plant_histology

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PLANT HISTOLOGY:

PLANT HISTOLOGY

PLASTIDS:

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

PLASTIDS: Structure:

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

PLASTID: Function:

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

THE CHLOROPLAST:

THE CHLOROPLAST Chloroplasts contain chlorophyll Fx = photosynthesis

CHLOROPLAST – Structure:

CHLOROPLAST – Structure

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:

Microscopy: Chloroplast plastids

THE CHROMOPLAST:

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

Chromoplast plastids:

Chromoplast plastids Capsicum annum

Chromoplasts:

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.

Chromoplasts: Daucus carota:

Chromoplasts: Daucus carota

LEUCOPLASTS:

LEUCOPLASTS 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

PLASTIDS: THE LEUCOPLAST:

PLASTIDS: THE LEUCOPLAST

Leucoplast  Chloroplast:

Leucoplast  Chloroplast

PLASTIDS:

PLASTIDS

CELL INCLUSIONS:

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

Lily Parenchyma Cross Section:

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

Vacuoles :

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

THE CELL WALL:

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

Cell Wall:

Cell Wall Cell wall and nucleus – Allium cepa

Cellulose:

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?

PLANT WALL CELLULOSE:

PLANT WALL CELLULOSE

Plant Matrix:

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

Pectin:

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

PECTIN:

PECTIN

Processes occurring in the plant:

Processes occurring in the plant Photosynthesis Respiration Ligninification Cutinisation Suberization Mineralization

Liginins & Lignification:

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

Ligninification:

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:

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:

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

CUTINISATION:

CUTINISATION

THE CUTICLE:

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):

CUTICLE (STAINED ORANGE)

SUBERIZATION:

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, water-resistant, protective tissue that displaces the stem epidermis as the plant undergoes an increase in diameter during the secondary growth phase..

CORK CELLS:

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

Cork Cells:

Cork Cells

MINERALISATION:

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 :

MINERALISATION Silica moleucle isolated from Equisetum arvense

LESSON TAKE-AWAY:

LESSON TAKE-AWAY Plastids Processes involved in Plantae

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