Formation of Secondary Medullary Rays - QS Study
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Formation of secondary medullary rays:

Secondary medullary rays are vertical plates of parenchyma cells running radically through the cylinder of vascular tissue in the stems and roots of plants. Medullary rays store and transport food materials.

(i) Secondary medullary rays are produced by the vascular cambium and terminate in xylem and phloem tissues.

(i.) Secondary medullary rays are formed from the cambium ring. They are formed by the activity of fascicular cambium.

(ii) During the process of the division of cambium, the cambium cuts out cells on both the outer and inner side.

(iii) The cells of same particular places of a cambium ring produce parenchyma tissue instead of xylem or phloem.

(iv) The narrow bands of parenchyma tissue run rapidly through secondary sylem and secondary phloem tissues.

(v) These narrow bands of parenchyma tissues are known as secondary medullae rays

Secondary medullary rays may be differentiated into xylem medullary rays and phloem medullary rays. These medullary or pith rays are essential for the radial conduction of the water, minerals and other organic substances. They transport the substances from centre to periphery.