All living things need food and water for growth and survival. Plants, like other living creatures also require food and water to live and grow. Without sufficient of these, they shrivel and finally die.

But it is interesting to know that plants prepare their own food where as the animals consume the food prepared by the plants. Leaving apart the non-green plants, all green plants prepare or cook their own food. Plants prepare their food with the help of water, air, and chlorophyll and in the presence of sunlight. This amazing process  is called photosynthesis.

The cells of the leaves of the green plants and in fact, all green parts like the stem and flowers of some plants contain the  marvelous substance known as chlorophyll.  Chlorophyll is a green pigment. These parts absorb the energy  from sunlight. This energy transforms dead inorganic chemicals into enliven organic chemicals.

But for the growth of living tissues, carbon is necessary. The plants obtain this carbon from the air. This carbon exists in the air in combination with oxygen in the form called carbon dioxide. Once the plants obtain carbon, they combine it with other substances to build various parts of the plant.

The most important of these substances, is water from which the plants get hydrogen and some other minerals which they need. These minerals are mostly compounds of Nitrogen, Sulphur, phosphorus, potassium, calcium, magnesium, sodium and iron.

The plants absorb water and minerals through their roots. We mark at times the  roots to be long at their tips.  One of the reasons for this is the fact that they can keep coming in contact with new acclaimed areas of the soil in their search for water and minerals. The root also contains numerous tiny root hairs projected from the surface and from the newly developed roots spreading into the soil to absorb water and minerals. Part of the water, thus absorbed, is utilized to manufacture sugar. The unused water gets evaporated from the leaves. When the rate of evaporation becomes  faster than the amount of water absorbed through roots, plants shrivel.

It is very interesting to note that no two leaves are exactly alike, even if they belong to the same plant and have the same shape and colour.

We see plants all around. We all are  convinced that it is the plant  kingdom  which is the storehouse of our food. Not only for the humanbeings, but also for all living beings, it is in fact, indispensable for providing food.

But, was there  a time when plants were nonexistent on the Earth?    According to the speculation of science, the answer is yes. The very first trace of life, almost 2 billion years ago, were found in sea as simple plants, while land was lifeless. Millions of years ago, tiny spots were seen on the surface of earth. Subsequently it was known that those spots were the specks of protoplasm. Protoplasm is the name given to the living material, may it be found in plants or animals. These original specks of protoplasms, according to the scientists were the origin of all our plants and animals.

The protoplasm specks joined      together, developed thick walls to become plants and settled down to staying in one consecrated place to call it a forest. Gradually they developed green colouring matter known as chlorophyll which enabled them to prepare food from substances present in the air, water and soil.

These primodical green plants had only one cell. Later they formed group of cells. As at that time they had no protective measure against heat and Sun, and thus they got drying out, they had to stay in water. Even today some descendants of these primodical plants still survive though they have metamorphosed quite a lot. We call them algae. Sea-weeds are example of these plants.

One group of plants developed which does not require chlorophyll for obtaining its food. This non-green group of plants is called Fungi. They include yeasts, moulds, bacteria and mushrooms.

Most of the strains of plant kingdom  seen on Earth today are evolved from the algae. Certain of these came out of the sea and developed rootlets that could anchor them into the soil. They also subsequently developed tiny leaves with an outer skin covering to provide protection from drying. These plants are termed as mosses and ferns.

About 425,000,000 years ago, a few tiny green plants emerged on land from some kinds of green sea weeds (algae). The first land plant appeared quite like the mosses, liveworts, and hornworts flourishing in damp, shady places. About 400,000,000 years ago more complex plants looked like ferns, horsetails, and club mosses appeared. Ferns were the first plants to possess roots, stems and leaves.

At the earliest, the reproduction of plants started by simple cell division. Such reproduction occurs in cases of bacteria and yeasts. Some by means of spores, which are tiny spot like cells simulating seeds. But, they did not contain store food as in seeds. As ages passed on, some of these plants developed flowers that bore true seeds.

       Gradually we now pretty far advanced in the field of development of plant kingdom. Two types of plants bearing different types of seeds appeared. One type of seed is seen in the naked eyes and another group concealed in the protective covering. Each of these to types again developed into several sub-types giving rise to plants of different lines. In this process, the plant kingdom came into existence, on our mother earth. This is the theory of modern botanical science.