HS-201 Exam 3

Light Duration

Number of continuous hours of light in a 24 hour period

Light Quantity

Number of light particles (photons) of different wavelengths (colors) that are capable of performing photosynthesis

Light Quality

Spectral distribution of the light emitted from a light source

8 effects on plant growth

1. Photosynthesis

2. Pigment Formation

3. Seed germination

4. Fall color

5. Growth habit

6. Size

7. Flowering

8. Fruiting

4 Plant Pigments

1. Carotene (orange)

2. Xanthophyll (yellow)

3. Chlorophyll (green)

4. Anthocyanin (Red)

Phototropism

Plant response to light

Auxin

Plant hormones produced in stem tip

Full sun (high light) area and plants that require full sun =

Growth occurs

Low light area and plant that requires high light =

No Growth; Slow death

Light Compensation Point

Rate of photosynthesis equals the rate of respiration (energy burned to maintain light)

Light Saturation Point

Amount of light beyond which no added benefit/growth is obtained

Site Selection

How much sun exposure does that area have, and what plants can survive in the area that you choose? (choosing where to plant specific plants)

Characteristics of Shade leaves

-Larger

-Thinner

-Greener

-Lower Light compensation point

-More efficient photosynthetic apparatus

Characteristics of Sun leaves

-Smaller

-Thicker

-Less Chlorophyll (Less green)

-Higher light compensation point

-Less efficient photosynthetic apparatus

Acclimatization and its 4 environmental factors

Slowly changing the environment's factors:

-Light

-Temperature

-Water

-Nutrition

Hardening Off (done before planting outside)

Introducing plants to a new environment slowly

-Vegetable transplants

-Houseplants

Techniques to adjust light quantity

etiolation and blanching

Etiolation

Growing plants in the partial or full absence of light

What plant chemical is missing when growing in the dark?

Chlorophyll

Blanching

growing technique to exclude light

-Young shoots of a plant are covered to exclude light to prevent photosynthesis and the production of chlorophyll

-Causes the plant to be pale in color

What causes the odor in urine to smell?

Sulphureous compounds

Do evergreens change colors as much as deciduous trees during the fall

NO

Fall color is influenced by?

genetics and environment

What stimulates the onset of fall color in deciduous plants

Decreasing day length and Decreasing Temperatures

What stimulates the formation of the abscission layer?

Decreasing temperatures and photoperiod

What slows down in a plant during fall?

Flow of water and nutrients, Production and flow of sugars, Chlorophyll synthesis

What color fades in leaves as fall progresses?

Green coloration

What pigments become visible in leaves during fall?

Yellow and orange pigments

Were yellow and orange pigments always present in leaves?

Yes!!! they were just hidden

What causes red coloration in leaves

Daily climactic conditions and sugar accumulation in the leaves… The right combo leads to a red pigment

Recipe for red pigmentation in leaves

-Warm sunny days

-Cool dry nights

-Sugar pool build up

-Night temperatures <45 degrees which stimulates the conversion of sugars to Anthocyanin

Which of the pigments form in the fall when climactic conditions are met

Anthocyanin

Fall climate influences...

sugar accumulation

Location influences...

climate

Does Microclimate Matter?

YES

Can Anthocyanin be found in parts of the plant other than the leaves?

YES

Photoperiodism

A plant growth response as influenced by the duration of light and darkness in a 24 hour period

When was Photoperiodism discovered?

1920

Who discovered photoperiodism (2 people)

Garner and Allard

Most prominent example of photoperiodism

Flowering

Other responses of photoperiodism

Seed germination, Rooting, Abscission

Abscission

the act of cutting; the natural separation of a leaf or other part of a plant

Three categories of angiosperms regarding photoperiodism

Long Day Plants (LDP), Short Day Plants (SDP), Day Neutral Plants (NDP)

Long Day Plants (LDP)

Plants that are stimulated to initiate flowering when the day length is longer

Short Day Plants (SDP)

Plants that are stimulated to initiate flowers when the day length is less

Neutral day plants (NDP)

Plants that simply flower at some stage of growth with no regard to the length of day or night

Photosynthesis facts

-100 billion tons of sugar produced by plants annually

-94% of dry matter in plants from photosynthesis (6% from soil)

-Only 1% of light that hits a leaf is used in photosynthesis

-Only 1% of water absorbed by plants is used in the photosynthesis reaction

Remember the equation of photosynthesis

6CO2 + 6H20 = C6H12O6 + 6O2

Plant Propagation

Process of creating new plants from existing ones.

