In adventive embryony, a type of apomixis, the embryo develops directly from the

The correct option is integuments or nucleus (often referred to as nucellus).

Step-by-step Explanation:

1. Understanding Apomixis:
Apomixis is a form of asexual reproduction in plants that mimics sexual reproduction but occurs without fertilization. It bypasses the processes of meiosis and syngamy (fusion of gametes), resulting in seeds that are genetically identical to the maternal parent plant.

2. What is Adventive Embryony?
Adventive embryony (also known as sporophytic budding) is a specific type of apomixis where an embryo develops directly from diploid vegetative/sporophytic cells of the ovule lying outside the embryo sac.

3. Identifying the Source Cells:
The maternal tissues of the ovule surrounding the embryo sac include:
- The nucellus: The central nutritive tissue of the ovule.
- The integuments: The protective outer envelopes or coats of the ovule.
Since these tissues are diploid (2n) and maternal in origin, any embryo arising directly from them bypasses fertilization and is genetically identical to the parent. During adventive embryony, these somatic cells divide, protrude into the embryo sac, and develop into functional embryos.

4. Why other options are incorrect:
- Zygote: An embryo developing from a zygote is the product of normal sexual reproduction (fusion of male and female gametes), not apomixis.
- Antipodals or synergids: These are haploid (n) cells of the gametophyte (embryo sac). Development of an embryo from these cells is known as apogamy.
- Accessory embryo sacs: This refers to other forms of apomixis like apospory or diplospory where an embryo sac is formed first, rather than the embryo developing directly from the sporophytic tissues themselves.