Lab -6- The Stem

Lab -6- The Stem
The stems of a plant represent elongate axes composed of nodes and internodes. Stems function as the principal supporting organ of the plant body, holding up and separating the leaves to increase their exposure to sunlight for photosynthesis, supporting the flowers for pollination, and holding up the fruits to increase their chances for effective dispersal. Stems contain vascular tissue for the conduction of materials throughout the plant body, and they produce new living tissue at apical meristems. Stems also can be modified for the storage of water or food,
Modifications of the Stem
In most plants, the stem is an upright structure that provides support for other parts of the plant body. Various types of stem modifications occur, however. You should be familiar with the following kinds of modified stems:
Stolons. Stems that run horizontally above ground are termed stolons or runners.
Rhizomes. Stems that run horizontally below the ground surface are termed rhizomes.
Tubers. The enlarged, fleshy tips of certain rhizomes (such as those of the Irish potato) are modifed for food storage and are temed tubers.
Bulbs. These are unusual below ground structures that consist of a shortened, upright stem with modified, fleshy leaves attached to it.
Herbaceous Dicot Stems