Growth characteristics and physiological disorders of cucumber grafted seedlings exposed to low temperatures

This study evaluated the growth characteristics and physiological disorders of different cucumber (Cucumis sativus L.) cultivars exposed to low temperatures. Cucumber (‘NakWonSeongcheongjang, NS’, ‘Sinsedae, SD’, and ‘Goodmorning backdadagi, GB’) seedlings were grafted onto the figleaf gourd (Cucurbita ficifolia ‘Heukjong’) seedling. The grafted cucumber seedlings were grown in a plant factory with artificial light at 10, 15, and 20°C, respectively. As the temperature decreased, plant height, number of leaves, leaf area, Fv/Fm, fresh weight, and dry weight decreased in all cucumber cultivars. And growth and development of the roots tended to be delayed as the temperature decreased. Chilling injury was observed in the leaves of cucumber seedlings at 10 and 15°C. At 10°C, the leaves of cucumber seedlings showed symptoms of albinism and necrosis. At 15°C, the leaves of cucumber seedlings turned yellow, and the SPAD value was significantly lower than other temperature treatments. In all treatments, the Fv/Fm of the three cultivars was below 0.72 and tended to decrease with decreasing temperature. This means all treatments were subjected to cold stress due to the low temperature, with a particular emphasis on the 10°C. Therefore, the results of this study suggest that the temperature in cucumber seedling nurseries should be increased to at least 15°C to mitigate the effects of cold stress.