Experts, why do we include secondary phloem under bark even though secondary phloem comes under vascular cambium?

Dear Student,

Bark is the outermost covering of stems and roots of old plants. It includes dead as well as some living part of plant stem. It is used as wood. It consists of cork (dead outermost protective tissue of older stem), cork cambium, cortex and phloem. Cork cambium or phellogen develops in the cortex region. Everything outside the vascular cambium is therefore regarded as Bark. The cells of the cambium ring become active and cut off new cells both towards the outer side and inner side. Cambium ring cuts off secondary xylem towards the inner side and secondary phloem towards the outer side. Due to more activity on the inner side, the amount of secondary xylem is more than that the secondary phloem. The primary and secondary phloem gets crushed due to the continuous formation and accumulation of secondary xylem.


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