When is emasculation necessary in artificial hybridization?

When the female parent bears bisexual flowers

The correct answer is Option (4) - When the female parent bears bisexual flowers

Emasculation is necessary in artificial hybridization when the female parent bears bisexual flowers.

Bisexual flowers, also known as perfect flowers, contain both male and female reproductive structures, including stamens (with anthers producing pollen) and a pistil (with a receptive stigma). In order to ensure controlled pollination and prevent unwanted self-pollination, the anthers of the bisexual flower need to be removed before they start dehiscing (releasing pollen).

Emasculation involves carefully removing the anthers from the flower bud using tools such as forceps. This step ensures that the flower cannot self-pollinate or receive pollen from undesired sources, allowing breeders to control the pollination process and ensure the desired pollen is used for fertilization.

Emasculation is not necessary when the female parent produces unisexual flowers. Unisexual flowers are either male (staminate) or female (pistillate) and naturally lack the reproductive structures of the opposite sex. In such cases, there is no need to remove anthers because the flowers already lack male reproductive organs. Instead, the female flower buds can be directly protected through bagging before they open and become receptive to pollen.

Therefore, emasculation is specifically required in artificial hybridization when the female parent bears bisexual flowers, as it allows for controlled pollination and prevents unwanted self-pollination or contamination from other pollen sources.