Plant Cells, Tissues, and Systems

Plant Cells, Tissues, and

SystemsSec C3.1

Unit C

Objectives• describe the specialized structures and

functions of cells in the leaf system• explain the transport system in plants• relate a multi-cellular level of

organization with cell, tissue, and system specialization

Multicellular vs Unicellular

• What are the advantages to having a large structure with lots of cells?

• Division of Labour• When a cell is specialized (performs

a particular function), it is more effective and efficient.

• A single-celled organism must multi-task (do many jobs).

Multicellular vs Unicellular

• Size • The surface area to volume ratio and

related rate of diffusion restricts growth in unicellular organisms.

• Efficient transport systems within multicellular organisms allow for growth.

Multicellular vs Unicellular

• Interdependence of Cells• A single-celled organism is

dependent on that one cell. • If a multicellular organism loses a

cell, the entire organism will not die. However, a cell not functioning properly (ex. cancerous) can cause problems for the rest of the organism.

Plant Structure• Plants are multicellular: made of many parts, each

with its own function – organized in increasing complex levels of organization

• Tissues= group of cells performing same function together

• Organs= tissues contributing to same function• System= group of interconnected organs (two in

plants)• Shoot system everything above ground• Root system everything below ground and aerial

roots

What about animals?• What are some examples of tissues,

organs and systems in humans?• Ex. Heart/cardiac tissue heart

circulatory system

Do now• Find the definition/function associated

with each of the following terms (workbook - chart)

MeristemDermal tissue/epidermisCuticleGround tissueVascular tissueXylem tissuePhloem tissueSieve tube cellsCompanion cells

How did you do?• Meristem- growth areas• Dermal tissue/epidermis- outer layer of

cells; responsible for exchange of matter and gases and protection

• Cuticle- waxy substance; resists attack and prevents water loss

• Ground tissue- majority of plant; strength and support (stem); food and water storage (roots); site of photosynthesis (leaves)

How did you do?• Vascular tissue- transport of materials; xylem and

phloem• Xylem- moves water and minerals from roots to

leaves; thick, non-living, perforated cells• Phloem- transports sucrose and other sugars from

leaves to other parts; made of sieve cells• Sieve tube cells- form continuous ducts;

perforated• Companion cells- direct activity of sieve tube cells

Plant Growth• Cells divide to grow and repair

damage. This cell division is called mitosis.

• In plants, increase in size results from the cell division in growth areas called meristems Rapidly

dividing cells - Cell walls thin, nuclei are large, vacuoles, small or absent

Meristems• Onion root tip – note different stages of

mitosis (cell division)

Specialization of Cells

• Once cells are no longer in the meristem, they will specialize• Produce products only for their

function

• The root and shoot systems are made up of 3 types of tissues:• Dermal Tissue (epidermis)• Ground Tissue• Vascular Tissue

Types of Tissue• Dermal Tissue

• Outer layer of cells that covers all herbaceous (non-woody) plants.

• Responsible for exchange of matter and gases into and out of the plant.

• Also protects the plant from disease. This is done by the cuticle (waxy substance), which resists attacks from micro-organisms and helps reduce water loss.

Types of Tissue• Ground Tissue

• Found underneath epidermis, it makes up majority of plant.

• Provides strength and support to the plant (stem).

• Involved in food and water storage (roots).

• Location of photosynthesis (leaves).

Types of Tissue• Vascular Tissue• Responsible for transport of material,

which occurs in xylem tissue and phloem tissue

Vascular Tissue - xylem

• Cells in xylem tissue allow transport of water

• Die when differentiate leaving empty tubes Long fibres in

celery are vascular tissue (both xylem and phloem)

Vascular Tissue - phloem

• Phloem Tissue• Formed from long sieve tube

cells (no nuclei), which are connected with companion cells (nucleated) that direct activity.

• Transports carbohydrates and water from the leaves to other parts of the plant.

Leaf Cross section

http://dendro.cnre.vt.edu/forestbiology/photosynthesis.swf

Vascular Tissue

Vascular tissue

From: http://www.youtube.com/watch?v=4V0VcNCRKTo&feature=related at 4:14

Vascular Bundles

Sieve tubes

More specialization: Roots

• Cells in root system will produce tiny hair-like projections called root hairs• Why is this beneficial for the

plant?• Increases the surface area for

absorption of water

Root hairs

Root hairs

More …• Dermal cells in shoot system produce a

cuticle• Why is this beneficial?• Prevents water loss

And last…• Lower epidermis in leaves have guard

cells• Form tiny pores called stomata for gas

exchange• Only cells with chloroplasts• Why is this important?• Photosynthesis!

Leaf Cross section

http://dendro.cnre.vt.edu/forestbiology/photosynthesis.swf

Leaf Cross section• Can you indentify some of the

structures?

How does water move up the plant?

• Gravity should pull water down – how does it move up from the roots to the leaves? How do all these specializations allow for this? Shall be investigating this in this section.

• http://www.youtube.com/watch?v=U4rzLhz4HHk&feature=related