Control and coordination


    • Plants produce hormones to coordinate and control growth and responses to light (phototropism) and gravity (gravitropism or geotropism). Unequal distributions of auxin cause unequal growth rates in plant roots and shoots.

(HT only) Gibberellins are important in initiating seed germination. (HT only) Ethene controls cell division and ripening of fruits.

(HT only) The mechanisms of how gibberellins and ethene work are not required.