Plant Phys Midterm

Auxin concentration

Depends on synthesis, transport, cellular uptake, and degradation, all regulated by plant homeostasis mechanisms.

Boysen Jenson experiment

Showed that auxin moves down the shaded side of a plant, causing phototropic curvature by testing how light direction affects growth. Demonstrated using agar blocks to transmit chemical signals.

DR5 reporter construct

Measures auxin response by indicating auxin activity in cells, often through a visual reporter like green fluorescent protein (GFP) to mark areas of high auxin concentration.

Auxin concentrations in young leaves

In young leaves, auxin concentration is higher at the leaf tip and gradually decreases towards the base.

Auxin concentrations in mature leaves

In mature leaves, auxin distribution becomes more uniform throughout the leaf.

Morphogen

Signaling molecule that forms a gradient and regulates cell fate and pattern formation in tissues based on concentration.

Examples of auxin as a morphogen

Root and shoot patterning, organ positioning (phyllotaxis), and vascular differentiation.

Gibberellin regulated system

Gibberellin binds to the GID1 receptor, leading to DELLA protein degradation via the proteasome. This degradation allows GA-induced gene expression, promoting stem elongation and seed germination.

Increased ABA synthesis times

Increased ABA synthesis occurs during seed maturation (promotes dormancy) and in response to drought stress (closes stomata to conserve water).

DNA organelles

DNA is found in the nucleus, chloroplasts, and mitochondria.

Basic unit of DNA

Nucleotide.

Complementary DNA strand

The sequence of the other DNA strand for 5' AGGTCGTGCAGAT 3' is 3' TCCAGCACGTCTA 5'.

Purines of DNA

Adenine and Guanine.

DNA backbone composition

The backbone of DNA is composed of phosphate and deoxyribose.

RNA base substitution

In RNA, the base uracil is substituted for the base thymine in DNA.

Template strand reading direction

The template strand is read in the direction 3' to 5'.

DNA composition percentage

In a DNA molecule, 30% is A & T. So 70% G/C so 25% G.

Key enzyme in DNA replication

DNA polymerase.

DNA replication process

The DNA replication process is called replication, and occurs in the nucleus.

Haploid and diploid numbers in humans

For humans, the haploid number is 23 and the diploid number is 46.

Primase function

Attaches a small RNA primer to the DNA strand.

Helicase function

Unwinds the double helix.

DNA ligase function

Forms a phosphodiester bond.

Types of RNA produced in the nucleus

Messenger RNA (mRNA), Transfer RNA (tRNA), Ribosomal RNA (rRNA).

RNA not translated into protein

The beginning mRNA is not translated and introns.

Diffusion

Ions or molecules moving in response to a concentration gradient.

Mass flow

Movement of ions or molecules in response to pressure.

Osmosis

Movement of a solvent across a semi-permeable membrane in response to a difference in water potential.

Water potential

Ability of water to do work. Availability of water.

Water potential equation

Water potential = solute potential + pressure potential + matrix potential + gravitational potential.

Components of water potential

Solute potential is the influence of solutes on water potential. Higher solute concentrations mean lower solute potential and so lower water potential.

Pressure potential

The influence of pressure on water potential.

Matrix potential

The attachment of water of plant or soil components.

Gravitational potential

The influence of gravity.

Permanent wilting point

The soil water potential is so low the plant can no longer regain water from soil even if all transpiration stops.

Xylem cell types

Tracheids, vessel elements, fibers, ray cells, parenchyma.

Transpiration driving force

A water potential gradient exists from the air (low) to the soil (high).

Humidity effect on transpiration

High humidity decreases transpiration.

Temperature effect on transpiration

High temperatures increase transpiration.

Soil moisture effect on transpiration

Low soil moisture decreases transpiration.

Wind effect on transpiration

Wind increases transpiration.

Stomatal number effect on transpiration

High stomatal number increases transpiration.

Leaf surface area effect on transpiration

High leaf surface area increases transpiration.

Root depth effect on transpiration

Shallow roots decrease transpiration.

Root quantity effect on transpiration

Fewer roots decrease transpiration.

Stomatal opening effect on transpiration

Open stomates increase transpiration.

ABA effect on stomata

ABA causes stomatal closure.

CO2 effect on stomata

CO2 when low causes stomates to open.

Leaf water potential effect on stomata

Low leaf water potential closes stomates.

Blue light effect on stomata

Blue light causes stomates to open directly.

Red light effect on stomata

Red light has an indirect effect as it increases Ps and lowers CO2 concentration.

Water stress effects on plants

Decreased leaf area, leaf abscission, change in leaf orientation, stomatal closure, decreases Ps, deeper roots, osmotic adjustment.

