CHAPTER 3: Plant-Water Relations Flashcards
For every ___ of organic matter
made by the plant, approximately _____ of water is absorbed by the roots, transported through
the plant body and lost to the atmosphere.
gram
500 g
A major difference between plant and animal cells that affects virtually all aspects of their relation with water is the existence in plants of the
cell wall
___ is essential for many physiological processes,
including cell enlargement, gas exchange in the leaves, transport in the phloem, and various
transport processes across membranes.
Turgor pressure
Turgor pressure also contributes to the rigidity and mechanical stability of
nonlignified plant tissues
Each cell contains a large water
filled
vacuole
In such cells the cytoplasm makes up only __ to ___ of the cell volume; the remainder is vacuole.
5 to 10%
Water typically constitutes ___ to ___ of the mass of growing plant tissues.
80 to 95%
most abundant and arguably the best solvent known
water
____ as a solvent, it makes up the medium for the movement of molecules within and between cells and greatly influences the ____, ____, ____ and other cell constituents.
Water
structure of proteins, nucleic
acids, polysaccharides,
Water forms the environment in which most of the _______ of the cell occur.
biochemical reactions
Plants continuously ____ and ___ water.
absorb and lose
Most of the water lost by the plant ____ from the leaf as the ____needed for photosynthesis is absorbed from the atmosphere
evaporates
CO2
On a warm, dry, sunny day a leaf will exchange up to ____ of its water in a __ ____.
100%
single hour
During the plant’s lifetime, water equivalent to ____ the fresh weight of the plant may be lost through the ____
100 times
leaf surfaces
Such water loss is called
transpiration
dissipating the heat input from sunlight
transpiration
Heat dissipates because the water molecules that escape into the atmosphere have ________, which breaks the bonds holding them in the liquid.
When these molecules escape, they leave behind a mass of molecules with _____ and thus a ___ of water.
higher than-average energy
lower-than-average energy
cooler body
For a typical leaf, nearly ___of the net heat input from sunlight is dissipated by transpiration.
half
In addition, the stream of water taken up by the roots is an important means of bringing ___ ____ ____ to the root surface for absorption.
dissolved soil minerals
Of all the resources that plants need to grow and function, ___ is the most abundant and at the same time the most ____ for agricultural productivity.
water
limiting
Water has special properties that enable it to act as a ___ and to be readily transported through the body of the plant.
solvent
Water has special properties that enable it to act as a solvent and to be readily transported through the body of the plant. These properties derive primarily from the
polar structure of the water molecule
The two intramolecular hydrogen–oxygen bonds form an angle of
105°
Oxygen has __ _____ in the outer orbitals; each hydrogen has one.
six electrons
The opposite partial charges (δ– and δ+) on the water molecule lead to the formation of ___ ____ ____ with other water molecules.
intermolecular hydrogen bonds
The water molecule consists of an
-oxygen atom covalently bonded to two hydrogen atoms
Reason why two O—H bonds form an angle of 105°
oxygen atom is more
electronegative than hydrogen
the weak electrostatic attraction between molecules; responsible
for many of the unusual properties of water
hydrogen bond
responsible
for many of the unusual properties of water
Because the oxygen atom is more electronegative than hydrogen, it tends to attract the electrons of the covalent bond. This attraction results in a
-partial negative charge at the oxygen end
-partial positive charge at each hydrogen.
Water is an excellent solvent: This versatility as a solvent is due in part to the ____ of the water molecule and in part to its ___
-small size
-polar nature.
The polar nature makes water a
particularly good solvent for ionic substances and for molecules such (2)
-sugars
-proteins
The extensive hydrogen bonding between water molecules results in unusual thermal properties, such as
high specific heat and high latent heat of vaporization.
the heat energy required to raise the temperature of a substance by a specific amount.
Specific heat
the energy needed to separate molecules from the liquid phase and move them into the gas phase at constant temperature –
Latent heat of vaporization
important component of temperature regulation in plants
transpiration
Water molecules at an air–water interface are more strongly attracted to neighboring water molecules than to the____ in contact with the ____.
gas phase
water surface
the energy required to increase the surface area.
Surface tension
not only influences the shape of the surface but also may create a pressure in the rest of the liquid
Surface tension
