Plant Growth & Reproduction

Transcription

1 Water loss (ml) Water loss (ml) Water loss (ml) Water loss (ml) 4/24/2014 Plant Growth & Reproduction BI 103 Plant-Animal Systems Turn in Homework #1 Lab Wed! (schedule change) no wind 4 ft 8 ft Wind Temperature Room temp. 20 C Cold 6 C Warm 22 C Time (min) Time (min) Normal Extereme light Light Control Stripped Ripped Herbivory Time (min) Time (min) 1

2 Learning Objectives How does pressure flow theory explain the movement of sugar in plants? Why do plants have flowers? Be able to identify the structures of a flower and describe what they do. What parts of the flower are female? Male? Be able to differentiate between different pollination syndromes Describe double fertilization and how fruit and seeds develop Understand why plants produce fruit How do plants grow? Growing areas need sugar for the synthesis of tissue and energy Phloem moves sugars Pressure-Flow Theory 2

3 How do plants transport sugar? Pressure-Flow Theory Transport occurs in Phloem water pressure differences are created indirectly by the production and use of sugar in different parts of the plant differences in water pressure drive the flow of fluid through the sieve tubes Source sink The Pressure-Flow Theory of Sugar Transport in Phloem xylem vessel phloem sieve tube sunlight 2 1 sugar source cell sugar source 3 sugar sink 4 sugar sink cell Fig

4 Gymnosperms Angiosperms Pterophytes Seeds Lycophytes Bryophytes Green algae: Chlorophytes Land plants Vascular tissue Angiosperm specific adaptations Unlike other plants they have: Flowers Double fertilization Fruit 4

5 Why do plants have flowers? In other words, what are the advantages of flowering? Discuss this question in groups Angiosperms: the Flowering plants Why do plants have flowers? Enlists partnerships with insects and other animals Less inbreeding Higher probability the pollen will reach the right plant They don t have to produce as much pollen 5

6 Alternating Generations In more advanced plants, the sporophyte generation is dominant. Alternation of generations modified Pollen= Male gametophyte Contains sperm Ovule= Female gametophyte Contains egg 6

7 How is pollen an adaptation to land? Allows fertilization to occur even in the absence of available water. water Moss fertilization Pollen grains Anthers with microspores 7

8 Microspore to pollen 1. The microspores divides by mitosis to produce two cells Generative cell (1n) Tube cell== vegetative nucleus (1n) 2. A two layered wall develops around the microspore to become the pollen 3. The generative cell undergoes division once more 3n total (3 nuclei) in pollen Double fertilization 1. Two pollen nuclei enter ovule 2. One fuses with the egg to form the zygote 3. The other fuses with 2 central cell nuclei to become the endosperm (3n), food for the zygote 8

9 Why do we see such diversity in the flowers we see? Theory: Coevolution of plants and pollinators Different flowers have evolved to attract different pollinators- plants have specialized to a specific group of pollinators Pollination syndrome Floral characteristics which attract a specific group of pollinator Bees, hummingbirds, moths etc Allows flowers to specialize May include mechanisms to exclude other pollinators 9

10 Pollination syndrome What are the advantages to specializing to one species or one group of pollinator? What are the disadvantage or risks? Most flowers are generalists and do not specialize. Blue Bees Symmetrical Smells sweet Pollen rewards Nectar rewards Pheromone rewards 10

11 Bees UV Markings Bees can see in UV! Blue UV marking Pollinators: Bees Symmetrical Smells sweet Nectar guides ---Example: Catalpa speciaosa 11

12 Bee specialization Pedicularis attollens, common name: Baby Elephant s head Bumble bee pollinated Specialized Pedicularis attollens 12

13 Buzz pollination Technique only used by bees to release pollen from anthers they must hit the right musical note! Example: Tomatoes, blueberries, manzanita (Arctrostaphylos) fcg&feature=related Red Long and tubular No odor nectar Birds: hummingbirds 13

14 Moths White flowers Sweet smell Open at night Long nectar spur with nectar Hawkmoth on Columbine (Aquileia) Moths Darwin s Orchid, Angraecum sesquipedale 14

15 Why are those spurs so long? Combination of: Moths don t want to get too close. Predators lurk! Plant needs moth to get close enough to reach pollen and stigma Predator: Crab spider 15

16 Bats Strong pedicle and petals Musky odor White Open at night & lots of pollen Ex: Sargo cactus Butterflies Sweet smell Vibrant colors Larger flowers Nectar rewards 16

17 Flies: rancid smell, tiny, green or reddish What is a fruit? 17

18 Fruit development Anther Becomes the seed! Becomes the fruit! Flower Fruit: Tomato 18

19 Flower Fruit Progression Apple: Malus pumila Flower fruit: Maple 19

20 Fruits A fruit typically consists of a mature ovary with seeds inside May be sweet but not necessarily Q: Why might plants produce fruit? 1. Take a min to write down an answer 2. Discuss your answer with another classmate Fruits protect seeds and aid in their dispersal. Seeds can be carried by: > wind > explosion > animals..to new locations 20

21 Dispersal Why might it be important for the seeds to be dispersed far away from the parents? Take a look at the handout After you read through it discuss the results with a group 21

22 Seed dispersal mechanisms Simple Fruits Develops from a single pistil. May develop from several fused carpels. (Compound) Examples: Pea, lemon, beans, peanut 22

23 Aggregate Fruit Develops from many separate carpels. From one flower. Examples: - raspberry - blackberry - strawberry Seed Dormancy Period before germination Allows seeds to wait out adverse environmental conditions Freezing winter Dry season Allows plant populations to recover after a disturbance Fire Flood Heavy grazing 23

24 Germination How do seeds go from dormancy to germination? Light Warm temperature Sometimes: Water Freezing Seed coat disruption 24

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