Plant Tissues: OverviewPlant Tissues: Overview

Meristematic and Permanent Meristematic and Permanent TissuesTissues

Meristematic tissues – localized Meristematic tissues – localized regions of cell divisionregions of cell division

Apical MeristemsApical Meristems Primary or Transitional Meristem Primary or Transitional Meristem Primary growth Primary growth

Lateral MeristemsLateral Meristems Vascular cambium Vascular cambium 2 2

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vascular tissue vascular tissue Cork cambium or phellogen Cork cambium or phellogen periderm periderm

Intercalary Meristems (found in the nodes of grasses)Intercalary Meristems (found in the nodes of grasses)

Root and Apical MeristemRoot and Apical Meristem

Root Apical MeristemRoot Apical Meristem

1. Root cap initials

2. Protoderm3. Ground

meristem4. Procambium5. Root cap

Lateral Meristems – secondary Lateral Meristems – secondary growth in woody plantsgrowth in woody plants

This stem has two lateral meristems. They are the vascular cambium and the cork cambium. (This is 1 year)

Lateral Meristem- 2 yearsLateral Meristem- 2 years

This is the 2This is the 2ndnd year and you can see there are two layers of xylem for each year and you can see there are two layers of xylem for each year. The pith is also referred to as the “Heartwood”year. The pith is also referred to as the “Heartwood”

Stems-InternalStems-Internal Monocot : Monocot : examples: corn, grassesexamples: corn, grasses

Dicot: Dicot: example: treesexample: trees

Stems-InternalStems-Internal

Simple Tissues – consisting of one Simple Tissues – consisting of one cell typecell type

Parenchyma – Parenchyma – thin walled & alive at maturity; thin walled & alive at maturity; often multifaceted.often multifaceted.

Collenchyma – Collenchyma – thick walled & alive at maturitythick walled & alive at maturity Sclerenchyma – Sclerenchyma – thick walled and dead at maturitythick walled and dead at maturity

Sclerids or stone cells – Sclerids or stone cells – cells as long as they are widecells as long as they are wide Fibers – Fibers – cells longer than they are widecells longer than they are wide

Epidermis – alive at maturityEpidermis – alive at maturity Trichomes – “pubescence” or hairs on epidermisTrichomes – “pubescence” or hairs on epidermis Root Hairs – tubular extensions of epidermal cellsRoot Hairs – tubular extensions of epidermal cells

ParenchymaParenchyma

CollenchymaCollenchyma

SclerenchymaSclerenchyma

Right-hand illustration modified from: Weier, Stocking & Barbour, 1974, Botany: An

Introduction to Plant Biology, 5th Ed.

SCLERIDS FIBERS

Epidermis – Epidermis – stoma, trichomes, & root hairsstoma, trichomes, & root hairs

http://www.ucd.ie/botany/Steer/hair/roothairs.html

Complex TissueComplex Tissue Xylem – water conducting tissue; Xylem – water conducting tissue; parenchyma, fibers, parenchyma, fibers,

vessels and/or tracheids, and ray cells.vessels and/or tracheids, and ray cells.

Phloem food conducting tissue; Phloem food conducting tissue; sieve-tube members sieve-tube members (no nucleus at maturity, cytoplasm present), (no nucleus at maturity, cytoplasm present), companion cells, fibers, parenchyma, and ray cells.  companion cells, fibers, parenchyma, and ray cells.  In flowering plants, sieve-tube members and In flowering plants, sieve-tube members and companion cells arise from the same mother cell. companion cells arise from the same mother cell. 

Xylem movement in stem/leafXylem movement in stem/leaf

XylemXylem

PhloemPhloem

Vascular Bundles with xylem & phloemVascular Bundles with xylem & phloem

Maize or Corn – vein in cross section

Alfalfa – vein in cross section