1.

Differentiate between the following:1. Sieve cells and Sieve tubes 2. Sclereids and fibres 3. Tracheids and vessels 4. Sclerenchyma and parenchyma

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1.

Sieve cellsSieve tubes
Sieve cells have no companion cellsSieve tubes always have companion cells
Sieve areas do not form sieve platesSieve areas are confined to Sieve plates
Cells are elongated and are unique long with tapering end wallsCells consist of vertical cells placed one above the other forming long tubes connected at the walls by sieve pores
Sieve pores are smaller and numerousSieve pores are larger and fewer in number
Sieve cells are found in pteridophytes and gymnospermsSieve tubes are found in angiosperms

2.

SclereidsFibre
Usually broadElongated narrow thread like
End walls bluntEnd walls tapering
Occur singlyOccur in bundles
Deep pitNarrow pits

3.

TracheidsVessels
Formed from single cellsMade up of number of cells
Ends are oblique and taperEnds are round and transverse
Fraction of a cm in lengthSeveral cms in length
Walls are thick,lumen-narrowWalls are less thick,lumen- wide

4

SclerenchymaParenchyma
Cells are thick walled and lignified.Cells are thin-walled and unspecialised.
Tissues are made up of dead cellThese are living cells.
No intercellular spaces between the cells are found.Cells are usually loosely packed with large intercellular space.
Provides strength to the plant parts.Stores nutrients and water in stem and roots.
The cells are long and narrow, making the plant hard and stiff. The tissue is present in the stem around vascular bundles in the veins of leaves and the hard covering of seeds and nuts.Some cells contain chlorophyll called chlorechyma and perform photosynthesis. Other cells have larger air cavities called arenchyma which provide buoyancy to the hydrophytic plants.


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