Transport in plants (13.4)and

Plant Reproduction5.3

Plant Tissues

Groups of specialized cells form tissues except when dormant (ex. during extreme cold or heat)

These tissues include dermal, ground and vascular tissue.

Plant Tissues Located In Various Organs

Dermal tissue

• Dermal tissue forms the outermost covering of the plant’s organs. It forms a protective barrier and controls the exchange of water and gases between the plant and its environment. An epidermal cell is one type of cell that forms dermal tissue.

Ground tissue

Ground tissue has several functions

Some ground tissue is responsible for photosynthesis, other tissues provide support for the plant’s body

Vascular Tissue

Vascular tissue is responsible for transporting water, nutrients and sugars throughout the plant (ex. xylem and phloem)

It also helps to provide physical support for the plant’s body

Vascular tissue (Xylem & Phloem)

• Xylem transports water and minerals from plant roots to other parts of the plant

• Phloem transports sugars from leaves to other parts of the plant

Sugar and Water Movement in Plants

Transpiration

• 90% of water that enters the leaf is lost out of stomata through transpiration

How is water transported 100m up without muscles?

• Positive pressure (pushing)– Root pressure

• Negative pressure (pulling)– Transpirational pull

Water Movement

• Water is moved up from the roots of the plants, up the stem and out the leaves by the Transpiration-Pull Theory (Cohesion-Tension pull theory).

Water Movement

• The theory is based on the three key properties of water:

1) Cohesion: the ability of water molecules to stick together

2) Adhesion: the ability of water molecules to stick to the sides of hollow tubes.

3) The high surface tension of water.

Water Movement

• Water molecules are absorbed into the roots through the process of osmosis.

• Here water is forced through the endodermis into the xylem, but only if the xylem has room for it.

Water Movement

• At the leaves, water is being used in photosynthesis or it is evaporated out of the leaf through the stomata (a process known as transpiration)

• Due to the cohesion of water molecules, as one is pulled out of the stomata or used in the leaf, another takes its place.

Water Movement

• Due to adhesion, the water is able to stick to the sides of the xylem tubes and not slide back down towards the root.

Water Movement

• This occurs throughout the entire length of xylem in the plant!

• Due to these properties, water can be pulled against the force of gravity upwards of hundreds of feet!

Water Movement

• As water is being pulled up through the stem, more water is forced through the endodermis of the root to replace water lost at the leaves, so there is a continual flow of water through the plant.

Sugar Movement

Sugar Movement

• This process is known as the Pressure-Flow Theory

• It was suggested by Ernst Munch, a German plant physiologist, in 1926.

Sugar Movement

1. Glucose is created at the leaf (The Source) during photosynthesis. Glucose is changed into the disaccharide sucrose in order to be transported in the plant.

Sugar Movement

2. This sucrose is actively transported (uses energy) into the phloem cells in the leaf.

3. There is a high concentration of sugar (sucrose) in the phloem at the source.

Sugar Movement

4. Because there is so much sugar in the phloem, some water moves in from the xylem to try and balance out the concentration.

5. This creates a high amount of pressure in the phloem near the source.

Sugar Movement

6. Meanwhile sugar is being actively transported into the root or any other storage area in the plant (The Sink).

7. Sinks have lots of sugar (usually joined together to form starch).

8. The phloem cells around a sink have low amounts of sugar and therefore water will leave them and cause them to have a low amount of pressure.

Sugar Movement

Sugar Movement9. Due to the difference in pressure in the phloem cells at

the Source and the Sink, sugar will be forced down the phloem along this pressure gradient.

• http://www.youtube.com/watch?v=-b6dvKgWBVY

Learning Check

• Pg 563, Q 25-30

• Pg 566, Q 1,2,3

Plant Reproduction

Angiosperms (flowering plants)• Plants that protect their seeds within the

body of a fruit.• Make up ¾’s of all plants, including:

–Trees, shrubs, herbs,

grasses, water plants…

Structure of a Flower

1. Pistil

2. Stigma

3. Style

4. Ovary

5. Stamen

6. Filament

7. Anther

8. Petal

9. Sepal

10. Receptacle

11. Stem

Male Reproductive Structure

The stamen consists of two parts: Anther and Filament

The anther is where meiosis occurs to produce haploid pollen

The filament is a stalk that supports the anther

Female Reproductive StructureThe pistil consists of

the stigma, style and ovary

The sticky stigma receives the pollen from the anther

The pollen grows a tube down through the style

Meiosis occurs in the ovary to produce haploid ovules

Reproductive Structures

• Petals: colourful

structures that attract pollinators.

