Plant Structure and Function

1. Plant Structure and Function Roots, Stems, and Leaves

2. What is a Plant? • Plants are living things that have roots, stems, and leaves ~ some have flowers • Plants are made of cells that have cell walls, a large central vacuole, and chloroplasts • Chloroplasts contain a green pigment called chlorophyll that play a role in photosynthesis

3. Photosynthesis 6H2O + 6CO2 ----------> C6H12O6+ 6O2

4. Origin and Evolution • There are between 260,000 and 300,000 plant species identified to date • Oldest fossil plants are about 420 million years old – descendants of algae (aquatic) • Cone-bearing plants, such as pines, probably evolved from a group of plants that grew 350 million years ago • Flowering plants did not exist until about 120 million years ago

5. Life on Land – Adaptations! Problem • Drying Out • Making Food • Reproduction • Gravity & Support • Getting water & nutrients • Solution • Waxy cuticle, stomata • Formed leaves • Develops spores & seeds • Bark (cork) & vessels; cell walls (cellulose) • Roots & vessels

6. Protections and Support - Leaf

7. Classification • VASCULAR: have tube-like structures that carry water, nutrients, and other substances through the plant • NONVASCULAR: do not have these tube-like structures and use other ways to move water and substances • Binomial Nomenclature: two word system of naming things, e.g., Quercus alba = white oak

8. Seedless Nonvascular Plants • Don’t grow from seeds; just a few cells thick and only 2 to 5 cm in height; no flowers or cones ~ reproduce by spores • Mosses -Liverworts -Hornworts

9. Nonvascular Plants and the Environment • Pioneer species: first organisms to grow in new or disturbed areas • As pioneer plant species grow and die, decaying material builds up; this, along with the slow breakdown of rocks, builds soil ~ as a result, other organisms can move into the area!

10. Seedless Vascular Plants • Reproduce by spores • Have long, tube-like cells that carry water, minerals, and food to cells throughout the plant • Can grow bigger and thicker because of this • 1,000 species of fern, ground pine, and spike mosses; 12,000 species of ferns! FERN GROUND PINE SPIKE MOSS HORSETAIL

11. Ferns • Largest group of seedless vascular plants • Fern leaves are called fronds • Ferns produce spores in structures on underside of fronds • Ferns that lived 360 million years ago grew as tall as 25 m, but today, tallest tree ferns are about 3 m to 5 m in height

12. Club Mosses • Ground pines and spike mosses • Have needle-like leaves • Spores produced at end of stem in structures that look like tiny pine cones • Endangered in some areas, as they have been collected to make wreaths

13. Horsetails • Stem is jointed and has a hollow center surrounded by a ring of vascular tissue; at each joint leaves grow out from around the stem • Spores are produced in a cone-like structure at the tips of some stems • Stems contain silica, a gritty substance found in sand – “scouring rush”

14. Importance of Seedless Plants • When ancient seedless plants died, they became submerged in water and mud before they decomposed – over time, plant material became coal! • Today, decaying plants are compressed into a substance called peat, which forms from the remains of sphagnum moss – used as low-cost fuel in places such as Ireland and Russia

15. Uses of Seedless Vascular Plants • Peat and sphagnum mosses used for gardening • Peat used as soil conditioner • Ferns used for weaving material and basketry • Rhizomes and young fronds of ferns are edible • Dried stems of one type of horsetail can be ground into flour • Folk medicines to treat bee stings, burns, fevers, and even dandruff!

16. Seed Plants • Have leaves, roots, stems, and vascular tissue; produce seeds • Gymnosperms and Angiosperms • Leaf made up of different layers of cells • Waxy cuticle • Epidermis (Stomata surrounded by guard cells) • Palisade layer – most food produced here • Spongy layer – veins containing vascular tissue found here • Lower Epidermis

17. Leaf Structure

18. Stems and Roots • Herbaceous stems: soft and green • Woody stems: hard, rigid • Roots have vascular tissue in which water and dissolved substances move from the soil through the stems to the leaves; roots also act as anchors • Roots can store food, e.g., carrots, beets • Absorb oxygen for use in respiration ~ making energy for the plant’s cells

19. Vascular Tissue • Xylem: hollow, tubular cells stacked one on top of the other to form a structure called a vessel; transport water and dissolved substances • Phloem: tubular cells that are stacked to form structures called tubes; move food from where it is made to other parts of the plant where it is used or stored • Cambium: between xylem and phloem; produces new xylem and phloem

20. Gymnosperms • Oldest trees alive • Produce seeds not protected by fruit; “naked seeds”; do not have flowers • Leaves needle-like or scale-like • Four divisions: • Coniferophyta: conifers-pines, firs, spruces, redwoods, junipers • Cycads • Gingkoes • Gnetophytes

21. Angiosperms • Vascular plant that flowers and has a fruit that contains one or more seeds • Division: Anthophyta • Monocots – one cotyledon used for food storage, e.g., corn, rice, wheat, barley, lilies, orchids, grass • Dicots – two cotyledons; shade trees, fruit trees; petunias; geraniums; snapdragons

22. Monocots • Flower parts in multiples of three • Leaves are more narrow than long • Vascular bundles show up as parallel veins in leaves • Vascular tissues are arranged as bundles scattered throughout the stem • Seeds have just one cotyledon

23. Dicots • Flower parts in multiples of four or five • Vascular bundles are the network of veins in the leaves • Vascular bundles occur in rings (annual rings in woody stems) • Seeds have two cotyledons

24. Life Cycles of Angiosperms • Biennials: complete their life cycles within two years • Annuals: complete their life cycles in one year • Perennials: take more than two years to grow to maturity

25. Some Products from Gymnosperms • Lumber, paper, soap, varnish, paints, waxes, perfumes, edible pine nuts, medicines

26. Some Products from Angiosperms • Foods, sugar, chocolate, cotton cloth, linen, rubber, vegetable oils, perfumes, medicines, cinnamon, flavorings (toothpaste, chewing gum, candy, etc.), dyes, lumber • FLOWER PARTS • SMARTBOARD REVIEW