Growth
Outline
Nutrients, Vitamins, and Hormones Plant Hormones Plant Movements Photoperiodism Temperature and Growth Dormancy and Quiescence
Development
Growth Increase in volume Differentiation Cell specialization Development Growth and differentiation
Nutrients, Vitamins, and Hormones
Nutrients - Furnish elements necessary to produce organic molecules Vitamins Participate in reactions catalyzed by enzymes Hormones Influence development
Plant Hormones
Auxins Production occurs in apical meristems
Promote cell enlargement
Plant Hormones
Gibberellins Production occurs in seeds, young leaves, and roots
Promote stem growth
Plant Hormones
Cytokinins Production occurs in root tips and germinating seeds
Regulate cell division
Plant Hormones
Abscisic Acid Production occurs in some cell organelles Prevents seeds from germinating while still on plant
Plant Hormones
Ethylene Produced by fruits, flowers, seeds, leaves, and roots
Promotes ripening in fruits
Plant Movements
Movements From Internal Stimuli Nutations Tiny spiraling Nodding Side-to-side Twining Large spiraling Contraction Pulling into ground by roots Nastic Non-directional
Plant Movements
Movements From External Stimuli Tropism is the movement toward an external stimulus and can be divided into three phases: - Initial Perception--perceive stimulus - Transduction--hormone distribution - Asymmetric Growth--uneven hormones result in greater elongation of cells on one side of plant
Plant Movements
Phototropism Growth response to light Positive or negative Gravitropism Growth response to gravity Positive or negative
Plant Movements
Turgor Movements Result from changes in internal water pressures Circadian Rhythms Leaves or petals in fold regular daily cycles, folding in the evening and unfolding in the morning - Controlled by a biological clock on approximately 24 hours cycles
Plant Movements
Solar Tracking Leaves twist on their petioles and perpendicularly orient to a light source Water Conservation Many grasses have cells that lose their turgor and roll up or fold during periods of insufficient water
Plant Movements
Taxis Movement involving either the entire organism or reproductive cells In response to a stimulus, the cell or organisms, propelled by a flagella or cilia, moves toward or away from the stimulus
Plant Movements
Taxis Chemotaxic Chemicals Phototaxic Light Aerotaxic - Oxygen
Photoperiodism
Photoperiodism--Day length is related to the onset of flowering in many plants Short-Day Plants will not flower unless the day length is shorter than a critical period Long-Day Plants will not flower unless periods of light are longer than a critical period
Photoperiodism
Intermediate-Day Plants will not flower if the days are too short or too long Day-Neutral Plants will flower under any day-length
Temperature and Growth
Each plant species has an optimum temperature for growth which may vary with a plant's growth stage, and a minimum temperature, below which growth will not occur
Dormancy and Quiescence
Dormancy - Period of growth inactivity in seeds, buds, bulbs, and other plant organs even when environmental requirements are met Quiescence - State in which a seed cannot germinate unless environmental conditions normally required for growth are present
Review
Nutrients, Vitamins, and Hormones Plant Hormones Plant Movements Photoperiodism Temperature and Growth Dormancy and Quiescence
Reminders
Read Chapter 11 Exam 4 Lab Practical 2