Dermal Tissue System Flashcards
What is the role of the dermal tissue system?
The dermal tissue system provides protection around the outside of the plant.
Which meristem produces dermal tissue?
The protoderm produces dermal tissue.
What are some of the components of the dermal tissue system?
the dermal tissue system includes…
- Waxy cuticle
- Trichomes (glandular or hairlike) (outgrowths of epidermal cells)
- Unspecialized epidermal cells (pavement cells)
- Stomata (specialized guard and subsidiary cells).
Later on, may include periderm covering epidermal cells.
What are the responsibilities of the dermal tissue system?
- UV protection
- Protection from herbivores
- Water and gas exchange
What is the cuticle?
The cuticle is a waxy layer continuously secreted by epidermal cells
minimizes water loss and may deter grazers + keep out pathogens; fatty substances they can’t break down. Can funnel excess water off leaves. Very resistant to decay.
May be overlaid with epicuticular wax.
How thick is the dermal tissue system?
Usually no more than a few cell layers thick.
What are trichomes?
Single or multicellular outgrowths.
Glandular (round dots) or hairlike form.
Root hairs are a type of trichome: outgrowth of epidermis.
How might trichomes be useful in the content of water?
Trichomes can prevent water loss through the stomata by creating a humid environment and trapping air with hair-like structures.
May also be possible for trichomes to absorb water and minerals (root hairs, airplants, bromeliads)
What are the functions of trichomes?
aim to hinder insects or grazers: may secrete oils or make it hard for them to climb over the plant.
Can act as thermal insulation: trap warm air.
Non glandular protect against predators. Some are stinging: needle-like to deter predators, tip breaks and chemicals released into the skin of predator.
How does water and gas exchange occur through the dermal tissue system?
Using stomata.
What are stomata?
Stomata allow the exchange of water and gases through guard cells: a pair of specialized epidermal cells which form a stomate.
Stomata are pores which open and close, controlled by turgor pressure. The cells adjacent are subsidiary cells which feed in ions to help create osmotic gradient. Microfibrils traversing guard cells help give them their shape.
Which side of the leaf do stomata usually form on?
- Stomata usually form on the lower side of the leaf, to reduce water loss through evapotranspiration.
How do guard cells form?
Guard cells form through asymmetric cell division.
How does guard cell asymmetric cell division work?
One unspecialized epidermal cell undergoes asymmetric cell division to produce a guard cell mother cell. This cell then splits symmetrically to form two guard cells.
What are the phases of guard cell division?
a) interphase
b) prophase
c) metaphase
d) telophase and cytokinesis
e) cytokinesis
f) early interphase
g) interphase
h) cell enlargement
