Studies on the evasive strategy for acid-soil stress by the extracellular released materials operating in the process of root elongation

(1)阐明了Al^<3+>的主要特异位点：利用离子电位阶数的差异进行了实验；艾尔^ < 3 + > > Yb ^ < 3 + > >拉^ < 3 + >。从根尖开始，原生质体表面合成β -葡聚糖的量依次为Al>Yb>La；β -葡聚糖普遍沉积在耐铝植物上，而在铝敏感植物上则有不均匀的点状沉积。合成的β -葡聚糖由部分1,3 - β -葡聚糖组成。金属处理根的FDA活力大小为Al<Yb<La，根外部分金属积累量较大，大小为Al>Yb>La。La诱导的不可逆质解、根系伸长抑制和钾流失最为严重。非合成β -葡聚糖条件下原生质体的聚集量依次为Al>Yb>La。这些结果表明，Al^<3+>的主要特异位点是根外和根尖部分的质膜。(2)利用根尖质膜表面负性分离耐铝根细胞：铝耐受性与根尖CEC不相关，但与质膜负性呈负相关。将无毒的Al(OH)_3与二氧化硅微珠（Al- smb）混合；Al-SMB的最高正电荷pH为5.3。将纯化的根尖原生质体与Al-SMB在此pH下混合，通过不连续梯度离心，最终在底部部分分离到可存活的耐铝原生质体。(3)无Al固体培养基的制备及根部释放有机酸的分析：通过向SMB中加入营养液，制备无Al的琼脂状固体培养基；它的物理性质与实际土壤条件相似。通过过滤Al-SMB收集根部释放的有机酸。(4)铝耐受性与有机酸相关性

(1) Elucidation of the primary specific site for Al^<3+> : Experiments were carried out by utilizing the difference of the order of ionic potential ; Al^<3+>>Yb^<3+>>La^<3+>. The amount of beta-glucan synthesizd on the surface of protoplasts from root tip was in the order of Al>Yb>La ; a universal deposition of beta-glucan on that from Al-tolerant, but a heterogeneous dotted deposition from al-sensitive plant species. The beta-glucan synthesized was composed in part of 1, 3-beta-glucan. FDA viability of root treated with metals was in the order of Al<Yb<La, and the accumulation of metals in the outer portions of roots was considerable in the order of Al>Yb>La. La induced most heavily the irreversible plasmolysis, the inhibition of root elongation, and the loss of K from roots. The aggregation of protoplasts in non-synthesizing conditions of beta-glucan was higher in the order of Al>Yb>La. These results indicate the plasma membrane of the outer and tip portions of roots as the primary specific site for Al^<3+>. (2) Isolation of Al-tolerant root cells based on the surface negativity of plasma membrane from root tip : Al tolerance was not correlated with CEC of root tip, but megatively correlated with the negativity of plasma membrane. Non-toxic Al(OH)_3 was mixed with silica microbeads (Al-SMB) ; the pH of the highest positive charge of Al-SMB was 5.3. Purified protoplasts from root tip were mixed with Al-SMB at this pH, and finally viable Al-tolerant protoplasts were isolated predominantly in the bottom fraction by centrifuging with a discontinuous gradient. (3) Preparation of solid medium without Al and the analysis of organic acids released from roots : By adding the nutrient solution to SMB, agar-like solid medium without Al was prepered ; physical properties of it resembled the actual soil conditions. Organic acids released from roots were collected by filtering the Al-SMB.(4) Relationship between Al olerance and organic acids rel