膜脂中不饱和脂肪酸的含量:决定膜相变温度 不饱和脂肪酸含量越高,引起膜相变的温度越低。 含不饱和脂肪酸越多的物种和品种,抗冷性越强 例:粳稻〉籼稻 >)Ratio of unsaturated and saturated fatty acids of membrane lipids of mitochondria isolated from chiling-sensitive and chiling- resistant tissues )Chilling-sensitive tissues: 》Bean shoot 2.8 > Sweet potato tuber 17 》 Maize shoot 2.1 》 Tomato green fruit 2.8 )Chilling-resistant tissues > Cauliflower buds 3.2 > Turnip root 3.9 》Pea shoot 3.8
膜脂中不饱和脂肪酸的含量：决定膜相变温度 • 不饱和脂肪酸含量越高，引起膜相变的温度越低。 • 含不饱和脂肪酸越多的物种和品种，抗冷性越强。 例：粳稻 > 籼稻 »Ratio of unsaturated and saturated fatty acids of membrane lipids of mitochondria isolated from chilling-sensitive and chillingresistant tissues »Chilling-sensitive tissues: » Bean shoot 2.8 » Sweet potato tuber 1.7 » Maize shoot 2.1 » Tomato green fruit 2.8 »Chilling-resistant tissues: » Cauliflower buds 3.2 » Turnip root 3.9 » Pea shoot 3.8
Three different chilling responses .(A)Compared with in lipid mutants of Arabidopsis. WT-type(left ) the fad6 (right) becomes chlorotic after 3 weeks at5°c (B)fad2 die after 7 weeks at6°c; c)Compared with WT-type(left), the fab1 (D) (right unaffected by upto1 week at2°c; D) After 4 weeks at 2°c, however,fab1 (right show clear symptoms of chlorosis and reduced growth
Three different chilling responses in lipid mutants of Arabidopsis. • (A) Compared with WT-type (left), the fad6 (right) becomes chlorotic after 3 weeks at 5°C; (B) fad2 die after 7 weeks at 6°C; • (C) Compared with WT-type (left), the fab1 (right) unaffected by up to 1 week at 2°C; (D) After 4 weeks at 2°C, however, fab1 (right) show clear symptoms of chlorosis and reduced growth
二、冻害( Freezing stress):主要由零下低温 使植物组织结冰所引起。 1、胞外结冰: 环境温度缓慢下降,质外体(细胞间隙)结冰, 引起胞质水分亏缺; 2、胞内结冰 环境温度骤然下降,质外体与共质体均结冰,冰 在形成或融化过程中对亚细胞精细结构的机械伤害。 HO temperature Cell wall Plasma Ice formation membrane in cell wall
二、冻害（Freezing stress）：主要由零下低温 使植物组织结冰所引起。 1、胞外结冰： 环境温度缓慢下降，质外体（细胞间隙）结冰， 引起胞质水分亏缺； 2、胞内结冰： 环境温度骤然下降，质外体与共质体均结冰，冰 在形成或融化过程中对亚细胞精细结构的机械伤害
植物耐受冻害的生理机制 1、膜稳定性:改变膜脂的构成(脂肪酸不饱和 度、膜固醇和脑苷脂的丰度、膜蛋白的性质) 2、基因表达改变:COR5 a gene,转基因拟南芥 表现强抗冻性; 3、抗冻蛋白(AFPs: antifreeze proteins 在低温驯化期间形成,专一分泌并累积与细 胞间隙; AFPs以大表面寡聚复合体覆盖于冰晶表面, 抑制冰晶的增大 AFPs存在于真菌、昆虫、鱼与植物(尤其 为过冬植物)中
植物耐受冻害的生理机制 1、膜稳定性：改变膜脂的构成（脂肪酸不饱和 度、膜固醇和脑苷脂的丰度、膜蛋白的性质）； 2、基因表达改变：COR15a gene, 转基因拟南芥 表现强抗冻性； 3、抗冻蛋白(AFPs：antifreeze proteins) 在低温驯化期间形成，专一分泌并累积与细 胞间隙； AFPs 以大表面寡聚复合体覆盖于冰晶表面， 抑制冰晶的增大； AFPs 存在于真菌、昆虫、鱼与植物（尤其 为过冬植物）中
A B B Water plus a purified AFP, a glucanase, from winter rye; c Water plus a crude extract of apoplastic proteins from cold-acclimated winter rye leaves
A、 Crystal growth in water; B、 Water plus a purified AFP, a glucanase, from winter rye; C、 Water plus a crude extract of apoplastic proteins from cold-acclimated winter rye leaves