6.4 - Development of Seeds and Fruits

Double Fertilisation and Development of Seeds and Fruits

Development of the Embryo and Endosperm

• The triploid endosperm nucleus divides by mitosis to form endosperm tissue.
• Endosperm tissue stores food, surrounds the embryo, and supplies nutrients to it.
• The zygote divides by mitosis to form a larger cell and a smaller cell.
• The larger cell develops into a suspensor, which anchors the embryo to the wall of the embryo sac.
• The smaller cell develops into an embryo consisting of the plumule, radicle, and cotyledon.

Relationship between Seed Structure and Ovule Structure

• Ovule $\to$ seed.
• Integument $\to$ two layers of seed coat that protect the embryo.
• Zygote $\to$ embryo.
• Triploid endosperm nucleus $\to$ endosperm tissue.

Relationship between Fruit Structure and Ovary Structure

• Ovary $\to$ fruit.
• Ovary wall $\to$ fruit pericarp, consisting of the exocarp, mesocarp, and endocarp.
• Stigma and style degenerate and leave a scar on the ovary wall.

Types of Fruits

Classification by Origin

Type	Development
Simple fruit	From a single carpel or several fused carpels in one flower; for example, pea
Aggregate fruit	From numerous carpels in one flower; for example, raspberry
Multiple fruit	From carpels of a cluster of flowers; for example, pineapple
Accessory fruit	From tissue outside the ovary but near the carpel; for example, apple