7 ;; Transport in Plants Flashcards
(11 cards)
class notes
transport
diffusion + nutrients
🔗water from roots to leaves, sugars from leaves to rest of plant
🔗LARGE SA:V RATIO is wanted, efficient diffusion. Increased nutrient uptake required for growth & repair
🔗Transpiration: evaporation of water from leaves in the form of water vapour
🔗Translocation: transportation of synthesised products (sugars) in plant
🔗Xylem: role - transport water & minerals.
-Hollow dead tubes. Continuous tube. Upward direction only bc water enters through root.
Thick wall of lignin is waterproof + structural support - Very strong.
🔗Phloem: transports sucrose (sugar)
-made of living cells.
-BIdirectional; travels in both directions
-pores where dissolved sugars are transported from cell to cell
-end walls (sieve plates)
-companion cells provide energy for tube cells.
🔗Stomata: tiny pores on (lower) epidermis of leaf.
-take in carbon dioxide from atmosphere
-release water vapour to atmosphere via transpiration + oxygen as a waste product of photosynthesis
-open and closes.
Open = there is water (inc in water); swells = turgid; guard cells change shape (becoming round); open stomata then INCREASE IN WATER VAPOUR LOST, INCREASE IN TRANSPIRATION
Close = not lots of water; shrink (flaccid); guard cells change shape; CLOSE stomata; DEC in water vapour lost, DEC. in transpiration
🔗2 types of plant tissue: meristematic tissue, permanent tissue
+Meristematic tissue: plant regions of continuous cell division & growth; either undifferentiated or incompletely differentiated.
+Permanent tissue (non-meristematic): plant cells no longer actively dividing.
🔗Permanent tissue:
+SIMPLE (ground tissue - simple, so consist of one cell type. parenchyma, collenchyma, sclerenchyma)
+ & complex (xylem + phloem - vascular tissue, consists of multiple cell types). Dermal tissue, complex, = epidermis.
🔗🔗Stems:
-vascular bundle in a ring - provide flexibility and support
-sclerenchyma - vascular bundle cap
-collenchyma - cortex beneath epidermis => flexible support against wind
-chlorenchyma / palisade - under epidermis
-no endoderm
🔗🔗Roots:
-vascular bundle in central = reduce damage from soil friction
-no sclerenchyma (soil provides support)
-no collenchyma -
-no chlorenchyma -
-no stomata -
-endodermis surrounds vascular bundle
🔗🔗PITH: central ‘stuffing’ tissue; becomes more obv as plant gets older. Mostly parenchyma. At middle of primary dicotyledon stem.
🔗Pericycle: ONE CELL THICK layer just INSIDE endodermis. NEW ROOTS can grow from this layer. FORMED FROM sclerenchyma.
🔗ENDOdermal (inside): single cell inner protective layer found in ROOTS; regulates water flow in and out.
🔗🔗 EPIDERMAL (out): outermost layer. Protection from EXTERNAL environment.
🔗 Distribution of phloem and xylem
> in roots (+), + shape is xylem, phloem is the outsides of the + circle. Both in centre to provide support for root as it pushes through soil.
> in stems (pills), little pills around a circle, phloem at top of pill and xylem is inside bottom. Both near edge to provide scaffolding that reduces bending.
> in leaves (big weird u shape), both make up a network of veins which support the thin leaves. Between spongey & palisade
🔗 xylem transports water and solute from roots to rest of plant upwards ;; phloem transports food from leaves to rest of plant bidirectionally
🔗Soil has water. Root hair cells absorb water. Transported up xylem in stem to leaves. Evaporates from leaves via transpiration. OUTER CELLS NON-LIVING made of lignin which is waterproof and structurally supports plant.
🔗xylem tissue - support+transport. made of several different cell types: vessel elements, tracheids, fibers, parenchyma cells.
🔗tracheids: dead cells with lignified walls. do NOT form vessels bc they have tapering ends. Water must pass in/out of tracheids through pits in walls.
🔗vessel element = vessel perforation plates, wider & shorter cells
🔗tracheids = tapering cells, water transport, structural support, thick walls
🔗fibres = thick walls, structural support, more strength, withstand mechanical stress.
🔗xylem parenchyma: yes nuclei, metabolic functions, storage, repair
🔗 phloem: TRANSLOCATION - movement of sucrose and amino acids - food substances - from stem to growing tissue and storage tissue.
🔗phloem - function: transport ONLY (solutes). made of phloem fibres, parenchyma, sieve tube elements, companion cells.
🔗SIEVE TUBE ELEMENTS: living cells but NO NUCLEUS, FEW ORGANELLES, THIN CYTOPLASM LAYER so NEED COMPANION CELLS. Joined end-to-end forming transport tube. SIEVE parts = end walls with lots of holes (allowing solutes to pass through).
