Download - Water Transport and Plant Signaling
Water Transport and Plant Signaling Proton Pumps Transport
proteins that pump H+ out
Membrane Potential is created, negative charge on the inside
positive on the outside. Protons end up flowing back into the
membrane, using their movement to do work. Cotransport The proton
gradient is used to actively transport other solutes in. Solute
Potential solute potential (osmotic potential) is proportional to
the number of dissolved solute molecules. (always negative)
Determines where osmosis takes water Pressure Potential Pressure
Potential- is the physical pressure on a solution. (negative or
positive) Determines where water is pushed or pulled. Water
Potential Water potential the combined effects of solute potential
and pressure potential. Determines where water will flow. Water
Pressure and Cells
Flaccid- has lost water Plasmolysis- shrinks and pulls away from
the cell wall (lower water potential outside the cell) Turgid-
swells and stays stiff agains the cell wall (lower water potential
in the cell) Paths to bring water in Apoplast- formed by connecting
cell walls
Symplast- connecting cytosol of cells Plasmodesmata- gaps that
connect neighboring cells Moving Water In Root pressure- water
flowing into the xylem from the root cortex due to ions in the
xylem** Water Up Transpiration the loss of water through
stomata
causing water (xylem sap) to be pulled up xylem (adhesion and
cohesion).** Transpiration Regulation
Guard cells, when turgid bow out and open stomata Day light or
decreased CO2 cause stomata to open Drought or flaccid cells cause
stomata to close Heat, wind, and dry condition cause excess water
loss. Moving water down Translocation- moving sugars down the
plants
Source cell- sugar producing (leaves), dumps sugars into sieve
tubes Water (phloem sap) is drawn into sieve tubes Sink Cell-
growing cells that consume sugars, takes sugars from the sieve
tubes. Plant Signaling Hormones and environmental cues are used for
signaling Auxin (IAA) Auxin- primarily causes young cell elongation
(loosens the cell wall) and lateral root formation, stops leaves
from falling, regulates fruiting, and causes vascular
differentiation. Cytokinins Cytokinins aid in stimulating cell
division
Auxin must be present with cytokinins to cause cell division The
ratio of Cytokinin to Auxin determines what undifferentiated cells
become, and control apical dominance. Gibberelins Gibberelins-
promote stem elongation, fruit production, and germination.
Brassinosteroids Brassinosteroids- similar affects as auxin. Also
prevents leafs from dropping and causes xylem to differentiate.
Abscisic Acid (ABA) Abscisic Acid inhibits plant growth. Keeps
seeds dormant, closes stomata during drought. Ethylene Ethylene
causes fruit to ripen, helps seedlings grow around obstacles,
apoptosis (senescence), and causes leafs to fall (abscission).
Florigen Florigen- hypothetical flowering hormones
Short day and Long day flowers grow on the same plant when grafted.
Phototropism Phototropism plant response to light
Blue light receptors controls things such as stem elongation and
stomata opening Phytochromes (red light receptors)- control things
such as seed germination and shade avoidance. Photoperiodism
Photoperiodism a plants response to a period of light. (like
flowering). ** Short Day plants flower in fall (soybean) Long Day
plants flower in spring (spinach) Day neutral dont rely on photo
period (rice) Gravitropism Gravitropism- plant response to
gravity
Roots respond positively Stems respond negatively ** Thigmotropism
Thigmotropism plant response to touch (vines) **