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BI 103: Tissues & Cells Lecture 4

Plant Anatomy

Tissues & Organs

I. Plants have three or four major groups of

organs:

1. Roots

2. Stems

3. Leaves

4. Flowers

II. Each organ is composed of tissues.

A tissue is a group of cells performing a similar

function.

-

Plant Anatomy: Vegetative Organs

Leaves:

Roots:

Stem:

Arise from stem

Arise from stem

Place leaves, buds,

& roots attach

Plant Anatomy: Vegetative Organs

Leaves:

Roots:

Stem:

Form = Function

Photosynthesis

Gas exchange

Light absorption

Anchorage

Storage

Transport

Absorption

Support

Transport

Storage

Wild Brassica oleracea

Broccoli

Cabbage

Kale

Brussels

sprouts

Cauliflower

Kohlrabi

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Plant Organs: human cultivation and manipulation

Plant Anatomy: Tissues

4 Tissues:

1. Meristematic

2. Ground

3. Vascular

4. Dermal

Plant Growth

Meristems – Tissues of plants that add

new growth. Regions of actively

dividing cells.

Apical – increases length/height (primary)

Lateral – increases girth. (secondary)

Plant Anatomy: Tissues and Cells

Meristematic

Tissue

Apical

Meristem

Pericycle Vascular

Cambium

Cork

Cambium

Functions of Meristematic Tissue:

• Growth

• Primary (length)

• Secondary (girth)

Primary vs. Secondary growth

Primary Growth

All plants

Vertical growth

up or down

Plant gets taller

Where: Meristem tissue

in roots & buds

Secondary Growth

Woody plants only

(only Dicots)

Horizontal growth: girth

Plant gets wider

Where: vascular

cambium, cork cambium

Apical Growth Root: pericycle

Shoot: Apical

meristem

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Apical Meristem

Aka lateral buds

Axillary Buds

Leaf

Primordia

Apical

Meristem

Axillary Bud

Primordia Older Leaf Primordia

(developing)

Lateral Meristems Produce secondary tissues that increase the

girth of roots and stems (= secondary growth).

> Vascular Cambium - Produces tissues that function primarily in support and conduction. i.e. makes transport system.

> Cork Cambium - Lies outside vascular cambium just inside the outer bark

> Produces bark

Secondary Growth

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Types of Tissues

Ground tissue system – Provides

support, stores starch and carries out

photosynthesis.

Vascular tissue – Conducts fluids and

helps strengthen roots, stems and

leaves.

Dermal tissue system – protects plant

from water loss.

Tissues and Cells

Ground

Tissue

Functions of Ground Tissue:

• Support: water filled vacuoles

• Storage: starch

• Photosynthesis

Parenchyma Collenchyma Sclerenchyma

Flexible Rigid

Large cell Small Cell

Thin cell wall Thickest cell wall

Ground Tissues

I. Parenchyma – pithy core, majority of

tissues in roots and shoots. These

cells photosynthesize in leaves.

II. Collenchyma – Cylinder shaped,

hold the plant together. Irregular

corners.

III. Sclerenchyma – Thick walls,

surrounds vascular tissues. Not

living when mature.

Tissues Produced By Meristems Simple Tissues

Parenchyma - Composed

of parenchyma cells

Parenchyma cells:

Thin, pliable walls

Living cytoplasm, often

containing large vacuoles and

various secretions

May remain alive a long time

Have spaces between them

Parenchyma cells

Consist of only one kind of cell

Tissues Produced By Meristems Simple Tissues

Collenchyma tissue -

Contains collenchyma

cells

Collenchyma cells:

Living cytoplasm

May remain alive a long time

Cell walls thick, and with

uneven thickness due to

extra primary wall in cell

corners

Pliable and strong, thus

providing flexible support

Collenchyma cells

Tissues Produced By Meristems Simple Tissues

Sclerenchyma tissue -

Thick, tough, secondary walls,

normally impregnated with

lignin

Dead at maturity

Function in support

Two types: sclereids and fibers

Sclereids - Stone Cells

Scattered in tissue

Cells as long as wide

Sclereids

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Fibers:

Sclereids

Tissues and Cells: Ground Tissue

Parenchyma In Leaf:

Mesophyll cells

Contain lots of

chloroplasts for

photosynthesis

In Stem:

Parenchyma form

pith for support

In Roots:

Parenchyma

contain extra

starch in the

cortex for storage

Tissues Produced By Meristems Complex Tissues

Complex tissues - Composed of two or

more kinds of cells.

Xylem

Phloem

Epidermis

Tissues and Cells

Vascular

Tissue

Functions of Vascular Tissue:

• Transport

• Support

Tracheids Vessel

Elements

Companion

Cells

Sieve Tube

Members

Xylem Phloem

Vascular Tissue

I. Xylem – water

conducting pipes.

Wood is mostly

xylem

II. Phloem – transports

sugars & proteins

Sap runs through

phloem

Secondary Growth

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Complex plant

conducting tissues

> xylem

>phloem

a young corn stem is

shown here.

Tissues Produced By Meristems Complex Tissues

Epidermis- Protective layer that is one cell-

layer thick covering all plant organs

Composed mostly of parenchyma cells, guard

cells of stomata, secretory glands and hairs

Leaf cross section

Tissues and Cells

Dermal Tissue

Epidermis Guard

Cells

Trichomes Root hairs

Functions of Dermal Tissue:

• Protection

• Regulates movement of materials

Trichomes:

Dermal Tissues I. Cuticle – waxy coating

II. Epidermis – for outer layer

III. Trichomes – Hairs for preventing water loss.

IV. Periderm – outer bark

V. Guard cells & Stomata

Tissues Produced By Meristems Complex Tissues

Constitutes outer bark.

Primarily composed of cork cells

Dead at maturity

While still alive, cytoplasm secretes

suberin (fatty substance) into walls.

Makes cork cells waterproof and helps

protect phloem

Periderm - Replaces epidermis when cork

cambium begins producing new tissue

Periderm

with lenticel

– Lenticels: Loosely arranged pockets of parenchyma

cells formed by cork cambium that protrude through

the surface of periderm.

Organs: LEAF

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Guard Cells

Review: Reproduction

Gametophyte: The multicellular, haploid stage in the life cycle of plants.

Sporophyte: The diploid form of a plant that produces , haploid, asexual spores through the process of meiosis – reduction division.

Assignments

Turn in Homework 2

Pg. 27 in lab manual due Wed in Lab

Exam Friday!