Secondary Xylem-Wood-6

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Gymnosperm Secondary Xylem

The secondary xylem of gymnosperms  is relatively simple. The axial system is composed of tracheids. The tracheids have different traits which depends on the overall growth status of the plant. Early wood which has tracheids with large diameters is produced during periods of rapid growth. Late wood tracheids with thick walls are produced during periods of stress. The alternation of early and late wood results in growth rings. Gymnosperm tracheids have well developed Bordered Pits which act like valves between adjacent tracheids.

Axial parenchyma is rare or absent.

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Transverse Sections through Pinus Secondary Xylem

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Tangential Sections through Pinus secondary Xylem

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Radial Sections through Pinus Secondary Xylem

Macerated Pinus Secondary Xylem which shows the relative homogenity of its Tracheids

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Bordered Pits in Pinus Tracheids

 

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Podocarpus Transverse section showing Secondary Xylem & Phloem Trasnsverse section of Podocarpus Secondary Xylem showing the relative uniformity of the Tracheids which comprise it.