Original Power Point Created by
Mr. Morgan
Modified by the GA Agriculture Education Curriculum Office
July 2002

Why Plants are a Vital Part of
CO
2
/O
2
Exchange

Animals breathe in air, use oxygen, and exhale carbon dioxide

Animals need oxygen to survive

Plants do the opposite- they take carbon dioxide from the air and give off oxygen

Through this cycle the correct balance of oxygen and carbon dioxide is maintained in the atmosphere

Why Plants are a Vital Part CO
2
/O
2
Exchange

The large-scale destruction of plants may lead to problems with the air we breathe

Why Photosynthesis is Essential to
CO
2
/O
2
Exchange

The broad surface area of the leaf absorbs sunlight to be used as energy

Carbon dioxide is taken from the air and the other nutrients (including water) are taken from the soil and transported to the leaves in the water through the xylem

Chloroplasts participate in a chemical process that converts their raw materials into usable food for the plant

Why Photosynthesis is Essential to
CO
2
/O
2
Exchange


The chemical reaction takes carbon dioxide and water and converts these materials to sugar and oxygen
6CO
2
+ 6H
2
O --> C
6
H
12
O
6
+ 6O
2
Photosynthesis occurs only in the presence of light

Respiration Importance in CO
2
/O
2
Exchange

Respiration is the reverse of photosynthesis

Sugar and oxygen are broken down, releasing carbon dioxide, water, and energy
 C
6
H
12
O
6
+ 6O
2
--> 6CO
2
+ 6H
2
O + energy

Respiration occurs 24 hours a day

Plant Growth Requirements
A.
Nutrients
B.
Air
C.
Water
D.
Light
E.
Correct temperature

How Light and Temperature affect
Plants

Light intensity- growth is greatly reduced at lower light intensities. Most plants cannot grow below 100-200 foot candles, about the level of light in an average room

The compensation point is the light intensity at which a plant will maintain itself but not grow

Temperatures at night are lower, therefore the plant goes through respiration

How Light and Temperature affect
Plants

Light duration- the length of the day helps plants distinguish what time of year it is

Some plants will only flower in the spring but can be induced to flower in the winter
(in a controlled environment) by extending the light duration

Temperatures during the day hours are higher and encourage plant development

Phototropism

Phototropism is the development responses of plants to the relative direction of the light

Thermotropism

Thermotropism is the plant characteristic in which a plant will grow towards areas with more desirable temperatures


Soil

Air
Places where Plants Get Nutrients for
Growth

Functions of Primary Nutrients

Nitrogen: fast growth, synthesis of organic compounds- including amino acids, proteins, coenzymes, nucleic acids, and chlorophyll

Phosphorus: energy storage and transfer

Potassium: photosynthesis, sugar translocation, and enzyme activation

Functions of Secondary Nutrients

Calcium: components of cell walls, cell growth and division

Magnesium: central part of chlorophyll, photosynthesis

Sulfur: amino acids and vitamins

Functions of Micronutrients

Iron: synthesis of chlorophyll

Boron: regulation of metabolism

Zinc: protein synthesis

Manganese: respiration, photosynthesis

Copper: enzyme activation

Chlorine: photosynthetic processes

Sodium: plant-water relations

Effects of CO2 Fertilization on Plant
Growth

Plant growth will increase as carbon dioxide increases, as long as carbon dioxide is the limiting nutrient

Five Types of Growth Regulators

Auxins: growth promoting hormone

Freshly cut stems are dipped into this

Gibberellins: stimulates growth in plants

Dwarf plants transform into normal sized plants

Kinins (cytokinins): influence in stimulation of cell division

Dormin: promotes flowering in some short day plants and promotes dormancy in buds and seeds

Ethylene: uniform ripening, sex conversion