Cold tolerance of native plants in the Lancang River dry–hot valley: an integrative physiological–biochemical assessment with implications for cold-resistance breeding

Zhang Yunchen¹Yang JianYin^1*Yuan Xu²Yang YanDong³Xiaodong Ji¹Ji JinNan¹Zhang Yan¹Huang Jiao¹

• ¹Beijing Forestry University, Beijing, China
• ²Lancang River Hydropower Co., Ltd., Yun Nan, China
• ³China Huaneng Group Co Ltd, Beijing, China

Extreme winter cold limits vegetation establishment in the Lancang River dry–hot valley. Selecting cold‑ tolerant native species is therefore critical for ecological restoration and for maintaining stable agricultural vegetation. We examined three shrubs, Sophora davidii Kom. ex Pavol., Vitex negundo L. var. microphylla Hand.‑ Mazz. and Rumex hastatus D. Don, and two herbs, Arthraxon lanceolatus (Roxb.) Hochst. and Artemisia vestita Wall. ex Bess. Seedlings were exposed to 25 °C to −35 °C in controlled chambers and membrane injury, gas exchange, chlorophyll fluorescence, osmolytes and antioxidant enzyme activities were quantified. The semi‑lethal temperature, defined as the temperature causing 50% loss of membrane integrity, differed strongly among species, from about −27 °C in Sophora davidii to about −5 °C in Arthraxon lanceolatus. Across the cooling gradient Sophora davidii maintained the lowest electrolyte leakage, retained part of its photosystem II efficiency, accumulated high proline and soluble sμgar concentrations and showed strongly increased superoxide dismutase activity, indicating strong intrinsic resistance to freezing injury. Multivariate analyses integrating chlorophyll fluorescence traits, membrane injury, osmotic adjustment and antioxidant variables identified photosystem II efficiency together with electrolyte leakage as the most informative traits and a robust screening set for cold tolerance. An integrated cold‑tolerance index based on principal component analysis and a membership‑function approach ranked the species as Artemisia vestita > Arthraxon lanceolatus > Vitex negundo var. microphylla > Rumex hastatus > Sophora davidii, which differs from the ranking based on semi‑lethal temperature alone. This discrepancy highlights the risk of inferring cold resistance from a single trait and shows that acute stress responses and long‑term freezing thresholds capture complementary aspects of cold tolerance. The derived physiological thresholds and multi‑indicator framework can guide the selection and breeding of native species for ecological restoration and cold‑resilient agricultural systems in dry–hot valleys of the Lancang River basin.