Developmental biology is the branch of biology that studies the processes by which organisms grow and develop from a single cell into a complex multicellular organism. Developmental biologists investigate how genes and environmental factors interact to shape the structure, function, and behavior of organisms.
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Development
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is the progression from earlier to later stages in maturation. It is the process whereby tissues, organs, and whole plants are produced.
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involves: growth, morphogenesis (the acquisition of form and structure), and differentiation.
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Growth
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refers to an irreversible increase in mass.
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Differentiation
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The process in which the cells of the apical meristems mature to perform specific functions.
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Morphogenesis
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is the acquisition of form, how a plant or organ acquires its distinctive shape or form.
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Plasticity
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is the ability to change form or shape in response to a change in environment; no genetic change is involved.
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Indeterminate growth
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Plant organ grow continuously
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Plant organ grow continuously Ex. Root and stem
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Determinate growth
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Organs stop growing after reaching a certain size.
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Ex. Leaves, flowers and fruits
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Primary growth
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is an increase in stem and root length
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Secondary growth
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is an increase in the girth of plant.
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cell
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basic structural and functional unit of plants
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basic structural and functional unit of plants
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Plant tissue systems fall into one of two general types:
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meristematic tissue
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permanent (or non-meristematic) tissue
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Meristems
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plant regions of continuous cell division and growth
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meristematic tissue
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is a group of identical cells that are in a continuous state of division
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initials
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Cells that remain as sources of new cell.
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derivatives
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The new cells displaced from the meristem.
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apical meristem
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intercalary meristem
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intercalary meristem
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Apical meristem
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A small mitotically active zone of cells found at the shoot tip or root tip
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Primary growth occurs as a result of the activity of apical meristem
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primary tissues
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Tissues derived from the apical meristems are
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Form primary meristems that produce the tissues of the stem and root
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a. Protoderm (which forms the epidermis)
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b. Procambium (which forms phloem and xylem)
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c. Ground meristems (which form parenchyma)
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are known as secondary meristems because they are responsible for secondary growth, or increase in stem girth and thickness
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Give increase in girth (secondary growth)
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Produces secondary vascular tissues
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Two lateral meristems: the vascular cambium and the cork cambium are responsible for secondary growth
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sometimes known just as cambium) is a cylinder of cells that forms new phloem and xylem.
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Division of the cells of the vascular cambium adds more cells to the wood(secondary xylem) and inner bark (secondary phloem).
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You can find out the age of a tree by counting the number of dark rings
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the outermost lateral meristem.
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It produces cork cells, which contain a waxy substance that can repel water.
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The phloem together with the cork cells form the bark.
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The cork cambium also produces a layer of cells known as phelloderm
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The cork cambium, cork cells, and phelloderm are collectively termed the periderm.
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Regions of meristematic tissue between regions of more mature tissues
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Occur only in monocots, at the bases of leaf blades and at nodes (the areas where leaves attach to a stem).
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Permanent tissue
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consists of plant cells that are no longer actively dividing
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Three main types:
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Dermal
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Vascular
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ground
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Alternation of generation
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All land plants (and some green algae) reproduce via the alternation of generations life cycle, where both the haploid and the diploid stage are multicellular.
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Sporophyte (Diploid stage)
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produces spores
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Gametophyte (Haploid) stage)
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formed from the spore and give rise to the haploid gametes
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Haploid (n)
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the quality of a cell or organism having a single set of chromosomes
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Diploid (2n)
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a cell or organism that has paired chromosomes
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Gamete
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a mature haploid male or female germ cell that is able to unite with another of the opposite sex in sexual reproduction to form a zygote
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Spore
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a minute, typically one-celled, reproductive unit capable of giving rise to a new individual without sexual fusion
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The reproductive structure found in flowering plants which is specialized for sexual reproduction
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Pollination and Reproduction
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Male Gametophyte (The Pollen Grain)
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Pollen
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is the male gametophyte in angiosperms and gymnosperms.
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microsporangium (micro = small)
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this is where ollen development occurs, located within the anthers.
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microsporangia (P of microsporangium)
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are pollen sacs in which the microspores develop into pollen grains.
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Embryo sac / female gametophyte
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is an oval structure present in the ovule of flowering plants.
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It possesses two haploid nuclei and six haploid cells which do not have cell walls.
