Flowering Plants (Angiosperms)

Transcription

1 Flowering Plants (Angiosperms)

2 Flowering Plants (Angiosperms) Inside ovary: Structures called ovules.. Meiosis occurs in these, producing four haploid female spores. Three of these disintegrate. The fourth spore divides 3x by mitosis eight nuclei in seven cells (one cell has two nuclei called the polar nuclei). Another cell is the egg cell.

3 Flowering Plants (Angiosperms) In the stamens: Anthers undergo meiosis four haploid male spores. Each spore contains a haploid nucleus that divides by mitosis two nuclei. Spore wall thickens around each nucleus pollen grain. Each pollen grain is a male gametophyte containing two cells: Tube cell (with one haploid nucleus) Sperm cell (which divides by mitosis to form two haploid sperm nuclei). Each anther can produce thousands of pollen grains.

4 Flowering Plants (Angiosperms) Pollination: : occurs with the transfer of pollen from stamens to carpel (Figs & 22.7, pp ). Either between flowers of the same plant, or between plants of same species. Sticky stigma at top of carpel can trap pollen. When pollen lands on stigma, it germinates and the tube cell develops into pollen tube, extending down style toward base of ovule in ovary. Sperm nuclei are carried to ovule via pollen tube. One sperm nucleus unites with egg: fertilization. The other sperm nucleus unites with polar nuclei, forming the triploid endosperm,, a nutrient-rich rich structure that nourishes the developing embryo inside the seed,, which consists of the embryo plant, the endosperm and a protective coating ( p. 670).

5 Flowering Plants (Angiosperms) Similarities between life cycles of mosses and flowering plants: Meiosis occurs just before spore formation. Alternation of generations between sporophyte and gametophyte generations.

6 Flowering Plants (Angiosperms) Differences: Flowering plants don t t require great amounts of water for fertilization. Gametophytes of flowering plants are smaller than those of mosses. Gametophyte that produces the egg and the spore that produces the gametophyte remain attached to sporophyte plant. Embryo (young sporophyte) ) grows for short time, then becomes dormant (enclosed in protective seed).

7 Flowering Plants (Angiosperms) Land plants illustrate trend toward increasing specialization of the sporophyte and decreasing specialization of the gametophyte. (Fig. 22.7, p. 671)

8 Flowering Plants (Angiosperms) In summary,, flowering plants are well adapted to terrestrial existence by: Vascular tissue Root systems Cuticle Sperm carried in pollen Spores protected on sporophytes Embryos protected in seeds

9 Many Flowering Plants Have Special Pollinators Flowering plants/angiosperms (phylum Anthophyta): Flower = reproductive structure of the plant. Pollinators: : insects, birds, bats, other animals. Wind can also transport pollen.

10 Many Flowering Plants Have Special Pollinators Cross-pollination pollination: pollen from one plant is transferred to carpel of another plant. Self-pollination pollination: pollen from flower falls on stigma of same flower. Many plants have evolved devices to prevent this from occurring.

11 Many Flowering Plants Have Special Pollinators Sepals and petals = sterile series, as they do not directly participate in reproduction. Act as protection for developing reproductive structures Function as pollinator attractants Stamens and pistils (carpels( carpels) ) = fertile series

12 Many Flowering Plants Have Special Pollinators Variety of flower structure is related to various means by which pollination occurs. Insect pollination: : flower large and brightly colored, possessing small nectar (sugar solution) glands (nectary( nectary). Wind pollination: : flower has small sepals and petals, or none at all; flower positioned high on plant; produce a lot of pollen; carpels with long, feathery structures with sticky fluid at tips for catching pollen.

13 Many Flowering Plants Have Special Pollinators Coevolution: : mutual evolutionary influence between two species, e.g. flowers and insects, or flowers and hummingbirds. Hummers do not have well-developed sense of smell, but can see color red very well. Flowers pollinated by hummers are typically red, with abundant nectar at base of long tube formed by petals. Makes it difficult for other species to rob nectar from flower. Hummers, with long beaks and tongues, can reach nectar. Hummingbird head is dusted with pollen when it visits flower for nectar. When bird visits female flower, the carpel is positioned so pollen is scraped onto carpel from hummer s s head. Both species benefit.

14 Flowering Plants Produce Fruits with Seeds After pollination and fertilization, seed begins to develop. Depending on plant, may be many seeds from one flower (compound( ovary). Plant embryo is protected within seed; seed is protected within fruit.

15 Flowering Plants Produce Fruits with Inside the seed: Seeds Cotyledons: : modified leaves; seed leaves (either one or two) that are part of the developing embryo. Endosperm: : food supply for developing embryo. Cells that will form the root.

16 Flowering Plants Produce Fruits with Examples of seeds: Beans and peas Examples of fruit: Seeds Apples and oranges (both of which have many seeds)typically Typically,, the fruit will decay or be eaten by some animal, which will deposit the seeds elsewhere to germinate.

