低温胁迫下2种木薯幼苗形态及抗渗透差异

为探究木薯的耐寒性及其在低温胁迫下抗渗透响应,对耐寒‘F200’木薯和低温敏感品种‘华南8号’（‘SC8’）木薯幼苗在人工低温条件下进行4 ℃低温处理,分别观测处理前和处理3、6、12、24 h下不同木薯品种生长表型情况以及渗透性物质含量变化情况。结果表明：随着胁迫时间的增加,‘F200’木薯幼苗上部和下部叶片出现轻度萎焉,而‘SC8’所有叶片均严重萎焉,顶部叶片甚至出现脱水现象;‘F200’木薯叶片受H₂O₂的损害轻于‘SC8’,相对于‘SC8’的损伤持续增加,‘F200’呈现先加重后减轻的趋势;随着低温胁迫时间的延长,木薯叶片的相对叶绿素含量呈现先急剧下降、再上升、后下降的过程;相对电导率（REC）和丙二醛（MDA）、可溶性糖（SS）、可溶性蛋白（SP）、脯氨酸（Pro）的含量均逐渐升高;低温胁迫下,‘F200’木薯的总叶绿素减少64.23%,且小于‘SC8’的78.15%,二者差异不显著;REC增加11.48%,且显著小于‘SC8’的188%;MDA增加14.74%,且显著小于‘SC8’的20.98%;Pro增加90.53%,显著大于‘SC8’的27.95%;SP增加12.96%,且大于‘SC8’的17.82%,二者无显著差异;SP增加45.18%,且显著大于‘SC8’的2.16%。可见,低温胁迫下,‘F200’木薯通过增强H₂O₂的清除能力、增强光合作用、增加渗透调节物质含量等途径,缓解了低温对木薯幼苗造成的伤害。低温耐受型木薯‘F200’和低温敏感型木薯‘SC8’的形态结构和生理指标在低温胁迫下存在明显差异,可作为木薯种质资源耐低温性评价的参考指标。

Anti-osmotic Response of ‘F200’ and ‘SC8’ Cassava Seedlings under Low Temperature Stress

In order to explore the cold tolerance of cassava and its response to osmosis under low temperature stress, the cold-tolerant ‘F200’ cassava and the low-temperature sensitive variety ‘Huanan 8’ (‘SC8’) cassava seedlings were treated at 4 ℃ under artificial low temperature conditions, and the treatments were observed separately. The growth phenotype of different cassava varieties and the change of osmotic substance content under 3 h, 6 h, 12 h, 24 h before and after treatment. With the increase of stress time, the upper and lower leaves of ‘F200’ cassava seedlings showed mild wilting, while all the leaves of ‘SC8’ were severely wilted, and the top leaves were even dehydrated. The leaves of ‘F200’ were less damaged by H ₂O₂than ‘SC8’. Compared with the continuous increase in the damage of ‘SC8’, ‘F200’ showed a trend of first aggravating and then reducing. With the extension of low temperature stress, the relative chlorophyll content of cassava leaves showed a process of first sharp decline, then rise, and then decline, relative conductivity and malondioxide, content of aldehyde, soluble sugar, soluble protein, and proline gradually increased. Under low temperature stress, the total chlorophyll of ‘F200’ cassava decreased by 64.23% and was 78.15% less than that of ‘SC8’, but the difference was not significant, the relative conductivity increased by 11.48% and was significant less than that of ‘SC8’ (188%), malondialdehyde increased by 14.74% and significantly less than that of ‘SC8’ (20.98%), proline increased by 90.53% and was significantly greater than that of ‘SC8’ (27.95%), soluble protein increased by 12.96% and was greater than that of ‘SC8’ (17.82%), but there was no significant difference between the two, the soluble sugar increased by 45.18% and was significantly greater than that of ‘SC8’ (2.16%). It can be seen that under low temperature stress, ‘F200’ cassava can alleviate the damage caused by low temperature to cassava seedlings by enhancing the scavenging ability of H ₂O₂, enhancing photosynthesis, and increasing the content of osmotic adjustment substances. This study would lay foundation for the in-depth study of the low temperature tolerance mechanism of cassava and the low temperature breeding. The morphological structure and physiological indexes of low temperature tolerant cassava ‘F200’ and low temperature sensitive cassava ‘SC8’ were significantly different under low temperature stress, which could be used as a reference index for evaluation of low temperature tolerance of cassava germplasm resources.