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Botany Exam 2
| Question | Answer |
|---|---|
| What are the 3 main functions of roots? | Firmly anchor plant into substrate; Absorb water and minerals; Produce hormones |
| What are the main characteristics of a seed? | Single large taproot that develops from the radical; Numerous small lateral/branching roots coming out of it |
| What is the first protrusion to grow from a dicot seed after germination? | Radical; A few days later the plummule grows |
| What is the plummule? | Embryonic shoot system |
| What is the radical? | Embryonic root system; still meristematic; Will compact soil system and start absorbing water/minerals |
| What is a taproot? | developed, finalized, mature structure of a radical; Can reach hundreds of meters into soil; Strong and fast-growing |
| What makes the root structure of monocot seeds different from dicot seeds? | A few weeks after germination, the radical starts dying; After radical is done, root system emerges from the stem; Do not grow from pre-existing roots; Increases absorptive and transport capacities; Adventitious roots form a mat |
| Starting from the top down, what is the order of structures in a root? | Lateral roots; Root hair zone; Zone of elongation; Root apical meristem; Root cap |
| How do hairs form in the root hair zone? | Many epidermal cells expand as narrow trichomes; Cells undergo vacuolization by fusing vacuoles |
| What is a root cap? | Protects apical meristem as it pushes through rough substrate; Layer closest to the meristem is meristematic; Grows by pushing cells forward; Cells on the edge grow toward the side and proliferate; Eventually cells on the outside of the cap die |
| How do mature root cap cells detect gravity? | By using starch grains |
| What is mucigel and how does it help root growth? | Complex polysaccharide rich in carbs and amino acids; Lubricates passage of root through soil; Causes soil to release nutrients; Fosters growth of beneficial bacteria near root tip |
| What is the quiescent center of the root apical meristem? | Mitotically inactive region of meristematic root; Reserved in case meristematic system is damaged |
| What is the zone of elongation? | Cells are enlarged (vacuolization); Nuclei are less distinct; No mature cells yet; Protoderm, provascular tissue, and ground tissue begin to differentiate |
| How can you observe when you are in the zone of maturation? | Production of root hairs growing outward |
| What is the zone of maturation? | Tissues are differentiated |
| What is the endodermis? | Innermost layer of cortex cells in roots; Cells are differentiated into a cylinder; Radical walls are encrusted with waterproof lignin and suberin (Casparian Strips); Controls minerals entering xylem |
| What is the role of Casparian Strips in the endodermis? | Block apoplastic pathway; Forces water to pass through cytoplasm; Checkpoint for nutrients and microbes entering xylem |
| What is the Stele? | All of the vascular tissue in roots; Cylinder of tissue interior to cortex; Xylem is in the center of stele; Phloem surrounds xylem |
| What is the difference in vascular tissue structure between monocots and dicots? | Dicots have NO PITH in the center of roots; Monocots DO have pith in the center of roots |
| What is the structure of metaxylem? | Inner wide cells |
| What is the structure of protoxylem? | Outer narrow cells |
| Where is protophloem found? | Outer side |
| Where is metaphloem found? | Inner side |
| What is the pericycle? | Irregular region of parenchyma cells between the stele and the endodermis; Has the capacity to become meristematic (dedifferentiation) |
| What is pith? | Small parenchyma cells that are tightly packed in the center of the stele |
| What is the vascular structure of monocot roots? | Ring of small lines of xylem form on outside of stele, all pointing towards center; Small dots of phloem between lines |
| What is the vascular structure of dicot roots? | Xylem makes crosses and phloem occurs between crosses (polyarchs) |
| How do lateral roots grow? | Layer of parenchyma cells in the pericycle becomes meristematic; Once root is generated, it has all the characteristics of a mature parent root; Some pericycle cells divide at small root primordium and organize into a root apical meristem |
| What are epiphytes? | Group of plants that live off of other plants instead of in the soil (orchids); Not woody, mainly herbs; Get nutrients from bark and air; Very thin epidermis |
| What is the specialized epidermis of epiphyte roots called? | Belimen; Often don't have root hairs |
| What are mycorrhizae? | Symbiotic associations between plant roots and soil fungi; Fungi gain sugars from roots; Plant gains nutrients and water from fungi |
| What is ectomycorrhizal fungi? | Fungal cells penetrate between outermost root cortex cells, but never penetrate cell wall; Typically in woody species |
| What is endomycorrhizal fungi? | Fungal cells penetrate root cortex and cell walls, but not plasma membrane |
| What is an arbiscule? | Ballon-like structure at the ends of fungal hyphae; Site of hormone secretion and secondary metabolites (makes nutrients in soil); Feeds symbiotic plants; Makes water available to plant cells |
| What does secondary growth do for woody plants? | Increases overall thickness; Allows them to grow taller and withstand environmental stress; Produces additional secondary vascular tissues (wood/bark) to enhance ability to transport water, nutrients, and signals |
| What is cambium? | Group of cells with the capacity to differentiate into a specialized tissue |
| What is vascular cambium? | Meristem producing secondary plant body; Generates xylem and phloem inside stem and root system |
