Anatomy of flowering plants


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Anatomy of flowering plants

  3. 3. AnatomyStudy of internal organisation ofliving organisms Histology Study of tissues & tissue system in multicellular organisms
  4. 4. 1. TISSUE• Group of cells, having common origin Tissues Meristematic Permanent Tissue Tissues Simple Permanent Complex Tissues Permanent 1) Parenchyma Tissues 2) Collenchyma 1) Xylem 3) Sclerenchyma 2) Phloem
  5. 5. 2. MERISTEMATIC TISSUES• Cells have power of division• A. Characteristics of Meristematic Tissues Cells are thin walled Have abundant cytoplasm Retain power of division No intracellular spaces
  6. 6. B. Classification of meristems :• Based on position in plant body• (i) Apical meristems• Occur at apices• Differentiate into primary tissues• Cause increase in length• Axillary buds are present in axils of leaves
  7. 7. (ii) Lateral meristems :Arranged parallel to the sides of organs ofplantCells produced by them differentiateinto secondary tissuesCause increase in width of plant organe.g., Fascicular cambium & cork cambium
  8. 8. (iii) Intercalary meristems :Meristems occur in between mature/permanenettissuesProduce cells that form primary tissuesCause increase in lengthOccur at bases of internodes & leaf sheaths ofgrasses & other monocots;They regenerate parts removed by grazinganimals
  9. 9. Based on origin (i) Promeristems :Group of meristematic cells in embryo /seedlingsGive rise to primary meristems
  10. 10. (ii) Primary meristems :Formed from promeristemsCells produced by them differentiateinto primary / secondary permanenttissuese.g., Apical meristems, fascicularcambium & intercalary meristem
  11. 11. (iii) Secondary meristems : Formed at a later stage inthe life of plant frompermanent tissues by processof dedifferentiation, e.g., Corkcambium & inter-fascicularcambium
  12. 12. 3. PERMANENT TISSUES• Cells have lost power of division & become structurally & functionally specialised Characteristics : Cells have lost power of division Undergone differentiation into specific types for a particular function 2 types: (i) Simple permanent tissues ( Tissue composed of 1 type of cell) (ii) Complex permanent tissues ( Tissue is composed of more than 1 type of cell)
  13. 13. B. Simple Permanent Tissues :(i) Parenchyma Cells are thin- walled Isodiametric Retain capacity to divide at maturity No intracellular spaces Main function is storage When parenchyma cells contain a number of chloroplasts they are called chlorenchyma & when they are arranged with regular system of intercellular air spaces, they constitute aerenchyma Forms major component of any organ of plant
  14. 14. (ii) CollenchymaCells living at maturityCells are variously shapedCell wall is unevenly thickenedOccurs below epidermis of dicot stemCells may possess chloroplastProvides strength & flexibility to growing organs
  15. 15. (iii) Sclerenchyma Cells are dead at maturity Cell wall is lignified evenly Gives mechanical support to organsHas 2 types of cells :(a) SCLEREIDS (STONE CELLS) : Oval/spherical & have very thick walls with narrow lumen Occur in shells of nuts & in pulp of fruits & in tea leaves(b) FIBRES : Elongated & thick walled cells Generally occur in groups Present in xylem , phloem & cortex & pericycle
  16. 16. C. Complex Permanent Tissues :(i) XYLEM : Forms continuous channel Concerned with transport of water & minerals Provides mechanical support Composed of tracheary elements, xylem parenchyma & xylem fibres(a) XYLEM VESSELS : Long cylindrical tubular structures formed by many cells End walls of vessel members have either single large opening / perforation / several small openings Have thick lignified walls Vessles are dead at maturity & found in angiosperms only
  17. 17. (b) XYLEM TRACHEIDS : Elongated cells Overlap one another at their slanting ends Do not have perforation plates Have thick lignified walls Dead at maturity(c) XYLEM PARENCHYMA ; Thick/ thin walls of cellulose Only living components of xylem Involved in short distance transport Help in storage of sugars, starch, lipids & tannins