Osmotic adjustment

Increase in solute concentration in meristematic areas lowers water potential and draws water to the meristem from other plant parts.

Guttation

Exudation of water from cut stems or intact leaves.

Hydathode

Terminal trachieds through which guttation occurs in leaves.

Cohesion

Attraction of like molecules.

Adhesion

Attraction between unlike molecules.

Transpiration

Movement of water from soil to the atmosphere, through a plant.

Cavitation

Water can withstand the tension placed on it by the 'pull' of transpiration until a gas bubble enters a vessel element or tracheid.

Surface tension

The attraction of water molecules to each other is stronger than their attraction to water molecules in the liquid/gas phase at the surface.

Capillarity

Water will move up a hollow tube by adhesion and cohesion.

Transcription

The manufacture of mRNA from DNA.

Translation

The manufacture of a protein from mRNA.

Gene

A sequence of nucleotides which code for the production of a particular protein.

Cell cycle phases

The G1 Phase, S Phase, G2 Phase, and M Phase.

Mitosis stages

Preprophase, Prophase, Metaphase, Anaphase, Telophase, Cytokinesis.

Cell wall expansion

Cell wall acidification is required for plant cell wall expansion.

Seed germination steps

Water imbibition, initiation of enzyme activity, hydrolysis and catabolism of storage compounds, synthesis of new cells and tissues, initiation of embryo growth, radicle emergence.

Functions of water during seed germination

Hydration of existing proteins, enzymes and organelles, transport of materials within seed, hydrolysis of storage compounds, turgor pressure for cell expansion.

Enzymes in catabolism

Starch: amylase, Lipids: lipase, Proteins: protease.

Lipid metabolism

Lipids are initially broken down to fatty acids and glycerol in the oleosome.

Malic acid

Formed from succinic acid in the mitochondria, enters the cytoplasm to form phosphoenol pyruvic acid.

Gluconeogenesis

The process by which phosphoenol pyruvic acid is used to eventually produce glucose.

Seed dormancy types

Temperature requirements, Photodormancy, Hard Seed, Immature Embryos, Presence of growth Inhibitors, Deficiency of growth promoters.

Wavelength of light for photoblastic seeds

Red light.

Phytochrome red (Pr)

Absorbs red light.

Phytochrome far red (Pfr)

Absorbs far red light.

Photoreversibility

The structural change when Pr absorbs red light and switches to Pfr, and vice versa.

Active Pfr

Transported to the nucleus to participate in protein-protein interactions affecting gene expression.

Gibberellins (GAs)

Hormones that promote fruit growth, stem growth, and seed germination.

Gibberellin biosynthesis stages

Stage 1: GGPPent-kaurene (proplastids), Stage 2: ent-kaureneGA12 (endomembranes), Stage 3: GA12 active GAs and inactive catabolites (cytoplasm).

Active GAs

GA4 and GA1.

GA deactivation

By enzymes such as GA2-oxidase, GA methyl transferase, and Elongated uppermost internode gene.

GA4 entry into meristem

GA4 can enter the meristem when GA2ox expression is switched off during floral induction.

GA transport vs. auxin transport

GAs are not transported in a polar way, while auxin is transported from stem apex to base.

GAs in seed germination

Synthesized in the embryo and induce alpha-amylase production in the aleurone layer.

Roles of GAs

Promote growth and elongation, mediate stress responses, promote seed germination, and promote flowering.

Sub1A gene

Allows rice plants to survive flooding by not growing.

GA receptor mutants

Do not respond to gibberellins, resulting in no increase in plant height.

Overexpression of gibberellin receptor

Results in hypersensitivity to GA application, leading to taller plants.

PIL5 gene

Inhibits germination by limiting GA accumulation and response.

Functions of cytokinins

Promote cell division in the shoot, delay leaf senescence, regulate nutrient allocation, promote nodule development.

Biologically active cytokinins

trans-zeatin and isopentyl-adenine.

Reversible cytokinin inactivation

Cytokinins can be conjugated to a sugar molecule.

Irreversible cytokinin deactivation

Cytokinins can be metabolized to an inactive form by cytokinin oxidase.

Cytokinin activity and leaf shape

Increased cytokinin activity in leaf margins results in increased leaf complexity.

Main role of cytokinins in tissue culture

Promote shoot growth.

LONELY GUY (LOG) mutants

Show reduced shoot branching and abnormal flowers due to reduced active cytokinins.

Roles of brassinosteroids

Cell elongation, pollen tube growth, seed germination, differentiation of vascular tissues.

Roles of ethylene

Control of fruit ripening, leaf and petal senescence, cell division and elongation.