h1

Why does the cactus look like that?

June 16, 2010

The first thing you notice about a cactus is generally the spines. Some have short, nasty little almost invisible fishhooks, some inches-long needles. Then there’s the form of the plant. Most cacti are plump, rounded, often stubby. They tend to be grayish-green in color. And they usually do not have obvious leaves.

Why?

Whenever you come across questions like this, think about the ecosystem where the organism lives. Cacti live in dry climates with a lot of sun, and few other plants, especially leafy ones.

So keeping cool is an issue. A light neutral color does not absorb a huge amount of the sun’s heat. There are very few plants with dark bark, or skins, or leaves in the desert.

Retaining moisture is perhaps the most important issue for a desert plant. The blunt, compact shape of cacti, their thick skins, and lack of leaves are all moisture-conserving features.

And lastly, toothsome, moist leaves would attract all kinds of herbivores. So the lack of leaves discourages plant-eaters, and the big spines and tough hide protect any soft, moist tissue a cactus does have.

Advertisements
%d bloggers like this: