Using transplants for growing pepper (Capsicum annuum L.) is widespread, but little is known about seedling response to transient N and P supply during tbe nursery growth stage. The objective of this work was to study the effect of steady and alternating N and P concentrations in solution culture on pepper seedling development, dry-matter production rate, and N and P uptake rates, to allow better control of production by transplants. Seedlings were grown in trays of pyramidal cells, packed with vermiculite and floated on well-aerated nutrient solutions of high (6 mM) or low (1 mM) N and high (0.25 mM) or low (0.01 or 0.03 mM) P. Dry-matter accumulation in seedling tops as a function of time conformed in all treatments to a first-order exponential equation. The growth rate constant was significantly higher in the high than in the low N or P concentrations. Root growth rate was less affected by the N and P solution concentration than was the top growth rate. Five-day-long alternations of solution concentration from high to low and from low to high N and P significantly changed dry-matter production rate and nutrient content in plants. Growth and uptake rates regained their original values when seedlings were re-exposed for 5 d to the original solutions. The rapid changes in growth rate were attributed to rapid variations in the flux of N and P uptake in response to changes in solution concentrations, which affected N and P concentration in plant organs. Varying N and P concentrations in tops affected drymatter production rate, whereas variations in N and P concentrations in roots influenced the flux of uptake of P and N, respectively.
Using transplants for growing pepper (Capsicum annuum L.) is widespread, but little is known about seedling response to transient N and P supply during tbe nursery growth stage. The objective of this work was to study the effect of steady and alternating N and P concentrations in solution culture on pepper seedling development, dry-matter production rate, and N and P uptake rates, to allow better control of production by transplants. Seedlings were grown in trays of pyramidal cells, packed with vermiculite and floated on well-aerated nutrient solutions of high (6 mM) or low (1 mM) N and high (0.25 mM) or low (0.01 or 0.03 mM) P. Dry-matter accumulation in seedling tops as a function of time conformed in all treatments to a first-order exponential equation. The growth rate constant was significantly higher in the high than in the low N or P concentrations. Root growth rate was less affected by the N and P solution concentration than was the top growth rate. Five-day-long alternations of solution concentration from high to low and from low to high N and P significantly changed dry-matter production rate and nutrient content in plants. Growth and uptake rates regained their original values when seedlings were re-exposed for 5 d to the original solutions. The rapid changes in growth rate were attributed to rapid variations in the flux of N and P uptake in response to changes in solution concentrations, which affected N and P concentration in plant organs. Varying N and P concentrations in tops affected drymatter production rate, whereas variations in N and P concentrations in roots influenced the flux of uptake of P and N, respectively.