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Botany: An introduction to Plant Biology (Plant Structure # # # # # #,…

- - - - xylem
        
        conducts water and minerals
        
        two types of conducting cells
        
        tracheids
        
        long/narrow
        
        the ends are pointed
        
        reticulate
        
        vascular elements
        
        ends are usually flat
        
        reticulate
        
        short/wide
      - Phloem
        
        transports sap. The sap is a water-based solution, but rich in sugars made by photosynthesis.
        
        two types of conducting cells
        
        Sieve cells
        
        sieve pores arrange in circumscribed areas called the sieve plate
        
        afford communication with similar adjacent cells
        
        walls contain perforations called sieve pores
        
        sieve tube membrane
        
        have transverse end walls
        
        Sieve tube members with proteins necessary for signaling and ATP in order to help them transfer molecules between different parts of the plant.
        
        transports organic compounds during photosynthesis
- - - - provascular tissue
        
        Primary phloem
        
        fasicular cambium
        
        vascular cambium
        
        secondary xylem
        
        secondary phloem
        
        cork cambium
        
        Primary xylem
      - Ground meristem
        
        cortex
        
        cork cambium(in some plants)
        
        pith
        
        interfasicular cambium
      - protoderm
        
        epidermis
        
        cork cambium (in some plants)
        
        cork
        
        phelloderm
- - - - vascular cambium: meristem that produces secondary plant body
        
        fusiform initials:The fusiform initials are elongated tapering cells that give rise to all cells of the vertical system of the secondary phloem and xylem
        
        axial phloem
        
        axial xylem
        
        Ray initials: a cell in the cambium that gives rise to cells of the rays
        
        phloem rays
        
        cork cambium
        
        cork: composed of phloem, cortex and epidermis. it is the outer layer of bark
        
        Phelloderm: a layer of parenchyma produced inwardly by a phellogen
        
        xylem rays
- - - - derived from fusiform initials
      - consists of tracheids and trachery elements that conducts water
      - it also consists of fibers. the hardness of the wood depends upon the fibers it consists
    - - deived from ray initials
      - Ray parenchyma cell
        
        upright cells: these cells have connection with axial cells
        
        procumbent cells: these cells have no direct contact with the axial cells
- - - - lowermost and the outermost of the four flower appendages.
      - modified leaves
      - they protect the flower bud as it develops. they also protect the flower from nectar robbing insects and birds.
      - all sepals together is called calyx.
    - - above sepals are the petals which is collectively called corolla
      - petals are like leafs but they have the pigment other than chlorophyll.
      - petals have to attract the right pollinators towards the plant.
    - - Above petals are the stamen collectively known as androecium
      - It is the male part of the plant and they produce pollen
      - Stamens have two parts: filament (its stalk) and anther (where pollen is produced).
      - anther is composed of diploid cells which undergoes various processes one of which is meiosis and finally forms microspores
        microspores is nourished by nearing anther cells called the tapetum
      - microspores initially remain in tetrad which later separates and it is called pollen.
    - - carpels constitute the gynoecium
      - capels have three main parts
        
        stigma: catches pollen grains
        
        style: elevates the stigma to a useful position
        
        ovary: megaspores are produced. ovary has ovules which develops into seeds after it is fertilized.
  - - - microspores develop in microgametophytes.
      - The pollen grains of gymnosperms and angiosperms are microgametophytes.
      - microspore divides into vegetative cell and generative cell( divides and forms two sperm cells called microgametes)
      - pollen grain land on stigma amd forms pollen tubes. the pollen tube extends downwards through which the sperm cell reaches the ovule.
    - - megaspores develop from megagametophyte
      - on one type the nucleus undergoes three mitotic division which ultimate reults to eight nucleate megaspore called the megagametophyte
- - - - drupe
      - pepo
      - pome
      - hesperidium
      - berry
    - - indehiscent fruits
        
        developing from a single carpel
        
        achene
        
        samara
        
        caryopsis
        
        developing from a compound gynoecium
        
        nut
      - dehiscent fruits
        
        developing from a single carpel
        
        legume
        
        follicle
        
        developing from a compound gynoecium
        
        capsule
        
        schizocarp
    - - aggregate fruits
      - multiple fruit
- - - - araceae
      - hydrocharitaceae
      - alismataceae
      - potamogetonaceae
      - ruppiaceae
      - zosteraceae
  - - - amaryllidaceae
      - asparagaceae
      - asphodelaceaea
      - asphodelaceae
      - alliaceae
      - hyacinthaceae
      - agavaceae
      - iridaceae
      - ruscaceae
  - - - it has about 3500 species which are easily recognizable by their solitary trunk.
      - they have scattered vascular bundles like that of most monocots
      - all species have simple leaves that are fully expanded y have either pinnate pattern or palmate one
      - egs: palm tree, coconut tree etc.
    - - this order contains grass family poaceae as well as cattalis, bromeliads and sedges.
      - it has 8000 species
      - they include grass as well as wheat, barley, oats, corn, sugarcane etc. bamboo also comes under this group
      - representative families of poales
        
