Download
1 / 74
750 likes | 871 Vues
Chapter 27 Opener. Figure 21.1 The Evolution of Plants. Figure 21.1 The Evolution of Plants (Part 2). Figure 21.1 The Evolution of Plants (Part 1). Figure 21.4 Alternation of Generations in Land Plants. Figure 21.4 Alternation of Generations in Land Plants. In-Text Art, Ch. 27, p. 557.
E N D
Concept 27.1 Most Angiosperms Reproduce Sexually Angiosperm gametophytes are microscopic. Female (megagametophyte), or embryo sac arises from a megaspore. Consists of 7 cells: 1 egg cell 2 synergids (attract pollen tube and receive sperm) 3 antipodal cells degenerate 1 central cell with 2 polar nuclei
Concept 27.1 Most Angiosperms Reproduce Sexually Male (microgametophytes), or pollen grains, arise from microspores. Consist of 2 cells: Generative cell divides by mitosis to form twosperm cells that participate in fertilization. Tube cell forms pollen tube that delivers the sperm to embryo sac.
Concept 27.1 Most Angiosperms Reproduce Sexually With a partner, discuss the differences between sexual reproduction in angiosperms and animals. Consider, for example, the products of mitosis and meiosis and the alternation of haploid and diploid generations.
Concept 27.1 Most Angiosperms Reproduce Sexually Draw a diagram of a flower and label all of the following: Anther Filament Ovule Sepal Stigma Carpel Ovary Petal Stamen Style [Note: If a real flower is available, see if you can identify all of these parts on the real flower, too.] Compare your drawing with your neighbors and discuss: 1. Did you draw a perfect or an imperfect flower? 2. Where is the male gametophyte? 3. Where is the female gametophyte? 4. Where is the sporophyte? 5. Which part will become the seed? 6. Which will become the rest of the fruit?
Concept 27.1 Most Angiosperms Reproduce Sexually Which of the following correctly describes an imperfect flower? a. Has male and female sex organs b. Has both stamens and carpels c. Has only male or only female sex organs d. I don’t know.
Concept 27.1 Most Angiosperms Reproduce Sexually Without looking at your notes, answer the following questions. 1. Is self-fertilization possible in dioecious plants? Why or why not? 2. How is self-fertilization prevented in monoecious plants? When you are finished, discuss your answers with a partner.
Concept 27.1 Most Angiosperms Reproduce Sexually Draw a fruit and label the following: The seed with the embryo The ovary wall Then answer the following questions: 1. What part of the flower are you eating when you bite into an apple? 2. What are the two main functions of fruit?
Concept 27.2 Hormones and Signaling Determine the Transitionfrom the Vegetative to the Reproductive State Genes that determine the transition to floral meristems have been studied in Arabidopsis. Meristem identity genesLEAFY and APETALA1 initiate a cascade of gene expression. Floral organ identity genes: homeotic genes; products are transcription factors that determine whether cells in the floral meristem will be sepals, petals, stamens, or carpels.
Concept 27.2 Hormones and Signaling Determine the Transitionfrom the Vegetative to the Reproductive State External cues that initiate gene expression for flowering: 1. Photoperiod (day length)—Some species flower only when days reach a specific length. Short-day plants (SDPs) flower only when the day is shorter than a critical maximum. Long-day plants (LDPs) flower only when the day is longer than a critical minimum.
Concept 27.2 Hormones and Signaling Determine the Transitionfrom the Vegetative to the Reproductive State Plants sense night length by measuring the ratio of Pfr to Pr. Day—more red light than far-red; by end of day most phytochrome is Pfr. At night Pfr is gradually converted back to Pr. The longer the night, the more Pr there is at dawn. A SDP flowers when ratio of Pfr to Pr is low at the end of the night; a LDP flowers when this ratio is high.
Concept 27.2 Hormones and Signaling Determine the Transitionfrom the Vegetative to the Reproductive State Phytochrome is located in the leaf. The signal for flowering must be a diffusible chemical that travels from the leaf to the shoot apical meristem. The diffusible chemical is the protein florigen.
Hormones and signaling determine the transition from the vegetative to the flowering state • The experiments reported on in fig. 27.8 were repeated using a long-day plant (LDP) that normally flowers with a 16-hour photoperiod. The plant was subjected to the light regimes listed in the table. • List the light regimes that should have resulted in flowering. • Predict the effect of adding a brief period of far-red light in the middle of the dark period of each light regime. • Predict the effect of adding a brief period of red light in the middle of the dark period of each light regime.
Figure 27.9 The Flowering Signal Moves from Leaf to Bud (Part 1)
Figure 27.9 The Flowering Signal Moves from Leaf to Bud (Part 2)
