The red coloration in plant stems is often due to the presence of pigments, such as anthocyanins. Anthocyanins are water-soluble pigments that belong to the flavonoid group, and they can appear red, purple, or blue depending on the pH of the tissue.
The expression of these pigments is influenced by a combination of genetic and environmental factors. In some plant species, certain varieties or cultivars may have a genetic predisposition to produce more anthocyanins, resulting in a red or purple coloration in the stems. Environmental factors such as light intensity, temperature, and nutrient levels can also influence the production of anthocyanins. For example, some plants may develop more red pigmentation in response to high light levels or as a protective response to environmental stress.
It's possible that the differences in stem coloration between the two plants are due to genetic variation or differences in their growing conditions. Even within the same species or variety, individual plants can exhibit variations in coloration based on genetic factors and their specific environment. If both plants are healthy, the difference in stem color is likely just a natural variation.