stem summary

stem, In botany, axis of vascular plants that emerges from the roots, supports the branches, bears buds and shoots with leaves, and contains the vascular tissues (xylem and phloem) that transport water, minerals, and food to other parts of the plant. Most stems have a pith (a central core of spongy tissue) that is surrounded by strands or bundles of conducting xylem and phloem, then by the cortex. In woody plants the outermost epidermis forms bark, with the cambium (an area of actively dividing cells) lying just below the bark. Lateral buds and leaves grow out of the stem at intervals called nodes; the intervals on the stem between the nodes are called internodes. In flowering plants, various stem modifications (rhizome, corm, tuber, bulb, stolon) let the plant survive dormantly for years, store food, or sprout asexually. All green stems perform photosynthesis, as do leaves; in plants such as cacti and asparagus, the stem is the chief site of photosynthesis.