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Plant Processes and Factors That Affect Them Original Power Point Created by Mr. Morgan Modified by the GA Agriculture Education Curriculum Office July 2002 Why Plants are a Vital Part of CO2/O2 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 CO2/O2 Exchange The large-scale destruction of plants may lead to problems with the air we breathe Why Photosynthesis is Essential to CO2/O2 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 CO2/O2 Exchange The chemical reaction takes carbon dioxide and water and converts these materials to sugar and oxygen 6CO2 + 6H2O --> C6H12O6 + 6O2 - Photosynthesis occurs only in the presence of light Respiration Importance in CO2/O2 Exchange Respiration is the reverse of photosynthesis Sugar and oxygen are broken down, releasing carbon dioxide, water, and energy C6H12O6 + 6O2 --> 6CO2 + 6H2O + energy Respiration occurs 24 hours a day Plant Growth Requirements A. B. C. D. E. Nutrients Air Water Light 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 Places where Plants Get Nutrients for Growth Soil Air 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
