Read the given functions of two plant growth regulators 'X' and 'Y'. X: It helps to initiate rooting in stem cuttings and promotes flowering in pineapples. Y: It is used for synchronising fruit-set in pineapples and hastens fruit ripening in tomatoes. Identify 'X' and 'Y' respectively.

Step-by-step solution

According to NCERT, auxins help to initiate rooting in stem cuttings, an application widely used for plant propagation. Auxins also promote flowering in pineapples. Ethylene is highly effective in fruit ripening, hastening the ripening of fruits like tomatoes and apples. It is also used to initiate flowering and for synchronising fruit-set in pineapples. Therefore, 'X' is auxin and 'Y' is ethylene. Answer: X - Auxin, Y - Ethylene