17 Flowering Plants Are the Most Diverse Group of Land Plants Plants vary in size and in the life spans of their shoots (above-ground parts). Trees: : leaves are high above ground to receive abundant sunlight. Can store large amounts of food reserves in trunk and roots. Allows them to survive through bad years. Long life spans.

18 Flowering Plants Most flowering plants are not trees. May be woody shrubs, e.g. roses and raspberries May be woody vines, e.g. grapes and others Most are herbaceous plants: non-woody (Fig.( 20.17, p. 627)

19 Flowering Plants Flowering plants are divided into two classes (Fig.( 20.16, p. 626): 1. Monocots 2. Dicots

20 13.11 Flowering Plants Monocots (monocotyledons): Fig , p. 626 Embryo contains a single cotyledon (seed-leaf) Floral parts in multiples of three (3) Leaves with parallel veins Includes grasses and grains such as wheat, rice and corn (all of which are major food plants of the world)

21 13.11 Flowering Plants

22 13.11 Flowering Plants Dicots (dicotyledons): Embryo contains two cotyledons Larger class than monocots Floral parts in multiples of four or five (4 or 5) Leaves with branching veins Includes most fruits and vegetables, e.g. carrots, lettuce, apples and grapes, as well as hardwood trees

23 13.11 Flowering Plants

24 Photosynthesis

25 Photosynthesis

26 Photosynthesis Occurs in the chloroplasts of plants.

27 Photosynthesis Energy source used by photoautotrophs can never be exhausted. Light = vibrating electric and magnetic field; acts like a wave. Wavelength (λ)) determines the light s s color and energy Shorter λ: : greater energy Longer λ: : less energy Visible light = just one narrow section of the electromagnetic (EM) spectrum UV light: : higher energy than visible range of light; few organisms have evolved to use this range of light for energy without being harmed by it.

28 Electromagnetic Spectrum

29 Photosynthesis Photoautotrophic cells have evolved an ability to capture some of the energy from the visible light spectrum via light-absorbing substances called pigments.

30 Photosynthesis Chlorophyll: : the green pigment found in the thylakoids which absorbs light.

31 Photosynthesis Two types of chlorophyll: a and b. They both absorb light in the violet/blue and orange/red ranges. Reflect green light

32 Photosynthesis In fall, as chlorophyll content in leaves declines, other, accessory pigments become increasingly visible. Some photosynthetic bacteria contain rhodopsin,, a light- absorbing protein, instead of chlorophyll.

33 Photosynthesis Two groups of reactions by which photosynthesis takes place: Section 4.3, pp Light reactions: : during which light-absorbing pigments in the thylakoids absorb light and convert it to chemical energy carried by short-lived, energy-rich rich molecules. 2. Calvin cycle: : A series of reactions by which sugars are synthesized from those energy-rich rich molecules. The products of the light reactions are used in the Calvin Cycle. The reactions of photosynthesis may be summarized by the following chemical equation: 3 CO H 2 O C 3 H 6 O O 2.

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35 Photosynthesis

36 Photosynthesis Light Reactions (Fig. 4.7, p. 109) Chlorophyll and other pigments absorb light energy.

37 Photosynthesis Light Reactions (Fig. 4.7, p. 109) Water is split into hydrogen and oxygen. Light energy is converted to chemical energy. Product of the light reactions: chemical energy that will power the Calvin cycle.

38 Photosynthesis Light Reactions:

39 Photosynthesis Light reactions in summary: Light forces electrons to flow from water to NADP + in the chloroplast. Electrons retain this energy in NADPH. Some of the NADPH is used to synthesize ATP. Thus, light energy is converted to two forms of chemical energy: ATP and NADPH. This energy will then be used to make sugars from carbon dioxide.

40 Photosynthesis The Calvin Cycle: Fig. 4.9, p. 111 Completes the process of photosynthesis. Converts the chemical energy of NADPH and ATP into sugars. The various steps by which this occurs are catalyzed by enzymes. Occurs in the stroma of the chloroplast.

41 Photosynthesis The Calvin Cycle:

42 Photosynthesis

43 Photosynthesis

44 Ch. 20 Outline Plants (Kingdom Plantae) I. Non-vascular plants 1. Liverworts (phylum Hepaticophyta) 2. Hornworts (phylum Anthocerotophyta) 3. True mosses (phylum Bryophyta)

45 Ch. 20 Outline II. Vascular plants 1. Non seed-producing a. Whiskfern (phylum Psilophyta) b. Club mosses (phylum Lycophyta) c. Horsetails (phylum Sphenophyta) d. Ferns (phylum Pterophyta) 2. Seed-producing a. Gymnosperms/conifers (naked seeds in cones): includes pines, firs, spruces, ginkgos, cycads. i. Pines, firs, spruces (phylum Coniferophyta: cone-bearing ) ii. Ginkgos (phylum Ginkgophyta) iii. Cycads (phylum Cycadophyta) b. Angiosperms/flowering plants (phylum Anthophyta: : seeds enclosed in fruit) i. Monocots ii. Dicots