PLANT ANATOMY

The science of the structure of the organized plant body learned by dissection is called Plant Anatomy. In general, Plant Anatomy refers to study of internal morphology, pertaining to different tissues. the study of plant cell and tissue structure The anatomy is one of branches of appearance Morphology where he teaches a plant form of the study of plant form apparent (abroad) is attributable to the taxonomy (Taxonomy= internal morphology) (Anatomy = internal morphology)

Plant tissues Systems Like other organisms, plant cells are grouped together into various tissues. These tissues can be simple, consisting of a single cell type, or complex, consisting of more than one cell type. Classification of tissues : Can be divided into plant tissue in the body based on the following : 1- Position 2- Type of cells 3- origin 4- Function

Tissue is a mass of similar or dissimilar cells performing a common function. :Tissues of Meristems Meristematic tissues are composed of cells that divide continuously

Function Meristems - Cell division - Cell elongation - Cell differentiation Classification of meristems Apical meristems: located at the growing points of stems and roots e.g. those present in stem and root apices. Intercalary meristems: present between two permanent zone, present at base of internodes e.g. sugarcane and maize. Lateral meristems : present laterally and cause increase in diameter of plant. Located parallel to the longitudinal axis of the member plant

Classification of meristems Apical meristems Intercalary meristems Lateral meristems

:Different types of mature tissues a- Parenchyma b- Collenchyma c- Sclerenchyma d- Epidermis h- Pericycle f- Endodermis j- Laticiferous tissue r- Cork (phellem) t- Tracheary tissue i- Sieve tissue s- Secretory structures n- Vascular tissue k –Nectaries

(Permanent Tissues (Mature Tissues The permanent tissues are formed by the differentiated cells, which become specialised to perform specific functions like protection, support, storage and conduction. The permanent tissues always differentiate from the meristematic cells, during the process of growth. The three kinds of mature tissues are dermal, vascular, and ground tissues. Primary dermal tissues, called epidermis, make up the outer layer of all plant organs (e.g., stems, roots, leaves, flowers). They help deter excess water loss and invasion by insects and microorganisms.

Types of Permanent Tissues The permanent tissues can broadly be distinguished into two types, namely 1. Simple permanent tissue: Tissues which are composed of two or more types of cells but contribute to a common function are called complex tissues. Xylem and phloem are the complex permanent tissues. They together form the vascular bundle. This tissue consists of only one type of cells, e.g. parenchyma, collenchymas and sclerenchyma. 2. Complex permanent tissue: This tissue is composed of more than one type of cells. Complex Tissue:

Parenchyma: Characters: 1- Simple living cells. 2- Have primary cellulosic thin wall with simple pits. 3- Have intercellular spaces. 4- They may be elongated, isodiametric or lobed.

1- In cortex and pith of stems and roots. Function: Occurrence: 1- In cortex and pith of stems and roots. 2- Associated with xylem and phloem. 3- In leaves and fruits. 1- In aeration. 2- In photosynthesis. 3- Storage of water, protein, minerals, etc.. 4- May become meristematic and divide.

2- Collenchyma Characters: 1- Simple living tissue. 2- Have primary cellulosic thick wall with simple pits. 3- May have intercellular spaces. 4- They are elongated cells.

Types: Lamellar: thickening on tangential walls. Angular: thickening on angles between the cells. Lacunar: thickening on walls facing the intercellular spaces.

Occurrence: Function: 1- Under epidermis of stems. 2- Cortical tissue and pericycle of leaves. They are plastic tissue used for mechanical support of soft plants.

sclerenchyma They are dead cells when mature with thick secondary walls, they are elastic tissue used for mechanical support. Sclerenchyma has two types; fibres and sclereids.

A- Fibres They are dead cells have pitted walled with narrow Lumina and pointed apices, xylary fibres are lignified while extraxylary fibres may be lignified or non-lignified.

B- Sclereids They are dead cells short, isodiametric, elongated or branched thick walled, pitted, lignified with branched lumina.

Vascular system in the plant Plants have two different types of 'transport' tissue Xylem and phloem. Both xylem and phloem are the vascular system. Xylem transports water and solutes from the roots to the leaves, phloem transports food from the leaves to the rest of the plant.

Xylem Xylem tissue : Water and mineral transport from roots to aerial parts (leaves) of the plant Xylem consists of : Tracheary elements . Tracheids . Vessels . Xylem fibers . Xylem parenchyma .

