Plant Growth, Development, and Reproduction PDF

Plant Growth, Development and Reproduction Dr. Luz O. Moreno National Abaca Research Center (NARCC) Dept. Plant Breeding & Genetics (DPBG) Visayas State University, Visca, Baybay, Leyte Co...

Plant Growth, Development and Reproduction Dr. Luz O. Moreno National Abaca Research Center (NARCC) Dept. Plant Breeding & Genetics (DPBG) Visayas State University, Visca, Baybay, Leyte Colloquium 2024 VSU, Visca, Baybay, Leyte Growth and development involve a series of complete, coordinated events beginning with germination, vegetative growth then reproductive phase Growth - irreversible increase in size a. Primary – growth resulting from activity of primary meristem (e.g. apical) b. Secondary – resulting from secondary meristem (e.g. lateral); increase in diameter Growth - The progressive development of an organism or the irreversible increase in size Usually expressed as dry weight (total of the part we're interested in such as grain), height, length, diameter increase in cell numbers by cell division and an increase in cell size plants have indeterminate growth (made possible by meristem), and as long as they live, continue to add new organs and tissues Growth of an annual plant related to time is an S (sigmoid) shaped curve for an or one growing season for a perennial plant Differentiation - the process by which an unspecialized cell develops into a specialized cell (cells take on a special form and function) Organization - orientation and integration of differentiated cells with the consequent attainment of form and structure of the complete organism ❑ Growth is a quantitative aspect of development; it is accompanied by differentiation and morphogenesis resulting to an orderly change in the complexity of the organism; biosynthesis of new protoplasmic constituent ❑ Development is a combination of both growth and differentiation (all changes that an organism goes through in its life cycle) ❑ Differentiation is the qualitative aspect of development; biochemical and structural changes to perform specialized function ❖ All plant growth occurs by cell division and cell elongation. Cell division occurs primarily in regions of undifferentiated cells known as meristem. ❖ Cell division in the apical meristem and subsequent elongation and maturation of the new cells produces primary growth ❖ The other type of growth, secondary growth, is the increase in girth of stems and roots. The factors that affect plant growth can be classified as genetic or environmental A. Genetic Factor (Internal control) ❑ The internal controls are all the product of the genetic instructions carried in the plant ❑These influence the extent and timing of growth and are med iated by signals transmitted within the cell, between cells, or all around the plant ❑ Intercellular communication in plants may take place via hormones (or chemical messengers) ❑ Yield potential and other traits such as quality, disease resistance, drought hardiness are determined by genes ❖ Genetic engineering is now becoming an important tool in changing a plants potential. ❖ A producer has control over the genetic factor by his choice of variety B. Environmental factors (External controls) ❑ All external conditions and influences affecting the life and development of an organism Temperature Moisture supply Radiant energy Composition of the atmosphere Soil aeration and soil structure Biotic factors Supply of mineral nutrients Absence of growth-restricting substances The external environments of the root and shoot place constraints on the extent to which the internal controls can permit the plant to grow and develop. Prime among these are the water and nutrient supplies available in the soil. Mechanisms that Control Growth and Development ❑ Genes ❑ Hormones (intrinsic factors) ❑ Environment (extrinsic factors) Genes + Environment = Phenotype (changes in gene expression is a principal factor in regulating development) Growth and development in plants, from seed germination to maturation; 1. are controlled by a chain of physiological processes 2. Basically includes 3 aspects namely; a. Growth b. Differentiation c. organization Nature of Plant Growth:  There is increase in size due to a.Cell division b.Cell enlargement c.Change in cell density  Distribution of growth is not uniform – it takes place in growth centers like; a.Meristems - production of new cells b.Regions of cell enlargement Growth Stages 1. Embryogenesis – part of seed development (e.g. zygote to embryo) 2. Vegetative development – include; a. Seed germination (from heterotrophic to photosynthetic) b. Development of vegetative plant 3. Reproductive development a.Flowering b.Pollination c.Fertilization to zygote Phases of vegetative stage; 1. Juvenile stage – germination period, seedling growth up to a point of growth when transition phase begins 2. Transition phase stage – the plant is gradually losing its juvenile characteristics and at the same time gradually acquiring the adult characteristics 3. Adult phase – the plant is already very capable of flowering; can readily respond to flowering stimuli Fundamental Abilities of Plants ❑ Totipotency The inherent capacity of a plant cell to develop into an entire plant if suitable environment is stimulated It implies that all information necessary for growth and reproduction of the organism is contained in the cell Fundamental…. ❑ Dedifferentiation The capacity of mature cells to return to meristematic condition and development of a growing point, followed by re-differentiation which is the ability to reorganize into new organs ❑ Competency The endogenous potential of a given cell or tissue to develop in a particular way Hormones (Plant Growth Regulators)  substances other than nutrients that are produced by plants that may qualitatively/quantitatively modify/control growth, development and movement  The response need not be promotive it can also be inhibitive  Usually translocated from production site to action site  Maybe effective even in minute concentrations ❑ Plant hormones play important roles in regulating developmental processes and signaling networks involved in plant responses to a wide range of biotic and abiotic stresses ❑They are also involved in plant defense signaling pathways ❑The effect on plant physiology is dependent on the amount of hormone present and tissue sensitivity to the plant regulator Plant Hormones (PGRs): Auxins (cell elongation) Gibberellins (cell elongation + cell division - translated into growth) Cytokinins (cell division + inhibits senescence) Abscisic acid (abscission of leaves and fruits + dormancy induction of buds and seeds) Ethylene (promotes senescence, epinasty, and fruit ripening) Other identified plant growth regulators include: Brassinosteroids Salicylic acid Jasmonites Plant peptide hormones Polyamines Nitric oxide Strigolactones Karrikiris Ps – conversion of light energy into useful chemical energy (most impt. life process) Respiration – oxidative breakdown of organic compounds into simpler forms with the concomitant release of energy Transpiration –loss of water from plants in the form of water vapor Translocation – movement of water throughout the plant system Assimilation – process of utilizing food for growth General overview of role of plant hormones in growth and development Plant Life Processes: A. Photosynthesis B. Respiration C. Water absorption and Transpiration D. Translocation E. Assimilation  PHOTOSYNTHESIS: AN OVERVIEW  The light reactions convert solar energy Chloroplast to chemical energy Light  Produce ATP & NADPH NADP+ ADP +P The Calvin cycle makes Light Calvin cycle reactions sugar from carbon dioxide – ATP generated by the light reactions provides the energy for sugar synthesis – The NADPH produced by the light reactions provides the electrons for the reduction of carbon dioxide to glucose  Types of photosynthesis  C3 (Calvin Cycle)  The majority of plants  C4  CO2 temporarily stored as 4-C organic acids resulting in more efficient C exchange rate  Advantage in high light, high temperature, low CO2  Many grasses and crops (e.g., corn, sugar cane)  CAM  Stomata open during night  Advantage in arid climates  Many succulents (e.g., cacti, bromeliads, agaves) Factors affecting Ps: (External)  Light (quality, duration & intensity) - plants differ in their light requirements, e.g. C3 (rice, soybeans, tobacco) & C4 species (corn, sugarcane, sorghum)  CO2 concentration  Water availability  Temperature  PHOTOSYNTHESIS  What affects photosynthesis?  Light intensity: as light increases, rate of photosynthesis increases PHOTOSYNTHESIS  What affects photosynthesis?  Carbon Dioxide: As CO2 increases, rate of photosynthesis increases PHOTOSYNTHESIS  What affects photosynthesis?  Temperature:  Temperature Low = Rate of photosynthesis low  Temperature Increases = Rate of photosynthesis increases  If temperature too hot, rate drops Factors affecting Ps: (Internal)  Photosynthetic enzyme systems)  Leaf resistance  Demand for Ps  Hormonal regulation  Genetic control  Leaf age  Mineral status What is transpiration? Transpiration is the process by which moisture is carried through plants from roots to small pores on the underside of leaves, where it changes to vapor and is released to the atmosphere. Transpiration is essentially evaporation of water from plant leaves. Transpiration also includes a process called guttation, which is the loss of water in liquid form from the uninjured leaf or stem of the plant, principally through water stomata. DAGHANG SALAMAT