transport in plants

to stay alive and thrive what are the three general classes of materials plants need to move through their body

• Mineral nutrients such as nitrogen, potassium, phosphorus, calcium, magnesium and sulfur;
   

• Water; and
   

• Sugars.

in plants where do mineral nutrients move from

from roots to shoots

where does water move in plants

from roots to shoots

during the growing season where do sugars move

 sugars move from shoots to roots for immediate use by root cells or storage;

after a period of dormancy where do sugars move

sugars move from storage areas back to the shoot systems

Most of the mineral nutrients that plants require to stay alive and thrive are also required by humans and other animals. Why

With minor exceptions, the same types of atoms make up the nucleic acids, proteins, carbohydrates, and lipids found in all organisms.

 What is the biggest reason that plants need to move water to their leaves during photosynthesis?

To replace water that is lost to the atmosphere when stomata are open and leaves are taking in CO₂ and releasing O₂.

are mineral nutrients at higher concentrations outside or inside the plant cell

inside

what are two ways plants get nutrients from the soil

1. Direct acquisition via active transport of nitrogen, phosphorus, and other mineral nutrients from soil to the interior of root cells.

2. Acquisition via barter—specifically, an exchange of sugars for mineral nutrients supplied by symbiotic fungi called mycorrhizae (my-co-RYE-zee).

what is the fungi plants have a symbiotic relationship with

mycorrhizae

what is a root hair

an extension of the cell membrane in epidermal cells.

what are proton pumps

hydrogen ions

what way do proton pumps in the epidermal cells of plant roots pump protons

they pump protons outside the cell

root hairs contain ion channels as well as proton pumps for what

ion channels for K⁺, Ca²⁺, Mg²⁺, and other key nutrients.

how are negative ions like hydrogen phosphate and nitrate able to enter the root hairs

by co transport

how are mycorrhiza and root system in contact

Fungal cells penetrate the root system itself and either grow between the cell walls of root cells or actually enter the cytoplasm of root cells. 

what does “fixation” refer to

a reduction reaction or set of reactions

what do nitrogen fixing fungus have that make them so beneficial to plants

they have an enzyme called nitrogenase which makes it easier to fix nitrogen for the plant

where are most mineral nutrients available

because their ionic forms carry a charge and stay in solution, most mineral nutrients are available in the water between soil particles.

what are the two major types of cells the xylem contains

tracheids and vessel elements

explains the structure of vessel elements

Vessel elements are short, fat cells that stack end to end, with openings at the top and bottom of each cell that allow water to flow straight up as through a pipe. 

explain the structure of tracheids

Tracheids are long, thin cells that have numerous gaps in their cell walls where water flows from one to the next.

what are meniscus

little concave divots on the surface of leafs that gold water

explain how water moves from root to shoot passively

1. This is because the forces on these liquid water molecules are asymmetrical—water molecules at the surface form hydrogen bonds with the water molecules below them, but not with the molecules in air above them.
    

2. The asymmetry in hydrogen-bonding at the surface of the liquid water creates tension, meaning a pulling force.
    

3. Each leaf interior has hundreds or thousands of these menisci, each creating a tiny pulling force.
    

4. The tension at the air-water interfaces in leaves is communicated all the way down to the roots. This is because the water molecules that fill the vascular system cohere to each other via hydrogen-bonding.
    

5. When water molecules evaporate at the surface and leave a meniscus, following a wet-to-dry gradient through open stomata, the tension in the column pulls water molecules up to replace them.

how do the water molecules remain together when going out the stomata

they bind together via hydrogen bonding

working xylem consists of cells that have what?

stiff walls but no organelles or cytoplasm or cytoskeletal components because the xylem cell is dead.

why is having the xylem dead more efficient for water transport

the empty cells conduct water more efficiently

what is the phloem

the sugar conducting tissue in the vascular system

where is the phloem found in the plant body

adjacent to xylem

what are the two main types of cells the phloem is comprised off

sieve elements and companion cells

is sugar movement passive?

no it requires ATP

explain the structure of sieve elements

Sieve elements are stacked end-to-end and make direct connections with each other via open pores. they also lack a nucleus and organelles

where are companion cells found

alongside sieve elements

are phloem cells dead like xylem cells

no

how do sieve elements get most or all of their proteins, ATP, and other molecules they need

from companion cells

essentially what are companion cells to sieve cells

they are their life support system

what is sap

the sugar that is transported throughout the plant body

what is the pressure flow hypothesis

the idea that sap moves from areas of high pressure to areas of low pressure

explain the how things are structured in order to allow sap to move into the sieve elements

photosynthetic tissue is next to companion cells who are next to sieve elements who are next to xylem cells so it all just transfers into the sieve element

does phloem sap move passively or actively down its pressure gradient

passively

what creates a pressure gradient in phloem

When water moves from xylem into the sieve elements in leaves, it builds up pressure inside those sieve elements.

do photosynthesizing tissues have high or low pressure

high pressure

do the phloem cells below photosynthesizing tissues that did not receive an influx of sugars and water have a high or low pressure

low pressure

what is the path taken when phloem sap reaches a sugar sink

that sugars are moving from sieve elements into companion cells and then into "sugar sink" cells

give a quick summary of how sugars move in the plant vascular system

1. Sugars are actively loaded into phloem in leaves and stems where photosynthesis is occurring, leading to a high concentration of sugars near sources.
    

2. Near sources, water moves from xylem to phloem via osmosis. The influx of water builds up pressure in the phloem.
    

3. Sugary sap moves passively down its pressure gradient, from sources to sinks.
    

4. Sugars in phloem sap are actively transported from the phloem into root storage cells and other cells that act as sugar sinks. This "offloading" step keeps the concentration of sugars in the phloem near sink cells low, and thus maintains the pressure gradient that moves sap from sources to sinks.

sink

The location where a substance is used or stored.

dormancy

•  A period when growth is not occurring, usually because conditions are too dry or too cold to support photosynthesis.

proton pump

• A membrane transport protein that actively transfers protons against their electrochemical gradient.

co transport

• Transport of two substances across a cell membrane by a membrane protein: one down its electrochemical gradient and one against its electrochemical gradient.

mycorrhizal fungi

•  Fungi that live in association with plant roots and exchange nutrients for sugars.

xylem

• The water-conducting tissue in the plant vascular system.

cohesion tension theory

• Tension created by menisci in leaves and the cohesion of water molecules throughout the vascular system draws water passively from roots to replace water lost when stomata open.

phloem

The sugar-conducting tissue in the plant vascular system.

bulk flow

• Movement of substances from areas of high pressure to areas of low pressure.

pressure flow hypothesis

• Movement of sugars from areas of high to low pressure, with high- and low-pressure areas in phloem created by the ATP-powered movement of solutes.