Lenticel

A lenticel is a porous tissue consisting of cells with large intercellular spaces in the periderm of the secondarily thickened organs and the bark of woody stems and roots of gymnosperms and dicotyledonous flowering plants.

[4] Before there was much evidence for the existence and functionality of lenticels, the fossil record has shown the first primary mechanism of aeration in early vascular plants to be the stomata.

Parichnoi were thought to eventually give rise to lenticels as they helped solve the issue of long-range oxygen transport in these woody plants during the Carboniferous period.

They also acquired secondary connections as they evolved to become transversely elongated to efficiently aerate the maximum number of vertical rays as well as the central core tissue of the stem.

[6] The evolutionary significance of parichnoi was their functionality in the absence of cauline stomata, where they can also be affected and destroyed by pressure similar to what can damage to stomatal tissue.

The development and increase in the number of these primitive lenticels were key to providing a system that was open for aeration and gas exchange in these plants.

[7] In plant bodies that produce secondary growth, lenticels promote gas exchange of oxygen, carbon dioxide, and water vapor.

[10][11] In oxygen deprived conditions, making respiration a daily challenge, different species may possess specialized structures where lenticels can be found.