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Objectives: 1) Differentiate between vascular and nonvascular plants. 2) Construct a diagram labeling the parts of a seed.

http://www.flickr.com/photos/mike_simons/1174054919/

Vascular Plants

* Most land plants are vascular.

•Possess vascular tissue which is comprised of strings of pipe-like cells

1) Xylem: a vascular tissue that transports water and minerals from roots to leaves.2) Phloem: a vascular tissue that transports organic nutrients from leaves to the rest of the plant

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Water Movement in Plants

1) For most plants upon maturity, xylem cells are dead, leaving just a series of cell walls linked together. However the cell walls are missing where one xylem cell touches another. Bottom line = big pipes that run through the plant. It is only in living xylem that water is transported.

2) Water DIFFUSES from the soil into the roots.

3) Two forces allow for water to travel up the plant.

1. Capillary Action: Water likes to stick to other substances (adhesion). This allows the water to “climb”up the tiny xylem pipes.

2. Transpiration: Water evaporates from leaves further up the plant. Since water molecules are “holding hands” (cohesion), when one leaves, it pulls the next one up. This keeps going on and on.

Sugar Movement in Plants

1) The pipes that make up phloem are a little different from those that make up xylem. Phloem is made up of individual sieve tube member pipes. Each pipe is separated from the next by a barrier called the sieve plate. It has little holes in it. Sieve tube member cells are alive.

2) Connected to the sieve tube members are companion cells. Companion cells (especially those in leaves) are full of water.

3) As sugar enters the sieve tube member the concentration of water is less in the sieve tube member, because the pipe is gunked up with sticky sugar. The water concentration is greater in the companion cell.

4) So water in the companion cell diffuses into thesieve tube member to “flush” the sugar down to the roots.

Very similar to a toilet.

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Two Types of Plant Growth

• Primary Growth: Most monocots and

dicots grow only at the tips of the plant.

Areas called apical meristems.

• Secondary Growth: Conifers and woody

dicots (trees). Horizontal growth that

occurs at the vascular cambium (makes

xylem and phloem) and the cork cambium

(gives rise to bark).

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Advantages of the Seed

#1 Seed Coat (Integument) = protection from drying out, injury, and disease.#2 Stored Food (Endosperm)= nourishment#3 Seed Dispersal = wind, animals, or water#4 Delayed Growth = seeds are in a state of “hibernation” until favorable conditions present themselves.#5 Radicle: Becomes the root.#6 Epicotyl: Shoot

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Alternation of Generations