figure 4.4 Plant growth What determines which plants are bigger than others, nature (genetics) or nurture (environmental conditions)? As you can see from the plants, it’s a combination of the two. Plant #1, for example, is much taller than #7 when the plants are grown at high or low elevation, but not when they’re grown in a different environment, a medium elevation. The interaction of nature and nurture is a basic fact of biological life.