硅对镉胁迫下香椿幼苗光合特性和离子吸收的影响

Effects of silicon on photosynthetic characteristics and ion absorption of Toona sinensis seedlings under cadmium stress

为探究硅对镉胁迫下香椿的缓解机制,以香椿幼苗为材料,采用水培法调查施加不同浓度硅(0、0.5、1.0和2.0 mmol·L^(-1))对镉(200μmol·L^(-1))胁迫下香椿幼苗的生长指标、渗透平衡、离子吸收、光合特性、抗氧化能力的影响。结果表明:镉胁迫显著抑制香椿幼苗的生长,降低其根系活力、离子含量、光合色素含量、净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr);而相对电导率、胞间CO_(2)浓度(Ci)、过氧化氢(H_(2)O_(2))和丙二醛(MDA)含量则显著增加。与单独镉处理相比,施加硅后,香椿幼苗的生长指标、根系活力、铁(Fe^(2+))、锰(Mn^(2+))、锌(Zn^(2+))、铜(Cu^(2+))离子含量、叶绿素和类胡萝卜素含量以及气体交换参数(除Ci)均显著提高,而镉离子(Cd^(2+))含量、相对电导率、Ci、H_(2)O_(2)和MDA的含量均显著降低。随着施硅浓度的增加,各项生理指标均呈现低促高抑的变化趋势。试验表明,镉胁迫下施加硅可以促进香椿幼苗的生长,增加其体内的离子含量,提高光合作用效率,维持细胞膜渗透平衡和清除体内活性氧,从而缓解镉胁迫对香椿幼苗的毒害作用,且硅浓度为1.0 mmol·L^(-1)时,综合缓解效果最佳。

To clarify the alleviation mechanism of silicon on Cd stress in Toona sinensis seedlings, we investigated the effects of silicon application with different concentrations(0, 0.5, 1.0 and 2.0 mmol·L^(-1)) on the growth index, osmotic balance, ion uptake, photosynthetic characteristics, and antioxidant capacity of Toona sinensis seedlings under Cd(200 μmol·L^(-1)) stress by hydroponics. The results showed that Cd stress significantly inhibited the growth of T. sinensis seedlings and reduced root vigor, ion content, photosynthetic pigment content, net photosynthetic rate(Pn), stomatal conductance(Gs), and transpiration rate(Tr), but significantly increased relative conductivity, intercellular CO_(2)concentration(Ci), hydrogen peroxide(H_(2)O_(2)) and malondialdehyde(MDA) content. Under Cd stress, the application of Si significantly increased growth index, root vigor, Fe^(2+), Mn^(2+), Zn^(2+), Cu^(2+)contents, chlorophyll and carotenoid contents, and gas exchange parameters(except Ci) of seedlings, while significantly decreased Cd^(2+)content, relative conductivity, Ci, H_(2)O_(2)and MDA content. The physiological indicators showed a low-promoting and high-suppressing trend with increasing silicon concentrations. Our results indicated that silicon application under Cd stress could promote the growth of T. sinensis seedlings, ion content and photosynthetic efficiency, maintain cell membrane osmotic balance, and scavenge reactive oxygen species, thus alleviating the toxic effects of Cd stress on T. sinensis seedlings. The strongest alleviation effect was observed at a silicon concentration of 1.0 mmol·L^(-1).