土荆芥挥发性化感物质对蚕豆叶表皮保卫细胞的影响

化感作用是外来植物土荆芥( Chenopodium ambrosioides)成功入侵的机制之一。为了探讨土荆芥挥发油的化感作用机制,该文以蚕豆( Vicia faba)叶的下表皮为材料,将表皮条孵育在分别含土荆芥挥发油、α-萜品烯和对伞花素的MES 2-( N-morpholino) ethanesulfonic acid]缓冲液中,25℃下光照培养30 min,采用吖啶橙/溴乙锭( AO/EB)双荧光染色法和Feulgen染色法,研究土荆芥挥发油、α-萜品烯和对伞花素对保卫细胞活性和细胞核形态的影响。结果表明：在土荆芥挥发油、α-萜品烯和对伞花素的作用下,蚕豆气孔保卫细胞活性降低,细胞核出现固缩、畸形或降解等细胞凋亡特征。随着处理剂量增加,保卫细胞活性显著下降,核异常率显著增加,表明土荆芥挥发油、α-萜品烯和对伞花素均对蚕豆保卫细胞具有细胞毒性,其中,挥发油毒性最大,α-萜品烯的毒性次之,对伞花素的毒性最小；Caspase抑制剂Z-VAD-FMK可缓解挥发油、α-萜品烯和对伞花素对保卫细胞的毒性,提高细胞活性,这种缓解效应随着抑制剂浓度的增加而增大。由此可见,土荆芥挥发油、α-萜品烯和对伞花素诱导蚕豆保卫细胞发生了Caspase依赖性的细胞凋亡。

Effects of volatile allelochemicals from Chenopodium ambrosioides on the stoma guard cells in leaf epidermis of Vicia faba

Chenopodium ambrosioides, an aromatic herbnative to tropical Central and South America, has become a major invasive plant in China. Allelopathy plays a crictical role in the successful invasion of C. ambrosioides, and has an allelopathic stress on neighbor plants. To explore the allelopathy mechanism, the effects of volatile oil from C. am-brosioides,α-terpinene and cymene on guard cell viabilities and nucleus morphology in Vicia faba leaves were investi-gated using epidermal strips bioassay, AO/EB fluorescent staining and conventional Feulgen staining. Epidermal strips of leaves were incubated in 2-( N-morpholino) ethanesulfonic acid ( MES) buffer containing volatile oil, α-terpinene and cymene for 30 min at 25℃ in illumination incubator. The results showed that volatile oil,α-terpinene and cymene resulted in the decrease of viabilities and increase of abnormal nuclei rates in guard cell of V. faba leaves. The cytotox-icity on guard cells decreased successively from volatile oil toα-terpinene to cymene. The apoptosis features including nuclear pyknotic, malposition, stretch and degradation were observed in guard cell under the treatments of volatile oil,α-terpinene and cymene. However, the guard cell survival rates increased when strips were exposed to volatile oil,α-terpinene and cymene combined with different concentrations of a caspase inhibitor Z-VAD-FMK. These results sugges-ted that the volatile allelochemicals from Chenopodium ambrosioides induced guard cell caspase-dependent apoptosis in Vicia faba leaves.