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Stem usually consist of three tissues: dermal tissue, ground tissue, and vascular tissue. [5] Dermal tissue covers the outer surface of the stem and usually functions to protect the stem tissue, and control gas exchange. [6] The predominant cells of dermal tissue are epidermal cells. [6]
Underground stems are modified plant parts that derive from stem tissue but exist under the soil surface. [1] They function as storage tissues for food and nutrients, facilitate the propagation of new clones, and aid in perennation (survival from one growing season to the next). [ 2 ]
The earliest vascular plants had stems with a central core of vascular tissue. [3] [4] This consisted of a cylindrical strand of xylem, surrounded by a region of phloem. Around the vascular tissue there might have been an endodermis that regulated the flow of water into and out of the vascular system. Such an arrangement is termed a protostele. [5]
Prickles on a blackberry branch. In plant morphology, thorns, spines, and prickles, and in general spinose structures (sometimes called spinose teeth or spinose apical processes), are hard, rigid extensions or modifications of leaves, roots, stems, or buds with sharp, stiff ends, and generally serve the same function: physically defending plants against herbivory.
Parenchyma is a versatile ground tissue that generally constitutes the "filler" tissue in soft parts of plants. It forms, among other things, the cortex (outer region) and pith (central region) of stems, the cortex of roots, the mesophyll of leaves, the pulp of fruits, and the endosperm of seeds.
The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. [1] In the human brain the brainstem is composed of the midbrain , the pons , and the medulla oblongata . [ 1 ]
Cross-section of a flax plant stem: 1. Pith 2. Protoxylem 3. Xylem I 4. Phloem I 5. Sclerenchyma 6. Cortex 7. Epidermis. In botany, a cortex is an outer layer of a stem or root in a vascular plant, lying below the epidermis but outside of the vascular bundles. [1]
A leaf (pl.: leaves) is a principal appendage of the stem of a vascular plant, [1] usually borne laterally above ground and specialized for photosynthesis.Leaves are collectively called foliage, as in "autumn foliage", [2] [3] while the leaves, stem, flower, and fruit collectively form the shoot system. [4]