Few plants survive in a desert because the climate is too dry.
Because there isn't enough water or moisture in the soil for plants to take up through their roots so normal plants can't survive in the desert.
Because not all of them find conditions that are suitable for germination. After germination a number will die or be eaten by pests, killed or damaged mechanically, die because of drought, frost etc. The more seeds the greater chance for the survival of a few plants.
The stem of terrestrial plants are strong to support themselves as they grow upward. Without this physical characteristic, they would simply fall over after growing a few inches.
Plants need quite a few things to grow, it needs sun, carbon dioxide and water to make food, the food is glucose this process is called photosynthesis. The "Vacuole" (a particular part of the plant), stores all the food. Water is also needed every so often, some plants for example a cactus, can store water inside it's body for up to a few years maybe, but other plants would need water every day.
Not many plants grow under casuarinas because of the needles. Plants dont have to grow everywhere, Apart from human cleared areas casuarina needles create some of the few gaps in the forest for animals to hang out in. I could tell you which species grow naturally under them in my area. But they may not be endemic to your area. There are a number of invasive weeds that are able to grow under Casuarinas. These are terrible plants and I certainly dont want people to grow them. Ehrharta erecta, Cyperus, Bidens pilosa. Plants can grow from runners or suckers in Casuarina needles also. An example of a tree that can grow by suckering through Casuarina needles is the Casuarina. =] . Go out and see what grows under them naturally in your area, and if you are going to grow some yourself insure that they are provenant to your area. read - What is provenant? I only propagate endemic provenant indigenous plants. I dislike people who treat plants like toys. "OW Look isn't that JESSAMINE pretty , I'm going to plant it everywhere because I'm an *&^%$#@". Know what I mean?
Fluorescent light works for most of plants and even aquarium fish. But when it comes to special races of plants, such as mariguana or some philotherms, HPS or MH can achieve a better effect. Check the link below for more detail about fluorescent light.
There is no or little farming in much or north Africa along with southern Africa because of the climate. It's getting farther away from the equator and the climate starts to get colder.
Few plants grow tall on the forest floor because there is a lack of sunlight.
There are few plants and animals hardy enough to survive in the Sahara’s arid climate.
dessert
There are a few plants that grow better with morning sunlight. Some of the plants are spring bloomers, pansy and sunflowers.
There can be more plants. But very few people know it.
nonvascular plants
The venus fly trap grows in a small region in North and South Carolina. There are few plants left in the wild, and are considered threatened.
There are quite a few plants that grow in low moisture climates. These plants will typically have very thick protective tissues.
A desert
There are quite a few plants that are fun to grow. Marigolds, nasturtiums, peas, beansprouts, and mustard are all easy and fun to grow from seeds. You can even grow a plant from a carrot top.
Few plants grow in the waters of a swift-flowing stream because the water's movement makes it tough for the plants to attach to any surfaces. Often, plants are pushed to the tidal pools or the mouth of the streams.