why are cacti suited to their environment?

Answer 1

Most cacti do come from warm weather/low rainfall areas of the world although there are exceptions. There are no known fossils of cacti, and it is not known with certainty when they developed the unique adaptations that enable them to live in the harsh environments that many of them survive in. Many scientists believe that cacti developed their physiological traits in response to changing climatic conditions several million years ago.
The major traits that people see when they first observe cacti is the abundance of spines on many species. These spines serve several uses, they guard against most browsing herbiverous animals by making the plant difficult and dangerous to chew. The spines also help to shade the plant, helping keep internal heat down. Finally the spines also can channel the infrequent rains to the base of the plant.
Another easily identified characteristic of many cacti is a waxy coating that sorrounds the plant over the skin, this often has a bluish cast to it, and may be damaged by careless handling. This is called a 'glaucus bloom' and help to reduce evaporation by the plant, this holds in more of the precious moisture so rare in the desert.
All advanced plants have leaf holes called 'stomata', these holes are what open to permit entry and exit of various gases and moistures, in cacti these stomata close tighter than in most plants further reducing the loss of moisture in the heat of the day.
Another thing these plants can do is to store up lots of water when it does fall, many have the ability to open themselves up accordion style to hold massive amounts of water. Then when the plant is loosing water, the pleats of the acordion fold up shading the plant more and reducing surface area exposed to the sun.
When the plant is stressed and not getting enough water it will often bend over as the 'hygroscopic' (water filled) pressure inside the plant diminishes. The hygroscopic pressure is what holds the plant up erect, as it lessens the plant loses its 'turgidity' and can no longer stand erect, as it bends over it's exposure to the sun is reduced, much of it is then shaded by the overhead portion and moisture loss is further lessened.
Root behavior is another adaptation that cacti have made in order to live, they tend to have roots that spread laterally for quite a way and may exist in a suspended state until the rains activate them, a small amount of moisture will cause the feeding roots to quickly grow out from the main roots, these feeders are what bring in the water and it's dissolved minerals and nutrients. After the rain is gone and as the soil dries these feeder roots die and disappear enabling the plant to live on it's stored water without having to spend energy and moisture keeping these roots alive that may not be needed for many many months.

Cacti are indeed very vigorous plants that have made a good go of it in their arid environments, they are joined in this by the old world succulents which are a good example of convergent evolution.

Answer 2

Most cacti have a very small surface area (some are nearly globular, for example), certainly much smaller than a leafed plant. This helps limit transpiration. They also have a waxy coating that helps further. besides their defensive use, the spines can help attract dew which the plant can absorb.

Answer 3

because cacti like warm dry weather i have some has house plants they like to be stood outside in summer and fetched in again for the winter they are really easy to look after

Answer 4

I don't know what its exaclty called but it's those chinese bamboo shoots. they're like a $1 each. but all you do is just have them in a small glass vase filled with water. i've had mine for 3 years and its such a low maintenance plant in a window less kitchen.

Answer 5

the colour, the spines, the thickness of the leaves, and the way the leaves are arranged all either help them to absorb light or to retain water

Answer 6

because they have long thin needles instead of leaves to minimise the surface area they can lose water from.

Answer 7

their surface texture is suited to retaining moisture, hence why most have spikes, keeping birds from breaking their surface and releasing water.

Answer 8

That's the why and way they evolved.

Answer 9

because of thin needles