Alice Church, age 12, of Columbus, Ohio, for her question: '
HOW MANY KINDS OF PLANTS ARE THERE?
There are more than 350,000 different kinds of plants on earth. Plants can be found growing in just about every part of the world.
The largest of all plants is the giant sequoia tree of California. This monstrous plant can be more than 290 feet tall and measure over 30 feet wide.
The smallest of all plants is the diatom. This tiny marine or fresh water algae can only be seen under a microscope. In a single drop of water, as many as 500 diatoms may be found.
Plants are also the oldest living things on earth. There's one bristlecone pine tree in California that started to grow 4,000 to 5,000 years ago.
All living things are divided into two groups: plants and animals. Almost all plants stay in one place, but nearly all animals move about under their own power.
Most plants make their own food from water, sunlight and air. Animals cannot make their own food but must eat either plants or other animals that eat plants.
Most plant cells have thick walls that contain a material called cellulose. Animal cells do not have this material.
It would be impossible for man to live without plants. He must have food and oxygen. The oxygen in the air comes from plants, and food comes from either plants or animals that eat plants.
The study of plants is called botany, and scientists who study them are known as botanists. Botanists say that more than half of the world's 350,000 kinds of plants are what they call flowering plants. This classification includes most fruits, grains, herbs, shrubs, trees and vegetables.
Botanists divide the world into five natural communities which they call biomes: the tundra and high mountains, forests, grasslands, deserts, and aquatic or water regions. Some plants can even be found in the Arctic areas where temperatures rarely go above 32 degrees Fahrenheit.
Flowering plants have four main parts: roots, stems, leaves and flowers. The roots, stems and leaves are called the vegetative parts of the plant, while the flowers and the fruits and seeds are known as the reproductive parts.
Plants create more of their own kind by either sexually reproducing or asexually reproducing. Flowering plants, cone bearing plants and ferns usually reproduce sexually, meaning a new plant is formed from the joining of two cells: male and female. Simple plants, such as fungi and algae, reproduce asexually.
All green plants are called autotrophs. They contain chlorophyll, which enables them to capture the sunlight used in producing the food and other materials they need for growth.
Not all plants are man's friends. Some types of weeds do no more than choke off useful plants. And other plants produce bits of pollen that cause such diseases as asthma and hay fever.