During the secondary growth in both stem and root, the peripheral tissues like epidermis, hypodermis and cortex are replaced by a new secondary tissue called the Periderm (bark). The periderm composed of three components: (1) Phellogen, (2) Phellem and (3) Phelloderm. The current post discusses the Similarities and Differences between hellem and Phelloderm with a Comparison Table.
(1). Phellogen: Phellogen is the cork cambium, a layer of meristematic tissue which produces the phellem and Phellogen together known as the periderm or bark.
(2). Phellem: Phellem is the actual cork, produce by the phellogen towards the outer side.
(3). Phelloderm: Phelloderm is the secondary cortex, produced by the phellogen towards the inner side.
Even though the phellem (cork) and phelloderm (secondary cortex) are produced by the same meristematic tissue (phellogen), they show many differences.
Similarities between Phellem and Phelloderm
Ø Both phellem and phelloderm are secondary tissues.
Ø Both are produced by the cork cambium – phellogen.
Ø Both are parenchymatous cells.
Ø Both form the component of bark.
Difference between Phellem and Phelloderm
Sl. No. Phellem Phelloderm 1 Commonly called as Cork. Commonly called as Secondary Cortex. 2 Produced by the phellogen towards the outer side Produced by the phellogen towards the inner side. 3 Composed of dead cells. Composed of living cells. 4 Cells are closely packed. Cells are loosely packed. 5 Main function is to provide protection. Main function is storage of food materials and ergastic substances. 6 Cells are highly suberized. Cells are not suberized. 7 Cells are impermeable to water Cells are permeable to water 8 Plenty of tannin occurs in the cells. Tannin deposition absent. 9 Pores or lenticels occur on the phellem. Pores or lenticels are absent in phelloderm.
(Image Source: CC Wikipedia)
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