硫对镉胁迫下小白菜镉富集、光合速率等生理特性的影响

以小白菜品种"七宝青"为材料,采用盆栽试验,研究外施硫(50 mg·kg^-1)对不同镉(Cd)处理水平(0、5、25、50、100 mg·kg^-1>)下小白菜生长、Cd吸收转运、光合特性及渗透调节物质含量的影响。结果显示,与单一Cd处理相比,5.25 mg·kg^-1 Cd处理水平下,外施硫显著促进了小白菜的生长,其株高分别增加了11.14%和21.16%,地上部干重分别增加了22.55%和19.90%,根部干重分别增加了27.83%和20.29%,叶绿素含量分别增加了11.81%和15.13%。外施硫降低了小白菜Cd的转运系数(TF)和地上部生物富集系数(BCF),提高了根部BCF。25 mg·kg^-1 Cd处理水平下,外施硫小白菜地上部Cd含量显著降低了24.82%,根部Cd含量显著增加了23.94%,TF值最小。5.25 mg·kg^-1 Cd处理水平下,外施硫能够明显缓解Cd胁迫对小白菜叶片光合作用的抑制,其净光合速率(Pn)分别增加了13.15%和15.22%,气孔导度(Gs)分别增加了13.81%和15.42%。25 mg·kg^-1 Cd处理水平下,外施硫小白菜叶片可溶性蛋白、可溶性糖、脯氨酸及抗坏血酸含量分别增加了20.82%、23.34%、26.79%和25.72%。研究结果表明,在25 mg·kg^-1 Cd处理水平下,外施50 mg·kg^-1硫显著减少了Cd从根部向地上部转移,降低小白菜地上部Cd含量,提高Cd胁迫下小白菜叶片的光合强度以及渗透调节物质的含量,对小白菜Cd毒害的缓解效应最为显著。

Effects of Sulfur on Cadmium Accumulation, Photosynthesis and Some Other Physiological Characteristics of Pakchoi(Brassica chinensis L.)Under CadmiumStresses

Sulfur has played important roles in the plant stress resistance. Here a pot experiment was performed to investigate the effects of exogenous sulfur(50 mg·kg^-1) on the growth, Cd uptake and transportation, photosynthetic characteristics and osmosis-regulating substances of pakchoi(Brassica chinensis L.) cultivar Qibaoqing under different Cd concentrations(0, 5, 25, 50, 100 mg·kg^-1). Exogenous sulfur significantly promoted the growth of pakchoi under 5 mg·kg^-1 and 25 mg·kg^-1 Cd, with the plant height increased by 11.14% and 21.16%, shoot dry mass increased by 22.55% and 19.90%, root dry mass increased by 27.83% and 20.29%, chlorophyll content increased by 11.81% and 15.13%, respectively, compared to no sulfur treatment. However, applying sulfur reduced the translocation factor(TF), shoot bioconcentration factor(BCF) of Cd, but increased BCF in roots. Under 25 mg·kg^-1 Cd stress, sulfur significantly reduced shoot Cd content by 24.82%, but increased root Cd content by 23.94%, thus yielding a minimum TF of 29.97%. Compared to no sulfur treatment, adding sulfur significantly enhanced the photosynthesis of pakchoi, with the net photosynthetic rate(Pn) increased by 13.15% and 15.22%, stomatal conductance(Gs) increased by 13.81% and 15.42%, respectively, under 5 mg·kg^-1 and 25 mg·kg^-1 Cd stress. In the treatment with 25 mg·kg^-1 Cd, sulfur also significantly increased the soluble protein, soluble sugar, proline and ascorbate content of pakchoi by 20.82%, 23.34%, 26.79% and 25.72%, respectively. These findings indicate that exogenous sulfur of 50 mg·kg^-1 could effectively alleviate 25 mg·kg^-1 Cd-induced toxicity to pakchoi through inhibiting Cd translocation from root to shoot, and promoting photosynthesis and osmosis-regulating substance contents.