Plant Form and Function Flashcards
What is a tissue?
A group of cells consisting of one or more cell types that together perform a specialized function.
What is an organ?
Consists of several types of tissues that together carry out particular function
What are apical meristems?
Populations of pluripotent stem cells that divide to produce new tissues and act as localization regions of cell growth.
What are lateral meristems?
Stem cells that add thickness to woody plants during secondary growth.
What are the types of meristems?
Shoot apical meristem (SAM): primary growth and axial growth, make up primary tissues
Root apical meristem (RAM): Primary growth and axial growth, make up primary tissues
Vascular cambium (VC): grows before CC; bifacial meristem that makes up secondary xylem (wood) and secondary phloem
Cork cambium (CC): grows after VC; replaces epidermis with periderm (cork, cork cambium, and phelloderm)
What are the three tissue systems in a plant?
Dermal tissues, vascular tissues and ground tissues.
What does the dermal tissue system consist of?
- Epidermis
- Cuticle
- Periderm (woody plants)
- Trichomes
What is the cuticle of a plant?
Waxy coating that covers the leaves of land plants and stems of non-woody plants to prevent water loss from the epidermis and act as a reflective surface to cool down.
What are trichomes?
Biotic outgrowths of shoot epidermis that reduce water loss, defend against insects, increase relative humidity by trapping water.
What does the vascular tissue system consist of?
Xylem: conducts water (+dissolved minerals) from roots to shoots
Phloem: transports nutrients from where they are made (typically leaves) out to the rest of the plant
What is a stele? What is the difference between the steele of roots, stem, and leaves?
The collective term for vascular tissue.
Roots: xylem in middle, phloem outside
Stem: xylem in middle, phloem on outside, sclerenchyma outisde phloem
Leaves: Xylem upwards, phloem downwards
What is the ground tissue?
Tissues that are neither dermal not vascular, made of specialized cells for storage, photosynthesis, support and transport
What is the pith and the cortex?
Pith: ground tissue internal to vascular tissue
Cortex: ground tissue external to vascular tissue
What are the type of differentiated cells of the ground tissue?
- Parenchyma cells
- collenchyma cells
- sclerenchyma cells
What do parenchyma cells do? How are they structured?
Least specialized cell in ground tissue that performs metabolic functions, store cellulose, sugar and proteins, and divides and differentiates. They have thin and flexible primary walls strengthened by lignin, but lack secondary walls.
What do collenchyma cells do? How are they structured?
Provide flexible support without restraining growth to support young parts of the plant shoot. They are grouped in strands and have thicker, uneven cell walls.
What is the structure of sclerenchyma cells?
Have thick secondary walls strengthened with lignin and are dead at maturity. Either sclereid (short and irregular) or fibers (long and slender, arranged in threads)
What does an angiosperm embryo develop into?
- Primary dermal, ground and vascular tissue
- SAM and RAM
- Cotyledons
What is the difference in the structure of eudicot seeds and monocot seeds?
Eudicot: embryo consists of two thick cotyledons
Monocots: embryo has one cotyledon
What is the purpose of seed dormancy?
Increases the chances that germination will occur at a time and place most advantageous to the seedling.
What triggers breaking of seed dormancy?
environmental cues such as temperature or lighting changes.
What does germination depend on?
Imbibition: uptake of water due to low water potential
What is the radicle?
Embryonic root that emerges first to anchor the shoot that follows.
What is the function of a root?
- Anchoring the plant
- Absorbing minerals and water
- Storing carbohydrates in the form of starch
What is the difference between the primary root and lateral root?
Primary: anchor the system into the soil by growing downwards
Lateral/secondary: explore the soil through environmentally responsive radial growth and determine the overall root system size
What occurs at the root apical meristem?
Primary root growth: RAM produces root cap to protect the root tip as it grows through the soil and produces no lateral appendages.
What are the three zones of cells following the root cap?
- Zone of cell division
- Zone of elongation
- Zone of differentiation/maturation
What is the purpose of root hairs?
to give more surface area for absorption of water and nutrients
What is the root cap?
