Abstract: By comparison of soil particle size and soil water content between turfy soil and yellow clay, the effects of soil water retention with yellow clay were analyzed. The results showed that leaf relative water content, the ratio of shoot and root, photosynthetic rate, stomatal conductance, transpiration rate, efficiency of water application and soluble sugar were observed to change with the intensification of soil clay under heavy drought conditions. The value of efficiency of water application arrived at 6.975 2 μmol·mmol^-1, which was 2-fold pure turfy soil. At the same time, the contents of sucrose and trehalose increased to 2.614 5 mg·g^-1 and 0.566 9 mg·g^-1. Soil water content also significantly increased to higher than 30%. The results indicated that Catharanthus roseus could obtain more available water from soil of higher ratio of yellow clay and the pure yellow clay is suitable for C.roseus to survive under the stress of heavy drought conditions.

Key words: Catharanthus roseus, soil clay, photosynthetic characteristics, soluble sugar