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The Three Plant Tissues
Terms in this set (26)
Plant's protective outer covering in contact with the environment. It facilitates water and ion uptake in roots and regulates gas exchange in leaves and stems.
Together with phloem and xylem form a continuous vascular system throughout the plant. The tissue conducts water and solutes between organs and also provides mechanical support.
This packing and supportive tissue accounts for much of the bulk of the young plant. It also functions in food manufacture and storage.
Where do the tissues manifest from?
All three tissue systems derive ultimately from the cell proliferate activity of the shoot or root apical meristems, and each contains a relatively small number of specialized cell types.
Parts of the Dermal Tissue
Epidermis, stomata, trichomes (hairs)
The primary outer protective covering of the plant body. Cells of the epidermis are also modified to form stomata and hairs of various kinds.
Parts of the Epidermis
The epidermis (usually one layer of cells deep) covers the entire stem, leaf, and root of the young plant. The cells are living, have thick primary cell walls, and are covered on their outer surface by a special cuticle with an outer waxy layer. The cells are tightly interlocked in different patterns.
openings in the epidermis, mainly on the lower surface of the leaf, that regulate gas exchange in the plant. They are formed by two specialized epidermal cells called guard cells, which regulate the diameter of the pore. Stomata are distributed in a distinct species-specific pattern within each epidermis.
(hairs) Appendages derived from epidermal cell. They exist in a variety of of forms and are commonly found in all plant parts. Hairs function in protection, absorption, and secretions; for example, young, single-celled hairs develop in the epidermis of the cotton seed. When these grow, the walls will be secondarily thickened with cellulose to form cotton fibers.
Trichomes are leaf hair cells, and developmentally derived from the dermal tissues of the plant.
In some plants these trichomes have evolved to provide either protective functions against herbivory (e.g. fireweed or peppermint), or have been adapted to provide nutrients to organisms that provide a mutualistic interaction (e.g. nectaries and pollenating insects)
Parts of the Ground Tissue
The ground tissues system contains three main cell types called parenchyma, collenchyma, sclerenchyma
Cells found in all plant tissue systems. They are living cells, generally capable of further division, and have a thin primary cell wall. These cells have a variety of functions. The apical and lateral meristematic cells of shoots and roots provide the new cells required for growth. Food production and storage occur in the photosynthetic cells of the leaf and stem (called mesophyll cells); storage parenchymas cells form the bulk of most fruits and vegetables. Because of their proliferative capacity, parenchyma cells also serve as sources of new cells for wound healing and regeneration
a specialized form of parenchyma cell, and is readily identified by elaborate ingrowths of the primary cell wall. The increase in the area of the plasma membrane beneath these cell walls facilitates the rapid transport of solutes to and from the cells of the vascular system.
Living cells similar to parenchyma cells except that they have much thicker cell walls and are usually elongated and packed into long ropelike fibers. They are capable of stretching and providing mechanical support in the ground tissue system of the elongated regions of the plant, and especially common in subepidermal regions of the stem.
Like collenchyma, they have strengthening and supporting functions. However, they are usually dead cells with thick, lignified secondary cell walls that prevent them from stretching as the plant grows. Two common types are fibers and sclereids.
Often form long bundles
Shorter branched cells found in seed coats and fruit
What kinds of mesophyll are found in parenchyma cells in leaves?
Pallisade mesophyll and spongy mesophyll
layer of cells directly below upper epidermis. Cells are rod-shaped and tightly packed against one another. Large numbers of chloroplasts contained in these cells.
irregular shaped cells with large air spaces between neighboring cells, with limited cell-cell contacts that allow for efficient gas exchange during photosynthesis and respiration (oxygen and carbon dioxide)
What do both forms of mesophyll have?
Both forms of mesophyll have thin primary cell walls, and can differentiate into other cell types when subjected to appropriate environments (hence, classification as parenchyma)
Primary cell walls
Primary cell walls are deposited during cell division and cell expansion and differentiation
Secondary cell walls
Secondary cell walls form in fully differentiated cells and are deposited between the primary cell wall and the plasma membrane
Collenchyma (pt 2)
have thickened primary cell walls
(but not secondary cell walls) and can therefore continue to elongate and expand. The thickened cell walls and elongated shape of collenchyma cells often provide additional structural support in stem and root tissues.
Sclerenchyma (pt 2)
differs from collenchyma in that cells
contain secondary cell walls and therefore are
(and often dead), and cannot continue to expand or change shape.
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