Xylem and Phloem in Plants

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Questions and Answers

What is the primary function of xylem tissue in plants?

Facilitating photosynthesis

Conducting water and dissolved compounds from roots to leaves (correct)

Storing starch and fats

Transporting nutrients from leaves to roots

Which of the following correctly identifies the types of cells found in xylem tissue?

Phloem parenchyma and companion cells

Xylem parenchyma, xylem fibres, tracheids, and vessels (correct)

Only vessels and tracheids

Root hairs and stomata

What function does xylem parenchyma serve in plants?

Conducting photosynthesis

Transporting food to non-photosynthesizing parts

Storing starch, fats, and other substances (correct)

Providing mechanical strength to roots

How does xylem parenchyma differ from other parenchyma types in tissue structure?

It can contain chlorophyll and other substances Signup and view all the answers

What happens to the cell walls of xylem parenchyma over time?

They thicken due to the deposition of lignin later in life Signup and view all the answers

Which misconception about xylem is incorrect?

Xylem is solely responsible for the transport of nutrients Signup and view all the answers

What type of xylem also serves as wood parenchyma?

Secondary xylem Signup and view all the answers

What provides mechanical strength to the plant?

Thick-walled parenchyma Signup and view all the answers

Which structure is primarily responsible for conducting water in xylem?

Tracheids Signup and view all the answers

Which characteristic is NOT true for xylem fibres?

Their cell walls are usually thin. Signup and view all the answers

What is another name for xylem fibres?

Wood fibres Signup and view all the answers

Which type of xylary fibre is characterized by a very narrow lumen?

Libriform fibre Signup and view all the answers

Which type of xylary fibre is intermediate between tracheids and libriform fibres?

Fibre-tracheid Signup and view all the answers

In primary xylem, where do xylem fibres originate?

From procambium Signup and view all the answers

How do the inner apertures of pit pairs in fibre-tracheids typically appear?

Slit-like Signup and view all the answers

Which type of xylary fibre lacks lignin or contains it in very small amounts?

Gelatinous or mucilaginous fibre Signup and view all the answers

What is the primary function of tracheids in vascular plants?

Conduction of water and minerals Signup and view all the answers

In which type of plants are tracheids exclusively found?

Pteridophytes and gymnosperms Signup and view all the answers

What type of pitting is characteristic of bordered pits in tracheids?

Scalariform pitting Signup and view all the answers

Which of the following is NOT a type of pit associated with tracheid walls?

Circular pits Signup and view all the answers

Which layer is described as highly hygroscopic in the secondary wall?

G-layer Signup and view all the answers

In what form do tracheids primarily occur?

Long and single-celled Signup and view all the answers

What type of thickening is observed in protoxylem tracheids?

Annular and helical thickening Signup and view all the answers

How do tracheids communicate with neighboring cells?

Via pits Signup and view all the answers

What is the primary function of vessels in plants?

Water conduction Signup and view all the answers

In which type of plants are vessels exclusively found?

Angiosperms Signup and view all the answers

Which of the following describes the shape of vessel units?

Long and cylindrical Signup and view all the answers

What type of pitting is NOT mentioned as a characteristic of vessel walls?

Random pitting Signup and view all the answers

Where do vessels originate in angiosperms?

Procambium and cambium Signup and view all the answers

What is the role of lignin in vessel cell walls?

Providing structural support Signup and view all the answers

What are the terminal ends of vessel members characterized by?

Being solid and non-perforated Signup and view all the answers

Which of the following best describes a perforation plate?

The part of a vessel member with perforations Signup and view all the answers

Study Notes

Xylem and Phloem

Xylem is primarily for transporting water and dissolved compounds from roots to stems and leaves.
Phloem transports food produced by photosynthesis from leaves to non-photosynthesizing parts like roots and stems.

Xylem Structure and Types

Xylem is a complex tissue composed of tracheids, trachea, xylem fibers, and xylem parenchyma, with functions of water and solute conduction and structural support.
Xylem and phloem form the conducting tissues in plants, both primary and secondary.
Primary xylem and phloem develop from procambium, secondary from cambium.

Xylem Parenchyma

Xylem parenchyma is a type of parenchyma that forms part of the xylem.
It's found in both primary and secondary xylem, originating from procambium and cambium, respectively.
Wood parenchyma is a term for xylem parenchyma in secondary xylem, with axial and radial arrangement, running parallel and perpendicular to the plant organ's axis.

Xylem Parenchyma Cells

Xylem parenchyma cells are typically irregular in shape, but can be rectangular, round, or oval.
Their cell walls are thin and mostly comprised of cellulose.
Over time, lignin can deposit on cell walls, causing them to thicken.
Pits frequently occur on the cell walls.

Xylem Parenchyma Functions

Xylem parenchyma stores starch, fats, and ergastic substances like crystals and tannins.
They sometimes contain chlorophyll.
The cells transport minerals, water, and other solutes.
Thick walled cells provide mechanical support when turgid.

Xylem Fibres

Xylem fibers, also called xylary or wood fibers, are long, elongated cells.
Their length usually exceeds their width greatly.
Xylem fibers have tapering ends that form a wedge shape.
Cell walls are typically thick, resulting from lignin deposition, and lumens are constricted.
Pits may be simple or bordered, occurring on the walls.
Xylem fibers may retain living contents for extended periods.

Tracheids

Tracheids are long, single-celled and non-living water-conducting elements of xylem, with strong, thick walls containing lignin,.
Tracheids are characterized by oblique or tapering ends, imperforate and mostly obtuse,
They are present exclusively in the xylem of pteridophytes and gymnosperms.
In primary xylem, tracheids originate from the procambium, while in secondary xylem, their development occurs from cambium.
Tracheids are angular in cross-section.
Lignin deposits unevenly; resulting in various forms of pitting: annular and helical in protoxylem; bordered and scalariform in metaxylem.
Tracheids are involved in water and mineral transport, giving strength and support.
They potentially store water as well.

Vessels

Vessels are long, cylindrical, and non-living water-conducting elements found mainly in angiosperms, with vertical rows of perforated cells.
Perforated end walls allow the formation of continuous tubes.
Vessel units have thick walls due to lignin deposition.
Vessels are found in both primary and secondary xylem and originate from procambium and cambium, respectively.
Perforation types include scalariform, opposite, and alternate, often present on the lateral walls.
Vessel units are also known as vessel members, vessel elements, or vessel units. Their end walls may be partially or completely unperforated.

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Description

Explore the essential roles of xylem and phloem in plant physiology. This quiz covers the structure, types, and functions of these vital vascular tissues, including details about xylem parenchyma. Test your knowledge on how these tissues contribute to water and nutrient transport in plants.