Ground Tissues: Cells and Tissues

1. Ground Tissues: Cells and Tissues • Parenchyma – These are the most abundant and versatile cells found in plants. • Storage - Plants store nutrients in Parenchyma cells. • Basic Metabolism – parenchyma cells are the primary sites of photosynthesis and protein synthesis.

2. Differentiation – When a cell changes to another type of cell to carry out a different function. • Redifferentiation – When that same cell changes back to carry out its original function

3. II. Collenchyma: support growing regions of shoots and therefore are found in stems and petioles.These cells actually develop from parenchyma cells, especially during mechanical stress.

4. III. Sclerenchyma – are rigid, nonstretchable secondary cells that support and strengthen nonextending portions of plants such as mature stems and are usually dead at maturity. The support of Sclerenchyma is usually attributed to it’s thick cell walls. • A. The first type of sclerenchyma cells are called sclereids, which are relatively short, and have a variety of shapes and are found singly or in groups. • B. The second type are fibers, which are long slender cells which usually occur in strands or bundles.

5. More about Sclereids: • They are found throughout plants such as in roots, leaves, stems, seed coats, and even in peanut hulls. • They usually form hard layers, such as in the core of an apple or the shell of walnuts.

6. More about Fibers – there are a number of uses of fibers. • Manila hemp – used for making ropes and cords • Agave – used to make course ropes and twines. • Cannabis – used to make rope and twine • Flax – used to make linen and other flexible, soft items such as sheets and even money. • Jute – used to make very coarse fabrics such as burlap, bags and sacks. This is the second most important fiber in the world behind only cotton. • Cotton – the single most important fiber in the world. however, cotton is not a sclerenchyma fiber, but a trichome, which is an extension or outgrowth of epidermal cells.

7. Cotton Flax linens Manila hemp Jute burlap sack

8. Agave Plant Agave fiber weaving Cannabis fiber plant

9. Cell Types

10. The Epidermis – • The outer walls of the epidermis are covered with a waxy , fatty, waterproof layer of cutin called a cuticle. • On the underside of wax palms is a thick layer of waxy epithelium called carnauba wax which is used to make candles, polishes and lipsticks.

11. Gas Exchange • Gas exchange is carried out through spaces or holes in the epidermis called stomata. • These Stomata are surrounded by cells known as guard cells which regulate gas exchange andthe loss of water. stomata Guard cell

12. The flat bricklike cells that lack chloroplasts and are transparent are called epidermal cells. • The structures inside plant cells that enable them to carry out photosynthesis are called chloroplasts.

13. Trichomes • Single celled or multicellular outgrowths of epidermal cells, often used to protect the seed. • The most economically valuable trichomes are cotton seed epidermis. • Some trichomes are used by carnivorous plants to to secrete enzymes used to liquify trapped prey and digest them • Root hairs are also trichomes. • Trichomes are also used by seeds for dispersal, especially those that are light and airy.

14. Vascular Tissues: Xylem and Phloem • Xylem carries water and dissolved nutrients in an unbroken stream from the roots upward to all parts of the plant. • Phloem transports dissolved organic materials, especially sucrose, for transport to all parts of the plant, NOT just downward.

15. Secretory Structures • Nectaries: structures that secrete nectar, a sugary substance that attracts insects, birds, bats, or other animals . • Internal secretorycells are large cells that contain tannins, resins, mucilage, and crystals. • Laticifers are secretory cells that contain latex. • Salt Glands secrete salt from marsh plants such as spartina

16. That’s all Folks!