Diverse responses of tomato to N and P deficiency

Tomato plants were grown hydroponically under different deficient regimes of nitrogen (N) and phosphorus (P) in the form of nitrate and phosphate. Results showed a severe reduction in growth, soluble protein and chlorophylls contents under N deficiency, which suggested accelerating of leaf senescence. Furthermore, it was accompanied by enhanced activity of peroxidase and sugars contents that were both correlated with increased shoot anthocyanins content. Under P deficiency, similar results were observed except reduced concentration of sugars and chlorophylls and that both peroxidase activity and anthocyanins contents were higher in P-deficient plants. On the whole, tomato showed reduced tolerance to N than P deficiency, although N deficiency was more damaging. Reduced content of soluble proteins was an important criterion of N and P tolerance. Plant tolerance to low P supply was accompanied by increased activity of peroxidases and accumulation of anthocyanins.