Analysis of Mechanisms in the Interaction Between Aluminum and Silica in Plant and Soil System.

(1)异原系安土中硅溶物含量高，铝含量低，硅与铝形成难溶沉淀。(2)这一现象很好地反映在以异生安多土为主的地区的河水中二氧化硅的含量。(3)在酸性土壤中，2 mM二氧化硅的存在减轻了铝对植物的生长伤害。(4)二氧化硅减轻铝毒性的作用机制主要是通过在根尖周围积累大量二氧化硅来阻止铝与根细胞表面的接触。结果表明，根系的排铝功能增强。(5)在高酸性土壤中，盐碱土生长良好，正常生长需要铝，施用二氧化硅对其生长没有刺激作用。这种现象可能是由于该植物对铝的需求量大，而生长介质中二氧化硅的共存又降低了铝的吸收率。(6)由疥疮链霉菌引起的马铃薯普通结痂病严重制约着全球马铃薯优质生产，目前尚无良好的防治方法。然而，澄清了较低浓度的铝对疥疮链霉菌生长的抑制作用，而不是抑制马铃薯生长的作用。马铃薯赤霉病有导电性土壤和抑制性土壤，但原因尚不清楚。本研究发现，马铃薯赤霉病容易发生在土壤溶液中硅含量较高的allophanic andosol等土壤中，从而使铝的浓度降低。相反，在硅浓度较低的土壤中，马铃薯普通赤霉病的发生率较低，从而使铝浓度较高。结果表明，前者为导性土，后者为抑制性土。(7)在高硅质导电土壤中，施用硫酸铝配合行施氮肥、表面施磷钾肥的施肥方法，可有效抑制马铃薯赤霉病的发生。采用上述施肥方法，块茎生长层周围土壤溶液中铝的活性较高，因为层内离子强度较低。少

(1) Allophanic Andosols, in which soluble silica content was usually high, had a characteristics with a low aluminum concentration, as silica and aluminum formed difficultly soluble precipitation. (2) This phenomena was well reflected to the silca concentration in the river water flowing through the areas where the soils were formed mainly by allophanic Andosols. (3) Growth injury in plants caused by aluminum in acid soils was alleviated by the coexistence of 2 mM silica in the growth media. (4) Mechanisms of the effect of silica on the alleviation of aluminum toxicity was mainly to prevent contact of aluminum on cell surface of roots by the accumulation of a large amount of silica around the root tips. As a result, the aluminum-excluding function of the roots became higher. (5) Melastoma malabathricum grown well in the highly acidic soils required aluminum for the normal growth and the growth was not stimulated by the silica application. This phenomena might be caused by the high alum … More inum requirement of this plant and the decrease of aluminum absorption by the coexistence of silica in the growth media. (6) Potato common scab disease induced by Streptmyces scabies is a serious constraint in the production of potato with good quality in the whole world, as the good method to prevent the occurrence of this disease has not been established. However, it was clarified that growth of Streptmyces scabies was inhibited by a lower concentration of aluminum than that inhibiting potato growth. It has been known that there are conductive soils and suppressive soils for potato scab, but the reason was unknown so far. In this study, it was found that potato common scab occurred easily in the soils such as allophanic Andosols which had a high concentration of silica in the soil solution, thus making aluminum concentration lower. On the contrary, occurrence of potato common scab was low in the soils which had a low concentration of silica, thus making aluminum concentration higher. It was demonstrated that the former was the conductice soil and the latter the suppressive soil. (7) When potato was grown in the conductive soils with a high silica concentration, it was indicated that application of aluminum sulfate together with a fertilizing method, in which nitrogen fertilizer was applied on the row and phosphate and potassium fertilizers are supplied on the soil surface, was effective for suppressing the potato common scab. By employing the fertilizing method described above, a high activity of aluminum in the soil solution around the tuber growing horizon was maintained due to the lower ionic strength in the horizon. Less