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Understanding Geotropism and Phototropism in Plants

This text explores two vital concepts in plant biology: geotropism and phototropism. Geotropism refers to the growth of plant roots in response to gravity, while phototropism describes the directional growth of plants toward light sources. Both processes are influenced by plant hormones known as auxins, which promote cell elongation and differentiation. The role of auxins in enabling plants to bend toward light or grow against gravity showcases their significance in plant adaptation and survival. Learn how these mechanisms work and the importance of auxins in plant growth.

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Understanding Geotropism and Phototropism in Plants

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  1. TROPIC RESPONSES Merighi Pietro

  2. Whatis a Geotropism? • A geotropismis the growthof living plants in responsetogravity. • Itisgivenby the downwardof the plantroots

  3. Whatis a Phototropism? • Itis the directionalgrowth in which the direction of the growthisdeterminedby the direction of the light source. • In otherwordsitis the growth and responseto a light stimulus.

  4. PlantAuxins • As withanimals , plantsalsouse a varietyofhormonestocontroltheirgrowth and development. A family ofhormonescalledauxins are commonlyfound in plants, and promote (and sometimesinhibit) growth.

  5. What are Auxins? • Auxins are produced in the meristems (tissuethatgrows) ofplants • Auxins are responsibile in promotingcellelongation, a processthatisrequiredbeforedifferentiationof a cell. Itisabletothisbypromoting the intakeof water, increasing the elasticityof the celltocopewith the increaseof water taken in by the cell. • (Oneof the most common auxinsis indole acetic acid.)

  6. Phototropism in Auxins. • Auxinsalso play a part in phototropism, anoccurancethayinvolvesplantsbending or movingawayfrom light. The shoottipisresponsiblefordirectionalmovementby the plant in responsetosunlight, asthisis the area whereauxins can befound. • Sunlighteradicatesauxin, meaningthat the part of the shoottipof the plantwhichisreacivingdirectsunlightwilhave the leastamountofauxin • The extra auxinpresent on the shaded side promotes more celldivision and elongation, causing the planttobendtowards the sunlightafterthislop-sidedgrowth.

  7. Geotropism in Auxins. • Geotropismis a similaroccuranceto the phototropismwhere the plantexihibitsdirectionalgrowth in responsetogravity. The shoottipillustrates negative geotropism (growsagainstforceofgravity) while the roottipexhibits positive geotropism (grows in the same direction asgravity).

  8. Questions….. • Whatis a geotropism and a phototopism? • What are Auxins?

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