Plant Tissues: OverviewPlant Tissues: Overview

Meristems, Simple Tissues, & Meristems, Simple Tissues, & Complex TissuesComplex Tissues

Many of the figures found in this presentation are from the internet site Many of the figures found in this presentation are from the internet site http://botit.botany.wisc.edu/images/130/ and a CD entitled “Plant Anatomy” by http://botit.botany.wisc.edu/images/130/ and a CD entitled “Plant Anatomy” by

Richard Crang & Andrey Vassilyev published by McGraw Hill. Richard Crang & Andrey Vassilyev published by McGraw Hill.

I. Meristematic TissueI. Meristematic TissueOrigin Origin : Promeristem, Meristem Primer, : Promeristem, Meristem Primer, Meristem Meristem

Sekunder Sekunder (cambium) (cambium)Location Location : apical, intercalar, lateral: apical, intercalar, lateral

II.II. Permanent TissuePermanent TissueEpidermisEpidermis : silica cell, stomata, trichomata, spine, velamen, : silica cell, stomata, trichomata, spine, velamen,

fan cells.fan cells.Parenchyme: assimilation, storage, water, vascular, Parenchyme: assimilation, storage, water, vascular,

aerenchyme, wound covering.aerenchyme, wound covering.SupportingSupporting: collenchyme,sclerenchyme (schlerenchyme fiber, : collenchyme,sclerenchyme (schlerenchyme fiber,

sclereid)sclereid)VascularVascular : xylem (tracheid, vessel element), phloem (sieve : xylem (tracheid, vessel element), phloem (sieve

tube element, companion cells)tube element, companion cells)CorkCork : feloderm, felem : feloderm, felem

Specialized Tissues in PlantsSpecialized Tissues in Plants RootsRoots

Absorbs water and Absorbs water and nutrientsnutrients

Anchor plant to the Anchor plant to the groundground

Hold soil in place and Hold soil in place and prevent erosionprevent erosion

Protect from soil bacteriaProtect from soil bacteria Transport water and Transport water and

nutrientsnutrients Provide upright supportProvide upright support

Specialized Tissues in PlantsSpecialized Tissues in Plants StemsStems

Support for the plant Support for the plant bodybody

Carries nutrients Carries nutrients throughout plantthroughout plant

Defense system to Defense system to protect against predators protect against predators and infectionand infection

Few millimeters to 100 Few millimeters to 100 metersmeters

Specialized Tissues in PlantsSpecialized Tissues in Plants LeavesLeaves

Main photosynthetic Main photosynthetic systemssystems

Suseptable to extreme Suseptable to extreme dryingdrying

Sight of oxygen/carbon Sight of oxygen/carbon dioxide intake and dioxide intake and releaserelease

MERISTEMATIC TISSUEMERISTEMATIC TISSUE

The cells of meristematic tissue are similar in structure The cells of meristematic tissue are similar in structure & have thin cellulose cell walls.& have thin cellulose cell walls.

The meristematic cells may be spherical,oval,polygonal The meristematic cells may be spherical,oval,polygonal or rectangular in shape. or rectangular in shape.

The meristematic cells contain few vacuolesThe meristematic cells contain few vacuoles Cells of meristems divide continuouslyCells of meristems divide continuously

OccurrenceOccurrence-Meristematic tissues are growth tissues & are -Meristematic tissues are growth tissues & are found in those regions of the plant that grow. According found in those regions of the plant that grow. According to their position in the plant, meristems are apical, to their position in the plant, meristems are apical, lateral & intercalary.lateral & intercalary.

FunctionFunction-the main function of meristematic tissue is to -the main function of meristematic tissue is to continuously form a number of new cells.continuously form a number of new cells.

Intercalary MeristemIntercalary Meristem

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

Apical meristemsApical meristems:-these are situated at the growing tip of :-these are situated at the growing tip of the stems & roots. At shoot apex & root apex. It brings the stems & roots. At shoot apex & root apex. It brings about the elongation of the root & stem. It results in about the elongation of the root & stem. It results in increase in the height of the plant, which is called primary increase in the height of the plant, which is called primary growth.growth.

Lateral meristemsLateral meristems-these are found beneath the bark (cork -these are found beneath the bark (cork cambium) & in vascular bundles of dicot roots & cambium) & in vascular bundles of dicot roots & stems(cambium).They occur in thin layers. Cambium is the stems(cambium).They occur in thin layers. Cambium is the region which is responsible for growth in thickness. It region which is responsible for growth in thickness. It causes the organ(stem or root) to increase in diameter . causes the organ(stem or root) to increase in diameter . This is called secondary growth.This is called secondary growth.

Intercalary meristemsIntercalary meristems-they are located at the base of leaves -they are located at the base of leaves or internode,e.g., Stem of grasses & other monocots.or internode,e.g., Stem of grasses & other monocots.

