Plant Tissues And Cell Types

What is a tissue exactly? A tissue is a group of cells that are structurally and/or functionally distinct, and that perform a common function. Tissues composed of just one kind of cell are called simple tissues While those composed of more than one cell type are called complex tissues.

Simple Complex Parenchyma is an example of a simple tissue (composed only of parenchyma cells) xylem is an example of a complex tissue (composed of tracheids, vessel members, parenchyma cells, and sometimes fibers)

Tissues are Organized into 3 Systems Vascular- like the plants blood stream where the transport of water and nutrients occu Ground – everything between Dermal and Vascular tissues Dermal- like the skin of the plant

All of these tissues were once Meristematic This is plant tissue where all of the growth through cell division happens. If mitosis (cell division) is happening then its meristematic tissue. Apical meristem is at the tips of shoots and roots Lateral meristematic tissue is where thickening growth takes place ·vascular cambium ·cork cambium

Simple Tissues – consisting of one cell type Parenchyma – thin walled & alive at maturity; often multifaceted. Collenchyma – thick walled & alive at maturity Sclerenchyma – thick walled and dead at maturity Sclerids or stone cells – cells as long as they are wide Fibers – cells longer than they are wide Epidermis – alive at maturity Trichomes – “pubescence” or hairs on epidermis Root Hairs – tubular extensions of epidermal cells

Parenchyma

Collenchyma

Sclerenchyma SCLERIDS FIBERS Right-hand illustration modified from: Weier, Stocking & Barbour, 1974, Botany: An Introduction to Plant Biology, 5th Ed.

Epidermis – stoma, trichomes, & root hairs http://www.ucd.ie/botany/Steer/hair/roothairs.html

Complex Tissue Vascular Tissues Xylem – water conducting tissue; parenchyma, fibers, vessels and/or tracheids, and ray cells. Phloem - food conducting tissue; sieve-tube members (no nucleus at maturity, cytoplasm present), companion cells, fibers, parenchyma, and ray cells. 

Xylem

Phloem

Vascular Bundles with xylem & phloem Maize or Corn – vein in cross section Alfalfa – vein in cross section

Examine a cross section of a Helianthus (sunflower) stem. Identify the vascular bundles, xylem, phloem, cortex, pith, and epidermis. To what tissue system (i.e.,vascular, dermal, and ground tissues) does each of these tissues belong? Find examples of collenchyma, parenchyma, and sclerenchyma cells.

Dicot Stem Epidermis Cortex (Collenchyma) Fiber Cap (Schlerenchyma) Phloem Xylem Pith (Parenchyma)