Contrasting Cold Tolerance and Underlying Physiological Mechanisms in Two Rye Varieties during Seed Germination and Seedling Stages
This study investigated the physiological mechanism underlying cold resistance differences between two rye(Secale cereale)cultivars,White BK-1 and Dongmu-70,during seed germination and seedling stages.The results showed that seed germination rate,germination potential,root length,stem length,and seedling biomass were all significantly greater in White BK-1 compared to Dongmu-70 under cold stress(4℃),indicating superior cold tolerance.Low temperature exposure resulted in damage to pho-tosynthetic tissues within rye mesophyll cells,leading to a significant decrease in net photosynthetic rate(Pn).White BK-1 exhibited a smaller reduction in Pn and a faster recovery rate after stress alleviation.Chlorophyll content in rye leaves initially increased with prolonged cold stress,followed by a subsequent decline.Additionally,chlorophyll a/b ratio decreased under cold conditions.Malondialdehyde(MDA)content increased in rye leaves under cold stress,but to a lesser extent in White BK-1.Exposure to cold stress triggered the accumulation of osmotic regulators in rye leaves,while antioxidant enzyme activity exhibited a biphasic response,initially increasing and then declining.White BK-1 displayed a more robust response to cold stress by maintaining higher levels of soluble sugars and proline accumulation,as well as sustaining greater Pn and antioxidant enzyme activity.
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