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The upcoming discussion will update you about the differences between Primary and Secondary Xylem.
Difference # Primary Xylem:
1. It is formed from pro-cambium of apical meristem.
2. It occurs in the primary plant body of all vascular plants.
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3. Primary xylem is found in all types of organs.
4. It occurs towards the center.
5. Primary xylem occurs in patches.
6. The xylem is differentiated into two parts, protoxylem and meta-xylem.
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7. A radial system is absent.
8. Annual rings are absent.
9. There is no distinction into sapwood and heartwood.
10. Fibres are few or absent.
11. The tracheids and vessels are long and comparatively less thick-walled.
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12. All types of thickenings can occur in tracheary elements.
13. Tyloses are usually absent.
Difference # Secondary Xylem:
1. Secondary xylem is produced from lateral meristem, called vascular cambium.
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2. Secondary xylem is formed during secondary growth only.
3. It is restricted to stems and roots of only perennial dicots and gymnosperms.
4. It occurs towards the outer side of primary xylem.
5. Secondary xylem forms a cylinder.
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6. There is no such distinction.
7. It is traversed by a radial system of xylem rays.
8. It may show annual rings.
9. A distinction into sapwood and heartwood is found in large woody plants.
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10. Fibres are generally abundant.
11. The tracheids and vessels are comparatively shorter and more thick-walled.
12. Usually pitted thickenings occur in the tracheary elements.
13. The vessels and tracheids of older xylem get blocked by the development of tyloses.
