Nutrient Transport in Plants Flashcards
Where does water containing dissolved mineral ions enter in land plants?
Through the root hairs
What is the transpiration stream?
The water column from the roots of the plant to the intercellular spaces of a leaf
What is transpiration?
evaporation of water from the stomata of leaves
How does water pass from the soil into root hairs?
Through osmosis as a result of the higher concentration of solutes in their cell sap
How does water pass from the root hairs, across the cortex to the xylem?
by 1 of 3 different pathways
- passing from one cell vacuole to the next by osmosis, through cell walls and all cell contents
- moving through the plasmodesmata (fine protoplasmic connections between neighbouring cells) from one cell to the next by osmosis
- moving between cells along and through the intercellular spaces and cellulose cell walls from cell to the next
What is an endodermal cell?
a cell of the central, innermost layer of living cells of the cortex in some land plants
What does water transport through the plant involve?
osmosis along a diffusion gradient from the leaves down to the roots and soil, root pressure causing water to move a limited distance up the stem until counteracted by the force of gravity, adhesion of water molecules to the walls of the vessels and tracheid and the spongy mesophyll cells, cohesion between the water molecules forming the thin water columns in the xylem and transpiration causing loss of water from the stomata of leaves
Why is the epidermis nearly waterproof and airproof?
It has a waxy outer surface of cutin which covers both surfaces of the leaf
What are guard cells?
Two modified epidermal cells surround each stoma. They occupy a small space but diffusion through the stomata is very efficient
What are factors affecting transpiration rate?
Light, temperature, humidity, wind and soil water
What is transolcation?
Movement of organic solutes in the phloem in any direction; also a chromosome aberration in which a segment of DNA has been moved to another chromosome
What is the sieve tube?
the element of phloem functioning to transport organic molecules within the plant; consists of thin-walled, elongated living cells arranged in a longitudinal row and forming a connected series by means of perforations in their end walls through which pass strands of cytoplasm
What is observed of movement of solutes in the phloem?
movement is often more rapid than can be accounted for by simple diffusion, speed of movement differs in different phloem cells, direction of movement within a given sieve tube may be reversed, up to 35 degrees Celsius a rise in temp increases rate of transolcation
