Presentation Plant AnatomyPresented to; Ma’m TayabaPresented by; Khadija MurtazaRoll No; 11031506-oo6Discipline; Botany(6th semester)

Epidermis and Epidermal Emergences

Epidermis;The epidermis is  "epi“in Greek meaning

"over" or "upon", which together with the dermis forms skin.

The epidermis is a single layered group of cells that covers plant’s leaves, flowers, roots and stems.

Structure of dermal tissue of leaf

Functions of epidermisIt forms a boundary between the plant and

the external environment. It protects against water loss, regulates gas exchange, secretes metabolic compounds, Absorbs water and mineral nutrients

(especially in roots) .

The epidermis of most leaves shows dorsoventral anatomy: the upper (adaxial) and lower (abaxial) surfaces have somewhat different construction and may serve different functions.

Woody stems and some other stem structures produce a secondary covering called the periderm that replaces the epidermis as the protective covering.

Discription;The epidermis is the outermost cell layer of

the primary plant body. In some older works the cells of the leaf epidermis have been regarded as specialized parenchyma cells, but the established modern preference has long been to classify the epidermis as dermal tissue, whereas parenchyma is classified as ground tissue. The epidermis is main component of the dermal tissue system of leaves and also stems, roots, flowers, fruits, and seeds; it is usually transparent.

Structure of dermal tissue of leaf;

Cells of epidermis;The cells of the epidermis are structurally

and functionally variable;Most plants have an epidermis that is a single

cell layer thick. Some plants which have periclinal cellular

division within the protoderm of the leaves, have an epidermis with multiple cell layers.

Examples; Ficus elastica  Peperomia

Cell differentiation in the epidermisThe plant epidermis consists of three main

cell types: 1-pavement cells, 2-guard cells and their subsidiary cells that

surround the stomata’ 3-trichomes,

Cell structure of leaf

Epidermal Emergences;Sharp projections modified on plant organ. An obvious adaptation against predation is

plant armature. Plant armature is properly termed as

an emergence.(These may be absent in reproductive

structures.)

Reasons of epidermal emergencesNatural selectionAdaptationEnvironmental effects

Plant Emergences;There are some plant’s emergences are

discussed which are as;Root hairsSpinesTrichomePrickles

Root hairs;Root hairs are lateral extensions of a single

cell and rarely branched.

Root hairs vary between 5 and 17 micrometres in diameter, and 80 to 1,500 micrometres in length.

Root hairs can survive for 2 to 3 weeks and then die off. At the same time new root hairs are continually being formed at the top of the root. This way, the root hair coverage stays the same.

Spines;A sharply pointed tough or woody structure is

called a spine.

Spines

Types;Some spine’s types are as;

stem spine: a spine is a modified stem axis (it may have leaf scars), which becomes determinate (i.e., it has a very limited period of growth).

leaf spine: a spine is a modified leaf or leaf primordium; also there may be a leaflet spine.

shoot spine: a spine is a modified stem and leaves. 

stipular spine: a spine is a sharp, modified stipule or stipel. 

petiolar spine: a spine is a modified petiole that remains after the blade is shed. 

root spine: a spine is a modified root that loses its meristematic apex and root cap.

bract spine: a spine is a modified leaf (bract) positioned below a flower or part of an inflorescence.

Trichomes;Trichomes  ( from the Greek

 trikhōma meaning "hair") are fine outgrowths or appendages on plants.

Example; Aerial surface hairs

Prickles; A small sharp pointed spine is known as prickle.

Some other emergences of plants

leaf emergence: a sharp projection is from the blade or petiole of a leaf, most commonly arising on the top or bottom of a principal vein or along the petiole.

stem emergence: a sharp projection is from stem axes, often associated with climbing or scambling habit.

fruit emergence: woody projection, sometimes with hooks, is on the outer fruit wall.

Inflorescence emergence: projection is from a bract.

bark emergence: projection is located on bark of the trunk or its branches.

Functions of emergences;Plant emergences have some functions which

are;• Protect from animals e.g spines. • These are the obvious adaptations against

predation .