Vasculature: xylem and transpiration Flashcards
what are vasc tissues
specialized in rpid and efficient movement of solutes and solvents throughout the pnat
what are xylem tissues
specialized in the movement of water throughout the plant
transport mineral elements
support
what are he types of xylem cells
tracheary elements
fibers
perenchyma cells
characteristics of the tracheary element cells
highly specialized unique cells
dead at maturity
lack of vacuoles, nucleus, cytoplasm
role of tracheary elements
create xylem
it is the death and hardeing of parenchyma cells
2 types of tracheary elemt cells
tracheids
vessel elements
what are tracheids
long narrow cells with a large surface area/volume ratio
considered to be the first vasc tissue evolved
found in all vasc plants
what are pit membranes
porous modified primary cell walls
allow water nut traps large molecules and gasses
how does water flow in tracheids
between them and through thepit membranes
when did vessel elemnts evolve
late in plant history
gnetidae have a form of vessel element that evolved differently
what are vessel elements
shorter and wider than tracheids
have specialized divisions between adjacent vessel elements
what are perforation plates
divides vessel elements
lacks primary and secondary cell wall
how does water flow in vessel elements
rapidly
what is a bad thing about vessels
they are more vulnerable to air embolisms
what are air embolisms
when a gas inside vasculature obstructs water movement
fiber cells are made of wghat
sclenrenchyma cells
what processes allow for bulk flow of water through the xylem
transpiration
adhesion/cohesion theory
where does all the water absorbed by the plant go
99% of the water is converted to water vapor and lost in the atmosphere aka transpiration
what does photosynthesis require
- max light exposure : large surface area of leaves relative to low volume inside the cell
- gas exchange: pores or stomata open passage between atmosphere and internal plant space
consequence of maximizing photosynthesis
maximizing water loss
how is water mainly lost in transpiration
through the stomata
what is a stomata
specialized dermal cells in the plant
what are guard cells
open and close stomata
controlled by environmental signals and solute concentrations in the cell
what is needed to open guard cells
increased turgor pressure in cells
how is turgor pressure increased
by drawing water into the celle through increasing the concentration of solutes in the guard cells
why is it important for plants to control the flow of water out of the plant
if it is unchecked, the plant will use up all the water inside it and not be able to replace it and wilt
is water transport in the plant active or passive
passive
how can bulk flow of watr be passive
thanks to water potential and natural chemical properties of water
where is water potential lower and higher in plants
lower =in leaves
higher= in roots
how does water flow
from cells with high water potential to low water potential
what is cohesion
attraction of 2 similar molecules to each other
what happens because of the slight polarity of water
+ charged at one and end - charged at the other
molecules attract each other and drag along other water molecules
what is adhesion in plants
water molcules are weakly attracted to the tracheary elements, adhere to them and pull other molecules along
what creates difference in water potential in the plant
transpiration
water moving through the xylem is a solution made of what
solutes = mineral elements solvent = water
what happens to minerals when water evaporates
the minerals are left behind in the leaves and it creates an area of significant low water potential
what is cohesion tension theory of water movement
combination of transpiration facilitating the movement of water in the plant and the cohesion/adhesion concept
when does transpiration stop
- plant needs to conserve water and closes stomata
- air is so humid that little transpiration takes place
what is root pressure
when roots actively import ions into the xylem and create a new gradient from roots to xylem water potential
