Abstract Application of superabsorbent polymers is an efficient approach for optimal use of water and for improvement of crop yield. In this research a greenhouse experiment based on complete randomized block was carried out with three replications to investigate the effects of bentonite (natural superabsorbent) on growth, biochemical and physiological properties of spinach (Spinacia oleracea). Treatments include three levels of bentonite (0, 40 and 80gr) and four level of humidity (100%, 75%, 50% and 25% of field capacity). Results indicated that there was significant difference between the effects of humidity, bentonite and their interaction on studied traits (dry and fresh weights of root and shoot, chlorophyll content, electrolyte leakage, proline content and antioxidative activity; p<0.01). Reduction of humidity from 100% to 75% of FC in bentonite-lacking beds was followed by growth indices with the root being the exception. Proline and phenolics content, electrolyte leakage and carbohydrate content were also enhanced; however, total chlorophyll content and antioxidative activity were decreased. The highest chlorophyll content was observed in the beds possessing the highest bentonite concentration. These results support the idea that application of sufficient bentonite can, to large extent, decrease harmful effects of drought stresson crops.

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