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