chapter 31 - living plant

products of photosynthesis…

can move up and down plant body

how many meters can water move upwards?

100m

most force is caused by…

transpiration

water molecules stick to each other due to…

polarity and hydrogen bonding

cohesion

water molecules stick to each other

adhesion

water molecules stick to the walls of the trachied or xylem vessels

hydrogen bonding

a weak electrical attraction between a partially positive hydrogen atom in one molecule and a partially negative atom (like oxygen, nitrogen, or fluorine) in another molecule

charged ions..

depend on facilitated diffusion of active transport to enter/exit cells (unlike water)

active transport

the movement of molecules and ions across cell membranes from a region of lower concentration to a region of higher concentration

passive transport

the movement of water, gases, and minerals across cell membranes down their concentration gradient without using cellular energy (ATP)

difference between active and passive transport

passive transport moves molecules down their concentration gradient without using cell energy, while active transport moves molecules against their concentration gradient using cellular energy in the form of ATP

proton gradient across membrane..

• can transport sucrose

• unequal concentration of solutes

osmosis

movement of solvent molecules (usually water) through a semi permeable membrane from an area of lower solute cocnentration to an area of higher solute concentration

diffusion

the net movement of particles from an area of higher concentration to an area of lower concentration

diffusion vs osmosis

Diffusion is the movement of particles from an area of high concentration to an area of low concentration, while osmosis is the specific movement of water molecules through a semipermeable membrane

hypotonic

lower concentration of dissolved solutes, higher concentration of water

hypertonic

higher concentration of solutes, lower concentration of water

plant cell in hypotonic solution

water moves into cell (turgor pressure rises)

plant cell in hypertonic solution

water moves out of cell (turgor pressure decreases)

turgor pressure

the internal hydrostatic force exerted by water inside a cell that pushes the plasa membrane against the rigid cell wall

plasmolysis

the process where a plant loses water in a hypertonic environment, causing the cytoplasm and plasma membrane to shrink and pull away from the rigid cell wall

water potential has two forces

1. physical forces (pressure, gravity)

2. concentrate of solute in each solution

water potential

the potential energy of water per unit volume relative to pure water/tendency of water to move form one area to anotjer

tonicity

how the solute concentration of one solution compares with another

solute potential

the effect dissolved substances have on water potential

pressure potential

the physical pressure placed on water

pure water has a solute potential of….

0

the more solutes dissolved…

more negative the solute potential becomes

pressure on side with higher solute concentration can…

fight against water movement

osmotic pressure

the minimum pressure needed to stop osmosis

aquaporins

proteins that help water move across cell membranes much faster (doorways)

mycorrhizal fungi

fungi that form a mutually beneficial relationship with plant roots

hyphae

thin threads that spread beyond reach of roots and root hairs. absorbs water and minerals, especially phosphorus

apoplast route - around the cells

water travels through the cell walls and spaces. between cells without crossing membrane

symplast route - through the cells

water travels through the cytoplasm of cells, passing between neighboring cells through tiny connections called plasmodesmata. it crosses a cell membrane to enter the symplast initially

plasmodesmata

microscopic channels that pass through the cell walls of plant

transmembrane route - across membranes

water repeatedly crosses cell membranes as it moves from one cell to another, passing through the cytoplasm and sometimes vacuoles

are routes mutually exclusive?

no

casparian strips

interconnected rings of waterproof suberin and lignin found in all walls of the ring of endodermal cells. orevents water and dissolved nutrients from passing through endodermis into steele

steele

central region of root containing vascular tissue

how plants use energy to absorb minerals from the soil, even when the soil has a lower mineral concentration than the plant

1. mineral concentrations are lower in the soil

   1. meaning the plant needs to move minerals from a lower to higher concentration

2. active transport uses energy

   1. plant cells use ATP to power protein pumps, which more hydrogen ions across the membrane against their concentration gradient. this creates and electrochemical gradient that can power the uptake of mineral ions through other transport proteins

