Chapter 27 - Plant Form, Function, and Evolutionary History

four major groups of vascular plants

- lycophytes

- ferns and horsetails

- gymnosperms

- angiosperms

stomata

Small openings on the underside of a leaf through which oxygen and carbon dioxide can move

guard cells

control the opening and closing of stomata

what happens when guard cells are in an open, high-volume state?

uptake of guard cells causes water to be drawn in by osmosis. As guard cells swell, they bow apart, opening the stoma

what happens when guard cells are in a closed, low-volume state?

release of solutes causes water to flow out of guard cells, closing the stoma

function of leaves

- gas exchange

- photosynthesis

- transpiration (moisture loss)

four major steps of CAM photosynthesis

1. Open stomata at night and collect CO2

2. Merge CO2 with PEP (phosphoenolpyruvate) via PEP carboxylase and store it (the 4C acid)

3. Close stomata at daybreak and fetch 4C acids from storage

4. Commence PSN

CAM Photosynthesis (Crassulacean Acid Metabolism)

The photosynthetic pathway in which carbon fixation takes place at night, and the resulting carbon acids are stored until daylight when they are broken down into pyruvate and CO2.

4C Photosynthesis

uses PEP and PEP carboxylase (Phosphoenolpyruvate)

- suppresses photoresperation

photorespiration

A metabolic pathway that consumes oxygen, releases carbon dioxide, generates no ATP, and decreases photosynthetic output; generally occurs on hot, dry, bright days, when stomata close and the oxygen concentration in the leaf exceeds that of carbon dioxide.

xylem function

long distance transport of water from roots to shoots

xylem structure and four cells types that make up the xylem

found inside vascular bundles

cell types:

1. tracheids

2. vessel elements

3. parenchyma

4. fibers

tracheary elements

tracheids and vessel elements

tracheids

DEAD, long, narrow cells bearing pits on side walls and end walls.

vessel elements

DEAD cells with open end walls (no pit membrane remains) called perforation plates; shorter and wider than tracheids.

plant vessels

vessel elements stacked end-to-end

Forces that Pull Water from the Soil

1) The evaporation of water from the leaves causes water to flow from the soil

2) Hydrogen bonds that form between water molecules allow water to be pulled through the xylem

3) The forces that develop in leaves must be large enough to overcome the capillary forces in the soil

Risks of xylem conduits

air, freezing, dehydration

phloem function

long distance transport of "phloem sap"

- sugars fixed during photosynthesis

2. amino acids

3. other PSN compounds

four phloem cell types

1. sieve tube members (STM)

2. companion cells (CC)

3. parenchyma cells

4. fibers

phloem vs xylem

root anatomy

zone of maturation

absorbs nutrients

- surface area provided by root hairs enhances uptake of the soil solution and its associated nutrients.

mycorrhizal associations

symbiotic interactions with soil fungi that increase a plant's ability to absorb minerals

what forms of nitrogen do plant roots absorb

ammonium

nitrate ions

rhizobia

soil bacteria that fix nitrogen after becoming established inside root nodules of legumes

- mutualistic relationship because the plant has a source of nitrogen and the bacteria is provided carbohydrates by the plant.

epiphytes

absorb nutrients from rainwater, dust and detritus that accumulate around their leaves or in the bark of the host.

parasitic plants

absorb water and other nutrients by penetrating the host tissue.

carnivorous plants

obtain nutrients from insects

carnivorous plant syndrome

1. Attract

2. Trap

3. Retain

4. Kill

5. Digest

6. Absorb

7. Use

where do plants get nitrogen

bacteria