HORMON PERTUMBUHAN

hormon pada tumbuhan memberi kesan kepada:

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. Ethylene 5. Abscisca (ABA)

They contain both naturally occuring hormone and synthetic substances

AUXINBending towards light (phototropism) Downward root growth in response to

gravity (geotropism)Promotion of apical dominanceFlower formationFruit set and growthFormation of adventitious root Major site of auxin synthesis is apical

meristem

GIBBERELLINS (GA)Cell division and elongationBreak seed dormancySpeed germinationProduced in the root growing tips stimulate

shoot growthIf any seed that hard to germinate, just

soaked them in GA solution

CYTOKININ Founds both in plants and animals Stimulate cell divisionProduce by actively growing tissues,

particularly roots, embryos, and fruitsProduced in roots and transported by xylem

sapUse frequently in tissue culture

ETHYLENEFounds in gaseous form Induces ripeningCauses 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 inhibitorIntroduce dormancy and prevents

seed germinationCauses abscission of leaves, fruits

and flowersCauses stomata to close

OTHER FACTORSFERTILIZATION 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.

THE END