Secretes polysaccharide slime and continually sloughs off as the root pushes through the soil. It produces signals to attract beneficial microbes and senses gravity to grow down into the soil.
What does the cross section of a eudicot root look like?
Xylem forms a cross in the centre, with phloem between the arms. The cortex is filled with parenchyma cells that store starch which form the endodermis in the centre.
Where is the endodermis and what does it do?
Innermost layer of cells in the root cortex that surrounds the vascular cylinder and regulates passage of substances from soil into the vascular cylinder.
What does the cross section of a monocot look like?
Core parenchyma cells are surrounded by a ring of xylem (inward) and ring of phloem (outward)
What is the pericycle?
The outermost cell layer in the vascular cylinder where lateral roots arise.
What is the difference between the tap root system and the fibrous root system?
Tap: tall plants with large shoot masses (found in eudicots and gymnosperms)
Fibrous: adventitious roots (lateral roots) that come from the stem (found in monocots)
What are root adaptations?
Prop roots (hold up plant)
storage roots (store sugar)
Green roots (photosynthesize)
Pneumataophores (allow roots to obtain air)
strangling aerial roots (support)
What are the functions of the shoot (stem and leaves)?
- Photosynthesis
- Transpiration (loss of water through open stomata)
- Transport (xylem and phloem)
- Reproduction (flowers, cones, leaves)
What are the parts of the stem organ?
- Nodes: where leaves attach
- Internodes: between leaves
- Axilliary Bud: Buds that have the potential to form a lateral shoot
- Apical bud: elongation of the main shoot (dominant)
What does the cross section of a eudicot stem look like?
Vascular tissue consists of vascular bundles arranged in a ring. The bundle has an outer sclerenchyma, middle phloem, and an inner xylem.
What does the cross section of a monocot stem look like?
Vascular bundles are scattered throughout the ground tissue rather than forming a ring
What are the type of differentiated plant cells of the xylem?
Tracheids: small pore, elongated cells that make up the xylem of all vascular plants
Vessel elements: large pore, elongated cells that are common to most angiosperms and a few gymnosperms that align from end to end to form micropipes.
What are the type of differentiated plant cells of the phloem?
Sieve-tube elements: alive at maturity but lack organelles. Has porous sieve plate that allow fluid to flow between cells along the tube.
Companion cell: nucleus and ribosomes serve both itself and the sieve-tube elements.
What does the shoot apical meristem do?
Initiates new stem tissue and new leaves with primary growth concentrated at the shoot tip. Primary growth is continuous and increases stem length through the stimulation of auxin and gibberellic acid (plant hormones)
What are leaves? What are their function? What are their structure?
Main photosynthetic structures of the plant initiated by the activity of the SAM. They intercept light, exchange gases, dissipate heat, defend plants from herbivores and pathogens. They consist of a flattened blade and a petiole, which joins the leaf to a node of the stem.
What are the types of leaves?
Simple leaf: blade not divided into leaflet
Compound leaf: blade is divided into leaflets (pinnate or palmate)
What is the difference between the pinnate leaf and the palmate leaf?
Both are compound leaves, but pinnate is attached along a petiole and palmate is connected at a central location
What are examples of modified leaves?
Spines, tendrils, reproductive leaves, storage leaves
What are stomata?
Pores found in the epidermis of the leaf that allow for gas exchange, changes in potassium ions and plant hormones, and act as avenues for evaporative water loss.
What are guard cells?
Cells that occur in pairs and flank the stoma and regulate open and closing. Open during the day and closed at night.
What is mesophyll?
ground tissue in a leaf that is sandwiched between the upper and lower epidermis.
What are the parts of the mesophyll of eudicots?
palisade mesophyll: upper part of leaf
spongy mesophyll: lower part of leaf (loose for air spaces and gas exchange)
What is the purpose of a bundle sheath?
Encloses and protects each vein (vascular bundle)
What is the difference between a monocot leaf and a eudicot leaf?
monocot: veins are straight
dicot: veins are branched
What are the advantages and disadvantages of a plant growing tall?
