Angiosperm Reproduction and Biotechnology

Page
6

Dispersal by Animals

Seeds carried to

ant nest

Seeds buried in caches

Seeds in feces

Barbed fruit

Slide 43

Plants reproduce sexually, asexually, or both

Many angiosperm species reproduce both asexually and sexually.

Sexual reproduction results in offspring that are genetically different from their parents.

Asexual reproduction results in a clone of genetically identical organisms.

Slide 44

Mechanisms of Asexual Reproduction

Fragmentation, separation of a parent plant into parts that develop into whole plants, is a very common type of asexual reproduction.

In some species, a parent plant’s root system gives rise to adventitious shoots that become separate shoot systems.

Apomixis is the asexual production of seeds from a diploid cell.

Slide 45

Advantages and Disadvantages of Asexual Versus Sexual Reproduction

Asexual reproduction is also called vegetative reproduction.

Asexual reproduction can be beneficial to a successful plant in a stable environment.

However, a clone of plants is vulnerable to local extinction if there is an environmental change.

Slide 46

Sexual reproduction generates genetic variation that makes evolutionary adaptation possible.

However, only a fraction of seedlings survive.

Slide 47

Mechanisms That Prevent Self-Fertilization

Many angiosperms have mechanisms that make it difficult or impossible for a flower to self-fertilize.

Dioecious species have staminate and carpellate flowers on separate plants.

Slide 48

Some floral adaptations that prevent self-fertilization

(a)

Sagittaria latifolia staminate flower (left) and carpellate flower (right)

(b) Oxalis alpina flowers

Thrum flower

Pin flower

Stamens

Styles

Styles

Stamens

Slide 49

Floral Adaptations that prevent self-fertilization: stamens and styles mature at different times or are arranged to prevent self pollination / self fertilization.

Oxalis alpina flowers

Thrum flower

Pin flower

Stamens

Styles

Styles

Stamens

Slide 50

The most common is self-incompatibility, a plant’s ability to reject its own pollen.

Researchers are unraveling the molecular mechanisms involved in self-incompatibility.