Plant Anatomy Lecture Notes PDF

Introduction to Plant Anatomy Dr. Gehad Abd-Allah Ragab Dr. Gehad  Plant Anatomy The branch of science which studies the internal structure of the plant body. Importance of anatomical studies: 1. helps in understanding of how the plant body function...

Introduction to Plant Anatomy Dr. Gehad Abd-Allah Ragab Dr. Gehad  Plant Anatomy The branch of science which studies the internal structure of the plant body. Importance of anatomical studies: 1. helps in understanding of how the plant body functions. 2. help us in solving taxonomic problems. 3. Essential for pharmacognosy Dr. Gehad  Plant Body organization The plant body is made up of cells. Cells represent the smallest structural and functional units of life. The cells are organized into tissues. Tissues form different organs. Dr. Gehad  The plant cell is formed from the protoplasm surrounded by the cell wall which protects and supports it. Protoplasm Cell wall Shape Protection Support Strength Dr. Gehad  Cell wall structure Middle lamella The middle lamella is the first layer of the cell wall, formed at the end of the cell division and deposited between the newborn cells. It composed of pectin to adhere Middle lamella Dr. Gehad cells to each others forming tissues  Primary cell wall Thin, elastic, expand during cell growth Composed of cellulose fibers (polysaccharides) imbedded in matrix of: Pectin, hemicellulose, and protein Secondary cell wall rigid non- elastic formed after cell maturation. Besides cellulose, hardening agents are added including Dr. Gehad lignin, cutin, or subrin. Dr. Gehad The cell wall structure 1- The middle lamella is the first layer of the cell wall, formed at the end of the cell division and deposited between the newborn cells. It composed of Pectin to make cells adhere to each others forming tissues 2- The primary cell wall deposited on both sides of the middle lamella elastic and can be stretched, composed of cellulose fibers and hemi-cellulose layers. 3- The secondary cell wall rigid non- elastic layers developed by the deposition on the inside surface of primary wall after cell full growth. It composed of celluloses, hemicellulose and other hardening agents such as lignin, cutin, or subrin to provide strength. Dr. Gehad Pits: are definite pores left without deposition of cell wall components, commonly formed in pairs on 2 adjacent cells. Plasmodesmata is cytoplasmic strands pass through the pits to connect the neighboring protoblasms. transport materials and stimuli between cells Dr. Gehad  Pits Dr. Gehad  The Protoplasm and its components Protoplasm is composed of plasma membrane containing cytoplasm and different organelles (protoplasmic -living contents). 1- Protoplasmic -living contents Nucleus -It is surrounded by nuclear membrane (double-layered), - contains dense bodies (nucleoli) and chromatin diffused in the nuclear sap. - During cell division the chromatin becomes organized into chromosomes. Endoplasmic reticulum is a continuous membrane bound system of flattened sacs and tubules, sometimes coated with ribosomal particles. Mitochondria surrounded by double membranes for respiration as energy factory. Dr. Gehad  The plastids surrounded by double membranes and classified depending on their function: ❖Chloroplast is plastid contains chlorophyll the photosynthetic pigment and specialized for photosynthesis in all green plant tissues. ❖Chromoplast is a plastid contains colorful pigments and gives colors to plant organs (e.g flowers, fruits…). ❖Leucoplast is a non-pigmented (Lacking photosynthetic pigments), and located in non-photosynthetic tissues of plants, such as roots, bulbs and seeds. They are specialized for nutrients storage (starch). Vacuoles are cavities in the cytoplasm, surrounded by vacuole membrane known as tonoplast. It regulate the turgidity and osmosis of the cell. Dr. Gehad The Protoplasm and its components 2- Non-protoplasmic (non-living) contents Storage or waste compounds such as starch grains, protein, oil bodies and mineral matters in crystals-form. Starch grains formed in plastids called amyloplasts. Starch grains show layering around a point, the hilum. Concentric grains with hilum at the center branched or unbranched. Excentric grains with the hilum on one side and may be simple or compound. Dr. Gehad  Organic Starch grains Concentric Ex-centric Dr. Gehad Calcium oxalate crystals formed mainly within vacuoles of actively growing cells: Druses are aggregated crystalline structures precipitated around a nucleation point as stare-shaped. Raphides are bundles of calcium oxalate needle-like crystals that are borne in the same cell. Dr. Gehad  Plant tissues A tissue is a group of cells having a common origin and usually performing a common function. Meristematic Permanent Tissues are classified into two main groups, namely, meristematic and permanent tissues based on whether the cells being formed are capable of dividing or not. Growth activity in plants is largely restricted to specialized regions of active cell division called meristems Dr. Gehad  Plant Body organization Each plant seed has an embryo. On germination, the embryo gives an embryonic shoot (plumule), embryonic root (radicle) and one or two seed leaves (cotyledons). After growth activity, active cell division is largely restricted to specialized regions of called meristems. Dr. Gehad  Meristematic tissues Group of undifferentiated cells have the same origin and divide continuously. Properties of meristematic cells 1. The shape of the cells may be oval, rounded or polygonal. 2. Thin walls due to the absence of secondary wall 3. Large nuclei 4. Dense cytoplasm. 5. Absence or few small vacuoles 6. Lack of intercellular spaces Dr. Gehad Dr. Gehad  Types of meristems according to position 1- Apical meristems: located at the apex of stems and roots responsible for primary growth and increase length of the plant. 2- Intercalary meristems: Part of the apical meristems separated during development, -located between permanent tissues away from the apex. -It increase the plant organ length and finally turned into permanent tissue. Ex: at the nodes, and leaf bases 3- Lateral meristems: found parallel to the long axis of the plant organs, and are responsible for increasing the plant thickness. Dr. Gehad Dr. Gehad Dr. Gehad