Advantges: Tall plants can get out of the shade of their neighbours and get more light for photosynthesis
Disadvantages:
1) weight of shoot increases
2) more support needed
3) more leaves = greater transport capacity
4) problems cannot be solved with apical growth
What does secondary growth do?
Increases the diameter, and therefore increasing the supporting and transport tissues, of stems and roots of woody plants. Occurs in the mature stem after elongation, but simultaneously with primary growth.
Where is secondary growth found and not found?
found in gymnosperms and eudicots; not found in monocots and monilophytes
What are vascular rays?
interweave in secondary vasculature to enable lateral transport of materials
What is the structure of the vascular cambium?
Cylinder of meristematic cells one layer thick developed from undifferentiated parenchyma cells. It is located outside the pith and primary xylem, and to the inside of the primary phloem and cortex. Forms xylem inwards, and phloem outwards.
What is the difference between early wood and late wood?
Early wood: formed in spring; thin cell walls for maximal water delivery
Late wood: formed in late summer; thick walled cells for stem support
What are tree rings?
Marks created by the meeting of early wood and late wood; used to estimate a tree’s age.
What is dendrochonology?
analysis of tree ring growth patterns to study past climate change
What is the difference between soft wood and hard wood?
Soft wood: uniform texture and predominated by non-fiber tracheids with small amounts of parenchyma and a resin canal (conifers)
Hard wood: variable texture/structure/colour and consists of heterogeneous cell types including vessel elements, tracheids, and parenchyma. There and colour variations (eudicots)
What is the difference between sap wood and heart wood?
Sap wood: actively conducting part of the wood (dead but most used); light coloured
Heart wood: no longer actively conducting (dead and unused); darker colour
What is cork?
Water impermeable, elastic, hydrophobic, extension of the periderm from the cambium that contains suberin.
What is the difference between the apoplast and the symplast?
Apoplast: external to membrane, including cell walls, extracellular spaces and the interior of dead cells.
Symplast: entire mass of cytosol of all living cells + plasmodesmata
What are the three transport routes for water and solutes?
Apoplastic: via cell wall
Symplastic: through cytosol
Transmembrane: across the cell wall and plasma membrane
What is the difference between osmosis and water potential?
Osmosis: ACT OF DIFFUSION of water affected by concentration and pressure
Water potential: MEASUREMENT OF WORK that combines the effects of solute concentration and pressure
What direction in terms of water potential does water move in a plant?
High water potential (soil) to low water potential (atmosphere)
How do stomata open and close?
Turgid: Guard cells bow outward and open the pore
Flaccid: Guard cells become less bowed and pore closes
what is bulk flow?
the movement of a mass of fluid that is due to the presence of a pressure gradient
What is the casparian strip?
Part of endodermal wall made of suberin that blocks apoplastic transfer of minerals and forces crossing of plasma membrane to enter vascular cylinder.
What is transpiration?
evaporation of water from a plant’s surface which gets replaced as water travels up from roots
How does the transpirational pull transport xylem sap?
- Water vapour in airspaces of leaf diffuse to low water potential area (atmosphere) and exit leaf via stomata
- As water evaporates, air-water interface retreats further into mesophyll cell walls.
- Surface tension of water creates negative pressure potential which pulls water and minerals from the root up.
What is translocation?
the movement of photosynthates in the form of phloem sap from the leaves to other parts of the plant
What is phloem sap?
Aqueous solution that is high in sucrose, traveling from a sugar source to a sugar sink via sieve tube elements in either the symplastic route or both symplastic and apoplastic routes
What is the difference between a sugar source and a sugar sink?
Sugar source: where sugars are made (chloroplasts of leaves)
Sugar sink: where sugars end up (roots, seeds, tubers)
What are plant hormones?
mobile chemical signals produced in low concentrations that act as regulators for specific physiological processes
what are the major plant hormones?
Auxin: for growth/increase
Cytokinins: for division
Gibberellins: for expansion/elongation
Abscisic acid: maturation/stress
Ehtylene: ripening/stress
Brassinosteroids
Jasmonates
Strigolactones
What is auxin? Where is it found?