| Where does the fascicular cambium occur? | Layer of cells between metaxylem and metaphloem of a vascular bundle |
| How is a cambium ring formed? | Some parenchyma cells between bundles of fascicular cambium resume mitosis; Connects fascicular cambium bundles to form cambium ring |
| Where does the secondary vascular tissue form? | Secondary phloem occurs along outer edge of ring; Secondary xylem (wood) occurs along inner edge of ring (towards center) |
| What are growth rings in wood? | Due to differential growth of early (Spring) wood versus late (Summer) wood; Spring wood has lots of wide vessels and is lighter; Summer wood has fewer and narrower, thick-walled tracheids and is darker; Drier during Summer |
| How does bark form? | As secondary tissues are added and pushed outward, tissues on the periphery either grow in circumference or are torn apart |
| What is cork cambium? | Phellogen; Cambium within secondary phloem; Storage parenchyma cells undergoing cell division; Produce more parenchyma (phelloderm) towards inner side; Produce cork (phellem) towards outer side |
| What is the Periderm? | Combination of cork, cork cambium, and phelloderm layers; Replaces epidermis |
| What tissues make up bark? | Periderm and secondary phloem |
| Where can cork cambium arise from? | Cortex (most common), epidermis, primary phloem, and secondary phloem |
| What tissues make up the outer bark? | All tissues outside the innermost cork cambium; Includes periderm (cork, cork cambium, and phelloderm) and dead secondary phloem tissues |
| what tissues make up the inner bark? | All secondary phloem between vascular cambium and innermost cork cambium |
| What purpose does the impermeability of bark serve? | Conserves water; Increases pathogen/pest resistance; Blocks oxygen absorption |
| How does bark become permeable to oxygen? | Rounded cork cells are produced (lenticels); Round shape prevents tight packing; Creates more intercellular space |
| What are Lenticels? | Type of stomata; Parenchyma with a lot of air space; When a new cork cambium arises interior to another, it forms a lenticel in the same place; Outer and inner lenticels are aligned |
| What is a flower? | Stem with leaf-like structures |
| What is fragmentation? | Most common type of asexual plant reproduction; Large veining plant grows several meters; Individual parts become self-sufficient by adventitious roots; If middle portion of plant dies, outer parts separate and act as individuals |
| What are the 4 main appendages of a flower? | Sepals; Petals; Stamens; Carpals |
| What is the sepal? | Outermost appendage; Modified leaves surrounding maturing flower parts; Protect bud as it develops; May be colorful |
| What is the term for all of the sepals combined? | Calyx |
| What are the petals? | Leaf-like, but contain pigments other than chlorophyll; Attract pollinators; Absent in wind-pollinated species; Located above sepals on the receptacle |
| What are all the petals combined called? | Corolla |
| What is the term for all of the sepals and petals combined? | Perianth |
| What are stamens? | Responsible for formation of male spores; Occur above the petals; Two parts, anther and its supporting filament |
| What are all of the stamens combined called? | Androecium |
| How is pollen created? | Diploid anther cells (microsporocytes) undergo meiosis to produce 4 microspores; Form a resistant cell wall to become pollen |
| What are carpels? | Female organ; Stigma catches pollen grains; Style elevates stigma; Ovary is where megaspores are produced |
| What are all of the carpels together called? | Gynoecium |
| What is the ovule? | Located on placentae within ovary; Has a central mass of parenchyma called a nucellus to feed ovules |
| Which structure develops into a fruit? | Ovary |
| How does sexual reproduction occur within the carpel? | Moist stigma makes pollen grains stick; Breaks down cell wall; Gametes are released into ovary |
| What is a callus? | Mass of cells that grows after zygote formation |
| What is an endosperm? | Feeds ovule; Formed at the same time as the zygote; 2nd male gamete within pollen grain merges with polar nuclei to form an endosperm; Has 3 nuclei; Eventually gets dissolved |
| What is the polar nuclei? | Byproduct of female gamete formation; Has 2 nuclei; Intermediate step in endosperm formation |
| What structures make up the short axis? | Radicle; Epicotyl; Hypocotyl |
| What is the Radicle? | Embryonic root; 1st appendage to emerge from seed |
| What is the epicotyl? | Embryonic stem; Part that generates the shoot system |
| What is the hypocotyl? | Root/shoot junction; Connects shoot to root system |
| What is the function of cotyledons? | Store nutrients used during and after germination; Leftover endosperm nutrients may be transferred to cotyledons as seed matures in dicots; Cotyledon does not develop and quickly dies in monocots |
| What is an albuminous seed? | Mature seed retaining their endosperm |
| What is an exalbuminous seed? | Endosperm is sparse or absent at seed maturity |
| What is a testa? | Seed coat; Integuments that surround the nucellus; Made of sclereids |
| What are the 3 layers of a fruit? | Exocarp– outer layer (skin/peel); Mesocarp– middle layer (fruit flesh); Endocarp– innermost layer (tough or thin, leathery, made of sclerenchyma) |
| What is the entire fruit called? | Pericarp |
| What type of symmetry do most flowers have? | Radial symmetry; Actinomorphic flowers |
| What type of symmetry to flowers with symbiotic relationships with pollinators have? | Bilateral symmetry; Zygomorphic; Easier to facilitate pollinator needs |
Created by:
monika.angner