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PLANT HORMONES

PLANT HORMONES. PLANT GROWTH SUBSTANCES. Plant hormones (growth substances) involved in various processes in plants: 1. Auxins : produced in the meristem (tip of plant), concentrates on the opposite side of the plant to the light source & when in excess it INHIBITS buds on the sides

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PLANT HORMONES

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  1. PLANT HORMONES PLANT GROWTH SUBSTANCES

  2. Plant hormones (growth substances) involved in various processes in plants: 1. Auxins: produced in the meristem (tip of plant), concentrates on the opposite side of the plant to the light source & when in excess it INHIBITS buds on the sides 2. Gibberellins – whole plant growth 3. Cytokinins– cell division 4. Inhibitors – one type = abscisic acid (ABA) – helps plants to adapt to their environment. STOPS growth. Concentration increases in stressed conditions. Therefore conserve resources. 5. Ethylene – for ripening fruits and flowers. It’s a gas. 5 types of HORMONES to affect the changes of the plant

  3. (abscisic acid) Plant hormones & growth

  4. PROMOTE CELL GROWTH AND CELL ELONGATION • CAUSE APICAL DOMINANCE • A High concentration of auxins INHIBITS the growth of lateral buds • CAUSE TROPIC MOVEMENTS • Playsrole in root development as wellas • Fruit development FUNCTIONS OF AUXINS

  5. Auxins stimulate growth in stems Auxins inhibit growth in roots

  6. Apical dominance Responses involving auxin

  7. Formation of adventitious roots Responses involving auxin

  8. Auxin produced by seeds promotes ovary tissue growth

  9. Auxinspromotefruitgrowth

  10. Breaking dormancy Seed germination Gibberellins

  11. Abscisicacidinhibitsfruitformation, causes leafabscision

  12. Fruit ripening (promotes) • Flowering (inhibits) • Abscission (promotes) • Sex expression in monoecious species (ratio of ♀ to ♂) Ethylene (CH2=CH2)

  13. Ripefruitgiveoffethylene

  14. Ethylenepromotesabscision

  15. Cytokinins

  16. Cytokininsstimulate plant development

  17. Use of plant hormones in agriculture

  18. Plant hormones can be used in gardening and agriculture to control how plants grow and develop… • Plant hormones are naturally-occurring chemicals but can also be produced synthetically for the following commercial uses: - • Growing cuttings • Ripening fruit • Killing weeds Agriculture

  19. A cutting is a part of plant that is removed from the main shoot • A cutting does not have roots and so has no supply of water or minerals… • Rooting powder contains plant growth hormones – dip a cutting into rooting powder and the plant hormones stimulate the cutting to grow new roots Cuttings

  20. Rooting Powder

  21. Cereal crops like wheat are grasses with narrow leaves– most weeds that grow in fields and gardens have broad leaves • Selective weed killers contain plant hormones at concentrations that will only affect plants with broad leaves • These selective weed killers upset the normal growth of broad-leaved plants and so kill off any weeds – the growth of cereal crops and grasses is not affected Weed Killers

  22. Hormone-basedweed-killers cause plantstogrowtoofast, killingthem in process

  23. Fruit is usually ripe and ready to eat when it is bought from a greengrocers or supermarket – fruit farmers are able to control when fruit ripens using plant hormones • Fruit that is picked before it is ripe is usually hard – there is less chance of unripe fruit being damaged when transported, which is important to the farmer and the buyer • Plant hormones can be sprayed onto unripe fruit during transportation – these hormones ripen fruit in time for its arrival in the shops (but you should wash your fruit before you eat it)! Ripening Fruit

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