局部根系盐胁迫对冬小麦生长和光合特征的影响

通过分根装置设置无盐胁迫(0|0)、局部根系150 mmol-L-1NaCl胁迫(0|150)、全部根系75 mmol-L-1NaCl胁迫(75|75)、全部根系150 mmol-L-1NaCl胁迫(150|150)4种处理,研究根系局部盐胁迫对冬小麦生长及光合特征的影响。结果表明:盐胁迫显著抑制了小麦幼苗的生长,并且随着盐胁迫浓度的增加,小麦受抑制程度加重;根系盐胁迫方式对小麦幼苗生长影响显著,局部根系胁迫处理(0|150)小麦幼苗地上部干重比等浓度150 mmol-L-1NaCl全部盐胁迫处理(150|150)增加23.5%,比等浓度75 mmol-L-1NaCl全部盐胁迫处理(75|75)增加17.2%。在局部根系盐胁迫下,非盐胁迫一侧根系(0|150-0)补偿生长,其根长、侧根数、侧根长比盐胁迫一侧根系(0|150-150)分别增加195.2%、206.2%和237.8%,盐胁迫一侧根系吸收的Na+部分向非盐胁迫一侧根系运输,盐胁迫一侧根系(0|150-150)的Na+含量比全部胁迫处理(150|150)减少12.1%。与全部根系盐胁迫相比,局部根系盐胁迫减少了Na+在叶片中的积累,降低了钠/钾值。局部根系盐胁迫叶片净光合速率、气孔导度、胞间CO2浓度和叶绿素荧光参数(Fv/Fm)均高于同浓度完全盐胁迫处理的小麦幼苗,进而增加地上部和根系的生物量。因此,局部根系胁迫显著缓解了全部盐胁迫对小麦地上部和根系生长的抑制作用。

Effects of partial root salt stress on seedling growth and photosynthetic characteristics of winter wheat

Most studies on plant salt stress have generally been conducted under uniform salinity in the root zone. However, the distribution of salinity in the soil is not always uniform under natural settings. Winter wheat is one of the main crops grown in salt-affected soils in China, with seedlings sensitive to salt stress. The effects of partial root salt stress on the growth and photosynthetic characteristics of winter wheat seedlings were investigated in this study using a split-root system in hydroponic culture. Each half root of the wheat seedlings was treated with either uniform (0|0 mmol L^-1, 75|75 mmol L^-1 and 150|150 mmol L^-1) or non-uniform (0|150 mmol L^-1) concentrations of NaCl, resulting in total or partial root salt stress. The results showed that salt stress significantly inhibited the growth of winter wheat seedlings, which inhibition increased with increasing NaCl concentration. Compared with total root salt stress treatments 150|150 mmol L^-1 and 75|75 mmol L^-1, partial root salt stress (0|150 mmol L^-1) increased shoot dry weight by 23.5% and 17.2%, respectively. Partial root salt stress compensated for root growth in none salt-stress conditions by increasing root length, lateral root number and lateral root length respectively by 195.2%, 206.2% and 237.8% over that in 150 mmol L ^-1 NaCl condition. In the 0|150 mmol L^-1 treatment, root Na⁺ content in 150 mmol L^-1 NaCl side of the treatment dropped significantly by 12.1% than that in either sides of 150|150 mmol L^-1 treatment. Also root Na⁺ content in salt-free side of 0|150 mmol L^-1 increased significantly over that in either sides of the 0|0 treatment. These results indicated that increased Na⁺] in roots in the salt-free side was possibly transported from the 150 mmol L^-1 NaCl side of the treatment. Partial root salt stress treatment also decreased Na⁺ concentration in roots and leaf Na⁺/K⁺ content. Also P_n, G_s, C_i, T_r and chlorophyll fluorescence parameters (F_v/F_m) were higher in 0|150 mmol L^-1 treatment than in total root salt stress. The improvement in plant growth under partial root salt stress was attributed to the reduction in leaf Na⁺ concentration and Na⁺/K⁺ ratio and the related increase in photosynthesis.