Plant Anatomy Lecture Notes PDF

Plant Anatomy Prof. Soad Bayoumi the cell wall & the cytoplasm & the nucleus  Cell Wall It is a wall which encloses all the cell contents and regulates the passage of liquids & gases with the adjacent cells through middle lamella, pores and plasmodesmata coming through pore Cell wall chemical...

Plant Anatomy Prof. Soad Bayoumi the cell wall & the cytoplasm & the nucleus  Cell Wall It is a wall which encloses all the cell contents and regulates the passage of liquids & gases with the adjacent cells through middle lamella, pores and plasmodesmata coming through pore Cell wall chemical composition Cellulose, hemicellulose, pectin, lignin, suberin and cutin Plant tissues are classified into Meristematic tissues Tissues where cells are constantly dividing are called meristems or meristematic tissues. These regions produce new cells. These new cells are generally small, six-sided boxlike structures will grow to many different shapes and sizes, depending on the needs of the cell. 1. Apical meristems 2. Lateral meristems  Apical Meristems These meristems are located on the tip of the root, stem etc. They help in the growth of the root system as well as the shoot system. The various cell divisions along with the cellular enlargement help in the growth (increase lenghth)of the stem above the ground and the growth of the root below the ground. Lateral Meristems present on the lateral side of the stem and root of a plant. These meristems help in increasing the thickness of the plants. The vascular cambium (xylem and phloem) and the cork cambium are examples of a lateral meristematic tissue. Secondary cortex Nonmeristematic tissues (permanent tissue) made of cells that are produced by the meristems and are formed to various shapes and sizes depending on their function in the plant and do not have the ability to produce new cells.  Parenchyma the most abundant of cell types found in almost all major parts of higher plants basically, sphere shaped and have thin cellulosic walls with intercellular spaces. may contain various secretions including starch, oils, tannins, and crystals. Modified parenchyma as - Chlorenchyma - Aerenchyma - Boundary parenchyma (epidermis, endodermis) - Storage parenchyma  Types of calcium oxalate in plants Styloid crystals of ca-ox Prisms and twins of In quillaia bark ca-ox in Hyoscyamus leaf Clusters of ca-ox In datura leaf Raphides of calcium oxalate in squill Crystal sheath in senna leaf Crystal layer in datura leaf  Epidermis - It is a protective layer (always single layer) - The cells are tabular without intercellular spaces except for the stomata, usually bigger in the upper than the lower epidermis - In surface view the cells are polygonal and isodiametric - The epidermis is covered by thin or thick protective film called cuticle.  Trichomes (Hairs) - Extension to the outside of the epidermal cells which my be very short and conical (papillae) or long and protruding (trichomes) - The trichomes are either non-glandular (covering) or glandular with a stalk and swollen head formed of one or more secreting cells (Volatile oil)  Stomata Each stomaEachconsists stomaofconsists two of two similar cells similar cellscalled calledguard guard cells (smaller than cells (smaller than epidermal epidermal cells containing chloroplast cells containing chloroplast and usually starch granules), parallel to and usuallyonestarch granules), another and enclosing between parallel to one themanother a small and lenticular or oval space called osteole. enclosing between them a small The cell surrounding the lenticular stomata areordifferent oval spacefrom the remaining called osteole. epidermal cells and called subsidiary cells The cell surrounding the stomata are different from the remaining epidermal cells and called subsidiary cells  Collenchyma belongs to supporting ground tissues. It is mostly found in leaves and stems. In leaves, it forms strands usually found above and below the midrib. In stems it forms a closed cylinder right beneath The epidermis or under the outer parenchyma layers. Their cell wall is thick composed of cellulose without intercellular spaces This tissue type of high tearing resistance provides flexibility.  Sclerenchyma type of mechanical ground tissues. In all parts of the plant. With non-living cells with thickened lignified cell wall. (Lignin is deposited into the secondary walls of the cells, what causes its death). A.Fibers sometimes found in association with a wide variety of tissues in roots, stems, leaves and fruits. elongated cells with and thick lignified walls with pointed ends and narrow lumen. B. Sclereids or stone cells Isodiametric cells and have very thick lignified cell walls. The main function of stone cells is to provide the plant with strong resistant and inflexible protection.  COMPLEX TISSUES Vascular tissue system made up of of varius type of cells (living and non-living cells) which perform different functions. The complex tissues act as single units and are also known as vascular tissues. Primary vascular elements derive from the procambium, while secondary vascular elements are produced by the cambium during the process of secondary thickening. procambium gives rise to the protoxylem and the protophloem, later it cuts off the elements of the metaxylem and the metaphloem. protophloem cells have typically thin cellulose walls They are of two types: Xylem and Phloem. Structure of wood (xylem) It is a conducting tissue and is composed of four different kinds of elements Fibres Tracheids Vessels Wood parenchyma  Tracheids Elongated cell with no sharp pointed ends when it is mature it is nonliving with lig. and different thickening walls Vessels Water conducting tube, formed from number of cells placed end to end, by partial or complete disintegration of their end-wall With thick lig. Wall (annular, spiral, reticulate, scalariform and pitted). scalariform pitted Wood parenchyma For food storage and conduction Elongated cell placed end to end with thin lig. Pitted wall Living containg starch, ca-ox,oil…etc b. Phloem or bast another type of conducting tissue like xylem which is responsible for conduction of organic substances. The phloem from the procambiunm is called primary phloem and that formed from vascular cambium is called secondary phloem The phloem is composed of four elements: a. Sieve tube elements b. Companion cells c. Phloem parenchyma (Bast parenchyma) d. Phloem fibers (Bast fibers) Phloem No Nucleus Has Nucleus Plasmodesmata  Medullary rays Radially elongated cells, with pitted wall For food storage and conduction Uniseriate-multiseriate containg starch  Plant tissues Non-Meristematic Meristematic (Permanent) Lateral Apical Complex Simple Xylem Phloem Parenchyma Collenchyma Sclerenchyma  Secretory structures External secretory Internal structures secretory structures Secretory Secretory Secretory Laciferous cells glands ducts str.  A. Secretory cells (idioblasts) single cells involved in secretion/accumulation include tanniferous cells, pigmented cells, crystalliferous cells, mucilaginous cells, and silica cells. One of most common types of secretory cells is called (oil cells) The cells may be isodiametric or less or more elongated into sac, tubes or branched Oil cell B. Secretory Cavities (Internal Glands) Special internal structure impeded in a mass of tissue and having cavities within which secretions as volatile oil, oleoresin, etc. They classified into Schizogenous Lysigenous Schizo-Lysigenously  Schizogenous developed by separation of cells thus enclosing a cavity which then become enlarged and and lined by secretory epithelial ▪ Lysigenous developed by breakdown of cells forming cavity (autolysis) that release secretion products as they degenerate. Schizo-Lysigenously The cavity develops at first schizogenously & later on increases in size by breaking down of the surrounding cells which produce the secretion C. Secretory Ducts or Canals Tube like structure containing secretions (as volatile oil in vittae of family Umbelliferae as anise fruit) They developed schizogenously D. Lactiferous Structures Cells or vessels contain latex (viscus emulsion or suspension of variable composition)