        bromeliaceae
        
        cyperaceae
        
        juncaceae
        
        poaceae
        
        typhaceae
    - - it contains some of the most familiar house plants like marantha, canathea, gingers, banana etc.
      - they have large showy flowers
      - its largest family zingiberaceae has around 1000 species
      - representative families
        
        cannaceae
        
        marantaceae
        
        musaceae
        
        strelitziaceae
        
        zingiberaceae
- - - - they produce a group of water soluble pigments called the betalains
      - their ancestral group may have lacked petals in their flowers.
      - endosperm develops a little and fails to continue growing
      - phloem plastids contains deposits of fibrous protein located as a ring just interior to the plastid membrane
      - representative families
        
        cactaceae
        
        caryophyllaceae
        
        amaranthaceae
        
        nyctaginaceae
        
        aizoaceae
        
        phytolaccaceae
        
        portulaccaceae
    - - highly modified plants most of which are parasitic
      - some are hemiparasitic while some are holoparasitic
- - - - the chromosomes will be already duplicated. these coil and become shorter and thicker
      - the duplicates homologous chromosome pair and crossing over occurs
      - nucleolus disappears
      - nuclear envelope disappears
      - longest phase of meiosis
    - - The centrioles are at opposite poles of the cell
      - homologous chromosome tightly coil and condense
        andbecome arranged on a plane equidistant from the poles called the metaphase plate.
      - Spindle fibers from one pole of the cell attach to one chromosome of each pair (seen as sister chromatids), and spindle fibers from the opposite pole attach to the homologous chromosome (again, seen as sister chromatids).
    - - A key difference between mitosis and meiosis is that sister chromatids remain joined after metaphase in meiosis I, whereas in mitosis they separate.
      - Anaphase I begins when the two chromosomes of each bivalent (tetrad) separate and start moving toward opposite poles of the cell as a result of the action of the spindle.
    - - A nuclear envelope reforms around each chromosome set, the spindle disappears, and cytokinesis follows. In animal cells, cytokinesis involves the formation of a cleavage furrow, resulting in the pinching of the cell into two cells. After cytokinesis, eachthe two progeny cells has a nucleus with a haploid set of replicated chromosomes.
      - The homologous chromosome pairs complete their migration to the two poles as a result of the action of the spindle. Now a haploid set of chromosomes is at each pole, with each chromosome still having two chromatids.
- - - - develops from embryonic root called the radicle
      - consists of lateral roots or branched roots
      - if the plant is perennial and woody, roots also go secodary growth
      - most monocots have the tap root system
    - - most monocots and some dicots have it
      - this arises because the radicle diesduring or immediately after germination; root primordia at the base of the radicle grow out and form the forst stage of fibrous root system
      - they are also known as adventitious root
      - this type of root system increases the absorptive and transport capacities of the root system
- - - - cortex
        
        growth occurs and destroys cortex and epidermis
        
        lateral root emerge
- - - - due to mutation there is decrease in the frequency of the existing alleles and there is increase in new alleles
      - the significance of mutation also depends on the population size.
    - - accidents are the events to which an organism cannot adapt.
      - if the population of a area has the same gene frequencies and sudden accidents happen in such area and the animals or plants are killed then that gene frequency is lost from earth.
    - - it is the process in which humans purposefully change the allele frequency of a gene pool.
      - for example: selective breeding of crop plants and domestic plants.
    - - the most significant factor causing gene pool changes also called survival of the fittest.
      - natural selection is the most important factor in evolution.
      - for natural selection to occur, there are two conditions necessary:
        
        the population must produce more offspring that can possibly grow and survive to maturity in that habitat
        
        the progeny must differ from each other in their types of alleles.
    - - the loss of an individual does not depend on a single factor, but it depends on many factors.
      - there are multiple internal and external factors that does carry out the selection process.
- - - - they had two kinds of xylem organization.
      - they had protostele: The most primitive form of stele, consisting of a solid core of xylem encased by phloem or of xylem interspersed with phloem.
      - also has another type of stele called siphonostele:a stele consisting of a core of pith surrounded by concentric layers of xylem and phloem
- - - - Bipinnately compound: leaves are twice divided
      - Trifoliate: a pinnate leaf with just three leaflets
      - Even pinnate: lacking a terminal leaflet
      - Pinnatifid: pinnately dissected to the central vein but the leaflets not completely separated
      - Odd pinnate: with terminal leaflet
      - Pinnately compound: leaflets arranged along the main or mid-vein
      - Palmately compound: leaflets radiating from the end of the petiole
  - - - parallel. monocot have this type of venation
      - reticulate( net-like): eudicots have this kind of venation
    - - lower order veins
      - secondary vein: vein branching from the primary vein
      - Primary vein: vein entering the leaf
- - - - Phloem: Transports the sugar produced by photosnthesis
      - Xylem: supplies water for photosynthesis
  - - - Functions
        
        Protection
        
        Protections against water loss.
        
        regulation of gaseous exchange
      - Types of cells in epidermis
        
        Epidemal cell
        
        Epidermal hair cell( trichomes)
        
        cells in stomatal complex
        
        Guard cells
        
        Subsidiary cells
    - - Most ferns and flowering plants' mesophyll has two layers
        