Sexual Reproduction

Seeds

Asexual Reproduction

Vegetative: Leaf, Stem, and Root

Advantages of sexual reproduction of plants

Less technology, Easy shipping, Genetic diversity, New colors, textures, and hybrids

Advantages of asexual propagation

No reproductive pressure, Bigger plants faster, Flowering faster, Clones and nostalgia with family plants, Mutation preservation

Controlling propagation environment

-Air

-Water

-Light

-Soil

Air

-Movement

-Gas Exchange

-Temperature

Water

-Quantity

-Frequency

-Humidity

Soil

-Nutrients

-Air and Water Capacity

-Temperature

-Support

Light

-Quantity

-Quality

-Location

Soil/Substrate/Media

Selected for:

-Water retention

-Drainage

-Sterility (no pests or diseases)

-Fine textured and penetrable

Which classes produce seeds

Angiosperms and gymnosperms

Seed sowing environment factors

Water, Air and Media, Light,

Water factors in seed sowing

-Adequate water at sowing

-Gently reduce during growth

Air and Media factors in seed sowing

-Warm to seed's optimal temp

-Low nutrient need initially in seeds

-Avoid too much moisture

Light factors in seed sowing

-Seeds buried at proper sowing depth

-Adjust as plants grow

-Increase to promote photosynthesis

Proper depth to plant a seed

1.5x the diameter of the seed!!!

Seed Selection and Info

-Seed packets provide culture needs

-Grow time varies by species and cultivar

-Sow depth

-Make sure to plan ahead and label your seeds

Seed Sowing and Containers

-Use tools for small seeds

-Match the pot size to the seed and growth rate

-Sow what you need... plus some extras

Seeding Conditioning

-Prevent seedlings from getting "leggy" (growing leg-like appendages)

1. Sow/plant deep

2. Provide adequate light

3. Rotate trays and pots

4. Move the stems

5. Avoid overwatering and overheating

6. Thinning: removing the extra plants you don't need

Seedling conditioning (tropisms)

Watch for tropisms

-Phototropism (light)

-Gravitropism (gravity)

-Thigmotropism (movement)

Gravitropism

The plants knowing which way is up and down

Thigmotropism

A directional growth of a plant in response to touch.

Potting up

Can help control seedling height

1. Sink stem up to the cotyledon

2. Not all plants love being sunk

3. Avoid seedling becoming root-bound

4. Don't pot up too much too fast

Hardening off/Acclimating

-Gradual condition to prepare plants for the outside environment

-Exposure to real, unfiltered light

-Avoid transplant shock

Asexual Vegetative Propagation

involves Roots, Stems, and leaves

Factors of Auxin

-Rooting hormone

-Produced at shoot tips

-Moves away from light

Cuttings

-Stock plant (the mother plant) provides stems, leaves, or roots

1.Ideally in vegetative or dormant growth stage

2. Cutting increases branching

Short survival

1. Time sensitive

2. Temperature Sensitive

3. Hydration sensitive

Stem cutting types

1. Herbaceous

2. Softwood

3. Semi-Hardwood

4. Hardwood

Stem cutting factors

-Node + Bud

-You can wound the base to promote rooting

-Don't be fooled by petioles (not a full stem)

Etiolation

Intentional blacking out of a stock plant so the Auxin remains at the shoot tips

No bud means

Might root but will not produce root/stem

Totipotency (leaf cuttings)

Cell's ability to differentiate into new tissues and become a complete fully functioning plant

using Leaf sections means…

No bud required

Root Cuttings

-Specialized propagation method of some species

-Carbohydrates stored in roots of dormant plants

Root cuttings are NOT...

Rhizomes

Cutting environment

-Water, air and media:

1. High humidity

2. Avoid dry-out

3. Reduce after "baby" roots form

4. Limit air flow

-Light

1. Reduce leaf area

2. Lower light reduces stress

3. Increase light as roots form

Grafting

Scion - Top portion develops into shoots

Rootstock - Bottom portion develops roots

-Cambium tissue connection is very important for grafting

-Must be same or closely related species

Grafting mutual benefits

-Disease resistance

-Cold Hardiness

-Structure and form

-Pollination technique

-The wow factor (aesthetic)

Grafting example

Dwarf Citrus

-Rootstock: Poncirus trifoiata

-4-6 inches

-Fruit: tart, 2 inches, and seedy

Scion: Citrus sinensis

-Washington Navel

-10-12 inches

-Fruit

Some roses can send up...

Suckers from roots

Another example for Grafting

Gilroy Gardens Circus Trees by Axel Erlandson

Simple and Tip layering

Bend flexible stem and bury in soil

Air Layering

Disrupt Auxin transfer mid-stem

Natural Layering

Stolons and Runners

Environment needed for layering

Dark and moist, perfect for root growth

Important for proper root growth

Keep moisture in and light away for root growth

Bonus propagation

When plants do the propagation, you just have to move them around

Division Bonus propagation

Crown separated into smaller bud sections. Rhizomes, Offsets & Pups, or Clumps

Bulbs Bonus propagation

-Basal plate bulbs

-Leaf Cutting bulbs

-Bulbils

Leaf Margin Bonus Propagation

-Kalanchoe plants (mother of millions)

Micropropagation (Tissue culture)

-Multiplication of plants in vitro (glass)

-Sterile conditions

-Hormone manipulation