plant phys exam 1 locked in

commonalities in plant life

• Primary producers
• Non-motile
• Terrestrial plants are structurally reinforced
• Terrestrial plants have mechanisms for
moving water, minerals, & photosynthates
• Terrestrial plants lose water continuously
via evaporation
• Meristematic growth is indeterminate
• Alternation of generations

middle lamella

• Ca and Mg

• binding agent between cell walls

primary cell wall

• thin

• characteristic of young, growing cells

secondary cell wall

• thicker and stronger

• lignin makes cell walls tough

simple pits

• facilitates water movement between cells

• gaps in the secondary wall with thin primary cell wall

pit pairs

• adjoining simple pits

cytoplasm

• everything except for the nucleus

• ions, molecules, organelles, cytoskeleton

cytosol

• liquid portion

• organelles suspended within

plasmodesmata

• channel connecting adjacent cells through cell wall

• filled with cytoplasm (derived from endoplasmic reticulum)

• allows movement of molecules from cell to cell through the symplast

• gated by deposition (opening/closing)

symplast/symplasm

• continuous system of cells interconnected by plasmodesmata

• allows for intercellular transport of water and solutes

• transport without crossing the plasma membrane with size restriction

apoplast

• mostly continuous system of cell walls, intercellular air spaces, and xylem vessels

how do plant viruses spread through the symplast

viral movement proteins expand the size exclusion limit

meristems

• apical meristem

• axillary buds (from nodes, branch shoots)

• pericycle (lateral roots)

• cambium (secondary growth

vascular cambium

• between xylem and phloem

• increases growth

• produces wood

cork cambium

• produces periderm (water-resistant protectant layer)

major plant tissue systems

• dermal tissue

• ground tissue

• vascular tissue

parenchyma tissue

• type of ground tissue that is involved in storage, photosynthesis, and tissue repair.

• small intracellular space

collenchyma tissue

• type of ground tissue that provides flexible support to young, growing parts of the plant. It has unevenly thickened cell walls.

• medium spacing of cells

sclerenchyma tissue

• type of ground tissue that provides rigid support due to its thick, lignified cell walls, often dead at maturity.

• large space between cells

dicot stems vs monocot stem

• dicot = vascular tissue in ring

• monocot = vascular bundles spread evenly

endomembrane system

• organelle functions, secretory processes, cell signaling, metaboilits and hormone production, membrane recycle, cell cycle, cell expansion

• ER, nuclear envelope, golgi apparatus, vacuole, endosomes, plasma membrane, oil bodies, peroxisomes, glyocysomes

• a network of membranes and organelles that work together to modify, package, and transport lipids and proteins within the cell.

independently dividing semiautonomous organelles of endosymbiotic origin

mitochondria and plastids

• energy metabolism and energy storage

• separated from cytosol by double membrane

• have their own DNA and ribosomes

fluid mosaic model

• biological membranes have molecular organization consisting of a double (bilayer) of either phospholipids or glycosylglycerides in which proteins are embedded

phospholipids

• hydrophilic head (containing a phosphate group)

• hydrophobic tails

• joined by a glycerol molecule

glycosylglycerides

• primarily found in chloroplast membranes

• consist of glycerol, attached to one or two sugar molecules and two fatty acids

protein functions

• enzymes

• transport molecules

• storage

• electron carriers

protein types

• integral = embedded in the lipid bilayers

  • transporters, signal transduction

• peripheral = bound to membrane by noncovalent bonds and hydrophobic interactions

  • receptors, microtubules, and actin microfilaments

Nucleus

• nuclear genome

• nuclear membrane

• nuclear pores

Endoplasmic reticulum

• composed of tubules arranged together in cisternae

• rough

  • secretory protein synthesis (carried to destination by vesicle)

• smooth

  • membrane phospholipids and carb synthesis

golgi apparatus

• golgi body = polarized stack of cisternae

• accepts tubules and vesicles from ER

• transport, modify, and package proteins and lipids

vesicle movement

• COP II = ER to Golgi

• COP I = Golgi to ER

• Clatherin = endocytosis (envagination)

oil bodies

• organelles that accumulate oil during seed development

• store triglycerides

• break down during seed germination

peroxisomes

• detoxify ROS

• glyoxysomes = associated with mitochondria and oil bodies

mitochondria

• site of cellular respiration

• synthesis of ATP from ADP and inorganic phosphate

types of plastids

• protoplastids

• etioplasts

• chloroplasts

• chromoplasts

• leucoplasts (store start and oils)

• amyloplasts (produce and store starches

the plant cytoskeleton

• microtubules

• microfilaments

microtubules

• tublin dimers

• (GTP/GDP)

