Phelloderm (Secondary Cortex)

Phelloderm, also called secondary cortex, is the innermost component of the periderm - a living tissue resembling ordinary cortical parenchyma, produced centripetally (inward) by the phellogen as its counterpart to the outward-facing phellem. Because its cells remain alive and, in many species, retain chloroplasts, phelloderm is not merely structural the way phellem is: it can photosynthesise and store food, giving the periderm a living, metabolically active inner layer even while its outer cork layer is entirely dead. Phelloderm cells are also loosely arranged, with genuine intercellular spaces between them - the opposite of phellem's tightly packed, space-free arrangement - and they lack suberin altogether, so unlike phellem they offer …