Plant hormone that promotes vertical growth, root formation, and leaf venation via cell and stem elongation. Synthesized in the SAM and young leaves, but found in developing fruit and seeds.
What is the practical use of auxin?
indolbutyric acid (IBA) stimnulates adventitious roots and is used in vegetative propagation of plants
2,4-D is a synthetic auxin that can kill plants and is used as a herbicide on eudicots
What are cytokinins? Where are they found?
hormones that stimulate cytokinesis, produced in actively growing tissues such as roots, embryos and fruits. They work together with auxin to control cell division and differentiation.
What is apical dominance?
a terminal bud’s ability to suppress development of axillary bud. controlled via cytokinins, auxin, and strigolactone.
what are gibberellins? where are they found?
Promotes rapid and uninhibited growth via cell elongation, originally found in rice pathogen gibberella. High concentration of gibberellins increase height, number of flowers, fruit growth, and it also signals seed germination.
What is abscisic acid?
plant hormone that affects seed dormancy and drought tolerance by slowing growth.
How does abscisic acid affect seed dormancy and drought tolerance?
Seed dormancy: allows germination in optimal conditions when removed by heavy rain, light, or prolonged cold
Drought tolerance: internal signal that enables plants to withstand drought by causing stomata to close rapidly and prevent water loss
What is ethylene?
C2H4 gas involved in fruit ripening and stress response via drought, flood, mechanical pressure, injury or infection.
What is senescence?
The pathway to programmed death of cells or organs; biological aging. In a plant, it is associated with a burst of ethylene.
What is leaf abscission?
When a plant drops its leaves in the fall, signalled by a change in the balance of auxin (cell growth) and ethylene (maturation)
What is the fresh and dry mass of a plant consisting of?
Fresh: 80-90% water
Dry: 4% inorganic substances from soil (50+), 96% CO2 assimilated into carbohydrates during photosynthesis
What are macronutrients?
essential elements required in large amounts to make macromolecules: CHOPKNS CaMg
What are micronutrients?
essential elements needed in small amounts: Cu, Ni, Mo, Zn, B, Mn, Fe
What is the difference between deficiencies of mobile nutrients vs less mobile nutrients?
mobile: affects older organs more (N, P, K, Mg, Cl, Zn, Mo)
less mobile: affect younger organs more (Ca, S, Fe, B, Cu)
What are the symptoms of nutrient deficiency (chem, path, drought, Mg, N, K, P) in plant leaves?
chem: burns
path: spots that spread
drought: curling to minimize surface area
Mg: purple underside and yellow veins
N: yellow tip that apreads to center
K: drying of tips and edges
P: red/purple marks
What is the rhizosphere?
layer of soil surrounding plants roots containing rhizobacteria that enhance plant growth via antibiotics/chemicals in return for nutrients
What is the nitrogen cycle?
- Nitrogen fixing bacteria converts atmospheric N to ammonia
- Ammonia takes on a proton from soil and creates ammonium
- nitrifying bacteria turns ammonium to nitrites and nitrates
- Nitrates are either absorbed through the roots or turned back into atomspheric N via denitrifying bacteria
Where are nitrogen fixing bacteria found?
Nodules: plant cells infected by bacteroid rhizobium contained in vesicles formed by root
What are mycorrhizae?
mutualistic associations of fungi and roots where fungi is supplied with sugar from the host plant, and the host plant is supplied with mineral absorption and growth factors.
What are the two types of mycorrhizal associations?
ectomycorrhizae: mycelium forms sheath over surface of the root without penetrating
arbuscular mycorrhizae: hyphae extend into root, penetrating cell wall but not plasma membrane
What is the difference between an epiphyte, a carnivorous plant, and a parasitic plant?
epiphyte: grows on another plant and obtains water and minerals from rain
carnivorous plant: photosynthetic but obtain nitrogen by digesting insects
parasitic plants: absorb sugars and minerals from living host plant
