IGCSE Biology Paper-3: Specimen Questions with Answers 317 - 318 of 358

Passage

Fig. is a drawing of a piece of plant tissue.

Type of Tissue

Question 317 (2 of 4 Based on Passage)

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Short Answer▾

The cells in this tissue do not contain some of the structures found in most plant cells.

State one structure that is missing from the tissue shown in Fig.

Explanation

Xylem sap consists mainly of water and inorganic ions, although it can also contain a few organic chemicals as well. The transport is passive, not powered by energy spent by the tracheary elements themselves, which are dead by maturity and no longer have living contents.

Question 318 (3 of 4 Based on Passage)

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What name is given to this type of tissue?

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Explanation

  • Xylem: The term xylem was first used by Nageli (1858) . Xylem is a conducting tissue which conducts water and mineral nutrients & is composed following:
  • Tracheid՚s: Term given by Sanio (1863) . They are elongated tubelike cells with tapering or rounded or oval ends and with hard and lignified walls. The cells are without protoplast and are dead on maturity. Tracheid՚s possess bordered pits. Maximum bordered pits are formed in gymnospermous tracheid՚s They also possess various kinds of thickenings, e. g. annular, spiral, scalariform, reticulate or pitted tracheid՚s.
  • Tracheae or Vessels: Vessels are rows of elongated tube-like cells, placed end to end with their end walls dissolved. Vessels usually do not occur in Pteridophyta and Gymnospermous xylems but in Pteridium, Selaginella (both Pteridophytes) and in Ephedra, Gnetum (Gymnosperms) vessels are present. In Angiosperms vessels are always present (Except Lotus, Wintera, Trochodendron)
  • Wood fibers: The long, slender, pointed, dead and sclerenchymatous cells. They possess mostly thickened walls and few small pits. They said the mechanical strength.
  • Wood (Xylem) parenchyma: The parenchyma cells which very frequently occur in xylem are termed wood parenchyma.

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