Unit 4- Plants

M. Lauria

Background on Plants The Plant

kingdom includes more than 270,000 species

Believed to have evolved from green algae (chlorophyta).

http://homepage.smc.edu/gallogly_ethan/travel_photos/misc/sean_mom_giant_redwood_tree.JPG

Adaptations to Land

In order to prevent water loss on dry land, plants have a cuticle (waxy covering).

Some have roots, stems and leaves to help obtain, transport, and use water and nutrients efficiently.

Use spores and seeds to protect reproductive cells.

Adaptations to Land (cont.) Some plants have vascular tissues

called xylem and phloem to help transport water and nutrients throughout the different parts of the plant.

Some have stomates to prevent water loss and control gas exchange with the atmosphere.

Stomates

Stomates are small openings along the surface of a leaf that control gas exchange.

They close when the plant is beginning to lose to much water. They open when the plant needs CO2

www.emc.maricopa.edu/.../ BIOBK/BioBookPS.html

Cross- Section of a Leaf

http://www.emc.maricopa.edu/faculty/farabee/BIOBK/leafstru.gif

Xylem

Conducts water Xylem cell is called a tracheid, its cell

walls are impermeable to water Vessel elements are xylem cells found in

angiosperms When these cells die, their cytoplasm

disintegrates and they are able to conduct water.

Phloem

Conducts a variety of plant nutrients and products

Phloem cells are called sieve tube elements, are positioned end to end and have holes that connect their interiors.

Companion cells are located next to sieve tubes and help to control them.

Cross Section of a Stem: Xylem and Phloem

cd.ed.gov.hk/.../ Root/Ranuculus%2011.jpg

Classifying Plants

From Modern Biology: Holt, Rinehart, and Winston

Non-vascular Plants Lack vascular tissue and do not

form true roots, stems or leaves. Are seedless, and need water to

reproduce sexually. Have an alternation of

generations- sporophyte and gametophyte.

Seedless Vascular Plants

Vascular plants can grow larger and live longer. Why?

Include: Ferns, whisk ferns, club mosses, horsetails.

http://www.ct-botanical-society.org/ferns/fernpics/phegopterishexa_frond.jpg

Alternation of Generations in a Fern

staff.jccc.net/.../ celldivision/images/fern.gif

Vascular Seed Plants Plants with seeds have a greater

chance at reproductive success than seedless plants. Why?

Two main groups of seed-bearing plants: gymnosperms (“naked” seed) and angiosperms (seed protected in fruits).

Gymnosperms Have specialized

male and female reproductive structures called scales.

Larger structure is called a cone.

http://www.pfc.forestry.ca/diseases/CTD/Group/Rust/lrg_images/fig30b.gif

Gymnosperms Conifers

(evergreens) include pines, spruce, fir, cedars, redwoods.

Leaves are needle-shaped.

Do not necessarily shed needles in the fall.

Pollen from a pollen cone fertilizes egg within a seed cone.

Seed within a seed cone is considered “naked.”

Angiosperms Flowering plants

are most widespread of all plants? Why?

Reproduce using pollination of flowers

Seeds are contained within a protective fruit.

Some flowers have both male parts (stamen- pollen producing) and female parts (ovary- egg producing)

Flower Parts

www.ncsu.edu/project/ agronauts/images/flower.gif

Alternation of Generations In Vascular Seed Plants

Sporophyte is the dominant form, and the gametophyte grows within the flowers or cones of the sporophyte.

http://www.stevedibler.com/photos/Nature-Scenery/Dogwood_tree.jpg