Plants Exam 3 Review

The region of the leaves that are responsible for photosynthesis

Mesophyll – where plants produce photosynthesis in leaves

spongy – leave gaps, not as efficient – pick up where palisade mesophyll cells left off (located under palisade cells)

palisade mesophyll cells – majority of photosynthesis

Flowering plant cycle: perennial vs annual plants

Perennials – energy is used to produce growth for following year and seeds (energy is split), holds off on blooming if necessary

Annual – energy is used to producing seeds, must bloom in its year

All the forces needed to push water

osmosis, capillary action, transpiration pull, root pressure, turgor pressure, active transport, diffusion

osmosis description

movement of water between high to low concentration, used to separate nutrients from water

Solute concentration is higher in cortex cells, lower in soil.

capillary action description

adhesion and cohesion move water up small cylinders

turgor pressure description

pressure that develops against walls because of the water entering the cell

transpiration pull description

water pushing out of stem consistently, as there is pressure behind it

transpiration rate

rate the stomata can open to keep flow of water going. keeps water moving from tip of root to tip of shoot, causes stomata to open.

active transport description

movement of molecules from low concentration to high concentration, requires movement against a concentration gradient

requires a proton pump in the plasma membrane

diffusion description

movement of molecules from high concentration to low concentration, movement along concentration gradient at a state of equilibrium, brings in nutrients and minerals

water potential definition

water continually moves through the stem, exiting through the stomata

translocation definition

use active transport to move from high concentration of sugar to low concentration of sugar. water is added to sugar to allow for easier, quicker movement

Pathway of water from the soil, through the plant, into the leaves.

Water enters from soil into root hairs -> cortex cells -> endodermis, filtered by Casparian strip, pass through passage cells, filter out pathogens spores -> pericycle -> xylem/phloem -> flows through xylem to palisade then spongy mesophyll -> diffuses out of stomata

describe the opening and closing of guard cells

Guard cells can photosynthesize to get the amount of energy needed to open and close. When close, guard cells require no energy.

Opening of cells – requires energy and the intake of potassium ions (lowers water potential) from adjacent cells, occurs at medium speed. Enters guard cells via osmosis.

Closing of cells – requires the exit of water and potassium ions from the cells

Pressure flow hypothesis. How does this work? What is involved?

Translocation of moving compounds from photosynthesis across the plant, requires active transport by companion cells. Transport from source to the sinks.

spring, summer, fall sinks

Spring: Buds/flowers, new roots, shoots

Summer: Fruits and seeds

Fall: Storage of nutrients into the cortex or trunk

limiting factors of photosynthesis

CO2, water availability, light intensity

general photosynthesis equation

6CO2 + 6H2O + Light energy -> C6H12O6 + 6O2

C3 photosynthesis equation

Fixes CO2 directly into a 3-carbon molecule (3-PGA) using RuBisCO

CO2 -> Calvin cycle using RuBisCO (in mesophyll) -> Glyceraldehyde 3-phosphate -> glucose/sucrose (out of mesophyll)

C4 photosynthesis equation

CO2 is fixed into a 4-carbon molecule by PEP carboxylase

CO2 -> C4 using PEPC (mesophyll) -> CO2 (bundle sheath) -> Calvin cycle (bundle sheath) -> glyceraldehyde 3-phosphate -> glucose/sucrose (out of bundle sheath cell)

CAM photosynthesis equation

CO2 is fixed into a 4-carbon organic acid using PEP carboxylase

CO2 -> C4 (night) using PEPC -> CO2 (night to day) -> Calvin cycle using RuBisCO (day, mesophyll) -> Glyceraldehyde 3-phosphate -> glucose/sucrose (out of mesophyll cell)

What products are made with photosynthesis?

Organic carbons, sugars (glucose), oxygen, starches, and cellulose

Why did C4 plants evolve and what makes them different from C3 plants?

