A.完全關(guān)閉 B.開(kāi)得更大 C.關(guān)不攏 D.開(kāi)閉無(wú)常
A.20-30% B.40-50% C.100% D.80-100%
A.土壤水分含量過(guò)低 B.土壤水勢(shì)過(guò)低 C.土壤鹽堿 D.土禳結(jié)冰