Biology Lecture plant histology

PLANT HISTOLOGY PLASTIDS  Only found in eukaryotic plants  = specialized organells – uinque to plants  Come in several forms  Fx = involved in metabolism PLASTIDS: Structure  Have a x2 (envelope) membrane  internal phases  Membrane system  Stroma/matrix  Why are they called plastids? PLASTID: Function  Contain ribosomes  Fx  mRNA translation in protein synthesis  Also contain a small amount of DNA  main types of plastids    Chloroplasts Chromoplasts Leukoplasts THE CHLOROPLAST  Chloroplasts contain chlorophyll  Fx = photosynthesis CHLOROPLAST – Structure 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  Microscopy: Chloroplast plastids THE CHROMOPLAST = the colour pigments which determines plant colour (green, yellow, red, orange, blue, etc) Chromoplast plastids Capsicum annum PECTIN Processes occurring in the plant  Photosynthesis  Respiration  Ligninification  Cutinisation  Suberization  Mineralization Liginins & Lignification  Lignins = propane polymeres  Lignins – Latin ‘Lignas’ = woody  Deposited in the cellulose network & are embedded in the cellulose fibres of woody plants Ligninification  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 LIGININ Cross Section of Angiosperm Stem After staining, G-type lignins are stained in brown and G+S lignins are red H, G & S lignin monomers G-type lignins = brown H+S lignins = red CUTINISATION THE CUTICLE  Cuticle = Ester of saturated fatty acids & oxyacids  Has an outer layer of wax  Fx = Reduce plant H20 loss  Cutinisation = process of cuticle formation CUTICLE (STAINED ORANGE) SUBERIZATION   = 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, waterresistant, protective tissue that displaces the stem epidermis as the plant undergoes an increase in diameter during the secondary growth phase CORK CELLS     Periderm (from cortex) Red – cork Yellow – cork cambium Red - phelloderm Cork Cells 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 MINERALISATION  Silica moleucle isolated from Equisetum arvense LESSON TAKE-AWAY • • Plastids Processes involved in Plantae ... sugar (glucose) molecules  The older the cell or the plant (herb) the more cellulose it’s going to contain  WHY? PLANT WALL CELLULOSE Plant Matrix = Ground substance/substance in which something... Tonoplast = differentially permiable  Fx – stores salts  Recycles materials in plants  Play an important role in plant turgor THE CELL WALL  Encloses the whole cell  Freely permeable  Cellulose...PLASTIDS  Only found in eukaryotic plants  = specialized organells – uinque to plants  Come in several forms  Fx = involved in metabolism PLASTIDS: Structure