Seed formation without fertilization in flowering plants involves the process of
A. Sporulation
B. Budding
C. Somatic hybridization
D. Apomixis

Hint: It is a term used in 1906 by Winkler. It is found in fruit crops more often than in field crops. Sexual fusion does not occur in this process.

Complete Answer:
A seed is a developing plant that is surrounded by a protective outer shell. Seed formation is part of the reproductive mechanism of seed plants, including gymnosperm and angiosperm, which are spermatophytes. After fertilisation by pollen and some development inside the mother plant, seeds are the result of the matured ovule. The embryo is produced from the zygote and the seed coat of the ovule integuments.

Now, let us find the solution from the options-
- Sporulation is a type of asexual reproduction in which a durable, resistant coat covers specialised cells and then separates from the parent plant. These spores are able to survive harsh environmental conditions and germinate to grow new plants by regular mitosis as conditions change. In non-flowering plants and in other microscopic species, spores are asexual reproductive structures. Thus, the option A is incorrect.
- Budding is a form of asexual reproduction in which, due to cell division at one specific location, a new organism emerges from a bud. Budding is an artificial mechanism of asexual or vegetative propagation of plants, also referred to as bud grafting. Thus, the option B is incorrect.
- In vitro fusion of isolated protoplasts to build a hybrid cell and its subsequent creation to form a hybrid plant is typically involved in Somatic hybridization. In somatic plant cell genetic manipulations and crop enhancement, plant protoplasts are of tremendous use. Thus, the option C is incorrect.
- Apomixis is a special process found to generate seeds without fertilisation in flowering plants. It is a form of asexual reproduction that mimics sexual reproduction and is frequently found in citrus varieties. For seed development, it does not require sexual fusion.

Thus, the correct answer is option D Apomixis.

Note: This approach assists in the processing of hybrid seeds and, when it falls to large-scale production, is cost-efficient. There seems to be an increase in yield. Often, seeing that there is no cross-fertilization, this approach helps to preserve a crop plant's good characteristics.