Under hydroponic condition, number and size of potato tubers are usually controlled by nutritional factors such as nitrogen (N), phosphorus (P), and pH. The main objective of the present study was to find an appropriate combination of N, P, and pH (with respect to tuber number) under hydroponic sand culture and to evaluate the physiological traits affected by nutrients and pH. A factorial experiment based on completely randomized design with four replications was conducted. Results showed that higher phosphorus concentration for 10 days increased tuber number per plant, but tuberization was not influenced by nitrogen interruption and intermittent reduction of pH. Neither N, P, nor pH treatments affected total nitrogen concentration of potato leaf, stem, and tuber. Higher phosphorus concentration increased the level of endogenous abscisic acid (ABA) and indole- 3-acetic acid (IAA), induced tuberization and thereby increased net photosynthesis rate of potato plants.

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