Pivotal role of fibrous roots in drought tolerance of saffron (Crocus sativus L.) and mitigation of oxidative stress by penconazole

We investigated the effects of PEG-induced drought on the antioxidative mechanisms of Crocus sativus L. and the mitigating effects of PEN on drought tolerance. Contents of H₂O₂ and MDA in fibrous roots were considerably lower than those in leaves and were attenuated by PEN pretreatment. Activities of CAT, SOD, and POX were significantly higher in fibrous roots than in leaves. Among antioxidative enzymes, POX activity in fibrous roots was 600-2000-fold higher than that in leaves. The increase in CAT and SOD activities under the influence of PEN in the fibrous roots is the main reason for the decrease in MDA levels and highlights the important role of this organ in the response to drought stress. A somewhat similar increase in CAT activity was also observed in the leaves under drought conditions due to PEN. Under drought, PEN led to a significant increase in carotenoid content and an elevated ratio of Chl a to Chl b in the leaves. However, in spite of the higher content of non-enzymatic antioxidants in leaves than in fibrous roots, the lower MDA levels in fibrous roots indicated greater efficiency of antioxidative enzymes in controlling membrane lipid peroxidation. In conclusion, the results demonstrate that PEN can mitigate oxidative damage in saffron under drought conditions by enhancing the activity of SOD (up to 275%) and CAT (up to 189%) and by increasing proline content (up to 50%) in fibrous roots.