Plant Cell and Tissues

Plant Cell and Tissues

Plant tissues are made of 3 basic cell types:

Plant cell have cell walls, plastids and a large vacuole.

3 basic types of plant cells:

Parenchyma: Are most common type of cell-stores starch, oils and water for the plant. These cells have thin walls and large water-filled vacuoles in the middle. Photosynthesis occurs in the green chloroplasts within parenchyma cells in leaves.

Collenchyma: Has cell walls that range from thin to thick, providing support while still allowing the plant to grow. These cells are most common in the younger tissues of leaves and shoots. The unique feature of collenchyma is that they are flexible. Their cell walls dont´t contain lignin, so they are stretchy and can change size.

Sclerenchyma: This is the stonger cell. These cell have a second cell Wall that is hardened by lignin, which makes these cells very tough and durable. They can´t grow within the plant like Collenchyma cells. They are found in parts pf the plant that aren´t lengthening anymore. Many of these cells die when they reach maturity. These cells form the major part of fruit pits and the outer shell of nuts. They are also found in the stem and leaf veins and are responsible for the gritty texture of pears.

Plant organs are made of 3 tissue systems:

Dermal tissue: This tissue covers the outside of a plant and protects it in a variety of ways. Is made up of live parenchyma cells in the nonwoody parts of the plant. Dermal tissue made of dead parenchyma cellas make up the outer bark of woody plant.

Ground tissue: This system makes up much of the inside of the plant. Provides support and stores materials in roots and stem. In leaves, is packed with chloroplast, where photosynthesis makes food for the plant. The ground tissue system consists of all three of simple tissues-parenchyma, collenchyma and sclerenchyma tissue- but parenchyma is the most common in ground tissues.

Vascular tissue:  This tissue transports water, mineral nutrients, and organic compounds to all parts of the plant. Plants can transport necessary fluids and nutrients throughout their systems. The vascular system is made up of 2 networks of hollow tubes somewhat like our veins and arteries. Each network consists of a different type of vascular tissue that works to move different resources throughout the plant. Xylem is the vascular tissue that carries water and dissolved mineral nutrients from the roots to the plant. Phloem is the vascular tissue that carries the products of photosynthesis through the plant.

The Vascular Systems

Water and dissolved minerals move through xylem:

Xylem contains other types of cells besides the basic cell types, that’s why is called a complex tissue.

One specialized cell in the xylem is called a tracheid. This cells are long and narrow. Water can flow from cell to cell in tracheids through openings in the thick cell walls. Some types of vascular plants have an additional kind of xylem cell called a vessel element. Vessel element are shorter and wider than tracheids.

The cohesion-tension theory proposes that the physical properties of water allow the rise of water through a plant. This theory is based on the strong attraction of water molecules to one another and to other surfaces.

The loss of water vapor from plants is called transportation. As leaves transpire, the outward flow of water lowers the pressure in the leaf xylem, creating a vacuum that pulls water upward.

Phloem carries sugars from photosynthesis throughout the plant:

Phloem carries plant nutrients, including minerals and sugars, throughout the plant. Phloem moves the products of photosynthesis out of the leaves to stems and roots.

Phloem tissue is alive. Phloem is a complex tissue made mostly of cells called sieve tube elements. Their name comes from the small holes in the end walls of their cells. These holes let the phloem fluids, or sap, flow through the plant. As they form, sieve tubes elements lose their nuclei and ribosomes.

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