干旱胁迫对甘薯苗期根系分化和生理特性的影响

以‘济薯26’和‘广薯87’为试验材料,采用砂培试验方法,以10%浓度的聚乙二醇(PEG-6000)模拟干旱胁迫,动态研究了干旱胁迫对甘薯发根分枝结薯期的3个不同阶段根系形态、内源激素、叶绿素荧光和活性氧代谢的影响.结果表明: 不同时期干旱胁迫均导致甘薯生物量显著降低,影响程度为移栽后第10天＞第20天＞第30天.与正常供水相比,移栽后10 d干旱胁迫导致甘薯平均直径和根体积下降幅度最大,其次是移栽后20 d,最后是移栽后30 d.双因素分析表明,不同时期和干旱胁迫显著影响了根系形态特征,且交互效应显著.不同时期干旱胁迫均显著降低了甘薯功能叶的叶绿素荧光特性,导致光合产物形成受阻,进而抑制了甘薯根系的分化.不同时期干旱胁迫均导致根系中促生长激素(吲哚乙酸和玉米素核苷)含量显著下降,抑制生长激素(脱落酸)含量显著上升,以及激素间比例失衡,从而抑制甘薯根系分化,且胁迫时间越早,甘薯根系分化受阻越严重.其中,济薯26根系分化受阻的严重程度显著低于广薯87.逐步回归分析表明,根内源激素和叶绿素荧光是影响平均直径和根体积的关键指标(R分别为0.936和0.972);通径分析表明,对甘薯平均直径和根体积的影响直接作用系数较大的是玉米素核苷、最大光化学效率和脱落酸.甘薯的水分临界期在发根分枝结薯期,其中移栽后第10天对干旱胁迫更敏感.在实际生产中,应加强栽苗后缓苗水分的供应.

Effects of drought stress on root development and physiological characteristics of sweet potato at seedling stage

The effects of drought stress on root morphology, endogenous hormones, chlorophyll fluorescence and active oxygen metabolism in three different stages of sweet potato rooting, branching and tubering stage were studied by sand culture method with 10% PEG-6000 simulating drought stress. The results showed that the biomass of sweet potato decreased significantly under drought stress in different periods, with the degree of drought stress being 10 days > 20 days > 30 days after transplantation. Drought stress significantly reduced the average diameter and root volume at the 10 days after transplantation, followed by the 20 days and 30 days. Both the main and interactive effects of different periods and drought stress significantly affected root morphological characteristics. Drought stress at different stages significantly reduced chlorophyll fluorescence characteristics, resulting in blocked photosynthate formation, and inhibited root differentiation. Drought stress affected the proportion of endogenous hormones in root (with decreases of indoleacetic acid and zeatin riboside contents but increases of abscisic acid contents) and thus inhibiting root differentiation of sweet potato. The earlier the stress time, the more serious the root differentiation of sweet potato was hindered. Across different drought-tolerant varieties, the severity of root differentiation blocked in Jishu 26 was significantly lower than that in Guangshu 87. Root endogenous hormones and chlorophyll fluorescence were the key drivers for the average diameter and root volume (R₁=0.936, R₂=0.972). Zeatin riboside, maximal photochemical efficiency, and abscisic acid had greater direct effects on average diameter and root volume of sweet potato. Sweet potato was more sensitive to drought stress in the 10th day after transplanting. Therefore, proper irrigation should be considered in case of drought in seedling stage of sweet potato.