The natural auxin produced by the placental tissue of the unfertilized ovary and responsible for enlargement of ovary into fruit is ---------------.

Step-by-step solution

Auxins are a class of plant hormones that play a crucial role in various aspects of plant growth and development. Indole-3-acetic acid (IAA) is the principal natural auxin found in plants. It is produced by the placental tissue of the unfertilized ovary and is responsible for the enlargement of the ovary into a fruit, a process known as parthenocarpy. NAA (1-Naphthaleneacetic acid) and 2,4-D (2,4-Dichlorophenoxyacetic acid) are synthetic auxins, while IBA (Indole-3-butyric acid) is another natural auxin but IAA is