- - AGRICULTURE CORE CURRICULUM - - (CLF7000) Advanced Core Cluster: PLANT AND SOIL SCIENCE (CLF7200) Unit Title: PRINCIPLES OF PLANT PHYSIOLOGY AND GROWTH ____________________________________________________________________________ (CLF7202) Topic: BASIC PLANT Time Taught in Year(s) GROWTH REQUIREMENTS 3 hours 3 and 4 ____________________________________________________________________________ Topic Objectives: Upon completion of this lesson the student will be able to: Learning Outcome #: (##) - List six basic growth requirements and indicate the importance of each (i.e., heat, mineral nutrients, water, light, gases, and support). ################################################### # The following is provided as supplemental # # material (i.e., review from the Basic Core) # # and should be used as seems appropriate to the # # instructor. # ################################################### Special Materials and Equipment: Refer to the activities for the topics Seed Germination and Climatic Factors Affecting Plant Growth. References: Hartman, H., Flocker, W., and Kofranek, A.PLANT SCIENCE, GROWTH DEVELOPMENT AND UTILIZATION OF CULTIVATED PLANTS. Evaluation: Quiz by instructor TOPIC PRESENTATION: BASIC PLANT GROWTH REQUIREMENTS A. There are six basic growth requirements for plants: heat, minerals nutrients, water, light, gases and support. B. Temperature (heat) requirements. 1. Growers depend on climatic records of their area to predict the dates of the last killing frost in the spring and the first killing frost in the fall. a. The time between the last killing frost in the spring and the first killing frost in the fall is the growing period. b. The greater the distance from the equator, the fewer "growing days" are available. c. All plants have optimum temperatures for maximum growth and flowering. 2. Most temperate zone plants grow between temperatures of 39 and 122 degrees Fahrenheit. a. These are generally the limits of plant growth. b. High temperatures alter the structure of active cells, leading to abnormal metabolism and death. c. Strong light raises plant temperatures because the absorbing leaves convert some light to heat. d. Plant parts are injured by high temperatures even when exposed for a short time. e. Low temperatures (above freezing) prevent plants from growing because cells need moderate amounts of heat energy to conduct metabolic processes. f. Freezing kills plant cells. 1) Frost kills because ice crystals disrupt the delicate structure of living cells. 2) Dormant seeds can survive freezing because they contain much less water than active plants. g. Low temperature injury is evident after the first killing frost in the fall. 1) As the sun shines on the leaves the following day, the damage is observed as blackened leaves. 2) Several frost protection methods can be successfully used. 3) These would include the use of wind machines, orchard heaters, irrigation techniques, and the use of various covers. C. Sixteen chemical elements are recognized as essential to normal plant growth. 1. Mineral nutrients are divided into groups according to the quantity used: a. The Macronutrients include nitrogen, phosphorous and potassium. b. The secondary mineral nutrients are calcium, magnesium, and sulfur. c. The micronutrients, used in the smallest amounts, include boron, copper, chlorine, iron, magnesium, molybdenum and zinc. d. Carbon, hydrogen and oxygen are not mineral nutrients, but they are essential elements. 2. All sixteen of these elements are essential but they are not needed in the same amounts. 3. Mineral nutrients are supplied to the soil by applying crop residues, animal manures, natural minerals, or chemical fertilizers. 4. The actual source of the nutrient, (organic or inorganic) is not important, but the nutrients must be available in the quantity needed. D. Water is one of the most important factors affecting plant growth. 1. Growing plant organs contain about 90 percent water. 2. Water is one of the raw materials for photosynthesis. 3. Over 99 % of the water entering a plant escapes through transpiration. 4. The presence, especially of sodium or chlorine, can be toxic to plants. 5. The amount of water necessary depends on the crop as well as the available sunshine during the season. E. Light has many influences on plants. 1. Light provides the energy for photosynthesis. 2. It affects seed germination. 3. It affects flower initiation and flowering. 4. It affects plant movement. (Phototropism) 5. Light affects differentiation of many tissues and organs. 6. Light control has an important role in agriculture. a. The control of plant density is a method of controlling the amount of light received by plants. b. Some pruning practices are based upon controlling competition for light within the plant to affect the crop size and quality. c. The reduction of light by shading is useful in many nursery operations. F. The two gases most important for the growth of plants are oxygen (02) and carbon dioxide (C02). 1. Oxygen is important in the respiration of all plant parts. 2. Plants use C02 for photosynthesis and they return 02 to the atmosphere. 3. Both plants and animals use 02 and give off C02 during respiration. 4. Pollutant gases in the air can be harmful to plants. a. The burning of fossil fuels adds these polluting gases into the air. b. Some of the harmful pollutants are ozone, nitrogen oxides, sulfur dioxide, fluorides, and ethylene. G. Several vegetables, grapes, fruit trees, and ornamentals require no physical support for best quality and profitable production. 1. Vegetable plants such as tomatoes, cucumbers, peas, and stringbeans are often staked or trellised for ease of culture and harvest. 2. Most grapevines are trained to trellises to improve berry quality and ease of harvest. 3. Many deciduous fruit trees are wired, roped, or propped to prevent limb breakage. 4. Some ornamentals are placed on trellises or arbors to gain maximum advantage of their foliage and flower characteristics. 7/20/90 sg #%&C