Chapter 36 Flashcards
A plant organ in which sugar is being produced by either photosynthesis or the breakdown of starch. Mature leaves are the primary sugar sources of plants.
sugar source
A mutualistic association of plant roots and fungus.
mycorrhiza
The leading explanation of the ascent of xylem sap. It states that transpiration exerts pull on xylem sap, putting the sap under negative pressure, or tension, and that the cohesion of water molecules transmits this pull along the entire length of the xylem from shoots to roots.
cohesion-tension hypothesis
The exudation of water droplets from leaves, caused by root pressure in certain plants.
guttation
A plant organ that is a net consumer or storer of sugar. Growing roots, shoot tips, stems, and fruits are examples of sugar sinks supplied by phloem.
sugar sink
A component of water potential that is proportional to the molarity of a solution and that measures the effect of solutes on the direction of water movement; also called osmotic potential, it can be either zero or negative.
solute potential
The physical property predicting the direction in which water will flow, governed by solute concentration and applied pressure.
water potential
(1) An aberration in chromosome structure resulting from attachment of a chromosomal fragment to a nonhomologous chromosome. (2) During protein synthesis, the third stage in the elongation cycle, when the RNA carrying the growing polypeptide moves from the A site to the P site on the ribosome. (3) The transport of organic nutrients in the phloem of vascular plants.
translocation
Swollen or distended, as in plant cells. (A walled cell becomes turgid if it has a lower water potential than its surroundings, resulting in entry of water.)
turgid
The evaporative loss of water from a plant.
transpiration
Vascular plant tissue consisting mainly of tubular dead cells that conduct most of the water and minerals upward from the roots to the rest of the plant.
xylem
The pattern of leaf attachment to the stem of a plant.
phyllotaxy
Vascular plant tissue consisting of living cells arranged into elongated tubes that transport sugar and other organic nutrients throughout the plant.
phloem
A phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall; occurs when the cell loses water to a hypertonic environment.
plasmolysis
A water-impermeable ring of wax in the endodermal cells of plants that blocks the passive flow of water and solutes into the stele by way of cell walls.
Casparian strip
A component of water potential that consists of the physical pressure on a solution, which can be positive, zero, or negative.
pressure potential
The drooping of leaves and stems as a result of plant cells becoming flaccid.
wilting
The living part of a plant cell, which also includes the plasma membrane.
protoplast
In plants, the continuum of cytoplasm connected by plasmodesmata between cells.
symplast
A plant hormone that slows growth, often antagonizing the actions of growth hormones. Two of its many effects are to promote seed dormancy and facilitate drought tolerance.
abscisic acid (ABA)
A plant adapted to an arid climate.
xerophyte
Limp. Lacking turgor (stiffness or firmness), as in a plant cell in surroundings where there is a tendency for water to leave the cell. (A walled cell becomes flaccid if it has a higher water potential than its surroundings, resulting in the loss of water.)
flaccid
Pressure exerted in the roots of plants as the result of osmosis, causing exudation from cut stems and guttation of water from leaves.
root pressure
The force directed against a plant cell wall after the influx of water and swelling of the cell due to osmosis.
turgor pressure
A physiological cycle of about 24 hours that persists even in the absence of external cues.
circadian rhythm
The diffusion of free water across a selectively permeable membrane.
osmosis
The movement of a fluid due to a difference in pressure between two locations.
bulk flow
The dilute solution of water and minerals carried through vessels and tracheids.
xylem sap
A unit of pressure equivalent to about 10 atmospheres of pressure.
megapascal (MPa)
The uppermost layer of vegetation in a terrestrial biome.
canopy
A channel protein in a cellular membrane that specifically facilitates osmosis, the diffusion of free water across the membrane.
aquaporin
The sugar-rich solution carried through a plant’s sieve tubes
phloem sap
