Male part of flower develops later than female part. In the same plant, pollen grains will not adhere to female part of flower. In the same plant, tube cell of pollen grain cannot grow down through female tissue to reach egg. Its synthesis is stimulated by auxin. Ethylene is a gas.
Ethylene inhibits fruit ripening.
Cytokinins from the root inhibit ethylene production. Attached to each other at two places. Contain proton pumps. Sensitive to the plant hormone abscisic acid. Use actin filaments to contract.