Arbuscular mycorrhizal fungi and balanced ammonium/nitrate ratio synergistically enhance cold tolerance of Hordeum jubatum by modulating root structural plasticity and ion homeostasis - Chongyuan Qin; Jinji Han; Jingnan Zhang; Bing Gao; Zhuoran Tan; Yingxin Han; Yinuo Pan; Jinghong Wang; Shuhua Lu (Rhizosphere, 2026)