Ethylene is a fruit ripening gaseous hormone. In most of the plants there is a sharp rise in respiration rate near the end of the development of fruit which sets in progress those changes which are involved in ripening of fruit. This sharp rise in respiration is called climacteric rise. Ethylene is responsible for early climacteric. ABA is a naturally occurring growth inhibitor in plants. It causes partial closure of stomata
under drought and thus acts as antitranspirant and is known as stress hormone.