Water Transport and Plant Signaling

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Transcript Water Transport and Plant Signaling

Water Transport and Plant
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.
• 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
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
Transpiration Regulation
• Guard cells, when turgid bow out and open
• Day light or decreased CO2 cause stomata to
• 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
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 – 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- promote stem elongation, fruit
production, and germination.
• 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 – causes fruit to ripen, helps seedlings
grow around obstacles, apoptosis
(senescence), and causes leafs to fall
• Florigen- hypothetical flowering hormones
Short day and Long day flowers grow on the
same plant when grafted.
• 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
• 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 don’t rely on photo period (rice)
• Gravitropism- plant response to gravity
• Roots respond positively
• Stems respond negatively **
• Thigmotropism – plant response to touch
(vines) **