Importance of Seed: Plant Growth, Germination, Hormones, Light, Gravity, and Nutrition
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Presentation Transcript
Chapter 9 Plant Growth
Importance of Seed • Most ag crops begin as seeds • Seeds compose ~70% of diets • Used for varied purposes • Cereals, oils, snacks • Beverages • Oils and dryers • Cosmetics, ointments, pharmas
Types of Seeds • Dicot • Leaf has two distinct halves • Stores energy in cotyledons • Monocot • One seed leaf • Stores energy in endosperm
Seed Germination • Water • Oxygen • Temperature • Light
Process of Germination • Moisture enters seed, seed swells • Coat ruptures, oxygen enters • Respiration provides energy • Cells multiply, growth bidirectional
Growth after Germination • Growth types • Increase in cell size • Increase in cell number • Cell differentiation • Mitosis occurs in meristem • Tips of stems and branches • Tips of roots
Plant Growth Hormones • Chemical substances that control or influence activities • Control growth in plants • Proper balance is essential • Stimulate or inhibit
Major Hormone Groups • Auxins • Cytokinins • Gibberellins
Effects of Light on Plant Growth • Phototropism (grow toward light) • Photoperiodism (respond to amount of daylight and darkness) • Blooming • Leaf shedding • Dormancy • Flowering intervals
Effect of Gravity on Plant Growth • Geotropism (grow toward gravity) • Plant grows in opposite directions • Stem: Negatively geotropic • Root: Positively geotropic
Plant Nutrition • All systems need nutrients • Nutrients provide energy • Come from air and soil • Proper balance is necessary • Macronutrients: In large amounts • Micronutrients: In small amounts
Nonmineral Nutrients • Carbon • Hydrogen • Oxygen
Primary Nutrients • Nitrogen • Phosphorus • Potassium
Secondary Nutrients • Calcium • Magnesium • Sulfur
Micronutrients • Iron • Chlorine • Copper • Zinc • Boron • Manganese • Molybdenum
Summary • Plants grow more efficiently due to human techniques • All use biology principles found in nature • Research uses these principles to grow food and fiber more efficiently