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

(1)Al^<3+>的第一特异位的确定：利用离子势顺序的差异进行实验：Al^<3+>Yb^<3 +>La^<3+>。根尖原生质体表面β-葡聚糖合成量的顺序为Al>Yb>La，耐铝植物原生质体表面普遍存在β-葡聚糖的沉积，而铝敏感植物则为不均匀的点状沉积。所合成的β-葡聚糖部分由1，3-β-葡聚糖组成。不同金属处理根的FDA活力大小顺序为Al<Yb<La，金属在根外部分的积累量大小顺序为Al>Yb>La。镧对根的不可逆性损伤、根伸长的抑制和钾素的损失最为严重。在不合成β-葡聚糖的条件下，原生质体的聚集性为Al>Yb>La。这些结果表明，根的外部和顶端的质膜是Al^<3+>的主要特异部位。(2)基于根尖质膜表面负性的耐铝根细胞分离：根尖CEC与耐铝性无关，而与质膜负性极显著相关。将无毒的Al（OH）_3与二氧化硅微球（Al-SMB）混合，其最大正电荷的pH值为5.3。将来自根尖的纯化的原生质体与Al-SMB在此pH下混合，最后通过用不连续梯度离心分离主要在底部部分中分离出存活的耐Al原生质体。(3)无铝固体培养基的制备及根系释放有机酸的分析：将营养液添加到SMB中，制备了无铝琼脂状固体培养基，其物理性质与实际土壤条件相似。通过过滤Al-SMB收集从根部释放的有机酸。(4)铝胁迫与有机酸的关系

(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