Introduction to Plants Chapter 22.1

Basic Plant Structure

Plants Are…

1) Multicellular

2) Eukaryotic

3) Autotrophic

4) Use Chlorophyll a or b

How Did Plants Originate?

First land plants appeared 500 mya Resembled present day mosses Released nitric acids on rock surfaces

which created soil Likely colonies of protists adapted to

dry environment…but how?

Links Between Algae and Plants

Both have protective cell walls Both contain chlorophyll used in

photosynthesis Both store food in the form of starches

Plants Must Adapt To Live On Land

1. Absorb nutrients from surroundings2. Prevent desiccation3. Reproduce without the aid of water

If plants adapt to these strategies, they can evolve on land

Why would a plant “want” to move onto the land?

A. Preventing Water Loss Cuticle: waxy coating that prevents

tissues from drying out Stomata-openings in the cuticle that

allow gas exchange to take place and also regulate water loss

Prevent Desiccation? Desiccation= Drying Out As plants evolved further away from water,

they needed to evolve a waterproof structure/coating (cuticle)

But, this structure needs pores (stomata) WHY? Think about what the plant needs for

photosynthesis… CARBON DIOXIDE!

Stomata

B. Autotrophic Leaf-organ that enables the plant to

trap and absorb light energy

Leaf Layers via microscope

C. Stabilization and Nutrient Absorption(Accomplished with roots and

mycorrihizea) Roots-organ that is used to reach and

transport water and minerals, anchor plants and store food

Earliest roots are rhizoids Fossils show fungi “helped” plants

before roots evolved

The Root Main function = absorb water Functional Part = root hair Structure from outside in:

– Epidermis with root hair= protection– Cortex=support/storage– Vascular Bundle: Phloem, Vascular Cambium*,

Xylem

*Vascular Cam: growth of new vascular tissue

Root Structure

D. Transportation System

Stem- Transport of water, food, and

minerals Support of plant Storage of materials

Structures of the Stem Epidermis (bark or green)=protection Cork cambium =new growth of bark/

epidermis Cortex = thick layer, sometimes contains

chloroplasts, mostly for support Vascular Bundle = contain transport tissues

towards the middle of the stem Xylem = transports water and minerals

(generally in the middle)

More Structures Phloem = transports sugars to all cells,

located outside the xylem Vascular cambium = separates the X

and P, contains new cells for vascular growth

Pith = central portion of stem of tree, for storage

E. Reproduce Without Water

Spores/Cones/Seed-protective coat which prevents a developing embryo from drying out

Advent of pollen and seeds make it possible to reproduce far away from water

Pollen = plant sperm, light weight and won’t dry out, carried via wind, water, animal, etc

Pollen Images via SEM