水禾对镉胁迫的生理响应

    目的   研究镉(Cd)胁迫下水禾Hygroryza aristata的生理响应,以利于水禾的保护利用。    方法   采用水培试验,设置2(T₁)、4(T₂)和6 (T₃) mg·L?1 3个质量浓度镉胁迫处理,以不添加镉为对照(ck),分别在处理0、4、8和12 d时,研究了不同镉胁迫处理对水禾的生长、光合生理和抗氧化酶活性的影响。    结果   随着镉质量浓度的增加,水禾株高呈逐渐降低的趋势,到处理12 d时,T₁、T₂和T₃的株高分别比对照降低了16.35%、21.27%和27.29%;根系总长度和根尖数均显著降低(P＜0.05)。水禾叶片的总叶绿素、叶绿素a和叶绿素b的质量分数呈降低趋势,叶绿素a/b也随之降低。水禾叶片的净光合速率(P_n)显著降低(P＜0.05),到处理12 d时,T₁、T₂和T₃的P_n分别比对照降低了55.44%、58.77%和96.47%;处理8 d后,T₁、T₂和T₃的P_n、蒸腾速率(T_r)和气孔导度(G_s)均显著降低(P＜0.05),胞间二氧化碳摩尔分数(C_i)则显著升高(P＜0.05)。水禾叶片的过氧化氢(H₂O₂)和丙二醛(MDA)的质量摩尔浓度随着镉质量浓度的增加逐渐升高,随着处理时间的延长,各处理H₂O₂和MDA质量摩尔浓度升高速率均呈下降趋势,最大升高速率均在0~4 d;T₃的脯氨酸(Pro)质量分数呈先升高后降低的趋势,在处理8 d时达到峰值,到处理12 d时,T₃的Pro质量分数比对照降低了53.85%。水禾叶片的超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性随着镉质量浓度的增加逐渐升高。    结论   镉胁迫下,水禾植株的生长和叶片的光合作用受到了明显的抑制。镉对水禾可产生严重的毒害作用,长期镉胁迫下,抗氧化酶在清除活性氧(ROS)、防御氧化伤害上发挥的作用有限,水禾抵御逆境胁迫的能力较弱。图4表2参47

Physiological responses of Hygroryza aristata to cadmium stress

    Objective   The purpose of this study is to observe the physiological responses of Hygroryza aristata to cadmium (Cd) stress, for protection and utilization of H. aristata.    Method   The effects of cadmium on the growth, photosynthetic physiology and antioxidant enzyme activities of H. aristata were studied using hydroponic test in which plants of H. aristata were treated with cadmium at concentrations of 0 (ck), 2 (T₁), 4 (T₂), and 6 (T₃) mg·L?1 and sampled at 0, 4, 8 and 12 days after treatment.    Result   The plant height of H. aristata gradually decreased as the concentration of cadmium increased. By 12 days after treatment, the plant height of T₁, T₂ and T₃ was 16.35%, 21.27% and 27.29% lower than that of ck, respectively. Similarly, the total length of roots and the total number of root tips decreased significantly(P＜0.05). The mass fraction of total chlorophyll, chlorophyll a and chlorophyll b in the leaves of H. aristata decreased, so did chlorophyll a/b. The net photosynthetic rate (P_n) dropped significantly(P＜0.05). By 12 days after treatment, P_n in T₁, T₂ and T₃ decreased by 55.44%, 58.77% and 96.47% respectively, compared with ck. After treatment for 8 days, P_n, the transpiration rate (T_r), and the stomatal conductance (G_s) in T₁, T₂ and T₃ decreased significantly (P＜0.05), while the intercellular CO₂ concentration (C_i) increased significantly (P＜0.05). Compared with ck, the mass molality of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) in the leaves of H. aristata increased gradually with the increase of cadmium concentration. With the extension of treatment time, the increasing rate of H₂O₂ and MDA mass molality in each treatment showed a downward trend, and the maximum increasing rate occurred between 0?4 d after treatment. The proline (Pro) content in T₃ first increased and then decreased, reaching a peak on day 8 and decreasing by 53.85% on day 12 compared with ck. The activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) in the leaves of treated H. aristata plants gradually increased with the increase of cadmium concentration.    Conclusion   Cadmium has a serious toxic effect on H. aristata, whose growth and photosynthetic activities are obviously inhibited under cadmium stress. Long-term cadmium stress limits the activity of antioxidant enzymes in removing reactive oxygen species (ROS) and protecting against oxidative damages, which further weakens the ability of H. aristata to resist adverse stress. [Ch, 4 fig. 2 tab. 47 ref.]