Lesson 34 : Plant Processes
Refer to chapters 23 & 24 in your textbook Learning Goals: 1. I can explain how plants are pollinated and fertilized. 2. I can explain how a plant germinates and grows. 3. I can explain how a plant alternates generations. 4. I can explain how a plant absorbs and transports nutrients. 5. I can explain how a plant exchanges gases with the environment. Major Plant Processes: 1.
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Pollination Fertilization Germination Alternation of Generations Uptake & Transport of Water & Nutrients Gas Exchange/Transpiration 1. Pollination • Pollination is the transfer of pollen to the female portions of the Nlower. • Types of Pollination: Animal, Wind, & Water • Gymnosperms are mostly wind pollinated, sometimes water or animal • Some angiosperms are wind or water pollinated, but most are pollinated by animals 1. Pollination • Flowers are an evolutionary advantage to plants because they attract animals that carry pollen with them to the next Nlower they visit • Animal-­‐pollinated plants have a variety of adaptations, such as bright colors and sweet nectar, to attract and reward them • Animals have even evolved body shapes that enable them to reach nectar deep within certain Nlowers (Ex. Hummingbird) • Animal pollination is much more efNicient than the wind pollination of most gymnosperms 2. Fertilization • Fertilization occurs when the pollen from the male part of the Nlower combines with the ovules (eggs) from the female part of the Nlower to create an embryo. • The embryo is protected inside a seed, and sometimes fruit, to protect it until the seeds are ready to germinate. 3. Germination • Germination is the growth of the plant embryo (breaking out of the seed) • Some seeds enter a period of dormancy (alive but not growing), until conditions are right for germination 4. Alternation of Generations • The life cycle of land plants has two alternating phases, a diploid (2N) phase and a haploid (N) phase. • The shift between the haploid phase and the diploid phase is known as the alternation of generations. 4. Alternation of Generations • Diploid (2N) plants have 2 sets of chromosomes • The diploid phase is known as the sporophyte, or spore producing plant. 4. Alternation of Generations • Haploid (1N) plants have 1 set of chromosomes • The haploid phase is known as the gametophyte, or gamete producing plant. • Remember, gametes are sex cells = eggs & sperm 4. Alternation of Generations An important trend in plant evolution is the reduction in size of the gametophyte and the increasing size of the sporophyte. 5. Uptake & Transport of Water & Nutrients • The uptake of water into the roots of a plant occurs through passive transport (no energy) • Water uses a speciNic type of passive transport called osmosis • The uptake of nutrients into the roots of a plant occurs through active transport (requires energy) 5. Uptake & Transport of Water & Nutrients Nutrients & water are absorbed through the roots, where they are sent to the vascular tissues: xylem (water) & phloem (nutrients) for transport to the rest of the plant. 5. Uptake & Transport of Water & Nutrients • Once water enter the xylem, it uses a combination of forces to “climb” from the roots to the leaves • Capillary Action is the movement of water through small spaces due to the forces from cohesion, adhesion, and surface tension 6. Gas Exchange/Transpiration • Plant leaves allow gas exchange between air spaces in the spongy mesophyll and the exterior by opening their stomata. • Leaves take in carbon dioxide and give off oxygen during photosynthesis. • When plant cells use the food they make, the cells respire, taking in oxygen and giving off carbon dioxide. • Transpiration is the loss of water through leaves. • Transpiration helps to cool leaves on hot days, but it may also threaten the leaf’s survival if water is scarce. *READ, DNC An Analogy for Transpira:onal Pull Imagine a chain of clowns who are 1ed together and climbing a tall ladder. When the first clown reaches the top, he falls off, pulling the clowns behind him up and over the top. Similarly, as water molecules exit leaves through transpira1on, they pull up the water molecules behind them.