不同状态绿豆根边缘细胞对Cd^(2+)的响应

RESPONSE OF MUNG BEAN ROOT BORDER CELLS TO CADMIUM IN RELATION TO THEIR STATUS

以绿豆(Phaseolus radiatus)为材料,采用琼脂悬空培养法和培养皿滤纸培养法,以不同浓度的Cd2+处理洗脱根边缘细胞和未洗脱根边缘细胞的绿豆根尖,研究了离体状态和活体状态绿豆根边缘细胞对镉毒的响应。结果表明:在Cd2+的诱导下,离体状态的绿豆根边缘细胞凋亡和分泌黏液,同时随着Cd2+浓度的升高,其存活率逐渐递减;Cd2+具有诱导根尖产生根边缘细胞的作用,根尖释放的根边缘细胞数量随着Cd2+浓度的增加先增多后减少,其中,50μmol L-1Cd2+处理在洗脱组和未洗脱组均呈现最大诱导效应;Cd2+对根边缘细胞的活性具有影响,随着Cd2+浓度的增加,根边缘细胞的存活率在未洗脱组逐渐降低,而洗脱组则先升高后降低。与对照相比,25μmol L-1,200μmol L-1,400μmol L-1Cd2+在各处理时间段具有显著性差异(p<0.05);根冠果胶甲基酯酶活性(PME)随着Cd2+浓度的增加呈现上升趋势,处理24 h高浓度Cd2+均会引起根冠PME活性的显著性升高(p<0.05)。以上结果表明,受到Cd2+胁迫时,绿豆根尖可释放更多根边缘细胞,并通过离体根边缘细胞形成黏液层、凋亡等来抵御Cd2+对根尖的毒害作用。

Mung bean （Phaseolus radiatus） was used as subject in this study exploring responses of root border cells to cadmium toxicity in vitro and in vivo with the methods of pre-suspended culture using agar pour plate and filter paper pad in the later part of the culture. In the experiment mung bean root tips with root border cells unwashed in group A and washed off in group B were treated with different concentrations of Cd2＋. Results show that Cd2＋ induced apoptosis and then mucus secretion of the root border cells in vitro. Survival rate of the root border cells in vitro decreased with increasing concentration of Cd2＋ . It was also found that Cd2＋ induced in vivo generation of root border cells, of which the number increased first and then decreased with the increasing Cd2＋ concentration. The maximum induction effect was observed when the roots were treated with 50 μmolL-1 Cd2＋ , regardless of whether the root border cells were washed off or not;Cd2＋ affected survival rate of the root border cells, and in Group A, the survival rate of root border cells decreased gradually with the increasing Cd2＋ concentration, but in Group B it increased first and decreased later. Compared with the control, the treatments of 25 μmolL-1 ,200μmolL-1 and 400 μmolL-1 varied significantly （ p 〈 0.05 ） , PME activity of root cap increased with increasing Cd2＋ concentration, and the effect was significant（p 〈 0.05 ）when the roots were treated with a high concentration of Cd2＋ concentration for 24 h. All the above - described findings indicate that mung bean root tips can release more root border cells under Cd2＋ stress, and the detached root border cells form a layer of mucilage and apoptotic cells to protect the root tips against Cd2＋.