Exam 2 - Plant Structure and Function

What does phloem move?

photosynthates, generally down, the plant.

sugars and energy

True/False

Phloem is dead at maturity.

False.

phloem is alive at maturity and not lignified

Phloem's Two Main Components

sieve tube elements

companion cells

Day length has what effect on sugar?

shorter days equate to more sugar build up in roots.

longer days equate to less sugar build up in roots.

Companion Cell Components

has vacuole, chloroplast, mitochondria, and nucleus

Connected Sieve Tube Element

the vessel for moving photosynthates

Companion Cell Purpose

the engine of moving things down the phloem

Sieve Element

cell of the phloem that is involved in long-distance transport of food substances (sieve cells and sieve-tube elements)

Reducing Sugars

reducing agents, holding electrons, more reactive

Nonreducing Sugars

major compounds translocated in the phloem

Aerobic Respiration

the process by which energy is released and stored as ATP for the plant to carry out its growth

Aerobic Respiration Equation

glucose + oxygen --- carbon dioxide + water + ATP

Four Major Reactions in Respiration

1. glycolysis

2. the oxidative pentose phosphate pathway

3. the krebs cycle

4. oxidative phosphorylation

Glycolysis

occurs in the cytosol.

starts with sugars.

ends with pyruvate.

sugars are converted to three carbon phosphates and provides the groundwork for the rest of respiration.

Oxidative Pentose Phosphate Pathway

occurs in plastids and cytosol.

starts with glucose.

results in a five carbon sugar and NADPH.

The Krebs Cycle

occurs in the matrix of the mitochondria.

starts with pyruvate moving into mitochondria.

ends with acetyl-COA

Oxidative Phosphorylation

Part of the electron transport chain.

occurs in the mitochondria.

starts with energy from electrons occurring in the previous steps (NADH)

ends with ATP

Acetyl-COA

formed when pyruvate first enters into the mitochondria

Pyruvate

end product of glycolysis

Resurrection Plants

plants whose tissues are able to dehydrate while remaining alive. the plant appears dead until water is added, when it rehydrates its tissues and appears to come back to life.

can lose 95% of their water and last months

Annual Plants

a plant that lives only one season

Downsides to Annual Plants

they don't have resistance or avoidance to droughts

Promoter

region of DNA that indicates to an enzyme where to bind to make RNA

Terminator

marks the end of a gene

Desiccation Tolerance

a traits that allows plant cells to survive extreme dehydration without damage to membranes

How much energy reaches each meter of the Earth

340 watts of sun energy per meter

How much sun energy is converted into photosynthates?

5%

Phototropism

leaves moving to obtain more sunlight

What color light does chlorophyll absorb/reflect?

absorb: red light

reflect: green light

How do cell shapes change in response to light?

spongy mesophyll gets larger in sun leaves than in shade leaves

facilitates gas exchanges + photosynthesis

Thickness of Leaves in Response to Light

leaves in the sun are typically thicker for more protection

Sieve Effect

the penetration of light used for photosynthesis through several layers of cells due to the gaps between chloroplasts permitting the passage of light.

Light Channeling

incoming light is propagated through central vacuoles

air-filled channels in stems create a light gradient, enabling them to perceive the direction of light and optimize leaf positioning for photosynthesis

Interface Light Scattering

air pockets generate lots of interfaces between air and water that reflect and refract light

Acclimation

ability to zigzag in response to their environment

Plasticity

how much adjustment takes place

Thylakoid

a flattened membrane sac inside the chloroplast, used to convert light energy into chemical energy.

Granum

stack of thylakoids

Stroma

fluid portion of the chloroplast; outside of the thylakoids

Carotenoids

an accessory pigment, either yellow or orange, in the chloroplasts of plants. By absorbing wavelengths of light that chlorophyll cannot, carotenoids broaden the spectrum of colors that can drive photosynthesis.

Antenna Complex

Part of a photosystem, containing an array of chlorophyll molecules and accessory pigments, that receives energy from light and directs the energy to a central reaction center during photosynthesis.

Z Scheme

very directional.

each step loses a little energy but this is what creates the consistent pathway.

light comes in and is handed through compounds AS ELECTRONS

Four Major Protein Compounds in Z Scheme

*sort of a relay race

1. photosystem 2

2. cytochrome

3. photosystem 1

4. ATP Synthase

Photosystem 2

initiated by: light absorption

finished with: strips electrons off of water

Cytochrome

a hydrogen carrier containing iron that moves electrons between PS1 and PS2

Photosystem 1

reduces NADP+ into NADPH

ATP Synthase

makes ATP and builds up stroma

Carbon Fixation Reactions

carbon is converted into glucose and other sugars.

