<p>The strain preservation of the heterozygote seems to be possible in an individual plant with an intermediate characteristic. This can be demonstrated by using the plant having an incomplete dominance characteristic. Using the strain of soybean (Glycine max L.) and tomato (Lycopersicon esculentum Mill.) leaves with the characteristic of incomplete dominance are the plant materials used to teach the concepts involving the phenotypic expression. It is considered that the factor of the phenotypic expression affects the synthesis of the photosynthetic pigment in soybean plant, and the chloroplast number in tomato plant.</p>