1. pertumbuhan bunga2. Kematangan tumbuhan3. Pertumbuhan akar4. Megubah bentuk dan mematikan daun, batang dan bahagian lain.5. Menghalang dan menggalakkan pemanjangan batang.6. Mempengaruhi warna tumbuhan dan pencegahan pengguguran daun
Hormones are naturally produced by plant. Plant growth regulators are chemicals applied by a horticulturist to regulate plant growth. In plant propagation , cuttings are dipped in a rottinh hormone to stimulate root development. In house production many potten flowering plant ( poinsettias, easter lilies) maybe treated with plant growth regulator to keep them short. Seedless grape are treated with plant growth regulator to increase the size of fruit • Regulators may be synthetic compound or may be natural hormone that were accepted from plant tissue.
Five group of plant growth-regulating compounds :1. Auxin2. Gibberelin (GA)3. Cytokinin4. Ethylene5. Abscisca (ABA) They contain both naturally occuring hormone and synthetic substances
AUXIN Bending towards light (phototropism) Downward root growth in response to gravity (geotropism) Promotion of apical dominance Flower formation Fruit set and growth Formation of adventitious root Major site of auxin synthesis is apical meristem
GIBBERELLINS (GA) Cell division and elongation Break seed dormancy Speed germination Produced in the root growing tips stimulate shoot growth If any seed that hard to germinate, just soaked them in GA solution
CYTOKININ Founds both in plants and animals Stimulate cell division Produce by actively growing tissues, particularly roots, embryos, and fruits Produced in roots and transported by xylem sap Use frequently in tissue culture
ETHYLENE Founds in gaseous form Induces ripening Causes leaves to drop Plant often increases in ethylene production in response to stress Often found in high concentration within cells at the end of plants life Leaf falls because of high ethylene
ABSCISIC ACID (ABA) General plant growth inhibitor Introduce dormancy and prevents seed germination Causes abscission of leaves, fruits and flowers Causes stomata to close
OTHER FACTORS FERTILIZATION The need to fertilize houseplant varies with rate of growth, ages of the plant, desire for growth and growing season. Frequency of feeding can vary from every 2 weeks to every several month during the growing season. A general rule for application frequency is fertilizing at half recommended strength, every 2 week from March to September. Do not fertilize most plant during winter month. Winter reduce light and temperature result in little or no growth. Most houseplants are dormant during winter Houseplants fertilizers come in several form : granular, crystalline, liquid, and tablet. Most are houseplants fertilizers are fairly concentrated. Never exceed the recommended application amount. Oftentimes, application should be even more dilute than recommended. Label recommendation are based on the ideal condition in greenhouse.
CARBON DIOXIDE(CO2) AND PLANT GROWTH Carbon dioxide and water are combined with the aid of light energy to form sugar. Some of these sugars are converted into complex compounds that increase dry solid plants substances for continued growth to final maturity. However, when the supply of carbon dioxide is cut off, or reduced, the complex plant cell structure cannot utilize the sun’s energy fully and growth or development is curtailed.
The amount of CO2 in the air is only 0.03% This compare to 78% nitrogen, 21% oxygen and 0.97% trace gases in normal air. The amount of CO2 are a plant requires to grow may vary from plant to plant but test show that most plants will stop growing when the CO2 level decrease below 150ppm Even at 220ppm, a slow down in plant growth is significantly noticeable The lack of adequate CO2 lowers the average plant yield quality and market value.