1- Vessels Each vessel is formed from a series of vessel elements jointed end by end, 2ry wall is deposited in different forms: a- Annular: 2ry wall deposits as rings in narrow vessels. b- Spiral: 2ry wall forms a spiral in slightly wider vessels.

c- Reticulate: 2ry wall forms network c- Reticulate: 2ry wall forms network. d- Sclariform: 2ry wall has elongated pits in vertical series. e- Pitted: 2ry wall is pitted and is formed in wider vessels. Functions: vessels are used for transport and mechanical support.

2- Tracheids Gymnosperms have tracheids only but in angiosperms the xylem consists of tracheids and vessels. The tracheids are shorter than vessels and have bordered pits on their common walls. The function of tracheids is water transport and mechanical support.

5- Phloem Phloem is the food conducting tissue which is formed of four elements; sieve elements, companion cells, parenchyma and fibres. Phloem tissue consists of : sieve elements : sieve cells . sieve tube . companion cell . Phloem parenchyma . Phloem fibes .

1- Sieve elements these include two types: a- Sieve cells: They are present in gymnosperms and lower vascular plants. They are long cells with tapering ends, having sieve areas on their walls. They have thin lining layer of cytoplasm, a large vacuole and they contain no nucleus.

They are present in angiosperms. b- Sieve tubes: They are present in angiosperms. They are arranged end by end in a long series. The common walls have sieve plate with sieve area. The sieve pores are transversed by protoplasmic strands which connect the protoplast of neighboring sieve elements. Sieve tubes contain no nucleus.

2- Companion cells these are special parenchyma cells associated with the sieve tubes of dicots and monocots. A sieve tube may has one or more companion cells. The sieve tubes and companion cells are connected by plasmodesmata. A mature companion cell has a nucleus, so there is a physiological relation between it and the sieve tube.

Functions of phloem : 1)sieve tubes transport organic compounds, 2)companion cells helps to regulate the metabolic activities of the sieve tube elements, 3)the phloem fibres give the plant mechanical strength, 4)the phloem parenchyma stores compounds such as starch.

Tissue Process What is moved Function Xylem Transpiration Moves water and minerals from roots to leaves التوصيل والدعامة Phloem Translocation Moves food substances from leaves to rest of plant التوصيل

6- Epidermis It occurs on the surface of plants and it is a complex tissue consisting of epidermal cells, stomata and trichomes (hairs).

Function of epidermis: 1- Protect the plant from water loss in transpiration. 2- It acts as boundary tissue surrounding the plant. 3- Exchange of gases through the stomata. 4- Storage of water and metabolic products.

1- Epidermal cells Shape: tabular in side view, isodiametric or elongated in surface view. Cell wall: straight, wavy walls.

Cuticle: epidermal cells are covered by an impermeable layer known as cuticle which varies in thickness. The cuticle may be smooth as in Stramonium or striated as in Belladonna. The cuticle is formed mainly of cutin which is an aggregate of modified fatty acids, partly combined with alcohols.

2) Stomata These are openings in the epidermis of stem and leaves. They occur in both surfaces or only on lower surface. In water plants they occur in upper surface. Types of stomata: The types are indicated either with regard to the characters of the guard cells or with regard to the epidermal cells surrounding the stomata.

3) Trichome Epidermal cells are sometimes extended outwards forming projections of variable shape and size. If it is short and conical it is called papillae and the epidermis is described as papillosed e.g. Coca, but if the projections are long and well protruding they form trichomes or hairs.

The part of trichome embedded in the epidermis is called foot while the free part is the body. Hairs are classified into glandular and non-glandular or covering hairs.

Non-glandular hairs

Unbranched Branched Unicellular e.g. cottony hair, cystolitic hair e.g. Lavender. e.g. Calendula. e.g.Cumin. e.g. Belladonna, stramonium Unbranched Non-glandular hairs 1- Simple branched 2- Stellate 3- Peltate: 4- Candelabra e.g. Karkadeh e.g. Olea Branched e.g. Tobacco. e.g. Verbascum

Glandular hairs

d- Branched stalk c- Pluriseriate stalk b- Biseriate stalk a- Uniseriate stalk e.g. Belladonna. Bicellular head e.g. Digitalis Unicellular head e.g. Mentha Multicellular head e.g. Labiaceous hair in Mentha clavate hair e.g. Belladonna Unicellular stalk Multicellular stalk e.g. Chamomile e.g. Cannabis. e.g. Hyoscyamus muticus