Combined influence of low temperature and drought on different varieties of rapeseed (Brassica napus L.)

In recent years, due to the change of farming system, delayed the sowing time of rapeseed, and low temperature and drought would affect the sowing quality, seedling growth, and rapeseed yield.Thirty-one rapeseed materials were screened for low-temperature drought resistance; Zayou15 (ZY15) was selected as low temperature and drought resistance, Huiyou48 (HY48) was established as moderate low temperature and drought resistance, and Huiyou49 (HY49) was identified as low temperature and drought-sensitive.Low temperature and drought stress significantly decreased the germination potential (GP), germination rate (GR), germination index (GI), seed vigor index (SVI) of rapeseed during the germination period and increased the average germination time. Drought intensified the influence of low temperature on germination traits. ZY15 exposed 74-98% germination in 4-5.5 days under 10, 15, and 20°C at all water potentials. HY48 revealed 44-98% germination in 4.5-7 days under 10, 15, and 20°C at all water potentials. Likewise, HY49 disclosed 41-97% germination in 5-8 days under 10, 15, and 20°C at all water potentials. The relative water content of leaves decreased considerably due to drought and low temperature. These also considerably affected the chlorophyll content(Chl). Low-temperature and drought resulted in significant increase of intercellular carbon dioxide (CO₂) concentration(Ci), significant reduction in net photosynthetic rate(Pn), stomatal conductance(Gs), transpiration rate(Tr), and a decrease in Fv/Fm. The activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbic peroxidase (APX) increased in rapeseed seedlings by low temperature and drought. The contents of auxin (IAA), gibberellin (GA), and abscisic acid (ABA) in rape leaves were increased under low temperature and drought, while the content of cytokinin (CTK) was decreased. The average performance of ZY15 was better than HY48 and HY49, while HY48 performance was better than HY49 under combine stresses. This study found that antioxidant enzymes and hormones are beneficial for plants to cope with adverse conditions. The current study confirmed that in rapeseed seedlings, the combined effect of low temperature and drought stress negatively impacts seedling growth and development, but this impact varies with varieties and surrounding conditions.