Students can go through AP Inter 1st Year Botany Notes 12th Lesson Histology and Anatomy of Flowering Plants will help students in revising the entire concepts quickly.
AP Inter 1st Year Botany Notes 12th Lesson Histology and Anatomy of Flowering Plants
→ Anatomically, the plant body is made up of different types of tissues.
→ The plant tissues are two types namely Meriste- matic and permanent.
→ A group of Immature cells which are in a state of Division are called meristematic tissues.
→ They may be apical or Inter calary or Lateral, based on the pisition.
→ A group of mature cells, which lost the power of division and acquire definite shape are called permanent tissues.
→ They are of three types namely, Simple, Complex and Special tissues.
→ A group of similar cells which perform same function are called simple tissues. They are Parenchyma, Collenchyma and Sclerenchyma.
→ A group of more than one type of cells and work together are called Complex tissues. They xylem and phloem.
→ Based on the structure and location, tissue systems are classified into three types. They are Epidermal tissue system, Ground Tissue system and vascular Tissue system.
→ Epidermial tissue system includes Epidermis, the stomata, Cuticle and Hairs.
→ The Ground Tissue system includes, tissues except Epidermis and vascular Bundles.
→ The Vascular Tissue System includes Xylem and phloem.
→ Vascular bundles may be collateral open (Dicot stem) collateral closed (Monocot stem) Radial (Roots) or Bicollateral (Cucurbita) type.
→ The Internal structure of Dicotylednous root shows Epidermis, cortex and stele. The stele shows xylem and phloem arranged radially and usually Tetrarch.
→ In the Internal structure of Monocotyledonous root, the stele shows xylem and phloem, arranged radially with Polyarch xylem.
→ In Dicot stem. Internally 15-20 Vascular bundles are present, arranged in one ring, called Eustele.
→ In Monocot stem, several vascular Bundles are present, Scattered irregularly in the ground tissue called attactostele.
→ In Dicot leaf. Internally Mesophyll is differentiated into palisada and spongy parenchyma where as in Monocot leaf, Mesophyll contains only spongy parenchyma.
→ Dicotyledonous stems and Roots Increase in Girth due to vascular cambium and Cork cambium is called secondary growth.
→ Intrafascicular cambium and Interfascicular cambium joined together to form cambial ring.
→ Spring wood and Autumn wood together called annual Ring. By counting the number of annual rings, the approximate age of trees can be estimated. This Branch of science is called Dendrochronology.
→ In older trees, the central part of the wood is dark brown and is highly durable called Heart wood or Duramen.
→ The peripheral part of the wood is light in colour and is known as sap wood.
→ The cortical cells become meristematic and form cork cambium or phellogen.
→ Phellogen, Phellem (Outer Cork), Phelloderm (Inner Secondary Cortex) together called periderm.
→ In old stem, lens shaped openings are formed called Lenticels, help in exchange of gases.
→ Annual ring : The spring wood and autumn wood that appear in a year as concentric ring in secondary organs of dicotyledons constitute annual ring. By counting the number of annual rings, the approximate age of trees can be estimated,
→ Autumn or late wood : The wood having vessels with narrow lumens is called autumn wood. It is formed in autumn season.
→ Bicollateral vascular bundle : Phloem is present on either side of the xylem separated by cambia.
→ Bulliform cells : These are the large, empty and colourless cells present in adaxial epidermis of isobilateral leaves. They help in rolling and unrolling of the leaves.
→ Casparian strips : These are water impermeable, waxy suberised bands deposited on tangential as well as radial walls of the endodermal cells.
→ Complex tissues : Permanent tissues having many different types of cells are called complex tissues.
→ Conjoint vascular bundle : This is one type of vascular bundle In which the xylem and phloem are present at the same radius of vascular bundle.
→ Endarch : The protoxylem lies towards the centre (pith) and the metaxylem towards the periphery of the organ. This type of arrangement of xylem Is found in stems.
→ Exarch : The protoxylem lies towards periphery and metaxylem lies towards the centre. This type of arrangement of primary xylem is found in roots.
→ Fibres : These are thick walled elongated and pointed cells of sclerenchyma generally occurring in groups.
→ Heart wood : The dark brown coloured central part of secondary xylem comprising of dead elements with highly lignified walls is called heart wood. It Is infiltrated with various organic compounds like tannins, resins, oils, gums, aromatic substances and essential oils. The heart wood does not conduct water but it gives mechanical support to the stem.
→ Lenticels : Lens shaped openings in the cork of woody trees are called lenticels. They show closely arranged parenchymatous cells. The lenticels permit the exchange of gases between the outer atmosphere and the internal tissues of the woody organs.
→ Meristems : These are specialised regions of active cell division in plants.
→ Periderm: Phellogen, Phellem and phelloderm are collectively known as periderm.
→ Phellem: Cork tissue formed from the cells cut off from the phellogen.
→ Phelloderm : Cells formed on inner side of cork cambium constituting secondary cortex.
→ Phellogen: It Is also called cork cambium which appears usually in cortex. This produces phellem and phelloderm.
→ Sap wood : The peripheral region of the secondary xylem Is lighter in colour and is known as the sap wood. It conducts water and minerals from root to leaf.
→ Sclereids : These are spherical, oval or cylindrical, highly thickened sclerenchymatous dead cells with very narrow lumens.
→ Simple tissues : Permanent tissues having all cells similar in structure and function are called simple tissues.
→ Spring or early wood : The wood having vessels with wide lumens is known as spring wood. It is formed in spring season.
→ Starch sheath : The endodermis is called starch sheath as the cells are rich with starch grains.
→ Stomatal apparatus : The stomatal aperture, guard cells and the surrounding subsidiary cells are together called stomatal apparatus.