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 surroundings 2. Prevent desiccation 3. 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