The Eudicot plant, morphology, meristems, cell types and tissues Objectives of the lecture: 1. To illustrate and name some essential parts of plants,

The Eudicot plant, morphology, meristems, cell types and tissues

Objectives of the lecture:

1. To illustrate and name some essential parts of plants,

2. show how they are produced,

3. discuss how cell and tissue structure are integrated with morphology,

4. give examples of some variation in morphology between species.

Text book pages:472-473,792-808,800-812

Figure 36-19

Plant cells have cell walls, vacuoles, and chloroplasts.

Adjacent plant cells are connectedby plasmodesmata.

Plasma membrane

Cell wall

Vacuole

Chloroplast

Mitochondria

Rough ER

Golgi apparatus

Smooth ER

Cell 1

Cell 2

Cell wall

Smooth ER

Cell wall

Plasma membrane

Plasma membranePlasmodesma

Plant cell walls are flexible but have considerable tensile strength

Communication between cells is through plasmodesmata

Figure 8-9

Cell walls consist of 3 types of layers

Secondary cell wall

Secondary wall: formed after cell enlargement is completed provides compression strength. It is made of cellulose, hemicellulose and lignin. The secondary wall is often layered.

Primary cellwalls

Primary wall: This is formed after the middle lamella and consists of a skeleton of cellulose

microfibrils embedded in a gel-like matrix of pectic compounds, hemicellulose, and glycoproteins.

Middle lamella

Middle lamella is formed during cell division. It makes up the outer wall of the cell and

is shared by adjacent cells. It is composed of pectic compounds and protein.

Figure 8-14Plasmodesmata create gaps that connect plant cells.

Tubule ofendoplasmic

reticulum passing throughplasmodesmata

Membraneof cell 1

Cell walls

Smoothendoplasmicreticulum

Membraneof cell 2

Cell wallof cell 1

Cell wallof cell 2

Plasmodesmata seen in Transverse Section: They are not simple openings as they have a complex internal structure.

A tissue is a cooperative unit of many similar cells performing a specific function within a multicellular organism

Tissues usually have cells that are specialized for particular functions

The vascular tissue system conducts water and nutrients from roots to leaves through specialized cells and conducts the products of photosynthesis, sugars, from leaves in different but equally specialized cells.

Tissues

Figure 36-16

Cross sections:Meristematictissue

Leaf

Stem

Meristematictissue

Root

Vascular tissuesystem (red)

Dermal tissuesystem (brown)

Dermal tissuesystem (brown)

Ground tissuesystem (gray)

Ground tissuesystem (gray)

Vascular tissuesystem (red)

Sh

oo

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mPlants comprises three main tissue types each with different functions.

There is continuity of these individual tissue systems through the plant

Dermal tissue – protection and interface with the environment

Ground tissue – frequently the site of storage, sometimes support

Vascular tissue – conduction of water and materials used in synthesis

lateral(axillary)bud

shoot tip(terminal bud) young leaf

flower

leaf

seeds(insidefruit)

witheredcotyledon

root hairs

root tiproot cap

node

nodeinternode

VASCULAR TISSUES

GROUND TISSUES

SHOOT SYSTEM

ROOT SYSTEM

primary root

lateral root

The angiosperm plant body

EPIDERMIS

Dermal tissue

A tomato plant

See Fig. 36.3 in your text book

Figure 36-23

new cells elongate and start to differentiate into primary tissues

new cells elongate and start to differentiate into primary tissues

Root cap

activity atmeristems

Shoot apical meristem

Actively dividing cells near the dome-shaped tip

The apical meristem’s descendant cells divide, grow and differentiate to form: Protoderm Ground meristem Procambium

activity atmeristems

Root apical meristem

Function of apical meristems

Figure 36-15

Apical meristems and primarymeristems in a root

Apical meristem and primarymeristems in a shoot

Leafprimordia

Apicalmeristemat tip ofshoot

Apicalmeristemin lateralbud

Groundmeristem

Protoderm

Procambium

Apicalmeristem

Root cap

What does a meristem look like?

ColeusApical meristem

Transverse section through the apical meristem and newly forming leaves

Longitudinal section through the apical meristem

Axilliary bud meristem

The axilliary meristem may develop into a foliated branch.

Coleus

L4 S8

Tissues

Meristems-> Tissues

procambium

primary pholemprimary xylempithprocambiumcortex

Meristems

Immature leafshoot apical meristem

ground meristemprocambiumprotoderm

Spiral thickening

Figure 23-7

Cotyledons

Hypocotyl

RootWild-typeseedling

Apicalmutant

Centralmutant

Basalmutant

Mutants lacking hypocotyls and roots in Arabidopsis

The MONOTERPOS gene encodes a transcription factor that regulates activity of target

genes and the MONOTERPOS protein is manufactured in response to signals from auxin

which is produced at the apex and occurs in a concentration gradient which provides

positional information.

The expression of genes that encode transcription factors determines cell, tissue and organ identity

The fate of a cell is determined by its position and not its clonal history

Developmental pathways are controlled by networks of interacting genes

Development is regulated by cell-to-cell signalling

Ligand-induced signalling: cell wall component chemicals that communicate local positional information

Hormonal signalling: auxin and others

Signalling via regulatory proteins and/or mRNAs through plasmodesmata

Regulation of developmental pathways

Plants of the day

CeleryPotatoCarrotBrussels sproutCabbage

Simple tissues of parenchyma, collenchyma and sclerenchyma

Transverse section

pholem

Important structural tissues of many angiosperms

xylem

epidermis

parenchyma

collenchyma

sclerenchyma

Pages 804-805 of your text book

Table 36-1

wx

b z

Figure 36-25

SclereidsFibers

Thick secondary cell walls

Sclerenchyma

Figure 36-24

Cross section of celery stalk Close-up of “string,” in cross section Collenchyma cells, in cross section

Collenchyma

Figure 36-22

In roots, parenchyma cells function incarbohydrate storage.

Chloroplasts

In leaves, parenchyma cells function inphotosynthesis and gas exchange.

Starchgranules

Parenchyma

Figure 36-18

Cortex

Cross section of a eudicot stem Cross section of a monocot stem

Epidermis

PithGround tissue

Vascular bundles

Figure 36-17

Root hair

Lateralroot

Vascular tissue

Ground tissue

Epidermal tissue

Apical meristem

Sloughed-offroot cap cells

Root cap

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Root meristem and structure

Roots must ‘force’ their way through the soil

Protection of the apical mersitem

Delayed initiation of lateral meristems

Different requirements for support and water collection and distribution

Zea mays root apex

Zea mays root apex showing the junction between root apex and the root cap

Lateral root development in Zea mays

A meristem develops from parenchyma and the lateral root grows out through the cortex

1. The structure of cell walls and how communication between plant cells may take place.

Things you need to know ...

2. Be able to define a tissue and give examples of cell types and functions within important tissues of the plant.

3. Define the structure of angiosperm plants.

4. Define the meristems of the angiosperm plant and describe how tissues develop from them