Plant Hormones

Practising a Healthy LifestyleEffects of Drug AbuseStimulantsDrugs that increase the actions regulated by the nervous system.Increase heart rate, blood pressure and breathing rateIncrease the release of neurotransmitters, leading to the feeling of energetic Examples: cocaine, nicotine, caffeine, amphetaminesLong term effects: circulatory problem, hallucinations and psychological depression.Effects of Drug Abuse2) DepressantsDrugs that slows down the activity of central nervous system.Slows down heart rate, blood pressure and breathing rateExamples: barbiturates, tranquillisers and heroinLong term effects: memory loss, inability to concentrate, respiratory disease, lung cancer, liver and brain damage, sleepiness, confusion, blood and liver diseases, convulsions, coma and deathEffects of Alcohol Abuse on HumansAlcohol is a depressant that slows down the rate of CNS.Slows down reflex, disrupt coordination and impairs judgement.Plant hormoneChemical substance which is produced by plant and influence the growth and development of the plant.Examples of plant hormones are auxins and ethylene (ethene)Role of Auxins in TropismAuxins control the growth movement of shoots and roots in plants. Auxins promotes elongation cells in the shoot and inhibit growth in the root.Type of response where the direction of growth movement is determined by the direction of stimulus is called tropism.TropismStimulusResponseRegion sensitive to stimulusPhototropismDirection of light from one sideShoots bend towards light (Positive phototropism)Roots grow away from light (Negative phototropism)Tips of shoot or rootGeotropismForce of gravityShoots grow upwards against the force of gravity (Negative geotropism)Roots grow downwards in the direction of gravity (Positive geotropism)

Ethylene (Ethene)Plant hormone which is synthesized during ripening of fruitsSpeed up ripening of fruits by stimulating the production of cellulase. Cellulase hydrolyses cellulose in plant cell walls thus making fruit soft. Also promotes the breakdown of complex carbohydrates into simpler sugar.Parthenocarpy : produces seedless fruit