Increasing Chilling Resistance of Cucumber Seedlings by Some Plant Growth Regulators

Plants with tropical origin including those of the Cucurbitaceae family are generally sensitive to chilling stress and harmed by low temperatures. In this study، we evaluated five plant growth regulators and compared the effectiveness of each substance in improving chilling stress tolerance of cucumber (Cucumis sativus L.، cv. Super dominos) seedlings. The experiment was conducted as a randomized complete block design with seven treatments including: control، seed and foliar application of Catechin and oxalic acid and foliar application of Metyl jasmonate، Metyl salicylat and salicylic acid with. After treatments، the seedlings were subjected to chilling 5h/day at 3oC for 7 days. 72 hours after chilling، all plants were evaluated with some chilling resistance indices and growth parameters. Results showed that application of Catechin، Oxalic acid and salicylic acid improved growth parameters and increased tolerance to low temperature of the seedlings as indicated by electrolyte leakage، proline and malondialdehyde content. These substances ameliorated the by chilling stress-induced injury via enhancing chlorophyll and proline content and subsequently decreases in leaf electrolyte leakage and malondialdehyde content. Catechin and oxalic acid were more effective in increasing chilling tolerance of cucumber seedlings، when applied with seed soaking method than with foliar spray. In general، it may be concluded that Catechin، oxalic acid and salicylic acid could be used effectively to protect cucumber seedling from damaging effect of chilling stress at the early stages of growth.