3. minerals enter through the steele and travel through the xylem

primary active transport

proton pumps use ATP directly to move hydrogen ions across membranes

secondary active transport

stored energy in the hydrogen gradient helps transport mineral ions, sometimes against their own concentration gradients.

primary vs secondary active transport

Primary active transport uses chemical energy from ATP directly to move molecules across a cell membrane against their gradient, while secondary active transport uses the electrochemical gradient created by primary active transport as its energy source

as ions move from root to soil…

tonicity of root cells increase

• results in movement of water to root cells and water potential and turgor pressure increase in those cells

humidity gradient

driving force of transpiration from 100% relative humidity inside the lead to much less than 100% outside the stomata

tensile strength

how much pulling force a material can withstand before it breaks

cavitation

when a bubble of air or water vapor forms inside the xylem. (bad)

minerals are transported through the xylem…

to other metabolically active part of plants

minerals abundant in xylem

phosphorus, potassium, and nitrogen, and iron

plants will move nutrients fro older tissues to growing regions

plants will move nutrients fro older tissues to growing regions

minerals relocated by xylem…

can only move upwards

guard cells

two sausage shaped cells on either sides of stomata.

• only epidermal cells with chloroplasts

• bend when turgid

• turgid in the morning (during photosynthesis), and lose turgor in the evening

• during the day, accumulates sucrose

• active pumping of sucrose out of guard cells in the evening may lead to loss of turgor and close the cell

with increased temperature and wind speed…

transpiration rates increase

when guard cells lose tugor…

stomata may close

phloem moves..

bidirectionally

translocation

movement of sugars and other nutrients throughout the phloem

pressure-flow model

how phloem moves stuff

source

where sugar comes from (performs photosynthesis)

sink

where sugar goes (uses or stores) or carbs

food storage roots…

can be sinks or sources

phloem loading

• sugars enter the phloem in the smallest vien at the source

• some sucrose travels from mesophyll cells to the companion and sieve cells via symplast

• much of the sucrose arrives t the sieve cell through apoplastic transport and moved across membrane using secondary transport, employing a sucrose symporter

• companion cells and parenchyma cells next to the sieve tubes provide the ATP energy to guide this transport

• unlike vessel and trachieds, sieve cells must be alive to participate in active transport

bulk flow occurs in sieve tubes without additional energy requirements

• because of water potential difference in sieve tubes vs nearby xylen cells, water flows into sirve tubes

• therefore turger pressure in sieve cells rises, causing pressure drives fluid throughout plant’s systems of sirve tubes,

• at sink, sucrose moves into sick cells passively (via plasmodesmata) or actively (first transported from sieve cells to apoplast)

• with the change in solute pressure, water moves out of the sieve cells by osmosis, and then most of it diffuses back into the xylem

• the turgor in the phloem at the sink drops, causing a mass flow from the stronger pressure at the source to the weaker pressure at the sink

hormones

chemical substances produced in small quantities in one part, then transported to another. response influenced by hormone type and tissue

auxin

the first plant hormone discovered

• increase the plasticity, allowing elongation

• multiple auxin reception sites are present

• produced in apical meristems and transported towards the base of a plant

• promote bilateral symmetry, root formation, and apical dominance

• promote activity of the vascular cambium and the vascular tissues

• pollination may trigger auxin release in some species, leading to fruit development even before fertilization has occured

charles darwin

discovered phototropism

Peter Boysen-Jensen and Arpad Paál

proved the phototropic bending of plants was caused by a mobile chemical signal (later named auxin) rather than just a physical or electrical effect

Frits Went

It provided the first concrete proof and isolation of a plant growth hormone (later named auxin

Winslow Briggs

demonstrated auxin causes bending

Ethylene

• known to defoliate plants when leaked from old timey gaslights

• production stimulated by auxin transport downwards from shoot apical meristem. in tissues around the lateral buds and prevent their growth

• suppresses stem and root elongation

pigments

molecules that are capable of absorbing light energy

chlorophylls

primary pigment molecules in photosynthesis