Gas exchange and nutrient content in leaves of physic nut irrigated with wastewater and doses of phosphorus

With the objective of evaluating leaf gas exchange and nutrient concentration in plants of physic nut irrigated with wastewater of domestic origin an experiment was conducted in protected ambient adopting randomized block in factorial layout, to study the effects of five levels of hydric reposition - HR (0.25; 0.50; 0.75; 1.00 and 1.25 times of water consumed by the plant), and two levels of phosphorus (135 and 200 g P2O5 plant(-1) year(-1)) with four repetitions. The data of leaf gas exchange were obtained using a portable photosynthesis meter (IRGA). To determine the nutrient content of the plant, fourth and fifth leaves below the inflorescence was used. The reduction in water supply provoked reduction in the rate of carbon assimilation, limiting the production capacity of the physic nut plants. The increase in level of hydric reposition with wastewater resulted increase in leaf gas exchange, notably in the rate of carbon assimilation. The accumulation of the nutrient follows the sequence: N > K > Ca > Na > Cl > Mg > P > S > Fe > Mn > Zn > Cu, and with the increase of water supply the leaf contents of phosphorus, zinc and copper increased. The doses of P2O5 did not influence the contents of studied elements.