Plant hormones known as auxins are vital for regulating plant growth and development. A key function of auxins is to stimulate ovary enlargement into fruit post-fertilization, a process termed fruit set, initiated by auxin production in the fertilized ovule.
Auxins contribute by:
- Promoting cell elongation in the ovary, thus enlarging the fruit.
- Influencing the production of other hormones like gibberellins, which are also involved in fruit development.
- Supporting the growth of tissues necessary for fruit formation.
Therefore, the correct answer is Auxin.