Plant Growth and Development PDF

PLANT GROWTH AND DEVELOPMENT Abrila M. Langbao  INTRODUCTION TO PLANT GROWTH AND DEVELOPMENT Key Concepts: Growth: Increase in size and number of cells. Development: The process through which a plant progresses from a simple structure to a m...

PLANT GROWTH AND DEVELOPMENT Abrila M. Langbao  INTRODUCTION TO PLANT GROWTH AND DEVELOPMENT Key Concepts: Growth: Increase in size and number of cells. Development: The process through which a plant progresses from a simple structure to a more complex form, including differentiation and maturation. Importance: Crucial for agriculture, forestry, and ecological systems  THE PLANT LIFE CYCLE Stages of a plant's life cycle: Germination: Seed absorbs water and begins to grow. Vegetative Growth: Roots, stems, and leaves develop. Reproductive Growth: Flowering and fruiting. Senescence: Aging and death of plant tissues.  FACTORS INFLUENCING PLANT GROWTH External Factors: Light: Photosynthesis, photoperiod, and light intensity. Water: Essential for nutrient uptake and biochemical processes. Temperature: Affects enzyme activity and metabolic processes. Soil: Nutrient availability, pH, and structure. Air: Carbon dioxide (CO₂) for photosynthesis. Internal Factors: Hormones: Auxins, cytokinin, gibberellins, ethylene, abscisic acid (ABA) are key in regulating growth and development.  PLANT HORMONES AND THEIR ROLES Auxins: Promote cell elongation, root initiation, and apical dominance. Cytokinin: Stimulates cell division and differentiation. Gibberellins: Regulate stem elongation, seed germination, and flowering. Ethylene: Influences fruit ripening and leaf abscission. Abscisic Acid (ABA): Involved in stress responses, seed dormancy, and stomatal closure.  STAGES OF GERMINATION Types of Germination: Epigeal: Cotyledons emerge above the soil. Hypogeal: Cotyledons remain below the soil. Key Events in Germination: Absorption of water (imbibition). Activation of enzymes. Growth of the embryo and emergence of the radicle.  VEGETATIVE GROWTH Key Processes: Cell Division: Occurs in meristems (apical, lateral). Cell Elongation: Growth in length due to water intake. Differentiation: Cells specialize into roots, stems, leaves. Factors Affecting Vegetative Growth: Light, nutrients, and water availability.  REPRODUCTIVE GROWTH AND FLOWERING Flower Development: Pollination: Transfer of pollen from male to female parts. Fertilization: Union of male and female gametes. Fruit Development: After fertilization, ovary develops into fruit. Environmental Factors: Photoperiod (day length) and temperature affect flowering.  SENESCENCE AND AGING IN PLANTS Senescence: Process of aging, leading to the breakdown of cellular components. Factors Influencing Senescence: Hormonal changes (decrease in auxin and cytokinin). Environmental stress (drought, temperature extremes). Nutrient deficiencies.  GROWTH REGULATORS IN AGRICULTURE Application of Plant Growth Regulators (PGRs): Promoting Growth: Use of gibberellins for seedless fruits, cytokinin for promoting shoot growth. Controlling Growth: Use of auxins for rooting cuttings, and ethylene for fruit ripening. Stress Management: ABA for drought tolerance and seed dormancy.  CLASSIFICATION BASED ON FUNCTION 1. Plant Growth Promoters: These regulators enhance growth by promoting cell division, cell enlargement, flowering, fruit formation, and seed development. Examples of growth promoters include: Auxins: Stimulate cell elongation and are crucial for root development. Gibberellins: Promote stem elongation, seed germination, and flowering. Cytokinins: Encourage cell division and delay the aging of leaves. 2. Plant Growth Inhibitors: These substances slow down or inhibit growth processes, often inducing dormancy or causing the shedding of leaves and fruits. The primary example is: Abscisic Acid: This regulator promotes dormancy and helps plants cope with stress by closing stomata and inhibiting growth. Ethylene: Though unique in that it can act as both a growth promoter and inhibitor, ethylene is primarily considered an inhibitor, influencing processes like fruit ripening and leaf abscission. FUNCTIONS OF PLANT REGULATORS CONT.  PLANT RESPONSES TO ENVIRONMENTAL STRESS Types of Stress: Abiotic Stress: Drought, salinity, extreme temperatures. Biotic Stress: Pest and pathogen attack. Adaptations: Leaf morphology changes. Root system development (deeper roots for water access). Hormonal changes (ABA for water stress).  CONCLUSION Summary: Plant growth and development is a complex process regulated by internal and external factors. Understanding these processes helps improve agricultural productivity, biodiversity conservation, and sustainable land management. Importance in Agriculture and Ecology: The knowledge gained from studying plant growth helps in optimizing crop yields, managing natural ecosystems, and addressing challenges such as climate change.  Disclaimer. All figures used in the slides are from Google.