++sieve tube elements = elongated, transport sugars/organic compounds
🔗COMPANION cells: one companion cell for every sieve tube element. CARRY OUT LIVING FUNCTIONS for self AND SIEVE CELL.
++ Provide ATP for active transport of solutes.
+++support metabolic activities, provide energy/nutrients to sieve tube elements
🔗Phloem parenchyma: dispersed throughout phloem tissue, storage, metabolic processes, maintain integrity.
🔗 fibres: long, slender, structural support
🔗
🔗
complex
- parenchyma
- collenchyma
- sclerenchyma
+ PARENCHYMA:
-thin-walled cell (packing tissues)
-isodiametric (iso=same, diametric = dimensions)
-metabolically active
-storage of starch
-air spaces between cells to allow gas exchange
-fill leaves, stem cortex & vascular tissue
+COLLENCHYMA: TOUGH
-modified parenchyma cells
-extra cellulose so more strength
-layer just below epidermis
-living, non-lignified cells. Needs to not be too rigid, for growth
-usually not found in roots bc already have soil as support, so collenchyma not needed
+SCLERENCHYMA: WITH LIGNIN
-dead cells with rigid lignified walls
-cannot stretch
-main structural support for plant
=> fibre: elongated with tapered ends. Mechanical strength (flexibility). Occur in bundles.
=> Sclereids: Broad and wide in shape with blunt end walls. Compression strength and rigidity. Occur in single or loose groups.
++ Leaves - mesophyll
meso = middle, phyll = leaves
=> palisade mesophyll: specialised parenchyma for photosynthesis
=> spongey mesophyll: specialised parenchyma for gas exchange and diffusion
systems
-root system: provides support for plant, absorbs nutrients
primary root develops first in germinating seed.
++ ppt
SYLLABUS important notes to recall
+ some mineral ions and organic compounds can be transported within plants dissolved in water
+transpiration involves the evaporation of water from the internal surfaces of leaves followed by diffusion of water vapour to the atmosphere
+ assimilates dissolved in water, such as sucrose and amino acids, move from sources to sinks in phloem sieve
tubes
Transverse SECTIONS: stems, roots, leaves.
-dicotyledonous (dicots) plants have: [4 traits]
& also have a ____ life cycle
Seeds that contain two cotyledons (seed leaves)
Network of veins
Leaves that typically have broad blades (leaf surface) and petioles (stalks)
Tap root with lateral branches
++Herbaceous dicots have a relatively short life cycle (one growing season) and non-woody tissue
Transport systems
Plants need transport systems to ______
like [3]
in order to…
++ examples
🔗need transport systems to meet their metabolic demands
🔗glucose, hormones, mineral ions -required for various processes within plants
🔗to efficiently move substances up and down
🔗+ Glucose from photosynthesis needs to be transported to parts of the plant that cannot photosynthesise
🔗+Water from the roots needs to be transported to the upper parts of a plant
🔗+Plants may store glucose in storage organs, e.g. tubers, and need to release this glucose and transport it to metabolically active parts of the plant
not diffusion bc
and so vascular system which…
-plants consist of many layers of cells
-so cant rely on diffusion from cell to cell to supply all needs
-this would be too slow
-so ∴ plants have a vascular system
-involving a network of vessels (vascular tissue) running thru leaves, stem, roots - 3 main organs involved in transport
+vascular system is comprised of 2 distinct types:
=xylem transports water & mineral ions from roots to rest of plant
=phloem transports sucrose and amino acids from source eg leaf to sink eg root
-xylem & phloem arranged together in vascular bundles
-bundles laid out differently in leaves, stem & roots
TIP ;;; WHEN DRAWING tissue plan diagrams (common in paper 3),
YOU MUST:
- Read the instructions carefully
- ensure large diagram
- Use a sharp pencil and do not shade (including the nucleus)
- Use clear, continuous lines
- When using an eyepiece graticule, use it to ensure you have correct proportions or if you are not using a microscope then endeavour to keep the proportions between tissues to scale
^ ++ When labelling, remember:
- Use a ruler for label lines (and scale line if appropriate)
- Label-lines should stop exactly at the structure (do not use arrows)
- Don’t cross label-lines over each other
- Label all tissues and relevant structures (those requested)
TIP ;;; If drawing from a low-power image:
- Do not draw individual cells
- Read the question carefully as you may only have to draw a portion of the image
- Include the magnification on the drawing
TIP ;;; If drawing from a high-power image:
- Draw only a few of the required cells
- Draw the cell wall of the plant cells
- Include the magnification on the drawing
Xylem
-Vascular tissue that carries dissolved minerals and water up the plant,
-provides Structural support
-& for Food storage
location of the vascular bundles is dependent on which organ they are in as the different organs are under different stresses:
-in roots:
