Sieve Tube Elements
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Differentiate between the following:
Sieve cells and tracheids
Callose plugs are formed during winter
in the end walls of tracheids
on the walls of vessels
on sieve plates
on the walls of sclereids
- Companion cells
- Sieve tube elements
- Tracheids
- Transfusion tissue
- Trichomes
- Guard cells
- Sieve elements
- Vessel elements
Balloon like expansions of xylem parenchyma into the lumen of the vessels in secondary xylem are called
plasmodesmata
pits
tyloses
lumen
Reason: Mature sieve tubes have parietal cytoplasm and perforated sieve plates.
- If both assertion and reason are true and the reason is a correct explanation of the assertion
- If both assertion and reason are true but the reason is not a correct explanation of the assertion
- If the assertion is true but the reason is false
- If both the assertion and reason are false
Given the diagram of L.S of a part of bark region of plant. Choose the answer with the correct combination of parts and alphabets.
A = hydathode, B = epithem, C = phellem, D = phellogen, E = phelloderm
A = lenticular opening, B = cortex, C = phellogen, D = phellem, E = phelloderm
A = stoma, B = secondary cortex, C = phellem, D = phellogen, E = phelloderm
A = lenticular opening, B = complementary cells C = phellem, D = phellogen, E = phelloderm
While xylem is always open and used for transport of water, phloem is open only when the food needs to be transported. Which of the following reasons supports this statement?
Sieve tubes have companion cells that control their activity. Xylem vessels have no such cells.
The sieve tube opening can be closed by callus, that can be dissolved when not needed.
Sieve tubes have valves that can open and close when needed
Sieve tubes have a large vacuole, no nucleus and a peripheral cytoplasm
