– Movement of molecules from a region of higher 

concentration to a region of lower concentration

from a region where water is more concentrated 

to a region where it is less concentrated

Process used to absorb 

and retain solutes against a diffusion, or 

electrical, gradient by expenditure of 

energy

-Molecules move along 

concentration gradient. 

– Moving from lower to higher 

concentration is against 

concentration gradient.

– State of equilibrium

-Molecules distributed 

throughout available space

– Rate of diffusion depends 

on pressure, temperature

and density of medium.

solution with higher solute concentration, lower water concentration

Water will flow into solution with higher solute concentration

If cell has hypertonic solution, cell with become turgid

solution with lower solute concentration, higher water concentration

water will flow out of solution with lower solute concentration

if cell has hypotonic solution, cell will lose water and plasmolysis will occur

equal concentrations of solutes

equilibrium of water molecules on both sides of membrane

cell will be flaccid, or limp

loss of water through osmosis

shrinkage of protoplasm away from the cell wall

-large molecules, such as celluose and starch, develop electrical charges when wet, and thus attract water molecules

-water molecules adhere to large molecules

-results in swelling of tissues

-imbibition is first step in germination of seed

-osmotic pressure + pressure potential

-measurement of which way water will tend to flow

-for pure water Ψw = 0; plant water potentials are usually negative

-less negative number -> water more likely to move elsewhere

-more negative number -> water more likely to come there

-enters from soil into cell walls and intercellular spaces of root hairs and roots

-crosses differentially permeable membrane and cytoplasm of endodermis, then into xylem

-flows through xylem to leaves and diffuses out through stomata

Ploem loading-Sugar enters by active transport into sieve tubes

-water potentential of sieve tubes decreases and water enters by osmosis

-turgor pressure develops and drives fluid through sieve turbes toward sinks

-food substances actively removed at sink and water exits sieve tubes, lowering pressure in sieve tubes

-mass flow occurs from higher pressure at source to lower pressure at sink

-water diffuses back into xylem

used by plants in greater amounts

-nitrogen, potassium, calcium, phosphorus, magnesium and sulfur

needed by the plants in very small amounts

-iron, sodium, chlorine, copper, manganese, cobalt, zinc, molybdenum and boron

-photosynthesis supports all/most life on earth

-photosynthesis produces oxygen for animals to breath

-heterotrophs use chemical products of photosynthesis for energy

-chlorophyll a and chloropyll b absorb in red and blue and reflect green

-carotenoids absorb blue-green light and reflect yellow or yelow-orange light

-when pigments absorb light, energy levels of electrons are raised

-energy from an excited electron is released when it drops back to its ground state

chlorophyll a, small amount of chlorophyll b, caotenoid pigment and P₇₀₀

1. In thylakoid membranes of chloroplasts

2. Water molecules split apart, releasing electrons and hydrogen ions; oxygen gas released

3. Electrons pass along electron transport system

4. ATP produced

5. NADP is reduced, forming NADPH (used in light-independent reactions)

1. In stroma of chloroplasts

2. Utilize ATP and NADPH to form sugars

3. Calvin cycle

-carbon dioxide combines with RuBP (ribulose bisphosphate) and then combined molecules are converted to sugars (glucose).

-energy furnished from ATP and NADPH produced during light-dependent reactions

-enzyme of first step of carbon fixation

-ribulose 1,5-biphosphate carboxylase/oxygenase

-adds carbon to RuBP

-Also adds oxygen to RuBP

-NADPH and ATP supply energy and electrons that reduce 3PGA to GA3P

-ten of the twelve GA3P molecules are restructured, using 6 ATP, into six 5-carbon RuBP molecules

-net gain of 2 GA3P, which can be converted to carbohydrates or used to make lipids and amino acids

