Biology Questions and Answers
- Are the xylem and the
phloem made of living cells?
The cells that constitute the xylem ducts
are dead cells killed bThe cells of the phloem are living y lignin deposition.cells.
- What is the importance of
lignin for the xylem
formation?
Lignin is impdeposited on the cell wall of the xylemortant because it is (^)
cells providing impermeability and
rigidity to the xylem vessels.
- What is root pressure?
Root pforces water ressure is the pressure tfrom the soil to behat
absorbed by the xylem due to the osmotic gradient between theof the root. It is (^)
interior of the root and the soil.
- What is capillarity? How is
this phenomenon chemically
explained? What is the
relevance of capillarity for
water transport in plants?
Capillaritywhich water m is the oves insidphenomenon throughe extremely
thin tubes (capillaries) aided by the
attractionthe capillary wall. Th between water e capillaritymolecul es and
phenomenon is possible bis a polar molecule and formsecause water
intermolecular hydrogen bonds.
Therefore there is electrical attraction(adhesion fwall and the water orce) between the capillarymolecules that then (^)
pull each other (cohesion force) since
they are bound. Not jother liquids may move inside ust water bcapillariesut (^)
by capillarity.
Capillaritytransport of water in is not too relevant fplants. Itor the
contributes oascension. nly to a few centimeters of
- What are the forces that
make water to flow within the
xylem from the roots to the
leaves?
Water enters thpressure and a watee roots due to the rootr column is
maintained within the xylem from the
roots to the leaves. Tfactor that makes water ascenhe most importantd is
transpiration, mainly in the leaves. As
leaves lose watcells tend to attracter by transpiration th more water creatingeir (^)
suction iproperty onside the xylf water that keeps itsem. The cohesion
molecules bound (one pulls the other)
by hydrogen bonds helps the process.
- What is tree girdling?
What happens to a plant when
that girdle is removed from
the stem (below the
branches)?
Malpighi’s girthe removal frdling, or tree girdling, isom a stem of a complete (^)
external girdle containing the phloem
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