  18. 18. (d) XYLEM FIBRES ( SCLERENCHYMA)Dead elementsProvide mechanical supportXylem formed in primary plant body by procambium is called primary xylem1st formed primary xylem is called protoxylemLater formed is called metaxylemIn stems, protoxylem lies towards pith & metaxylem towards periphery ; suchan arrangement is called endarchIn roots, protoxylem lies towards periphery & metaxylem towards pith ; suchan arrangement is called exarchXylem constituents formed by fascicular cambium constitue secondary xylem
  19. 19. (ii) PHLOEM• Concerned with transport of organic substances• Composed of sieve elements, companion cells, phloem parenchyma & phloem fibres
  20. 20. (a) SIEVE TUBES: Formed by elongated sieve tube members Cross walls have number of perforations Mature sieve tube has peripheral cytoplasmFunctions are controlled by nucleus of companion cellsMembers are characteristically present in angiosperms
  21. 21. (a) SIEVE CELLS : Sieve areas are found to occurthroughout the end walls & lateral walls Cells are living, but lack nucleus Found in lower vascular plants
  22. 22. (c) COMPANION CELLS:Found in association with sieve tube membersSieve tube elements & companion cells are connected by pit fields Help in maintaining the pressure gradient
  23. 23. (d) PHLOEM PARENCHYMA : Cells are elongated & cylindrical Have dense cytoplasm & prominent nucleusStores food materials & other substances Absent in monocot plants
  24. 24. (e) PHLOEM FIBRES (BAST FIBRES) : Found along with other elements of phloem Elongated & thick walled cells Dead at maturity Absent in primary phloem 1st formed primary phloem is known as protophloem Later formed is known as metaphloemElements formed by fascicular cambium constitute secondary phloem
  25. 25. TISSUE SYSTEM IN PLANTS• 3 tissue sysytems: (i) Epidermal tissue system (ii) Vascular tissue system (iii) Ground/ fundamental tissue system
  26. 26. (i) EPIDERMAL TISSUE SYSTEM• Forms outermost covering of plant body• Consists of epidermal cells, epidermal appendages & stomata• Epidermis is outermost layer• Epidermis is single-layered• Each cell has small amount of cytoplasm & large vacuole• Outer surface is covered with thick layer• Cuticle prevents loss of water from aerial part of plants• Epidermis is interrupted by small pores called stomata• Stoma is surrounded by 2 guard cells
  27. 27. • Guard cells are bean-shaped in dicot plants & dumb bell in monocots• Outer wall is thin & inner wall is thick• They possess chloroplasts & carry out photosynthesis• Epidermal cells in their vicinity become specialised in their size & shape• Stomatal apparatus – stomatal aperture, guard cells & surrounding epidermal cells• Epidermis also bears appendages• Root hairs are unicellular elongation of epidermal cells of the root• Appendages on stem epidermis are called trichomes• Help in preventing water loss by transpiration• Glandular/ secretory in many plants
  28. 28. (ii)VASCULAR TISSUE SYSTEM• Includes xylem & phloem• They occur as discrete strands called vascular bundles• Occur along same radius, vascular bundle is called collateral• When strip of cambium is present b/w xylem & phloem – open vascular bundle• No cambium in vascular bundle – closed vascular bundle
  29. 29. • 2 phloem poles occur in a vascular bundle , separated from central xylem – bicollateral vascular bundle• Xylem & phloem occur along different radii, alternating with each other – radial bundle• When protoxylem is towards periphery & metaxylem is towards centre – exarch• When protoxylem is towards centre & metaxylem is towards periphery - endarch
  30. 30. (iii) GROUND TISSUE SYSTEM• Ground tissue – all tissues except epidermis & vascular bundles• Consists of simple permanent tissues• Parenchyma cells present in cortex, pericycle; pith & medullary rays• Ground tissue in leaves - mesophyll
  31. 31. My special thanx goes to my biology teacher Mrs AlermeluNatchair who gave and confirmedthis permission and encouraged me to go ahead.