Plant Growth and Development Quiz

Plant Growth and Development

• Plant growth is an irreversible increase in size, whereas development involves progressing through life stages like germination, vegetative growth, flowering, fruiting, and senescence.

Key Processes

• Cell Division: Growth begins at the cellular level through mitosis.
• Cell Elongation: After division, cells lengthen, contributing to overall plant size.
• Cell Differentiation: Cells become specialized into different tissues and organs (e.g., roots, stems, leaves).

Plant Growth Stages

• Sprout: Seed contains nutrients for germination and early leaf development.
• Seedling: Developing roots and spread require balanced nutrients.
• Vegetative: Nitrogen is important for stem and foliage growth.
• Budding: Plants need extra phosphorus during blooming.
• Flowering: Potassium is essential for healthy flowers and fruit.
• Ripening: Plants require water and no additional nutrients during final stage.

Growth Phases

• Embryonic: Starts after fertilization, during seed formation.
• Vegetative: Focuses on root and shoot system development.
• Reproductive: Flowering, pollination, and seed formation stages.

Hormonal Regulation of Growth

• Auxins: Promote cell elongation, apical dominance, phototropism, and gravitropism.
• Gibberellins: Stimulate stem elongation, seed germination, and flowering.
• Cytokinins: Promote cell division, delay leaf senescence, and encourage lateral bud growth, working against auxins.
• Ethylene: Involved in fruit ripening, leaf abscission, and stress responses.
• Abscisic Acid (ABA): Regulates stress responses, seed dormancy, and stomatal closure during drought.

Environmental Influences on Growth

• Light (Photoperiodism): Day length affects flowering (long-day vs. short-day plants). Photosynthesis converts light into chemical energy.
• Water: Crucial for turgor pressure, nutrient uptake, and transport.
• Temperature (Optimum Growth Range and Thermoperiodism): Optimal temperature ranges exist for growth and development, affected by daily temperature fluctuations.
• Nutrients: Macronutrients (e.g., Nitrogen, Phosphorus, Potassium) and micronutrients (e.g., Iron, Zinc) are essential for growth and development.

Flowering

• Flowering is the transition from vegetative growth to reproductive development, enabling seed production.
• Factors Influencing Flowering:
  • Photoperiod: Plant response to day/night length (short vs. long-day plants).
  • Vernalization: Cold temperatures may initiate flowering.
  • Hormonal Control: Gibberellins can promote flowering in specific plants.
• Stages of Flower Development:
  • Flower Induction: Triggers flower development based on external and internal cues.
  • Floral Initiation: Reproductive meristem development into floral organs.
  • Flower Maturation: Fully developed floral organs for pollination.

Importance of Flowering

• Reproduction: Flowers are the reproductive structures enabling seed production.
• Agriculture: Successful flowering is crucial for crop production.
• Pollinator Attraction: Flowers attract pollinators (e.g., bees, butterflies) for cross-pollination.

Leaf Senescence

• The natural aging process in leaves.
• Types: Whole plant, sequential, and stress-induced senescence.
• Visible: Yellowing due to chlorophyll breakdown.
• Molecular Aspects: Hormone regulation changes (e.g., decline in cytokinins, increase in ethylene and ABA).
• Importance:
  • Nutrient Recycling: Redistributes nutrients.
  • Stress Response: Defense mechanism under stress.
  • Ecosystem Contributions: Organic matter decomposition.
  • Controlled Cell Death: Prevents uncontrolled decay and facilitates nutrient recovery.