-Allows C3 plants to survive under hot dry conditions

-helps dissipate ATP and accumulated electrons, preventing photooxidative damage

-forms CO2, and PGA that can reenter Calvin cycle

-No ATP formed

-may reduced rate of CO2 fixation by 33-50%

1. CO₂ converted to organic acids in mesophyll cells

2. Form 4-carbox, oxaloacetic acid, instead of PGA

3. PEP carboxylase converts CO₂ to carbohydrate at lower CO₂ concentrations than does rubisco

-similar to C4 photosynthesis in that 4-carbon compounds produced during light-independent reaction, however:

-organic acids accumulate at night (stomata open)

-converted back to CO₂ during day for use in Calvin cycle (stomata closed)

-take up CO₂ at night using C4 pathwy

-store malate in vacuole

-malate -> CO₂+pyruvate for C₃ pathway during day

-stimulate enlargement of cells by increasing cell wall plasticity

-triger production of other hormones

-delay development processes such as fruit and leaf abscission, and fruit ripening

-promote cell enlargement and stem growth, cell division in cambium, initiation of roots and differentiation of cell

-inhibit lateral branching

-most dicots and a few monocots grow faster with an application of GA

-dramatically increases stem growth

-regulate cell division

-synthesized in root tips and in germinating seeds

-cell enlargement

-differentiation of tissues

-development of chloroplasts

-stimulation of cotyledon growth

-delay of aging in leaves

-has inhibitory effect on stimlatory effects of other hormones

-prevents seeds from germinating while will on plant

-helps leaves respond to excessive water loss (interferes with transport or retention of potassium ions in guard cells, causing stomata to close)

-produced by fruits, flowers, seeds, leaves and roots

-can trigger itso own production

-used to ripen green fruits

-production almost ceases in absence of oxygen

-causes leaf abscission

-stimulate cell division and elongation in stems, promote pollen tube growth, slow root growth, delay leaf abscission, enhance ethlene synthesis and in general act a lot like auxins although it appears to be through different pathways

-have gibberellin-like effects on plant stem elongation

-known from legumes and a few others

-hormones typically act by binding to a protein at membrane (reception)

-secondary messengers are produced in cell (signal transduction)

-cell response is activated (response)

-generally, monocots less sensitive than dicots and shoots less sensitive than roots

-indoleacetic acid (IAA)

-Phenylacetic acid (PAA)

-4-chloroindoleacetic acid (4-chlorolAA)

-Indolebutyric acid (IBA)

-suppression of growth of lateral (axillary) buds

-believed to be brought about by auxin-like inhibitor in terminl bud

-root and shoot development in tissue culture regulated by auxins and cytokinins

-seed germination regulated by gibberellins and ABA

-nutations

-nodding movements

-twinning movements

-contractile movements

-nastic movement

-phototropism

-gravitropism

-other tropisms such as thigmotropism, chemotropism, thermotropism,...etc.

-responses to touch

-plant produces ethylene on touched side which inhibits growth

-traumotropism-wounding

-electrotropism-electricity

-skototropism-dark

-aerotropism-oxygen

-result from changes in internal water presures and often initieated by contact with objects outside of plant

-sleep movement (circadian rhythms)

-solar tracking (twist on petioles)

-water conservation movements (bulliform cells)

-pigments that control photoperiodism

-red light

-play role in other plant responses: 

-plant development, changes in plastids, production of anthocyanins, and detection of shading

-blue, light-sensitive pigments that play a role in circadian rhythms and interact with phytochromes to control reactions to light

-P_r - absorbs red light at 660 nm

-P_fr - absorbs far-red light at 720 nm

-leaves actually sense photoperiod

-light induced leaves can be grafted on other plants to stimulate flowering

-hypothetical substance that promotes flowering; never isolated

-perhaps a combination of compounds?

-perhaps related to disappearance of an inhibitor?

-each plant species has optimum temperature for growth and minimum temperature below which growth will not occur

-thermoperiod-optimum night and day temperatures

-optimum temp may change with growth stage of plant

-lower night temp often result in higher sugar content and in greater root growth

-growth of many field crops is roughly proportional to prevailing temp