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

Basswood – root in cross sectionBasswood – stem in cross section; 1, 2, 3 year old stems

PARENCHYMAParenchyma cells are oval,round,polygonal or elongated in Parenchyma cells are oval,round,polygonal or elongated in shape. The cell wall is thin & encloses a dense cytoplasm which shape. The cell wall is thin & encloses a dense cytoplasm which contains a small nucleus & surrounds a large central vacuole. contains a small nucleus & surrounds a large central vacuole. OccurrenceOccurrence-the parenchyma is widely distributed in stem,roots,-the parenchyma is widely distributed in stem,roots,

FunctionsFunctions--Parenchyma maintain the shape & firmness of the plant due to Parenchyma maintain the shape & firmness of the plant due to its turgid cells. The main function of parenchyma is to store & its turgid cells. The main function of parenchyma is to store & assimilate food. Parenchyma serves as food storage tissue .assimilate food. Parenchyma serves as food storage tissue .Transport of materials occurs through cells or cell walls of Transport of materials occurs through cells or cell walls of parenchyma cells. Parenchyma cells are metabolically active; parenchyma cells. Parenchyma cells are metabolically active; their intercellular air spaces allow gaseous exchange.their intercellular air spaces allow gaseous exchange.

Isodiametric Parenchyma Cell containing Isodiametric Parenchyma Cell containing Chromoplasts: Each red dot is a Chromoplast that Chromoplasts: Each red dot is a Chromoplast that

Contains Carotenoids.Contains Carotenoids.

Elongate Palisade Parenchyma with Elongate Palisade Parenchyma with ChloroplastsChloroplasts

Parenchyma from Potato with large Parenchyma from Potato with large AmyloplastsAmyloplasts

Parenchyma Cells containing Parenchyma Cells containing Amyloplasts. Amyloplasts.

Shoot Apical MeristemShoot Apical Meristem

PERMANENT TISSUE

These tissues derived from the meristematic tissues but their cells have lost the power of division & have attained their definite forms. Permanent tissues are classified into two-simple & complex.Permanent tissue-these tissues are composed of cells which are structurally & functionally similar. They are :I.EpidermisII.ConnectiveIII.Vascular

ParenchymaParenchyma

Surface View of  Epidermis from a Leaf: Note the Surface View of  Epidermis from a Leaf: Note the undulating Epidermal Cells plus the Stomata (S) and undulating Epidermal Cells plus the Stomata (S) and

Trichomes (T).Trichomes (T).

COLLENCHYMA It shows many of the features of parenchyma but is It shows many of the features of parenchyma but is

characterized by the deposition of extra cellulose at characterized by the deposition of extra cellulose at the corners of the cells. In collenchyme ,intercellular the corners of the cells. In collenchyme ,intercellular spaces are generally absent. Collenchyme cells are spaces are generally absent. Collenchyme cells are elongated in shape. They often contain a few elongated in shape. They often contain a few chloroplasts.chloroplasts.

OccurrenceOccurrence-the cells of collenchyma are located below -the cells of collenchyma are located below the epidermis of dicotyledon stem & petiole. the epidermis of dicotyledon stem & petiole. Collenchyma is absent in monocot stems,roots & Collenchyma is absent in monocot stems,roots & leaves.leaves.

FunctionsFunctions- collenchyma is a mechanical tissue;it - collenchyma is a mechanical tissue;it provides mechanical support & elasticity. provides mechanical support & elasticity.

SCELERENCHYMA Composed of dead cells and sclerenchyma are

greatly thickened with deposition of lignin. The cells of sclerenchyma are closely packed without intercellular spaces.

Found in stems,roots,veins of leaves. Functions-the sclerenchyma is mainly mechanical

& protective in function. It gives strenght,rigidity,flexibility & elasticity to the plant body &,thus,enables it to withstand various strains.

XYLEM Nature-xylem is a vascularXylem is composed of cells of

four different types:tracheids and vessels element (bounded by thick lignified. Vessels are very long tube-like structures formed by a row of cells placed end to end. They conduct water).

Functions-i. The main function of xylem is to carry water & minerals

salts upward from the root to different parts of shoots.ii. Since walls of tracheids,vessels of xylem are lignified, they

give mechanical strength to the plant body.

PHLOEMPHLOEM Nature-Phloem is composed of following two

types : 1.sieve tubes;2.companion cells; Functions-phloem transport

photosynthetically prepared food materials from the leaves to the storage organs & later from storage organs to the growing regions of the plant body.

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

XylemXylem

PhloemPhloem

Vascular Bundles with xylem & phloemVascular Bundles with xylem & phloem

Maize or Corn – vein in cross section

Alfalfa – vein in cross section

Periderm – cork & parenchymaPeriderm – cork & parenchyma

TWIG WITH LENTICELS

Secretory StructuresSecretory Structures nectar (flowers) from nectaries nectar (flowers) from nectaries oils (peanuts, oranges, citrus) from accumulation of oils (peanuts, oranges, citrus) from accumulation of

glands and elaioplasts. glands and elaioplasts. resins (conifers) from resin canals resins (conifers) from resin canals lacticifers (e.g., latex - milkweed, rubber plants, lacticifers (e.g., latex - milkweed, rubber plants,

opium poppy) opium poppy) hydathodes (openings for secretion of water) hydathodes (openings for secretion of water) digestive glands of carnivorous plants (enzymes) digestive glands of carnivorous plants (enzymes) salt glands that shed salt (especial in plants adapted to salt glands that shed salt (especial in plants adapted to

environments laden with salt). environments laden with salt).