 |  Biology, 6/e Author Dr. George B. Johnson,
Washington University
Author Dr. Peter H. Raven,
Missouri Botanical Gardens & Washington University
Contributor Dr. Susan Singer,
Carleton College
Contributor Dr. Jonathan Losos,
Washington University
Early Plant Development
Answers to Review Questions|
Chapter 40 (p. 806)
1. The first cell division of the zygote forms the basal cell that will become the suspensor and the upper, smaller cell that will become embryo. The embryo cell divides radially, forming a ball. The outer layer of the ball is the protoderm. The perpendicularity of the mitotic plane to the cell surface maintains the single layers of cells.
2. The failure of a mutant Arabidopsis to produce a root while producing a shoot indicates separate genetic control.
3. Seeds provide for dispersal, dormancy, food storage, and protection for the embryo. Perfectly viable seeds will fail to germinate until oxygen and water enter through the seed coat. A variety of events may be required to make the seed coat permeable.
4. There are many fruit adaptations that aid dispersal and fruits often enrich the soil upon which they fall. A fruit is a ripened ovary. The ovary is a part of the carpel provided by the parent sporophyte. Since the ovary and embryo represent two different sporophyte generations produced by two different fertilizations, their genotypes are probably not the same. The seed wall and the fruit wall are provided by the same sporophyte and should have the same genotype.
5. The embryo produces gibberellic acid that signals the aleurone to produce α-amylase that breaks down the endosperm.
6. By emerging first, the root anchors the plant and increases its water and nutrient absorption.
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2002 McGraw-Hill Higher Education