Abstract
Some effects of mineral components of culture medium, i.e. total ionic concentration, Cation/Anion ratio, NH+4/NO3- ratio, and minor elements, affecting the growth of Bletilla striata seedlings were investigated.
1. Total ionic concentration of medium has markedly affected the growth of seedlings. At the level of 20meq/l, the growth of roots was more stimulated than that of shoots, and the roots produced were healthy in appearance.
At the level of 40meq/l, both shoot and root grew well in the case where the ratio of Ca++ to K+ was held within an appropriate range.
At the level of 60meq/l, the fresh weight of the shoot was heavier than that produced at lower ionic concentrations. However, their root growth was inferior to that achieved at lower nutrient levels and globular seedlings were observed.
2. The requirement for cation was lower than that of anion, and the partial replacement of cation by sodium had no effects. However, that of anion by chlorine caused a decrease of growth.
3. The ratio of NH4+ to NO3- has markedly affected the growth of seedlings, and it may be required to maintain the ratio below 1.0 for better plant growth. Irrespective of concentration of nitrate ions or total ions, the growth of root was excellent at lower levels of NH4+.
The optimum ratio of NH4+ to NO3- increased from 40/60 to 70/60 as total ionic concentration increases. The optimum ratio for the growth of both shoot and root seems to be about 40/60 or less.
4. The addition of minor elements to the basal medium caused inhibition of seedling growth. Inhibitory effects were caused by addition of minor elements except Fe-EDTA, though alleviated by the addition of Fe-EDTA.
