PLANTS

I collect and cultivate cacti. “Cacti are the group of closely related plants that have clusters of spines and that are native to North and South America.” (MAUSETH et al., 2002).

What defines a cacti, and makes it different from other plants, is the presence of a structure called the areole, from which clusters of spines form from. Those spines are modified, highly-specialized leaves that had its surface area reduced to prevent water loss. They are not capable of photosynthesis, however. In cacti, it’s the stem (meaning the body) that is responsible for the photosynthesis and for the gas exchanges.

First, we have the reduction of the size of leaves, and even the loss of them, to reduce the loss of water, which led to the development of succulent tissue that was able to store that much needed water, so the plant could survive in environments with not a lot of rain throughout the year. Spines also serve as a way to protect themselves from animals trying to get to that water stored.

Then, they evolved another four important characteristics: the development of bark late in life, essential since the photosynthesis is made by the stem; the loosening of the cortex cells, which allowed oxygen to leave the cactus more quickly, necessary since oxygen is what’s toxic to the plant; the evolution of flexible ribs, so it can adapt its body as it gains and as it loses water; and the creation of cortical bundles, which are tissues that carry water and transport sugars more quickly.