PLANT DIVERSITY Chapter 22

Introduction to Plants  Multicellular  Eukaryotes  Cell walls  Cellulose  Develop from Embryos  Photosynthetic  Chlorophyll a & b

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

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

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

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

Angiosperms  Developed unique reproductive organs called flowers  Flowers contain ovaries which surround and protect seeds

Diversity of Angiosperms  Monocots- one cotyledon (seed leaf)  Dicots- two cotyledons

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

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

ROOTS, STEMS & LEAVES Chapter 23

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

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 Schlerenchyma function in support

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.

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?

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

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.

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

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

Xylem and Phloem Transport

REPRODUCTION IN SEED PLANTS Chapter 24

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

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

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.

Seed dispersal  Animals- eat the fruit and pass the seeds  Wind and water- float

Seed Dormancy  Factors such as temperature and moisture can cause seeds to end dormancy and germinate

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

PLANT RESPONSES & ADAPTATIONS Chapter 25

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

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

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

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

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

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