Angiosperm

Seed Plant Evolution

There are three major reproductive advantages to using seeds, which are gametophyte reproduction, easier dispersal, and pollen which eliminates the need of water for fertilization.

Seeds are important for dispersal

Seeds are complex multi-cellular structures that are resistant to environmental stress and can remain dormant. They consist of a sporophyte embryo, food supply, and a protective coat.

The embryo develops from the fertilized egg, which is derived from a spore, and is retained within the sporangium. The sperm, which is also derived from a spore, is produced by a pollen gran and released from a sporangium.

Monocot vs Dicot

Cotyledon: the portion of the embryo that will become the first leaves

Monocotyledon (monocots): plants with one cotyledon

Dicotyledon (dicots): plants with two cotyledons

Monocots usually have parallel veins, complexly arranged vascular bundles, a fibrous root system, and floral parts arranged in multiples of three.

Dicots usually have netlike veins, vascular bundles arranged in rings, a taproot system, and floral parts in multiples of four or five.

Reproduction of the Flower

Flowers are the reproductive structure.

Pollen travels by air or on animals.

The stamen and the anther are the male parts of the flower.

The stigma, style, and ovary are the female parts of the flower.

Fruit

Fruits usually consists of a mature ovary, but they can also include other flower parts. They represent large investments of a plant’s energy and nutrient resources.

Simple fruits have one ovary. Two types of simple fruit are dry fruits and fleshy fruits. Dry fruits with one seed either have the ovary wall and seed coat fused (grain) or the ovary wall is hard but can be separated (nut). Dry fruits with two or more seeds have an ovary with several cavities (cotton) or an ovary with one cavity (legume). Fleshy fruit either have an ovary with one seed surrounded by stone (drupe) or an ovary with many seeds. In the case of an ovary with many seeds, all of the ovary tissue is soft, and the flower tissue doesn’t develop into fruit (berry). Instead, the fruit develops from the tissue of the flower base, and the ovary wall forms the core around the seeds (pome).

Compound fruits have multiple ovaries. Multiple fruit are fruit formed from the ovaries of many flowers. Aggregate fruit are fruit formed from several ovaries on one flower.