Plant diversity

1. Plant diversity Chapter 22

2. Introduction to Plants • Multicellular • Eukaryotes • Cell walls • Cellulose • Develop from Embryos • Photosynthetic • Chlorophyll a & b

3. What Plants Need… • Sunlight • Water • Minerals • Gas exchange • And movement of water and nutrients throughout the plant body

4. Bryophytes • Depend on water for reproduction • Lack vascular tissue • Must draw water by osmosis • Thus are very low to the ground • Mosses, liverworts, hornworts

5. Seedless Vascular Plants • Contain vascular tissue that transports materials throughout the plant against gravity • Xylem- carries water • Phloem- carries nutrients • Club mosses, horsetails, ferns

6. Seed Plants • Adaptations allow these plants to reproduce in areas without water • Flowers, cones, pollen, and seeds • Gymnosperms bear seeds directly on surface of cones

7. Angiosperms • Developed unique reproductive organs called flowers • Flowers contain ovaries which surround and protect seeds

8. Diversity of Angiosperms • Monocots- one cotyledon (seed leaf) • Dicots- two cotyledons

9. Diversity of Angiosperms • Woody Plants- made of thick cell walls that support the plant • Trees, shrubs, vines • Herbaceous Plants- do not produce wood as they grow • Dandelions, sunflowers

10. Angiosperm Life Spans • Annuals- grow, flower, produce seeds and die in one season • Petunias, pansies, zinnias • Biennials- germinate and grow slightly in the first year; produce flowers and seeds in the second and then die • Foxglove, parsley, celery • Perennials- live many years; may die back in winter but replace itself in the spring • Maples, honeysuckle, grasses

11. Roots, stems & leaves Chapter 23

12. Specialized Tissues in Plants • Roots • Absorb water and dissolved nutrients • Anchor plants to the ground • Stems • Support the plant body • Carries nutrients up the plant • Leaves • Contain the photosynthetic systems

13. Plant Tissue Systems • Dermal Tissue- “skin” • Protects against water loss • May give added surface area • Vascular Tissue • Xylem- tracheids& vessel elements • Phloem- sieve tube elements & companion cells • Ground Tissue • Parenchyma- storage & support • Collenchyma and Schlerenchymafunction in support

14. Plant Growth • Meristematic Tissue- produces new cells by mitosis • Primary growth • New cells at the tip of the stem or root are undifferentiated • Apical meristem • Gradually as the cell matures, it differentiates.

15. Roots • Taproots- dicots • Fibrous Roots- monocots • Mature roots have an epidermal layer and a central cylinder of vascular tissue separated by ground tissue called a cortex • Can you guess what root hairs are for?

16. Stems • Produce leaves, branches, & flowers • Hold leaves up in the sunlight • Transport nutrients • Primary growth- length • Secondary growth- width • Wood

17. Leaves • Optimized for absorbing light & photosynthesis • Blades collect sunlight and are attached to the stem by a thin stalk called a petiole. • Compound leaves are divided into many separate leaflets.

18. Leaf Functions • Transpiration- loss of water through the leaves • Plants keep stomata open just enough to allow photosynthesis to take place but not so much that they lose too much water

19. Transport in Plants • The combination of root pressure, capillary action, & transpiration provides enough force to move water through the xylem of even the tallest plants. • Capillary action results from a force called adhesion

20. Xylem and Phloem Transport

21. Reproduction in seed plants Chapter 24

22. Reproduction with Cones & Flowers • Gymnosperms- cones produced by mature sporophyte plant • Pollen cones- male • Seed cones- female

23. Structure of Flowers • Composed of specialized leaves • Sepals- outer part of flower • Petals- often brightly colored • Stamens- male • Anther & filament • Carpels- female • Pistil- ovary, style, stigma

24. Life Cycle of Seed Plants • Reproduction takes place in the flower • After pollination and fertilization, seeds develop in structures • fruits • Most gymnosperms are wind pollinated. • Most angiosperms are pollinated by animals.

25. Seed dispersal • Animals- eat the fruit and pass the seeds • Wind and water- float

26. Seed Dormancy • Factors such as temperature and moisture can cause seeds to end dormancy and germinate

27. Plant Propogation • Vegetative reproduction- produce plants from horizontal stems, plantlets, and roots. • Cuttings, grafting, or budding can also be used in agriculture.

28. Plant responses & adaptations Chapter 25

29. Plant Hormones • Control growth and development, & a plant’s responses • Auxins- produced in apical meristem; stimulate cell elongation • Cytokinins stimulate cell division/growth; cause seeds to sprout • Gibberellins produce dramatic increase in size of stems & fruits • Ethylene stimulates fruits to ripen

30. Plant Responses • Gravitropism- (auxin) • Roots grow downward • Phototropism- (auxin) • Stems grow to light • Thigmotropism- touch • Photoperiodism- causes timing flowering & growth • Winter Dormancy- growth &photosynthetic activity decreases

31. Plant Adaptations • Many aquatic plants have tissues with large air spaces to allow in oxygen • Salt-tolerant plants have special cells to pump out excess salts • Xerophytes “dry plants”- desert plants with extenive roots, reduced leaves, and thick stems

32. Nutritional Specialists • Live in environments with low levels of nutrients in the soil • Carnivorous plants- lack N-fixing bacteria due to acidic/wet conditions • Parasitic plants- lack chlorophyll and must extract nutrients and water from host plants

33. Epiphytes • Grow on other plants • Not rooted in soil • BUT ARE NOT PARASITES! • Most found in tropical rainforests • They gather their own moisture and produce their own food

34. Chemical Defenses • Protect against insect and animal attack • Some are poisonous • Some imitate hormones that prevent insects from reproducing • Aspirin, codeine, & nicotine are derived from plants