Vascular System Flashcards
What are tracheids and vessel elements together called
Tracheary element
What kind of cell wall do to tracheids and vessel element have
Lignified cell wall
Where does differentiation takes place in xylem
In tracheary element
What happens in differentiation
Specification, enlargement, patterned cell wall deposition, programmed cell death and cell wall removal
How are pits different from pores?
Pits are the cavity in the secondary cell wall and pores do not have any wall.
What are the two types of perforation in the vessel element?
Simple and compound perforations are found. Compound perforation all of three types: -
Reticulate
Scalariform
Foraminate
Who lacks vessel in the xylem?
Gymnosperm
What kind of cell is xylem parenchyma? What is its function?
Xylem parenchyma is a living and thin walled cell. It helps in storage of starch or fat.
What are xylem fibres? What are their function?
They are highly thick and dead cells. They help in mechanical function. They are either septate or aseptate.
What are the two types of xylem fibres?
Fibre tracheids and libriform fibre
What are sieve tube elements?
They are elongated living cells.
What are the organelles that are lost after maturation of seive tube element?
They lose a nucleus tonoplast, golgi bodies and ribosomes.
What do mature seive tube element have?
They have SER, mitochondria and plastids.
What does a gymnosperm have instead of seive tube element and companion cell?
They have seive cells and albuminous cells.
What is the name of protein that phloem has that help in plugging the phloem?
P protein and callose
Where is p protein and callose are synthesized?
P protein synthesized in immature seive cells and callose synthesized in plasma membrane by callose synthase.
Which one is a reversible mechanism for plugging the sieve tube element?
P protein
What organelles does companion cells have?
They have a dense cytoplasm, mitochondria, nucleus, golgi bodies, ER and chloroplast.
What are the three types of companion cells?
Ordinary companion cell, transfer companion cell and intermediary companion cell
Where is phloem parenchyma absent in
Monocotyledons
What is Fick’s law?
J = -D (∆c/∆x)
What is a turgor pressure?
Pressure exerted outwards against the cell wall.
What is incipient plasmolysis ?
The first sign of shrinkage of protoplast
What is the relationship of water potential with solute potential
Inversely proportional
What are the three zones of development in roots
Zone of differentiation, elongation zone and meristematic zone
What are the two pressures that help in the absorption of water in the roots?
Hydrostatic pressure and transpiration
What are the three pathways in which the water moves from the cell?
Apoplastic, symplastic and transmembrane pathway
What is casparian strip made of?
Suberin
Who proposed cohesion tension theory?
Dixon and Jolly
What is cavitation or embolism?
Presence of a bubble in the xylem sap.
What are the three types of transpiration?
Stomatal, cuticular and lenticular transpiration
What happens when the blue light falls on the stomata?
When the blue light falls on the stomata, zeaxanthin activates signal transduction cascade that activates serine and threonine. They activate H+ ATPase and protons get pumped out. K+ and Cl- is taken in by proton chloride symporter. Malate synthesis and sucrose synthesis occur.
Why does stomata opens?
Due to turgor pressure
Transpiration ratio?
The ratio of the number of water molecules transpired to form a CO2.
What is the transpiration ratio of C3 C4 and cam plants
C3 500
C4 250
CAM 50
What is guttation
Exudation of water molecule via hydathodes at night
Why does guttation occur?
Due to positive hydrostatic pressure
What is the major pathway taken by water to reach xylem
Apoplastic
What is the major pathway to reach xylem taken by ions?
Symplastic
Functional unit of phloem
SE-CC complex
Major sink during early stage and major sink during reproductive stage
During early stage: Roots and leaves
Reproductive stage: tubers, seeds and fruit
What kind of sugars are present in the phloem sap
Sucrose, raffinose, stachyose and verbascose.
What are present in the phloem sap
Organic solutes, amino acids, inorganic acids, hormone, RNAs
Is sugar alcohol present in the phloem sap
Yes
Which sugar isn’t tolerated in the phloem sap
Glucose
Who gave pressure flow hypothesis and what was in it?
Münch gave the hypothesis. It said that mass flow of phloem sap occurred due to the pressure gradient between source and sink.
What is leakage retrieval mechanism
Loading and unloading occurs throughout the whole seive tube element
What is the name of the uniporter that transfers sucrose down the concentration gradient from mesophyll cell
SWEET
What is polymer trapping mechanism
Sucrose when symplatically enters the companion cell, it becomes raffinose. Since raffinose is a large molecule it can’t go back, hence it has to go to the seive tube element.
What is the major path from which phloem loading takes place
Symplastic loading
Nitrogen is found in which form in phloem?
Glutamate and aspartate
Which ion is most abundant in phloem?
Potassium
