Angiosperm Reproduction and Biotechnology

CHAPTER 38

ANGIOSPERM REPRODUCTION AND BIOTECHNOLOGY

I.Student misconceptions

1.The angiosperm life cycle is very difficult for students to master.Students find it hard to recognize that a tiny pollen grain and an embryo sac retained within the ovule of the sporophyte really represent separate generations.It is essential that students have a good understanding of the generalized alternation of generations life cycle in plants before they attempt to understand how this life cycle is modified in angiosperms.

2.Students do not fully appreciate how fundamentally different plant life cycles are from the more familiar animal life cycles.Most students think of the embryo within the seed as the offspring of the sporophyte. They do not recognize that a seed actually contains structures contributed by three distinct generations of plants: the new sporophyte embryo, the remains of the female gametophyte, and the seed coat produced by the embryo’s “grandparent.”

3.Double fertilization is puzzling to many students.They may be confused by the 3n condition of the endosperm, uncertain about how this triploid nucleus is produced, and unclear about the significance of this event to angiosperm reproduction.

4.Many students mistakenly think that fruit is the product of syngamy, containing genetic contributions from both parents. The issue is: Flower produces fruit and fruit produces seed versus fruit develops only if seed is formed.

II.Pre-test to identify student misconceptions prior to addressing the material covered in Chapter 38

1.Double fertilization:

a.Is characteristic of seed plants

b.Results in the fertilization of egg by sperm and polar nuclei by pollen tube nucleus

c.Produces a diploid sporophyte and a triploid endosperm

d.Results from the fusion of the male and female gametophytes of angiosperms

e.Prevents the production of infertile pollen grains

2.The gametophyte generation of an angiosperm is represented by:

a.An anther

b.A pollen grain

c.An ovary

d.An ovule

e.An embryo sac

III.How can instructors address and correct the misconceptions that students have about angiosperm reproduction and biotechnology?

1.Clarify for students that fruits are mostly contributed by the sporophyte and that the young sporophyte within the seed is the product of syngamy. Point out that in order to get the same quality of fruit next season as this season, the grower must use tissue derived from the sporophyte, such as a graft, rather than planting the seed within the fruit.

2.If students are familiar with the fern life cycle, pointing out the homologous structures and stages of ferns and angiosperms may help them to understand that the pollen grain and the embryo sac within the ovule represent adult individuals of the gametophyte generation.

IV.Post-test to identify whether students have corrected their misconceptions

1.List the products and explain the significance of double fertilization in angiosperms.

2.“A seed contains structures contributed by three distinct generations of plants.” Explain this statement.