil matrix: nitrate is mobile while phosphorus is not. Thus, plant strategy to facilitate their uptake can be different. Recently, it was suggested that some high nitrate demanding plants could increase root conductivity to chase mobile nitrate around the soil matrix. However, fast changes in root hydraulic properties in the case of immobile phosphorus may not be an optimal strategy. The aim of this study was to analyze short and long-term hydraulic properties of Eucalyptus grandis plants that might reflect its strategy of optimization of nutrient acquisition. E. grandis has low nitrogen and high phosphorus needs. Transpiration, whole plant resistance and single root resistance of eucalypt plants grown in high and low nitrogen combined with high and low phosphorus availability were measured. In general, plants grown under high nitrogen availability had higher transpiration rate than plants grown under low nitrogen. Sudden addition of nitrate reduce transpiration rate irrespective if plants had been grown under high or low nitrogen and phosphorus. Addition of phosphorus did not change transpiration rate. Plants grown under high nitrogen had lower whole plant resistance than plants grown under low nitrogen conditions. Addition of nitrate did not change either single root or whole-plant hydraulic resistance. Therefore, fast changes in transpiration rate observed after the addition of nitrate would be due to changes in stomatal conductance. While plant hydraulic architecture results from long-term exposure to nitrogen availability. Adaptive significance of observed responses suggest that E. grandis behavior aims primarily at water conservation either short-term reduction in transpiration when nitrate needs are met by sudden addition of nitrate or long-term higher adjustments in whole-plant resistance to water loss at low nitrogen availability when water loss is not paid by higher nitrogen uptake.