transport in plants Flashcards
Diffusion
Diffusion is the spontaneous movement of particles or molecules from an area of higher concentration to an area of lower concentration. It occurs due to the random motion of particles and does not require energy input.
Facilitated diffusion
Facilitated diffusion is a type of passive transport in which molecules or ions move across a cell membrane with the help of transport proteins. These proteins create channels or carriers that facilitate the movement of specific substances across the membrane, following the concentration gradient.
Active transport
Active transport is the process by which cells move molecules or ions across a membrane against their concentration gradient. It requires the input of energy, usually in the form of (ATP). Active transport allows the cell to accumulate substances or maintain concentration gradients that are different from the surrounding environment.
Osmosis
Osmosis is the movement of solvent molecules, typically water, across a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration. It occurs to equalize the concentration of solutes on both sides of the membrane and can be important for maintaining water balance in cells and tissues. Osmosis does not require energy input.
Describe how water moves from the soil to xylem via the intracellular route and
the extracellular route
In the intracellular route, water moves from the soil to the xylem through the cytoplasm of root cells. It enters the root hairs through osmosis, driven by the concentration gradient. Once inside the root cells, water moves from cell to cell through the interconnected cytoplasmic channels or plasmodesmata. It crosses multiple cell membranes and continues its journey until it reaches the xylem vessels in the root.
In the extracellular route, water moves through the cell walls and intercellular spaces of the root tissue. It passes through the apoplast, which is the network of interconnected cell walls. This movement is driven by the cohesive properties of water and the capillary action. As water molecules adhere to each other (cohesion), they are pulled upward through the apoplast, creating a continuous column of water. Eventually, the water enters the xylem vessels, which are specialized transport tissues for water and minerals.
Both the intracellular and extracellular routes contribute to the overall movement of water from the soil to the xylem, providing a pathway for water absorption and transport in plants.
Describe how transpiration pulls xylem sap up the plant. Include terms cohesion,
adhesion, guard cells, and stomata.
Transpiration pulls xylem sap up the plant through a combination of cohesion, adhesion, guard cells, and stomata.
Water molecules in the xylem form a continuous column due to cohesion, where they stick together. When water is lost through the stomata (tiny openings on the leaf surface), it creates a negative pressure or tension in the xylem.
Adhesion allows water molecules to adhere to the walls of the xylem vessels, helping to counteract gravity and preventing the water column from breaking.
Guard cells surround the stomata and can open or close them to control the loss of water vapor. When the stomata open, water molecules can escape through evaporation, creating a pull on the water column in the xylem.
This transpiration pull, driven by the combined forces of cohesion, adhesion, and the opening of stomata, allows water to be pulled up the plant from the roots to the leaves, supporting the transport of nutrients and maintaining plant hydration.
Describe how sugar is moved from a source to a sink
Sugar is moved from a source to a sink in plants through a process called translocation. Sugar molecules, mainly in the form of sucrose, are actively loaded into the sieve tubes of the phloem at the source region. This creates a pressure gradient that drives the flow of sugar-rich sap through the phloem to the sink region. At the sink, sugar is actively unloaded from the phloem and utilized or stored in surrounding cells for growth, metabolism, or storage.
Water can follow two pathways in plants, extracellular and intracellular
routes. How do these pathways differ?
a) The extracellular route is for water; the intracellular route is for nutrients.
b) The extracellular route is entirely external to cell membranes except the
endodermal cell membrane; the intracellular route is inside of cells.
c) The extracellular route is for nutrients; the intracellular route is
for water.
d) The extracelluar route is used in phloem; the intracellular route
is used in xylem.
b) The extracellular route is entirely external to cell membranes except the
endodermal cell membrane; the intracellular route is inside of cells.
In the extracellular route, water moves through the cell walls and intercellular spaces external to the cell membranes, except for the endodermal cell membrane. In contrast, the intracellular route involves water movement inside the cells.
If you added a chemical to leaves to stop stomatal opening, what would
happen to the xylem?
a) The xylem cells would die.
b) The water in the xylem would stop moving.
c) Phloem sap would leak into the xylem.
d) The xylem would swell.
b) The water in the xylem would stop moving.
If stomatal opening is prevented by adding a chemical to the leaves, it would lead to a decrease in transpiration. Transpiration helps create a negative pressure or tension in the xylem, which pulls water up through the plant. With stomata closed, there would be a reduced movement of water from the roots to the leaves. As a result, the water in the xylem would stop or significantly slow down its upward movement.
If a potato tuber sends sugar to the rest of the plant during spring but
receives sugar from the rest of the plant during summer, it moves from being
_____.
a) a source to a sink
b) a store of salts to lacking them
c) a below-ground structure to an above-ground structure
d) a vegetative organ to a fruit
a) a source to a sink
In spring, when a potato tuber sends sugar to the rest of the plant, it acts as a source. It produces and supplies sugar to support the growth and development of other plant parts. However, during summer, the tuber receives sugar from the above-ground parts of the plant, acting as a sink. It stores the excess sugar produced by the leaves through photosynthesis, which will be used for energy and growth in the future.
