Lecture 4 Flashcards
seed:
consists of an embryo and nutrients surrounded by a protective coat
living seed plants are:
gymnosperms and angiosperms
what type of spore do seed plants produce?
two types of spores, which develop into either male or female gametophytes
megasporangia:
produce megaspores that give rise to female gametophytes
ovule:
consists of a megasporangium, megaspore, and one or more protective integuments
microsporangia:
produce microspores that give rise to male gametophytes
microspore:
develops into a pollen grain that consists of a male gametophyte enclosed within the pollen wall
fruit:
formed when the ovarian wall thickens and matures due to fertilization of an ovule
-Fruits protect seeds and aid in their dispersal
-Mature fruits can be either fleshy or dry
-Various fruit adaptations help disperse seeds
pollen:
pollen grains make water unnecessary for fertilization
seeds:
survive better than unprotected spores and can be transported long distances
what does the success of plants depend on?
their ability to gather resources from their environment and transport them to where they are needed
stems:
as conduits for water and nutrients and as supporting structures for photosynthetic leaves
branching:
There is a trade-off between growing tall and branching; the more energy invested into branching, the less energy available for growth in height
soil:
contains resources mined by the root system
root growth can adjust to local conditions
3 transport routes for water and solutes:
- apoplastic
- symplastic
- transmembrane
apoplastic route:
through cell walls and extracellular spaces
symplastic route:
where water and solutes cross a plasma membrane once and then travel through the cytosol
transmembrane route:
where water and solutes repeatedly cross plasma membranes as they pass from cell to cell
Plasma membrane permeability:
controls short-distance movement of substances
does active or passive transport occur in plants?
both
what do plant cell membranes have?
have ion channels that allow only certain ions to pass
4 ways solutes are transported short distances via transmembrane routes:
a. H+ and membrane potential
b. H+ and cotransport of neutral solutes
c. H+ and cotransport of ions
d. ion channeles
osmosis:
the diffusion of water into or out of a cell that is affected by solute concentration and pressure; high concentration to low concentration
water potential:
a quantity that includes the effects of solute concentration and physical pressure
megapascal:
Water potential is abbreviated by Ψ and measured in a unit of pressure called the megapascal (MPa)
Ψ = 0 MPa for pure water at sea level and at room temperature
do solute concentration or pressure affect water potential in plants?
both; pressure is physical and concentration proportional to molarity
turgor pressure:
the positive pressure exerted by the plasma membrane against the cell wall and the cell wall against the protoplast. This is maintained by hydrological movements that are based on osmotic diffusion
transpiration:
the loss of water vapor through the stomata and drives the transport of water and minerals from roots to shoots via xylem
active transport:
enables essential minerals to accumulate at much higher concentrations in roots compared to the surrounding soil
symplast/apoplast:
water can cross the cortex via
waxy Casparian strip of the endodermal wall:
blocks apoplastic transfer of minerals from the cortex to the vascular cylinder
what must water and minerals cross in the apoplast to enter the vascular cylinder actively and selectively to avoid toxin uptake?
plasma membrane of an endodermal cell
what does the transport of xylem sap involve?
transpiration
cohesion-tension hypothesis:
transpiration and water cohesion pull water from shoots to roots. Transpired water is replaced as water travels up from the roots
as water evaporates from leaves, higher to lower concentrations of water,
the air-water interface retreats into the mesophyll cell walls
The surface tension of water at the air-water interface creates a negative or positive pressure potential in pulling water up?
negative
what regulates the rate of transpiration?
stomata
guard cells:
open and close stomata to help balance water conservation with gas exchange for photosynthesis
what causes the stomata to open and close?
tugor pressure
turgid =
guard cells bow outward and the pore between them opens
flaccid =
guard cells become less bowed and the pore closes
hormone abscisic acid:
produces in response to water deficiency and causes the closure of stomata
how are sugars from sources transported?
sinks via phloem
process of translocation:
The products of photosynthesis are transported through phloem
sugar source:
an organ that is a net producer of sugar, such as mature leaves
sugar sink:
an organ that is a net consumer or depository of sugar, such as roots, buds, and fruits
where must sugar be loaded before being exported to sinks?
sieve-tube elements in phloem
companion cells:
enhance solute movement between the apoplast and symplast
Which reflects the correct relationship of water potentials for a typical tree on a sunny day?
leaf Ψ < trunk Ψ < soil Ψ
