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Biology Unit 2 Topic 4
Plants and Properties…read more

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Plant Minerals
Minerals needed for plants to grow healthily
-Nitrates - N
-Phosphates - P NPK ­ Three most
needed in fertilisers
-Potassium ­ K
Needed to make amino acids and therefore proteins (for
Needed in DNA and many hormones.
Deficiency symptoms - small and stunted growth and yellow,
older leaves.
Needed in production of chlorophyll and used as the activation
of some plant enzymes, also used in synthesis of nucleic acids.
Deficiency symptoms - pale, yellow areas on old leaves and
growth is slowed.…read more

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Plant Minerals
Needed to make:
-ATP and ADP and so energy transfer in cells
-Structural molecules offer support
-Nucleic acids (DNA)
Deficiency symptoms ­ very dark green leaves with purple
veins, growth stunted.
Needed to combine with pectin in the middle lamella to
form calcium pectate which holds the plant cells together.
Also has role in permeability of cell membranes.
Deficiency symptoms ­ growing points die back, yellow
crinkly leaves.…read more

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Mineral Transport
Minerals in the soil water are often very
low concentrations. Often lower than the
concentration of the root cell cytoplasm.
Therefore they have to be moved up a
concentration gradient by Active
Carried by apoplast or symplast
pathways, same as water pathways.
Plants can be used to extract minerals for
energy and to remove metal ions that
contaminate the ground for safe use.…read more

Slide 5

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Transport of water from root hair to xylem
Water moves from root hairs to xylem tissue due to water potential
gradient (osmosis)
Three possible routes:
Apoplast pathway (via cell wall)
Symplast pathway (via cytoplasm)
Vacuolar pathway (via vacuole)
Symplast dominates however when transpiration rates are high more
water travels by apoplast pathway.
Before it is allowed to go to the xylem the casparian strips stop too
much water from passing through.
Plant can increase pressure difference between top and bottom of xylem
by raising the water potential at base of vessels:
·Active transport of mineral ions into water vessels in root lowers water
potential of solution in xylem this causes water to be drawn from
surrounding water cells.
·The influx of water increases hydrostatic pressure at base of vessel,
although root pressure may help move water up xylem vessel, it's not
essential or significant in causing water to move up most plants.…read more

Slide 6

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Plant Cell Organelles
Cell Wall ­ extracellular
Rigid, made of cellulose, proteins, and carbohydrates. Boundary
around plant cell outside cell membrane providing structural
There are 100s of cellulose molecules that make up a microfibril,
these wrap around the cells and the more vertical the spiral and
the closer the turns the stronger the cell is. Cell wall is
permeable to everything dissolved in water. It can be
impregnated with suberin (cork) or lignin (wood) which affects
the permeability.
It consists of several layers:
The middle lamella's first to form when the cell divides. Made of
pectin, a polysaccharide which acts like glue, holding cells
together. Combines with calcium forming calcium pectate
binding cellulose on either side. Microfibrils build up on both
sides of the middle lamella. Primary cell walls are flexible and
secondary cell walls are more rigid. Hemicelluloses harden it
more and some plants lignin is added.…read more

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