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KMID : 1024519960050060813
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Journal of the Environmental Sciences
1996 Volume.5 No. 6 p.813 ~ p.826
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Effects of Aluminium on Growth, Chlorophyll Content, ALAD Activity and Anatomy of Root rind Shoot in Azuki Bean (Vigna angularis) Seedlings
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Koo Suh-Young
Hong Jung-Hee
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Abstract
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The toxic effects of aluminium (Al) on growth, chlorophyll content, acid dehydratase (ALAD) activity and anatomy of root and shoot were investigated in 7-day-old azuki bean (Vigna angularis) seedlings. Significant depressions in root elongation was observed in the low concentrations of Al (50, 100 and increasing Al concentrations caused a sharp decline of root and shoot growth. The degree of inhibition was dependent upon Al supply. Exposure to 50 Al or more inhibited root elongation within 1 day. In the 50 Al treatments, a recovery of root growth was seen after 7 days exposure. In contrast, lateral root initials was little affected by Al exposure. Al toxicity symptoms and growth responses were more well developed in the roots than in the shoots. Analysis of Al localization in root cells by hematoxylin stAlning showed that Al entered root apices and accumulated in the epidermal and cortical cells immeadiately below the epidermis. There was a good positive correlation between the level of chlorophyll and ALAD activity. Increasing Al concentrations caused a decrease in total chlorophyll contents, accompanied by proportional changes in ALAD activity, suggesting a cootr-dinated reduction of a photosynthetic machinery. Al exerted specific influence on the morphology of root ann shoot. At higher concentrations of Al the roots induced drastic anatomical changes. The epidermal cells were disorganized or destructed while the cortical cells exhibited distortion of cell shape and/or disintegration. The diameter of root and transectional area of cortical cells decreased considerably with Al treatment. In the shoot Al also enhanced reduction of diameter of shoot and cell size. Gross anatomy of leaves treated with Al did not differ significantly from the controls, except for fewer and smaller chloroplast. Our results indicate that toxic effect of Al appear to be manifested primarily in roots and secondarily on shoots, and changes in root morphology are related to changes in the root growth patterns. Results are further discussed in re181ion to the findings in other plant species, and it is concluded that Al causes morphological, structural and, presumably, functional damage to the roots of the species investigated.
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KEYWORD
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root growth, chlorophyll content, ALAD activity, morphology, Vigna angularis, aluminium
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