Final answer:
When the primary epidermis of a stem is shed, the plant protects the exposed cortex tissue using periderm, which develops cork cells that form a protective substance called suberin, creating a new barrier known as bark. The cuticle also aids in minimizing water loss, and additional structures like trichomes help deter herbivory and further reduce transpiration.
Step-by-step explanation:
When the primary epidermis of a stem is shed or damaged, the exposed tissue becomes vulnerable. However, plants have a way of protecting this newly exposed tissue. Beneath the epidermis in woody plants lies the periderm, which includes the cork cambium.
The cork cambium generates new cells that become cork cells. These cells produce a substance called suberin, which makes the cells impervious to water and gases, essentially protecting the stem much like the epidermis did. Over time, these cork cells form a protective barrier known as bark, which prevents water loss, protects against pathogens, and mitigates physical damage. The cuticle, a waxy covering on the epidermis, similarly aids in protection by minimizing water loss.
Plants can also develop additional layers of epidermis or increase the thickness of the cuticle in response to very hot or cold conditions, further safeguarding against water loss and environmental stresses. Moreover, structures such as trichomes (hair-like extensions) can deter herbivory and reduce transpiration. This adaptive capacity to fortify the dermal tissue ensures that plants maintain their structural integrity and physiological functions even after the primary epidermis is compromised.