Chapter 3 Plant growth & Development

Growth Factors

Chemical Energy Photosynthesis Respiration Net Photosynthesis

Temperature Zone of tolerance Optimum temperature

Nutrients & water

Growth Substances

Auxins- 1st group of plant hormones to be discovered, mid

1930’s Adventitious root initiation Weed control (2-4D) Inhibition of stem sprouting Tissue culture

Gibberellins-

Increasing fruit size of seedless grapes Stimulating seed germination * seedling

growth Promoting male flowers in cucumbers Overcoming the cold requirement for some

plants

Cytokinins-

No important agriculture use at this time.

DNA & RNA

Ethylene

Fruit ripening Flower initiation Changing sex expression (female flowers in

cucumbers & pumpkins) Degreening oranges, lemons grapefruit Harvest aids

Inhibitors

Abscisic Acid Synthetic

Used to regulate plant growth

Growth inputs & quality

Timing Amounts

Patterns of plant growth & development Vegetative Phase

Reproductive Phase

Temperature & Vernalization

Some plants need lower temperatures for flower induction

Temperature ranges are 32-500 F Examples are cereal grains (wheat, barley, rye) Some can be induced to flower by colder temps

(spinach, peas, lettuce) Must reach a maturity before vernalization can begin Hormone induced (gibberellins) Look at table 3.1

Light & Photoperiod

Some plants needs a certain number of hours of day length to flower

Short day plants (i.e. poinsettias, strawberries, mums) need long nights uninterrupted to flower

Long Day plants (i.e. spinach sugar beets) need short nights

Day neutral (i.e. tomatoes)

Floral stimulus is transmitted form leaves to meristem

Vegetative to flowering Different photoperiods needed to induce Once apex has changed to flower tissue

irreversible Flower initiation to anthesis varies.

Flowering Response to Photoperiod length of day Long Day Plants greater than13 hours Short Day Plants less than12 hours Day Neutral Plants = no response

Look at table 3.2 & 3.3