The influence of external conditions on the formation of the anatomical structure of the leaf.

External conditions affect the shape and modifications of the sheet. For example, in arid areas, where there is little water and moisture, the sheets flatten. This helps them to store more water and not die in drought conditions. Aloe vera is an example of such a plant. You have also observed thorns or thorns in many plants, but did not realize that they could be of stem and leaf origin. Leaves, in the process of evolution, change and perform a protective function. Plus, the thorns help reduce volatility. Such thorns / thorns are found in roses, barberry.