• Sepals: surround and protect the flower bud.

Learning Check

• Pg 584, Q 1-6

Structural Differences

• Complete Flowers– Sepals, petals, stamens and pistils

• Incomplete Flowers– Missing one or more of the above

• Perfect Flowers– Have both pistils and stamens

• Imperfect Flowers– Have either pistils or stamens, but not both

• Monoecious– plants have individual flowers that are

imperfect but they have both male and female flowers (oaks, corn)

• Dioecoious – Plants that have reproductive structures

divided between two plants (willow)

Pollination

• Self-pollinating plants– Pollinate themselves (either same flower or

elsewhere on plant– Loss of genetic variation

• Cross-pollinating plants– Most angiosperms– Receive pollen from another plant– Ensures genetic diversity

Pollination

Wind, insects or other animals transfer pollen from the anther of one flower to the stigma of another

Flowers vary depending on pollination mechanism

Pollination VectorsWind Pollination: Dull, scentless flowers with reduced petalsBees/Butterfly Pollination: Brightcolor, nectaries, scent. They sip nectar, get pollen on coats, transfer pollen from flower to flower

Bird Pollination: Nectaries, brightcolors, tube-like flowers

Moth Pollination: White petals, open at night

Fly Pollination:Rank odor, fleshcolored petals

Seed and Fruit Development

After fertilization, the petals and sepals fall off flower

Ovary “ripens” into a fruit

The ovule develops into a seed

Seed Dispersal Mechanisms-Allow plants to colonize new areas and

avoid shade of parent plant

Wind Dispersal - Flight mechanisms, like parachutes, wings, etc. Ex. Dandelion, maples, birch

Animal Dispersal - Fleshy fruits which animals eat, drop undigested seeds in feces or burrs which stick to animals’ coats

Gravity Dispersal - Heavy nuts fall to ground and rollex. acorns

Water Dispersal - Plantsnear water create floating fruitsex. coconuts

Learning Check

• Pg 586, Q 7-12

• Pollen Grain • Anther Sac

Pollen grains contain two haploid cells produced through meiosis.

1- The Tube cell – will grow the pollen tube. 2- The Generative cell – will go through mitosis to create two sperm cells.

OvaryEach ovule within an ovary has a micropyle (an opening for the pollen tube).

The ovules’ megasporangium undergo meiosis to produce four haploid cells (3 die leaving 1 megaspore)

The megaspore undergoes mitosis 3 times to produce 8 haploid cells within the embryo sac.

Fertilization

After pollen lands on the stigma, a pollen tube grows down through the style to ovary

Generative cell creates the two sperm nuclei

Double fertilization occurs: one sperm fertilizes the egg one sperm the two polar nuclei together

Result of Double Fertilization

The sperm nucleus and egg nucleus join to form a 2n (diploid) embryo

The other sperm nucleus and the two polar nuclei join to form a 3n (triploid) endosperm. The endosperm is the food supply for the embryo.

First link

SEED GERMINATION• Seeds initially germinate as they absorb

water, bursting the seed coat so the growing plant can produce energy

• This starts a chain of chemical reactions which will result in the development of a plant embryo

STEPS IN SEED GERMINATION

1. Water is added (most important)– Activates enzymes necessary for cellular respiration in the

maturing seedling so it can produce the energy needed to grow

2. Seeds are exposed to heat– Chemical energy in seed’s starch is converted to glucose

during germination

3. Seeds are exposed to light– Chemical energy in seed’s starch is converted to glucose

during germination

4. Oxygen is available

Seed Germination

• Radicle is first part of embryo to appear (develops into root)

• Hypocotyl appears above soil (photosynthetic tissue)

SEED DORMANCY

• Dormancy is the block of complete germination of a viable seed under favourable conditions

• Advantage: Germination is delayed until conditions are favourable for the survival of both the seed and the maturing plant

– Ex. Even though some conditions are favourable in late November, dormancy occurs due to the onset of winter.

• Seed banks are a plant strategy to ensure that not all the seeds of one species germinate in a single year. This insurance save a species in the event of a catastrophic drought, extreme cold, etc.

Jigsaw

• Each person take two techniques in artificial propagation and explain it to the class (pg 590-591)