        Palisade layer
        
        has many chloroplast than spongy layer
        
        has intercellular spaces
        
        it lies beneath adaxial epidermis
        
        Spongy layer
        
        the cells are not tightly packed
        
        has fewer chloroplast than that of palisade layer.
    - - Xylem: cells that bring water and mineral from the root to the leaf
      - Phloem: cells that move sap produced by photosynthesis in the leaf, out of the leaf
- - - - freely permeable membrane: allow all solutes to pass freely across the membrane
      - completely impermeable: do not allow anything to pass
      - selectively permeable: only allows selective substances to pass.
- - - - similar function to that of the guard cells
      - they can either accumulate or expel potassium and thus adjust the turgidity and water potential of the cell
    - - these are the molecular pumps which helps in transport of the molecules
      - the number of transfer cells depends on the surface area of the plasma membrane
    - - during night time, the guard cells are in hydraulic equilibrium because of which the water entering the cell and leaving the cell is of same rate
      - at sunrise, potassium is pumped into guard cells which increases solute concentration finally leading stomatal pore to open
  - - - water transport through xylem
        
        cohesion tension hypothesis of water transport is the mostly accepted hypothesis
        
        water in plant is lost by transstomatal transpiration and transcuticular transpiration
        
        a vessel having cavitation means the vessel can never conduct water again
      - control of water transport by guard cells
        
        bulk water movement through xylem is influenced primarily by water loss in the atmosphere
        
        whenever the soil has adequate amount of water, water loss is actually advantageous.
        
        for healthy and turgid plants, light often controls the guard cell water relation.
        
        water stress ; release of abscisic acid that prevents water loss.
      - properties of water
        
        movement of water through xylem depends on the properties of water
        
        liquid water is cohesive
        
        water adheres firmly to soil particles
        
        water is heavy and lifting it to the top of a tree needs a lot of energy
    - - phloem is responsible for the transport of sugar
      - in some plants sugars are actively transported by sieve elements while in some it is transferred by polymer trap mechanism
      - the actual amount of sugar and other nutrients transported per hour by phloem is called mass transfer.
      - sinks are sites that receives the transported phloem sap
- - - - layers of soil: after many years from the date of formation of a new soil, the soil divides into three layers:
        
        B horizon: it is called the zone of deposition and consists of humus and clay. it is rich in nutrients.
        
        C horizon: it is mostly composed of parent rock and rock fragments.
        
        A Horizon: it is called zone of leaching and consists of litter and debris
    - - at equator all days are 12 days long. therefore, no seasonal variation occurs.
      - at higher latitudes to either north or south, summer days be much longer, as do the winter nights. so variation can be seen on these regions.
      - Above arctic and antarctic circles, mid summers days are 24 hours long, so are the mid winter nights. so almost no plants can be see here.
- - - - ramdom distributuion: this term is used when there is no obvious, identifiable pattern to the position of the individuals.
      - clumped distribution: the distribution in which the spacing between plant is either small or large.
      - uniform distribution: distribution in which all the individuals are evenly spaced from their neighbors.
  - - - r-selected species are those that emphasize high growth rates, typically exploit less-crowded ecological niches, and produce many offspring, each of which has a relatively low probability of surviving to adulthood
      - a disturbance usually produces r selection
      - r selected species typically are annuals or small shrubby perennials.
      - they have few defense against predators
      - they reproduce quickly and population growth is extremely rapid
    - - K-selected species, also called K-strategist, species whose populations fluctuate at or near the carrying capacity (K) of the environment in which they reside.
      - k selected species face intense competition from other plant species.
      - Douglas firs redwoods and bristle cone pines are good examples of k selected species
- - - - Morphology
        
        the leafy stems are gametophytes
        
        the moss gametophores grow from an apical meristem that contains a prominent apical meristem
        
        derivative cells subdivide producing the tissues if the stem and the leaves.
      - Water Transport
        
        in some family of mosses innermost cortex is composed of cells called hydroids that conduct water and dissolve minerals
        
        species that have hydroids also have leptoids which acts as a function of sieve cells.
        
        majority of mosses lack lack hydroids and leptoids : water is conducted along the exterior of their stems by capillary action.
      - development
        
        growth of gametophore begins when spore germinate and sends out a long, slender chlorophyllus cell.
        
        this cells undergoes mitosis and produce potonema
        
        potonema organize a apical meristem and grow upright as a stem which is called a gametophore.
      - reproductiion
        
        gametophore produce gametogonia. sperm produced in icrogametogonia and eggs are produced in magagametogonia.
        
        after sperm cells mature, antheridium breaks and liberates sperm cells. sperm cells swim towards eggs. after meeting fertilization occurs.
    - - A sporophyte is a multicellular diploid generation found in moss
      - It produces haploid spores that develop into a gametophyte.
      - The gametophyte then makes gametes that fuse and grow into a sporophyte
    - - the small size and lack of conductng tissues are two critical factors in the metabolism and ecology of mosses
      - many species of mosses grow permanently in moist habitats such as rain forests. this helps to compensate the inability o them to retain water.
      - sme mosses are tolerant o dessication