Effect of hardening treatments on chilling stress tolerance of cucumber seedlings

Chilling stress is major limiting factor on growth and development of tropical crops like cucumber in early of growing season. In this research, the possibility of chilling hardening of cucumber seedlings was investigated through pretreatment of drought and temperature. The factorial experiment was consisted of two factors including cucumber cultivars (i.e. Super dominos and Super star) and hardening treatments (control, 10 °C, and 15 °C as well as 10% and 20% PEG) based on CRD in three replications in 2017. After applying treatments and providing them 48 h opportunity to be recovered, the seedlings were subjected to 3 °C for a six days period and 6 h for each day. The results showed that hardening increased cucumber growth under chilling stress. Hardening treatments improved seedlings’ chlorophyll content, chlorophyll a/b ratio, relative water content, proline accumulation, and hydrogen peroxide while reducing electrolyte leakage content. It was not observed a significant difference between cultivars in terms of measured traits. The highest chilling tolerance was obtained by 10 and 20% PEG. Overall, the results of this experiment showed that employing drought and temperature pretreatments are able to mitigate the harmful effects of chilling on cucumber seedlings.