C4 plants adapted to an increase in temperature and light and a decrease in water. C4 can be correctly fixed in the bundle sheath cell because there is no access to O2. C4 plants can take in the maximum amount of CO2 by converting it to oxolactic acid and then malic acid.

Why are the C4 plants more beneficial?

Can produce x4 as much carbon compared to C3 plants. They do not allow photorespiration to occur, have high productivity in heat, light, and dry conditions.

C4 plant structures

Kranz Anatomy – mesophyll cells with smaller chloroplasts and well-developed grana

Bundle sheath cells – large chloroplasts with numerous starch grains

Mesophyll cells – contain enzyme PEP carboxylase

CAM plants and their structures, how the system works

CAM photosynthesis allows arid plants to minimize water loss in arid environments by opening stomata at night. CAM photosynthesis produces 4C compounds during light independent reactions and converts back to CO2 during the day for use in the Calvin cycle.

similarities in C3, C4, and CAM plants

All use photosynthesis to CO2 and sunlight into sugars. Use the Calvin cycle to synthesize glucose from CO2.

differences in C3, C4, and CAM plants

C3 plants: Produce C3 compounds, using RuBisCo directly, all steps occur in mesophyll, stomata open during the day

C4 plants: Produce C4 compounds w/ PEP carboxylase, steps occur in mesophyll and bundle sheath cells, stomata open during the day

CAM plants: Produce C4 compounds w/ PEP carboxylase, all steps occur in mesophyll, stomata open at night

auxins role

Regulate cell elongation, plant growth, directional development, phototropism, gravitropism, and apical dominance in plants.

cytokinins role

responsible for lateral growth of plants

gibberellins role

Regulate cell division, tissue and chloroplast development, and delaying the aging of leaves

ethylene role

Regulates growth, development, stress responses, and aging. Causes leaf abscission

abscisic acid role

Has an inhibitory effect on the stimulatory effects of other hormones

What is the major importance of Auxins?

Auxins are important because they act as master plant hormones that dictate overall plant development. Without them, the plant does not grow upward and cannot sense light or gravity.

What balances auxin to produce apical dominance?

Cytokinins

Why is apical dominance so important for younger plants?

Rapid upward growth is necessary to outcompete neighboring plants for sunlight. It also establishes a strong central stem that lateral growth can continue off of later, once the plant is established. Additionally, focus on a primary shoot provides better resource efficiency for a plant that does not have much energy to spare.

What hormones are used to produce roots or shoots in tissue culture?

Shoots – Auxins

Roots – Cytokinins

Why was plant movement so important for plant growth?

Helps plants maximize resources and energy efficiency, navigate the environment, and anchor themselves.

Explain how phototropism helps plants maximize their growth

Phototropism helps plants maximize their growth by allowing sections of the plant to seek or avoid light. Positive phototropism allows for shoots to seek the optimal amount of photosynthesis, outcompeting neighbors for the best area. Negative phototropism allows roots to grow away from light, growing deeper into the soil, providing better anchorage and nutrient access

Photoperiodism tracks the amount of day and Night time, which is more important?

Night – determines when plants will flower

When exactly will a long day plant bloom vs a short day plant?

Short day – will not flower unless day length/light is shorter than a critical period

Long day – will not flower unless day length/light is longer than a critical period

Why can’t a plant that begins blooming can’t revert this process?

FT begins to be transported throughout the plant and cannot be reverted to nonprojected. Hormones are chemically binding, and signal transduction cannot be stopped.

signaling pathway: steps and description

Reception – protein/signal is received

Transduction – Signal is amplified throughout the cell

Response – Transcription factor undergoes transcription and then translation, before de-etiolation response proteins are produced to mediate the issue at hand

why are multiple pathways needed to trigger the same response?

Plants do not have a centralized nervous system, therefore need multiple mechanisms to trigger a response in its independently acting cells. The mechanisms for response must cover all of the separately acting cells it needs to, leading to multiple pathways being required.