Abstract
Two-year old seedlings of Cryptomeria japonica and Chamaecyparis obtusa were cultivated to examine the effect of root sphere acidity on the plant growth in the nutrient solution culture, for assessing the soil acidification stress, which may contribute to the conifer decline. Acidity of one fifth Hoagland's nutrient culture solution was adjusted to the pH ranging from 3.5 to 6.0 by HC1 and NaOH.
The results of current cultivation experiment for 15 weeks suggested that the growth performance of both Cryptomeria japonica and Chamaecyparis obtusa was best under the lowest pH level of 3.5-4.0. Both species, however, decreased plant dry weight at high pH level. Total cation contents in the leaves and roots of both species cultivated at pH 3.5-4.0 were highest.
These results suggest that both species have a characterstic adaptability to such a low pH condition. Therefore, potentiality that soil acidification stress in the pH range of 3.5 to 4.0 will induce growth reduction, is an ineffective factor for the growth suppressionof both conifer species.