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POLLINATION
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The transfer of pollen from a male part of a plant to a female part of a plant, later enabling fertilization
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Self-pollination
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is pollination of a carpel by pollen from the same flower or another flower on the same plant
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Cross-pollination
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is the pollination of a carpel by pollen from a different individual
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Methods of Pollination
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Biotic Pollination
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◻ involves pollinators (also called pollen vectors)
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Abiotic Pollination
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◻ wind, water and rain
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Double Fertilization
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Double fertilization involves two sperm cells; one fertilizes the egg cell to form the zygote, while the other fuses with the two polar nuclei that form the endosperm.
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Embryogenesis
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is the first stage of the development of a new organism from its first cell named zygote, which appears as a result of the sexual fertilization.
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After double fertilization.
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each mature ovule develops into a seed
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the ovary develops into a fruit enclosing the seed(s)
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Seeds
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are protective structures that contain plant embryos and nutritive tissue to support the embryo until it can survive on its own
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A typical seed contains:
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a. Seed coat
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b. Endosperm/cotyledon
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c. single embryo
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1. Seed coat
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They are the protective outer covering of a seed. The seed coat is formed from the outer covering of the ovule called the integument.
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It usually contains two layers:
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testa – the thick outer layer
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tegmen – the delicate inner layer.
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FUNCTIONS:
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Protecting the seed from physical and mechanical damage
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Preventing the seed from germination even under favorable conditions of growth (seed dormancy)
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Preventing the excessive loss of water from the seeds
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Acting as a physical barrier against the entry of parasites
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2. Endosperm
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It is a tissue that is rich in oil, starch, and protein.
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Non-endospermic or exalbuminous seeds
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Characterized by the complete absence of the endosperm, such as the seeds of the pea plant, groundnut, and gram.
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Endospermic or albuminous seeds
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Characterized by the presence of the endosperm, such as the seeds of millets, palms, and lilies.
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Functions:
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-Storing of reserve foods that provide nourishment to the developing plant
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-Protecting the embryo, the next part of the seed, by acting as the mechanical barrier
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3. Embryo
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the young plant that is developing inside the seed coat.
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contains the underdeveloped tissues of leaves, stem, and roots of a plant.
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Epicotyl
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The tiny shoot of an embryo, from which the entire shoot system develops. The tip of the epicotyl is called plumule.
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Hypocotyl
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The stage of transition for the growing shoot and root of the embryo
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Radicle
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The tiny root of the embryo
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Cotyledons
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They are the leaves of the embryo that provide nourishment to the developing plant.
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Functions
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Giving rise to a new complete new plant
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Storing food and nourishing the baby plant
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two types of cotyledons
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monocotyledonous or monocots
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embryo with one cotyledon and
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dicotyledonous or dicots
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– embryo with two cotyledons.
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scutellum
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The single cotyledon
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is connected directly to the embryo via vascular tissue (xylem and phloem).
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Food reserves are stored in the large endosperm
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The two cotyledons in the dicot seed also have vascular connections to the embryo.
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In endospermic dicots
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the food reserves are stored in the endosperm.
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non-endospermic dicots
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The triploid endosperm develops normally following double fertilization, but the endosperm food reserves are quickly remobilized and moved into the developing cotyledon for storage
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dormancy
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mature seeds enter a period of inactivity, or extremely low metabolic activity:
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Germination
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is the development of a plant from a seed after a period of dormancy.
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Germination depends on imbibition, the uptake of water due to the low water potential of the dry seed
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Any structure that develops from a fertilized ovary and contains seeds of the plant.
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The ovary surrounding the ovules develops into a fruit that contains one or more seeds.
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Vegetable
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is actually not a scientific term and simply refers to the edible part of the plant: roots/tubers, stems, leaves, etc.
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fruit
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is the seed-containing part of a plant
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is the fleshy or dry ripened ovary of a plant.
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While the seeds are developing from ovules, the ovary of the flower is developing into a fruit, which protects the enclosed seeds and, when mature, aids in their dispersal by wind or animals.
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Fertilization triggers hormonal changes that cause the ovary to begin its transformation into a fruit. If a flower has not been pollinated, fruit typically does not develop, and the entire flower usually withers and falls away
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the ovary wall becomes the pericarp, the thickened wall of the fruit.
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Exocarp
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the outer layer
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Mesocarp
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middle layer
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Endocarp
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inner layer
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The shoot system consists of two portions:
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the vegetative (non-reproductive) parts of the plant,
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leaves and the stems,
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the reproductive parts of the plant,
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flowers and fruits.
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The root system
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which supports the plants and absorbs water and miis usually underground.
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primary plant body
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derived from shoot and root apical meristem
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composed of primary tissues
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constitutes the herbaceous parts of a plant
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secondary plant body
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derived from meristems other than apical meristem
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composed of secondary tissues
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