Salicylic acid mitigates the effects of mild drought stress on radish (Raphanus sativus) growth.

Water deficit is the most critical factor limiting plant growth and production and salicylic acid (SA) has potential for stress mitigation in plants; therefore, we evaluated the effect of SA on radish (Raphanus sativus L.) growth and ecophysiology under water deficit. Plants were sprayed with SA (100 μM) or water (control), and irrigated at 80% (W80), 60% (W60), 40% (W40), and 20% (W20) of field capacity. The SA treatments and drought stress started 7 days after sowing and lasted until the end of the cycle (30 days after sowing). The morphophysiological analyses showed that radish plants had impaired growth at the lower water supply levels, but the treatment with SA reversed these growth restraints under moderate stress, leading to increases in shoot mass at W40 and storage root mass at W60 and W40. SA treatment also reversed the reduction of storage root volume at W60. The tendency of water deficit to increase F _O and reduce F _V/ F _M suggests possible damage to the photosystem II of drought-stressed plants. The parameters of gas exchange and photosynthetic pigments showed maintained photosynthetic efficiency, but total photosynthesis decreased due the lower shoot dry mass. Overall, exogenously applied SA reversed the growth restraints at W60 and W40, which revealed that SA was effective in mitigating the effects of moderate water deficit on biomass accumulation and partitioning in radish plants. Water is essential for crop production, and global warming is aggravating the threat of drought. To overcome this, we evaluated the potential of salicylic acid, a natural plant product, to induce drought tolerance in radish; salicylic acid was efficient in reversing the reduction in radish production at mild drought. This discovery will help farmers to avoid crop losses at moderate drought and to ensure food security worldwide. [ABSTRACT FROM AUTHOR]