Angiosperm Reproduction and Biotechnology

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Some plants reject pollen that has an S-gene matching an allele in the stigma cells.

Recognition of self pollen triggers a signal transduction pathway leading to a block in growth of a pollen tube.

Floral Adaptations that prevent self-fertilization:

Slide 51

Vegetative Propagation and Agriculture

Humans have devised methods for asexual propagation of angiosperms.

Most methods are based on the ability of plants to form adventitious roots or shoots.

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Clones from Cuttings

Many kinds of plants are asexually reproduced from plant fragments called cuttings.

A callus is a mass of dividing undifferentiated cells that forms where a stem is cut and produces adventitious roots.

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Grafting

A twig or bud can be grafted onto a plant of a closely related species or variety.

The stock provides the root system.

The scion is grafted onto the stock.

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Test-Tube Cloning and Related Techniques

Plant biologists have adopted in vitro methods to create and clone novel plant varieties.

Transgenic plants are genetically modified (GM) to express a gene from another organism.

Slide 55

Test-tube cloning of carrots

(b) Differentiation into plant

(a) Undifferentiated carrot cells

Slide 56

Protoplast fusion is used to create hybrid plants by fusing protoplasts, plant cells with their cell walls removed.

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Protoplasts

50 µm

Slide 58

Humans modify crops by breeding and genetic engineering

Humans have intervened in the reproduction and genetic makeup of plants for thousands of years.

Hybridization is common in nature and has been used by breeders to introduce new genes.

Maize, a product of artificial selection, is a staple in many developing countries.

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Maize - Corn: a product of artificial selection

Slide 60

Plant Breeding

Mutations can arise spontaneously or can be induced by breeders.

Plants with beneficial mutations are used in breeding experiments.

Desirable traits can be introduced from different species or genera.