Calvin-Benson Cycle

starts with carbon and ends with glucose

light-independent reactions

Three Steps of Calvin Benson

1. carboxylation

2. reduction

3. regeneration

Carboxylation

starts: CO2 and water

ends: unstable carbon that goes on to make oxygen

glues carbon into substrate

Reduction

starts with tri-phosphoglycerate.

ATP makes ADP and one phosphate.

NADPH turns to NADP

the "making" part of the cycle- releases energy

Regeneration

starts with ADP, P, Triphosphates

Restores the pool of ribulose 5-phosphate

ribulose-5-phosphate

The five-carbon sugar ribulose, phosphorylated at carbon 5.

Photorespiration

reaction that consumes oxygen and releases carbon dioxide but generates no ATP and decreases photosynthetic output

generally occurs on hot, dry, bright days, when stomata close and the oxygen concentration in the leaf exceeds that of carbon dioxide.

C4 Carbon Cycle

prevents rubisco from becoming an oxygenase which causes rubisco to grab onto CO2.

Rubisco

enzyme that converts inorganic carbon dioxide molecules into organic molecules during the final step of the Calvin cycle

Oxygenase

one or both oxygen atoms are incorporated into substrate

Kranz Anatomy

Specialized leaf structure in C4 plants - wreathlike arrangement of mesophyll cells around a layer of bundle leaf cells

Gradient Between Water and Air

the gradient between how wet the air is and how dry the plant is determines how much water the plant sucks up

Stomata Structure

located on the bottom of leaves- typically.

flanked by guard cells

Stomata Purpose

gas exchange and movement of water

Guard Cells

control the opening and closing of stomata

Closed Stomata

conserves water. causes cells to lose turgor pressure and become wilted. guard cells have collapsed.

Open Stomata

gas exchange and water loss occurs. guard cells are turgid.

Role of Potassium in Guard Cells

pumped in: potassium brings water with it

pumped out: potassium brings water out of stomata and causes the leaves to go flaccid

What determines whether the stomata is open

the amount of light hitting the chloroplasts

If a lot of light is hitting the leaf, there are good conditions for photosynthesis, and the stomata will open to take in photosynthesis

Water Structure

polar molecule that is bent

Grapevine Bleeding

Water uptake driven by root pressure pushes air bubbles out of the xylem (cavitation) that have formed over consecutive freeze/thaw cycles

Why does grapevine bleeding happen?

there is a giant rush of xylem sap once roots start waking up that restores the processes

after pruning grapevines, xylem sap will seep out of wounds after roots start taking up water again- shows that the roots/plant are "waking up" again

Diffusion

Movement of molecules from an area of higher concentration to an area of lower concentration.

Aquaporins

channel proteins that facilitate the passage of water- makes water move super fast

Peter Agre

discovered aquaporins

Gated Channels

open or close in response to a stimulus- doesn't control the way that water moves

Bulk Flow

water moving a long-distance in the xylem due to pressure (most often a pressure gradient).

account for much of the water flow through the soil and roots

Osmosis

diffusion of water across a selectively permeable membrane

Pressure Gradient

Pressure difference between two points

Benefits of Plant Membranes Being Semipermeable

Allows water and small uncharged substances to move across them easier than larger/charged solutes

Turgor Pressure

caused by water coming in through osmosis and creating pressure inside living plant cells

Plasmolysis

collapse of a walled cell's cytoplasm due to a lack of water

thirsty cells

Water Potential

measures the tendency of water to move from one location to another

Equation for Water Potential

solute potential + pressure potential + gravitational potential

Gravitational Potential

always negative

Water flows...

water will always flow to the more negative area

Shoot Apex

shoot apical meristem + overlapping leaf primordia

Interdeterminate Growth

SAM is continuously meristematic - the plant will keep going

Determinate Growth

SAM hits a certain milestone in development and stops differentiating

Phyllome

Collective term for all leaves of a plant.

Abaxial

lower surface of leaf

Adaxial

upper surface of leaf

Phyllotaxy

the arrangement of leaves on a stem, is specific to each species

Three Main Leaf Arrangements

alternate, spiral, decussate

Alternate Leaf

one leaf per node

Spiral Leaf

one leaf at each node and the leaves forming a spiral around the stem

Decussate Leaf

two leaves per node, spiraling up

Reticulate Veins

smaller veins forming a network - dicot plants

Parallel Veins

veins that run in straight lines next to each other - monocot plants

Auxin

A plant hormone that speeds up the rate of growth of plant cells

Cytokinin

Stimulates cell division and growth of lateral buds. Causes dormant seeds to sprout.

Ethelyne

Plant Hormone that stimulates ripening of fruit and inhibits flower development - controls senescence