TROPIC RESPONSES. Merighi Pietro. What is a Geotropism ?. A geotropism is the growthof living plants in response to gravity . It is given by the downward of the plant roots. What is a Phototropism ?.
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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.)
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.
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).