21.1

a collenchyma cell

A collenchyma cell 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. They often form into strands. For example, celery strings are strands of collenchyma cells.The unique feature of collenchyma cells is that they are flexible. Their cell walls don't contain lignin, so they are stretchy and can change size. As a young leaf grows, collenchyma cells can elongate and still give the leaf structure.

a parenchyma cell

A parenchyma cell is the most common type of plant cell—stores starch, oils, and water for the plant. These cells have thin walls and large water- filled vacuoles in the middle.

cell types

The tissue systems of plants may consist of simple tissues from the basic cell types: parenchyma, collenchyma, and sclerenchyma.

xylem

Xylem is the vascular tissue that carries water and dissolved mineral nutrients up from the roots to the rest of the plant.

a sclerenchyma cell

a sclerenchyma cell is the strongest. These cells have a second cell wall that is hardened by lignin, which makes these cells very tough and durable. But the lignin also makes these cells very rigid. Unlike collenchyma cells, they can't grow with the plant. Therefore, sclerenchyma cells are found in parts of the plant that aren't lengthening anymore.

dermal tissue

dermal tissue covers the outside of a plant and protects it in a variety of ways. Dermal tissue called epidermis is made up of live parenchyma cells in the nonwoody parts of plants. On leaves and some stems, epidermal cells may secrete a wax-coated substance that becomes the cuticle. Dermal tissue made of dead parenchyma cells makes up the outer bark of woody plants.

ground tissue

ground tissue makes up much of the inside of a plant. Ground tissue provides support and stores materials in roots and stems. The ground tissue system consists of all three of the simple tissues—parenchyma tissue, collenchyma tissue, and sclerenchyma tissue—but parenchyma is by far the most common of the ground tissues.

phloem

phloem is the vascular tissue that carries the products of photosynthesis through the plant.

tissues

there are three groups of tissue systems in plants: dermal, ground, and vascular tissue systems

vascular tissue

vascular tissue transports water, mineral nutrients, and organic compounds to all parts of the plant.