• can “treadmill” throughout the cell

• orientation determines expansion in the cell wall

• a microscopic tubular structure present in numbers in the cytoplasm of cells, sometimes aggregating to form more complex structures

microfilaments

• actin subunits

• (ATP/ADP)

motor proteins

• myosins = move along microfilaments (towards + end)

• kinesins = move along microtubules

cell cycle

• Interphase

  • G1: pre-DNA for replication

  • S: replicate DNA

  • G2: prepare for mitosis

• mitosis: replicated chromosomes are aligned, separated, and distributed in an orderly fashion to form two daughter cells

chromosome

a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes

mitosis

• prophase: chromosomes condense

• metaphase: nuclear membrane re-assimilated into the ER

• anaphase: chromatids pulled towards poles, poles pushed apart

• telophase (& cytokinesis): microtubules, ER, vesicles. cell plate formation

cell wall function

• structure and turgot

• diffusion barrier

• herbivory barrier

why are cell walls valuable for humans

• paper and textiles

• wood

• synthetic fibers and plastics

• burned for fuel

• carbon capture

classes of cell wall polysaccharides

• cellulose: insoluble in water, high tensile strength

• pectin: hydrophilicc, gel-forming polysaccharides

• hemicellulose: polysaccharides with B-linked backbones

• Lignin: alkyl-aromatic heteropolymer

cellulose synthase

An enzyme responsible for the synthesis of cellulose, forming part of the plant cell wall structure.

cell expansion

• tip growth: localized (root hairs, pollen tubes), driven by actin microfilaments

• diffuse growth: expansion over the wall surface, drive by moth microtubules and actin microfilaments

viscoelastic properties (cell wall)

• intermediate of solid and liquid, more liquid when expanding

what structures drive axial polarity (primary growth)?

radial polarity?

• apical meristem

• vascular cambium, cork cambium

water is used as a source of

electrons

water is used for

• hydrostatic structure/ turgor pressure

• dissolving and transporting nutrients

• control gas exchange

• transport across membranes

properties of water

• hydrogen bonds (strong IMF)

• polar structure of the molecule (polarity makes water an excellent solvent)

• oxygen is more electronegative than hydrogen

• tetrahedral

• high specific heat (energy to raise the temp of a substance a set amount) and high latent heat of vaporization (energy to separate molecules from liquid to gas phase)

cohesion

mutual attraction between molecules

adhesion

attraction of water to a solid substance due to hydrogen bonds

surface tension

• energy required to increase the surface area of a gas-liquid interface

• water adheres strongly to itself and creates the LEAST amount of surface area

capillarity

• liquid wets the walls of tube = increases surface area

• surface tension acts to decrease surface area = pulls liquid up

• wetting continues from higher level = liquid rises

• liquid reaches a height at which its weight is exactly balanced by surface tension

tensile strength

• maximum force per unit area that a continuous column of water can withstand before breaking

caviation

• formation of vapor cavities in a liquid when the pressure decreases below the liquid's vapor pressure, often leading to bubble formation.

• bubbles due to tension

water potential

• measure of the free energy of water per unit volume

• pressure potential + solute/osmotic potential + matric potential

• soil water potential = solute + pressure + gravity (solutes is usually negligible)

hypertonic

• plasmolyzed cell

• water leaves

isotonic

• flaccid cell

• same inside and outside

hypotonic

• turgid

• water moves into the cell

rate of water exchange between cells

• movement across a cell membrane decreases with time

• rate approaches 0 exponentially

aquaporins

• integral membrane proteins

• that facilitate water transport across cell membranes.

soil-plant-atmosphere continuum (cohesion hypothesis)

• water movement is drive by transpiration and follows a continuous path from the soil, through the root, stem, leaf, and into atmosphere

effect of drought

• inhibition of growth and photosynthesis

• cell expansion reduced

• stimulation of root elongation

• plant may accumulate solutes to maintain turgor pressure, build xylem conduits capable of transporting water under large tension

  • low solute potential allows roots to extract water from saline water without allowing excessive levels of salt to enter (halophytes)

pressure-volume curve

• small changes in plant cell volume cause large changes in turgor pressure

bulk flow of water

driven by gravity and pressure

plant uptake of water

pressure gradient

water moves into root hairs (higher surface area) via

• apoplast

• symplast

• transmembrane

root pressure and guttation

• root pressure increases when transpiration is low

• positive hydrostatic pressure builds in xylem (ions absorbed from soil), buildup of solutes in xylem sap > decreases xylem solute potential and water potential = more water absorption

vessel elements vs tracheids

• vessel elements only in angiosperms

  • have pits, perforation plates allow vessel elements to be stacked in a conduit

• tracheids

  • water flows through pit pairs

boundary layer

• an unstirred layer of air close to the leaf

  • thick = gentle gradient, slow diffusion

  • thin = steep gradient, fast diffusion

essential nutrients

• an intrinsic component in the structure or metabolism of the plant

macro nutrient

• needed or used by the plant in large quantities

• from water/air:

