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PLANT HISTOLOGY

PLANT HISTOLOGY

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PLANT HISTOLOGY

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  1. PLANT HISTOLOGY

  2. Only found in eukaryotic plants = specialized organells – uinque to plants Come in several forms Fx = involved in metabolism PLASTIDS

  3. Have a x2 (envelope) membrane 2 internal phases Membrane system Stroma/matrix Why are they called plastids? PLASTIDS: Structure

  4. Contain ribosomes Fx  mRNA translation in protein synthesis Also contain a small amount of DNA 3 main types of plastids Chloroplasts Chromoplasts Leukoplasts PLASTID: Function

  5. Chloroplasts contain chlorophyll Fx = photosynthesis THE CHLOROPLAST

  6. CHLOROPLAST – Structure

  7. CHLOROPLAST: Structure • highly developed membrane system • Tiny, flattened membrane-bound sacs  Thylakoids • Form grana • grana are rather important: as all the photosynthetic pigments are found within the grana. • Grana are connected to each other by fibres called • Stroma lamella

  8. Microscopy: Chloroplast plastids

  9. = the colour pigments which determines plant colour (green, yellow, red, orange, blue, etc) THE CHROMOPLAST

  10. Chromoplast plastids Capsicum annum

  11. Chromoplasts • Chromoplasts develop from mature chloroplasts. • Why don’t all chloroplast change into chromoplasts? • Fx = store pigment. • Pigment is formed when thylakoids and the stroma lamella break down.

  12. Chromoplasts: Daucus carota

  13. Leucoplasts are colourless plastids Found: roots non – photosynthesising tissue May become specialized for bulk storage of starch, lipid or protein. Called amyloplasts (starch) elaioplasts (fat storage) proteinoplasts (protein storage) Can change into chloroplasts/chromoplasts LEUCOPLASTS

  14. PLASTIDS: THE LEUCOPLAST

  15. Leucoplast  Chloroplast

  16. PLASTIDS

  17. CELL INCLUSIONS = Any non-living mass, found within the cell • Can be - floating around in the cytoplasm - stored in an organelle like a plastid or vacuole - secreted by a cell, either outside the cell, or secreted into the cell wall. • E.g: starches, waxes,, crystals, alkaloids, tannins, etc. • Fx = pharmacological & medicinal value

  18. Lily Parenchyma Cross Section . • Note the large nucleus and nucleolus in the centre of the cell, mitochondria and plastids in the cytoplasm.

  19. Tonoplast = differentially permiable Fx – stores salts Recycles materials in plants Play an important role in plant turgor Vacuoles

  20. Encloses the whole cell Freely permeable Cellulose fibrils – NB component. Functions of the cell wall? THE CELL WALL

  21. Cell Wall Cell wall and nucleus – Allium cepa

  22. Cellulose • Cellulose is a linear polymer, made of millions of sugar (glucose) molecules. • The older the cell or the plant (herb) the more cellulose it’s going to contain. • WHY?

  23. PLANT WALL CELLULOSE

  24. Plant Matrix = Ground substance/substance in which something else originates/develops or is contained. • Responsible for the attributes of plant dietary fibre. • Made up of hemi-cellulose (not glucose, mostly Xylose – wood sugar) – malabsorbtion • Hemi-cellulose provides little strength (unlike cellulose). • Mucilages = hemi-cellulose

  25. made up of pectinic acid (made up of polymeres of galacturonic acid) Pectin is mainly found in the middle lamella. Pectin

  26. PECTIN

  27. Processes occurring in the plant • Photosynthesis • Respiration • Ligninification • Cutinisation • Suberization • Mineralization

  28. Lignins = propane polymeres Lignins – Latin ‘Lignas’ = woody Deposited in the cellulose network & are embedded in the cellulose fibres of woody plants Liginins & Lignification

  29. Lignin Fx = added rigidity to cell walls Fills the spaces in the cell walls between cellulose, hemicellulose and pectin Fx = decreases xylem permeability (NB role in the transport of H20 & nutrients) Fx = plant defence: protects against destructive environmental enzymes Ligninification

  30. LIGININ Cross Section of Angiosperm Stem. After staining, G-type lignins are stained in brown and G+S lignins are red.

  31. H, G & S lignin monomers G-type lignins = brown H+S lignins = red.

  32. CUTINISATION

  33. Cuticle = Ester of saturated fatty acids & oxyacids. Has an outer layer of wax Fx = Reduce plant H20 loss Cutinisation = process of cuticle formation THE CUTICLE

  34. CUTICLE (STAINED ORANGE)

  35. = Formation of cork (phellem) Fx – protection from excessive H20 loss - added protection Suberins making up cork are similar to cutins making up cutins (unsaturated fatty acids instead of saturated fatty acids) Suberins – impermeable to gasses & water Cork = non-living, water-resistant, protective tissue that displaces the stem epidermis as the plant undergoes an increase in diameter during the secondary growth phase.. SUBERIZATION

  36. Periderm (from cortex) Red – cork Yellow – cork cambium Red - phelloderm CORK CELLS

  37. Cork Cells

  38. MINERALISATION = inorganic salts are deposited into the cell wall  stronger cell wall  stronger plant. E.g. Silica formation in Equisetum. Medicinal uses of Equisetum Pre-historic uses of Equisetum

  39. Silica moleucle isolated from Equisetum arvense MINERALISATION

  40. LESSON TAKE-AWAY • Plastids • Processes involved in Plantae