The principal parts of a plant are the root system and the above ground portion consisting of stems, leaves, flowers and seeds I) the root system, 2) the stems and leaves, 3) the reproductive part made up of flowers or seeds. The roots have two main functions to absorb plant nutrients and water from the soil. As to stems and leaves, the food used in growth is manufactured in the leaves. This process is known as photosynthesis. To support the leaves and to connect then with the roots are the main functions of the stem. The shape and the position of the leaves vary to a considerable extent with the species. A flower is the part of the plant where seeds are produced. All parts of a plant must be developed well and proportionally enough to function properly If conditions for plant growth are bad, the plant will be too weak to develop its parts well.