9.2.Transport in Angiosperms

1. Outline how root system provides a large surface area for mineral and water uptake by means of
branching:extensive branching of roots greatly increases overall root surface area exposed to extracellular fluid
root hairs: individual root epidermal cells grow extensive elongations greatly increasing the surface area of individual rot epidermal cells to extracellular fluid
2. List ways in which mineral ions in the soil move to the root
diffusion of mineral ions down concentration gradients
mass flow of water in soil carrying ions, when water drains through the soil
mineral ions move into fungal hyphae which grow around plant roots in mutualistic relationship, and then from the hyphae into the root
3.Explain the process of mineral ion absorption from the soil into roots by active transport
because the concentration of mineral ions is usually lower in the soil than in the root,active transport is used to concetrate mineral ions in the root
because active transport requires ATP, root epidermal cells are rich in mitochondria and require a supply of oxygen for cellular respiration
active transport:ATP oxidation provides the energy for protons to be pumped from the inside to the outside of root epidermal cell membranes which is chemiosmosis, producing a H+ membrane potential
cations, such as K+ are driven from the extracellular fluid into the intracellular fluid, through membrane channels by their electrical charge replusion from the H+'s concentrated in the extracellular fluid
anions such as NO3-, move from the extracellular fluid into the intracellular fluidm through membrane channels, by co transport with H+, which moves down its diffuion gradient
4.State that terrestrial plants support themselves by means of thikened cellulose,cell turgor, and lignified xylem
thickened cellulose:both xylem and phloem cells have thick secondary cell walls composed primarily of cellulose, providing rigidity
cell turgor:plant cell vacuoles have low water potential;water enters the cell and vacuole by osmosis, causing the cell to swell aagainst its wall with a pressure against the cell wall which provides rigidity
lignified xylem:vascular tissue cells reinforced with helical or ringshaped thickenings of the cellulose cell wall impregnanted with lignin, which makes the cell walls hard, providing resistancem to pressure
5. Define transpiration
the loss of water vapor from the leaves and stems of plants
6. Explain how water is carried by transpirtaion stream including:
-structure of xylem vessels
a.thick walled elongated vasuclar tissue cells
which are rranged end to end
connected by perforated end plates
b.xylem cells die at maturity
leaving a continous mictorube for transporting water and sisolved mineral ions
from the roots to the above ground portins of the plant
-Transpirtaiton pull
a.evaportaion:water vapor diffuses from the most air spaces of the spongy mesophyll where water potential is higher , to the drier air outside where water potential is lower and stomata
b.Cohesion as the spongy mesophyll air spaces lose water by evaportation water potential decreases
water flows through xylem where water potential is higher
through the mesophyll to the air spaces, down its water potential gradient
the cohesion of water molecules, due to hyrdgoen boding
enables transpirtation to pull water up the narrow xylem vessels
without these colum sof water breaking apart
c.adhesion
cell walls of xylem evessels are charged which attraact to water molecules
the adhesive matter of water to xylem vessels walls moves them up the stem against gravity
adhesion is important when sap starts to rise in plants that were leafless through the winter
adhesion also helps prevent the column of water filled xylem vessles from breaking
d.transpirtation
solar powered evapopration from the leaves
creates a continous transpirational pull
transmitted all the way from the leaves to the roots
7. State that gurad cells can regulate transpiration by opening and closing stomata
8.State that the plant hormone abscisic acid causes the closing of stomata
9.Explain how the abiotic factors light temperature, wind, and hmidity, affect the rate of transpirtaion in a typical terrestrial plant
light
1.guard cells close stomata in darkness, so transpiration is much greater in light
2.open stomata increases rate of diffusion of C02 needed for photosynthesis
3.but also increasing transpirational water loss through stomata
Temperature
1. rate of transpiration water loss through stomata is doubled for every 10 degrees celcius increase in temperature
2.higher temperature also increases the rate of diffuion and reduces the relative humidity in the air outisde of the leaf
wind
1. removes water vapor from leaf reducing water potential around elaf
2.thus increasing water potential graident between the leaf and its surroundings
3.therefore increasing the rate of transpirational water loss
humidity
1. as humidity idecreases, water potential around the leaf is reducded
2.thus increasing the water potential gradient between the leaf and its surroundings
3.and therefore increasing the rate of transpirational water loss
10.Outline four strucutural adaptions of xerophytes
-reducing leaves:minimizes water loss by reducing leaf surface area
-thickened waxy cuticle:minimizes water loss by limiting water loss through epidermis
-reduced number of stomata:minimizes water loss through leaves
-succulence:stems specialized for water storafe maximizes rention of water available during infrequent rains
11.Outline the role of phloem in active translocation of sugars and amino acids from the source
to sink (fruits, seeds, roots)
-translocation-the movement of substances from one part to another in the phloem
-symplastic route-sucrose manufactured in mesophyll cell travles in intracellularly to phloem sieve tube members
-apoplastic route-sucrose manfactured in mesophyll cells travels extracellularly to companion cells and STMs
a.proton pumps:driven by ATP, pump H+ into extracellular environment
b.sucorse enters companion cells and STMs by co-transport
C. as H+ moves down its concentration gradient back into companion cells and STMS
-pressure flow in a sieve tube:
a.loading of sucrose into the STMs at the source
b.reduces the water potential inside STMs causing water to enter by osmosis
c.absorption of water potential insideSTMs causing water to enter by osmosis
d.that forces the phloem sap to flow along the tube
e.gradient of pressure in the tube is reinforced by the unloading of sucrose
f.and the consequent loss of water, from the sieve tube at its sink