Plant water relations 1 Flashcards
what is hydrolysis?
the breakdown of bigger molecules into smaller molecules
why is water important to metabolic processes?
participates directly as a reactant in key metabolic reactions such as photosynthesis
water provides critical hydration for ______
enzymes
enzymes are always ____
proteins
what do enzymes need hydration
to carry out important biochemical processes and be functional
what is considered an important solvent?
water
water delivers ____ to roots and other plant parts
soil minerals
______ transport is the transport of soil minerals to the roots and other plant parts
xylem
water delivers sugars from the site of ______ to the site of ______
synthesis to utilization
________ transport delivers sugars from the site of synthesis to the site of utilization
phloem
_______ contributes to the most mass of the cell
water
how does water contribute to the most mass of a cell?
by filling and expanding the cell’s vacuole which comprises about 90% of the cell
what is responsible for turgor pressure?
the filling of the vacuole
plants must maintain _____ to remain erect
turgor
water is _____ yet _____
polar yet neutral
what makes a water molecule polar?
the asymmetrical electron distribution
neighboring water molecules _____ each other
attract to
water can form ______ bonds with other _____ groups
hydrogen bonds with other polar
______ are responsible for many unique and important properties of water
hydrogen bonds
what is water of hydration?
a tightly bound shell of water around proteins
what % of total cell water does water of hydration account for?
~5-10%
bound water or vital water are other terms for
water of hydration
water of hydration is critical for ____ and _____ of protein molecules and membrane structure
stability and activity
slight reduction of _____ is enough to cause severe alterations of protein/membrane structure
water of hydration
water has a _____ latent heat of vaporization
high
what is the energy needed to convert one gram of water to one gram of water vapor at 20C?
590 cal
what is evaporative cooling?
the reduction in temperature resulting from the evaporation of a liquid which removes latent heat from the surface the evaporation takes place on
where in horticulture crop production have you seen the practical use of evaporative cooling?
fan-pad greenhouse cooling system and cooling off buds
on a fan and pad cooling system is drier or wetter air better for most efficient evaporative cooling?
drier
how is evaporative cooling used to prevent buds in a late spring frost?
by delaying bud break
non-dormant buds need to get to certain heat units in order to break and grow. what prevents these heat units from occuring?
evaporative cooling
_______ is responsible for cooling of leaves during a hot summer day through transpiration
latent heat of fusion
does water have a high or low specific heat?
HIGH
what moderates the temperature around large bodies of water?
the high specific heat of water
_____ rapidly conducts heat away from the source of application
water
does water have a high or low thermal conductivity?
high
define latent heat of fusion
heat released when one gram water is converted to 1 g of ice
what is the latent heat of fusion for water?
80 cal/g of water
water ____ the object on which freezing occurs
warms
how can water be used to protect plants from freezing damages?
by sprinkling water at low volumes frequently
is the viscosity of water high or low
low
what keeps the viscosity of water low?
hydrogen bonds
what property of water facilitates water transport in plants?
viscocity
hydrogen bonding is responsible for the ____ properties of water
cohesive
define cohesion
attraction of like molecules to each other
define adhesion
the attraction of dissimilar molecules to each other
describe cohesion and water
water molecules attract to each other
describe adhesion and water
water molecules attract to solid phase stuctures
what two forces are crucial for water movement up the tall tree
adhesion and cohesion
high cohesive forces leads to
high tensile strength
does a water column remain in tact even under high tension/pull by a negative pressure?
yes
the attraction of water molecules leads to an extremely high
breaking point
define cavitation
breakage of water column
what is the driving force of movement into and through plants
water potential
what does water potential tell us?
which way water will move and gives us measure of general water status in plants
define water potential
the chemical potential of water
what kind of work in plants does water potential do
diffuse water through soil, move water across membranes, cause turgor pressure in cells resulting in growth, and pull water up trees
water potential is the thermodynamic way of defining ______ of water
free energy
water moves from ___ free energy to ____ free energy until an equilibrium is obtained
high to low
why is free energy of water lower in hypertonic solution
- because increasing solute concentration in water decreases the mole fraction of water in solution 2. mole fraction of water is directly proportional to the free energy of water
the ______ the solute concentration of a solution the _____ the water potential
high; lower
____ is the highest free energy (0)
pure water
__ Mpa = ___ bar = ___ atm
1; 10; 10
an increasing negative value for water potential is increasingly ____ water potential
lower
water ALWAYS moves from _____ water potential to ______ potential
higher to lower
define passive transport
movement along (down) the water potential gradient
is water potential electrically active or passive
passive
define active transport
movement against the water potential gradient
water potential=
solute potential + pressure potential
define osmotic pressure
the hydrostatic pressure as the volume of a solution increases
osmotic potential is defined as
the negative of the osmotic pressure
net water movement can be stopped or even reversed if
sufficient pressure is applied to equal or exceed the osmotic pressure
why is the term potential used rather than pressure
because isolated solutions have no pressure they only have the potential to do so
if any solutes are present solute potential is
negative
the higher the concentration of solutes the ______ the solute potential
more negative