  • C, H, O

• from soil

  • N, P, K, Ca, Mg, S

micro nutrient

• needed or used by the plant in small quantities

• from soil:

  • B, Cl, Cu, Fe, Mn, Mo, Ni, Zn

non-essential nutrients

• not necessary for the vital physiological processes of the plant

Nitrogen uptake form and use

• NO3-, NH4+

• aboveground biomass

Phosphorus uptake form and use

• H2PO4-, HPO₄²⁻, PO4³-

• roots, blooms, and fruits

Potassium uptake form and use

• K+

• overall health and disease resistance

Sulfur uptake form

SO4²-

Calcium uptake form

Ca2+

Magnesium uptake form

Mg2+

Group 1 Nutrients

• part of carbon compounds

• N, S, P

Group 2 Nutrients

• important for structural integrity

• Si, B

Group 3 Nutrients

• remain in ionic form

• K, Ca, Mg, Cl, Zn, Na

Group 4 Nutrients

• involved in redox reactions

• Fe, Mn, Cu, Ni, Mo

Hoagland solution

ammonium, nitrate, and highest concentrations of other elements without becoming toxic

group 1 deficiency symptoms

• Nitrogen: major component in chlorophyll, proteins, nucleic acids

  • inhibited growth, chlorosis in older leaves (mobile), thin woody stems, purple leaves

• Sulfur: component in amino acids and vitaminds used in metabolism

  • chlorosis in young leaves (immobile), stunted growht, anthocyanin accumulation (purple leaves)

• Phosphorus: compound in plant cells, sugar-phosphate intermediates in photosynthesis, make up plant membranes

  • stunted growth, dark green or malformed leaves, necrotic spots, delayed maturing or flowering

Group 2 deficiency symptoms

• Silicon: structural component in lignin

  • only equisetaceae require Si

  • susceptibility to lodging, metal toxicity. reduced growth and stress resistance

• Boron: structural component in cell wall

  • black necrosis on young leaves, stiff and brittle stems, loss of apical dominance, necrosis on fruits and tubers

group 3 deficiency symptoms

• Potassium: regulates osmotic potential

  • mottled or marginal chlorosis, necrosis at leaf tip/margin/between veins, curling leaves, short internode, susceptible to root-rotting fungi

• Calcium: important to structural development and cell wall division

  • necrosis of young meristematic regions, deformed leaves

• Magnesium: activation of enzymes and synthesis of DNA

  • chlorosis between leaf veins, occurring in older leaves

• zinc: enzyme and chlorophyll synthesis

  • reduction in internodal growth

group 4 deficiency symptoms

• Iron: transfer of electrons

  • interveinal chlorosis, white leaf

• Manganese: activates several enzymes, plays a role in photosynthetic reaction in which oxygen is produced from water

  • interveinal chlorosis, small necrotic spots in young or old leaves

• Copper: redox reactions, plastocyanin (electron carrier in photosynthesis)

  • dark green leaves, necrotic spots, necrosis at tips of young leaves

• Molybdenum: component of several enzymes, plays a role in nitrogen assimilation

  • interveinal necrosis and necrosis in older leaves

why is detecting deficiencies tricky

• deficiencies of several elements may occur simultaneously in different plant tissues

• mobile vs immobile elements

• deficiencies or excessive amounts of one element may induce deficiencies or excessive accumulations of another

• some virus-induced plant diseases produce similar symptoms to nutrient deficiencies

treating nutrient deficiency with fertilizers

• chemical, organic, and foliar fertilizers, humic acid chelation

how does soil pH affect nutrient availability

• pH is controlled by hydrogen ion concentration

• root growth > in acidic soil

• pH determines nutrient availability

  • acidity weathers rocks producing K+, Mg²+, Ca²+, and Mn²+

  • increases solubility of carbonates, sulfates, phosphates

  • decomposition of organic matter lowers soil pH

Nutrient and plant growth: “too much of a good thing”

• accumulation of salts

• accumulation of heavy metals

• different elements are absorbed at different portions of the root

• allocation to root growth may depend on available nutrients

solute transport

• molecular and ionic movement from one location to another

• regulated by membrane proteins (short distances)

• translocation: larger-scale transport between plant organs, or between plant and the environment. regulated by membrane transport into phloem cells of leaf and storage cells of root

passive transport

• “downhill”

• spontaneous movement of molecules down a gradient of free energy or chemical potential until equilibrium is met

active transport

• “uphill”

• movement of a substance against a gradient of chemical potential. requires work.

chemical potential

• sum of the concentration, electric, and hydrostatic potentials

• molecules move from high to low chemical potentials

• electrical membrane potential (voltage)

• diffusion potential develops as a result of diffusion