Abscission layer formation is accelerated by . . . . . . .

When an unripe banana is sealed in a polythene bag,it remains green for many days. But if an apple is also sealed in the same bag,the banana ripens and turns yellow within a few days. The reason is that apple

$PGR$ which was discovered by Cousins .........

Which of the following is used to artificially ripen banana fruits?

Which combination of gases is suitable for fruit ripening?

Describe: $(1)$ volatile endocrine