The best known of the inhibitor hormones; inhibits growth and prolongs
Acid Growth Hypothesis
Explains phototropism by suggesting that increased acidity in the walls of
certain cells (stimulated by the hormone auxin) increases their flexibility
and expandability, so that more water can diffuse into the cells and cause cell
Movement of substances across cell membranes that requires energy expenditure on
the part of the cell; contrasts with passive diffusion, or osmosis.
The pathway from the root surface to the core by which water moves along cell
walls and through intercellular spaces, bypassing the cells themselves.
One in a class of plant hormones that stimulates (among other things) cell
elongation, secondary tissue growth, and fruit development.
One in a class of plant hormones that promotes cell division and tissue growth.
Plant in which blooming is not affected by photoperiod, so that flowering
occurs independently of the duration of day and night.
A plant hormone that controls fruit ripening and promotes senescence (aging).
Name given to the hypothetical hormone that might control flowering in plants.
One of a class of plant hormones that stimulates stem elongation, germination,
and conversion of the embryonic food source into usable sugars.
Reaction of a plant to gravity; a stem grows against gravity, roots toward
A hormone is a chemical that affects the ways in which an organism functions; it
is produced in one part of the plant body but, by traveling to target cells
throughout the body, affects many other parts as well.
One in a class of plant hormones that inhibits growth and prolongs dormancy in
buds and seeds.
Hormone-stimulated leaf loss; caused by the formation of a weak, thin-walled
abscission layer at the base of the leaf.
Plant in which blooming is affected by photoperiod so that flowering occurs
when the hours of darkness in a 24-hour photoperiod fall below a certain level.
The passive diffusion of water across a membrane. Osmotic concentration refers
to the concentration of solutes (dissolved substances) in the water; when the
osmotic concentrations of two regions differ, water will flow from the area of
low concentration to the area of high concentration. In contrast, the solutes
themselves will flow from areas of high osmotic concentration to areas of low
Vascular tissue composed of cells that are living at maturity; transports
the products of photosynthesis throughout the plant body.
An organism's response to the length of day and night within a 24-hour period
(photoperiod); in many plants, this phenomenon determines when flowering will
The process by which plants and other
light energy into vital organic materials.
The growth of a plant toward a light source, resulting from the rapid elongation
of cells on the dark side of the plant; stimulated by auxin.
Pigment in leaves that allows them to measure the duration of day and night.
The mechanism by which sugars are transported through the phloem, from
sources to sinks; dependent upon the high turgor pressure of sources
and the low turgor pressure of sinks.
An outgrowth of a plant root that provides an increased surface area for the
absorption of water and dissolved minerals from the soil.
Plant in which blooming is affected by photoperiod so that flowering occurs when
the hours of darkness in a 24-hour photoperiod rise above a certain level.
A living conductive cell of phloem.
Regions of the plant, such as growing tissues, that are in need of nutrients;
characterized by low turgor pressure.
Nutrient-rich region, such as a leaf, that supplies sugars for the rest of the
plant; characterized by high turgor pressure.
The pathway from the root surface to the core by which water enters the root
hair membrane and travels through the cytoplasm of adjacent cells, via
channels that connect their contents.
A cell that receives hormone signals.
Transpiration-Adhesion-Ttension-Cohesion; the mechanism by which scientists
theorize that fluids are pulled upward through the xylem (driven by
transpiration, the evaporation of water from the leaf, and the cohesion between
Reaction of a plant to touch; results from differential cell elongation.
The process by which a plant loses water to its environment through evaporation.
Long-term growth of a plant toward or away from a stimulus as a result of
differential cell elongation.
Relatively rapid, easily reversible plant movement, occurring in response to a
stimulus, that results from changes in turgor pressure in certain plant
The force that the contents of a plant cell exert on the cell wall after the
osmotic entry of water into the cell.
Mechanism of internal water and nutrient transport, made up of the vascular
tissues xylem and phloem, that is characteristic of
A conductile component (either xylem or phloem) of the system that transports
food and nutrients throughout the plant body.
The pressure that causes water to move across a membrane; water always moves
naturally from areas of higher water potential to those of lower water
Vascular tissue composed of cells that are dead at maturity; transports
water and dissolved minerals upwards from the roots to the shoot.