Module 7 - Epidermis Flashcards
Superficial layer of cells in young stems, roots, and foliar structures, as well as in flowers, fruits, and seeds. Undifferentiated in the apical meristem, absent in the root cap.
Epidermis
Functions of the epidermis
Functions:
Protection
Restriction of transpiration
Storage of water and various metabolic products, absorption, and photosynthesis
Strengthen and support the plant
Restrict entry and exit of organisms and toxic substances
Origin of the Epidermis
- From the outermost cell layer of the SAM
- If shoot apex has tunica corpus organization, it arises from the outermost layer of tunica
- In roots, epidermis may be related developmentally to the root cap
- Protoderm: primary meristem origin
Haberlandtʼs term “________” is the primordial epidermis.
Others define this as undifferentiated epidermis.
Organs with little or no secondary growth usually retain the epidermis as long as they exist.
Protoderm
Type of epidermis only one layer in thickness
Uniseriate
Type of Epidermis with several layers of cells
Multiseriate
T/F In Multiseriate Epidermis is always synchronized leading to more expanded inner than outer layers
False, Sometimes the division is unsynchronized leading to uneven layer thickening
Origin of the epidermis.
outermost layer of tunica
T/F The periderm is regarded as the primordial epidermis.
False, protoderm
Why are the inner epidermal layers more expanded that the outer epidermal layers?
Asynchronous cell division
A ground meristem derivative responsible for secreting cuticle and storing fat that resembles a multiple epidermis,
hypodermis
Function of the velamen radicum
Storage for epiphytic plants
Structures that prevent the widening of the stomatal aperture during stoma opening.
Stomatal Rings
Give the function of hydathodes.
Permanently open pores for water release in the form of dew.
Product of incomplete cell division that embeds itself into the epidermis
Cystolith
T/F Velamen is dead
True
Function of Velamen Radicum
store water and nutrients
resemble those of a multiple epidermis but are derived from the ground meristem.
Hypodermis
The cells have thin radial walls; the outer wall may be as thick or thicker than those of adjacent ordinary epidermal cells. The walls are composed of cellulose and pectic substances. The outer walls have cuticle, and the cells are highly vacuolated, containing water.
Bulliform Cells