HOW DO SUNFLOWER ALWAYS FACES THE SUN

The sunflower always faces the sun  it begins the day in east and follows the sun,this is because of phototropism. Phototropism is a growth madiated response of a plant to stimulation by visible light. The response is stimulated by a harmon called auxin present in the stem. Auxin promotes length wise growth of the plants. The auxin ,beta indy lacetic acid (IAA),is formed either from amino acid,tryptophan,or from the break down of carbohydrates known as glycosides.They promote growth by acting on the chemical bond of hydrate on the cell wall. In positively phototropicc plants when one side of the plant is shaded,greater quantites of auxin are produced on the darker side.This causes that side of the plant to grow fast.In the case of the sunflower,the phenoomenon is pronounced so as to make the flower turn towards the sun.