plant nutrition Flashcards
what is photosynthesis
process by which plants manufacture carbohydrates from raw materials using energy from light.
photosynthesis word equation
C a r b o n D i o x i d e \+ W a t e r l i g h t \+ c h o l o r o p h y l l −−−−−−−−−−−→ G l u c o s e \+ O x y g e n
photosynthesis symbol equation
6 C O 2 \+ H 2 O l i g h t \+ c h o l o r o p h y l l −−−−−−−−−−−→ \+ C 6 H 12 O 6 \+ 6 O 2
how does CO2 enter a leaf
The carbon dioxide diffuses through the open stomata of the leaf of a plant and water is taken up through roots.
use of chlorophyll for photosynthesis
Chlorophyll is a dye, which traps light energy and converts it into chemical energy for the formation of carbohydrates and their subsequent storage.
experiment for need of chlorophyll for photosynthesis
Take a potted plant with variegated (green and white) leaves.
Destarch the plant by keeping it in complete darkness for about 48 hours.
Expose the plant to the sunlight for a few days.
Leaf boiled in water for 2 minutes to break down cell walls, denature enzymes and allow for easier penetration by ethanol.
Warmed in ethanol until leaf is colourless to extract chlorophyll, which would mask observation
Dipped in water briefly: to soften leaf
Leaf is placed on a white tile and iodine is added. If starch is present, colour will be blue-black and if absent, it will remain orange
experiment for need for light in photosynthesis
Destarch the plant by keeping it in darkness for 48hrs
Place a stencil over part of a leaf
Place the leaf in sunlight for 4-6 hours
Remove the stencil and test for starch
+ve result = parts which received light turn black
-ve result = parts which didn’t receive light remain yellow/brown
experiment for carbon dioxide need in photosynthesis
Take two destarched potted plants.
Cover both the plants with bell jars and label them as A and B.
Inside A, keep NaHCO3 (sodium bicarbonate). It produces CO2.
Inside B, keep NaOH (Sodium hydroxide). It absorbs CO2.
Keep both the set-ups in the sunlight for at least 6 hours.
Perform the starch test on both plants.
The leaves of Plant A will turn black after the starch test
The leaves of Plant B will remain orange/brown after starch test
what is a limiting factor
Limiting factor: something present in the environment in such short supply that it restricts life processes.
light intensity as limiting factor
As the amount of light increases, the rate of photosynthesis increases (a-b)
The limiting factor is light
Increasing the amount of light after a certain point has no effect on the rate (c)
The limiting factor is now carbon dioxide or temperature
carbon dioxide concentration as limiting factor
As the amount of carbon dioxide increases, the rate of photosynthesis increases (a-b)
The limiting factor is carbon dioxide
Increasing amount of carbon dioxide after a certain point has not effect on rate (c)
The limiting factor is now light or temperature (warmth)
temperature as limiting factor
As temperature increases, the rate of photosynthesis increases until it reaches optimum temperature 40°C (a)
The limiting factor is the temperature
Increasing the temperature above 40°C will cause the enzymes to denature (b)
This will decrease rate of photosynthesis
how is glasshouse systems adapted for plants
To increase the crop yield, farmers control the limiting factors:
CO2 enrichment: paraffin is burnt to increase CO2 concentration by three times the original amount and doubling the yield
Optimum temperature: thermostatically controlled heaters make the temperature right for enzymes to work
Optimum light: light has a high intensity for more photosynthesis, the correct wavelengths (red and blue not green) and duration controls production of fruit
leaf structure
Cuticle: waxy layer that prevents water loss from top of the leaf
Epidermis: transparent cell that allows sunlight to pass through to the palisade cell
Palisade: found at the top of the cell and contains many chloroplasts which absorbs sunlight.
Spongy mesophyll layer: irregularly shaped cells which create air spaces to allow gaseous exchange to take place; do not contain many chloroplasts
Vascular Bundle: made up of xylem and phloem
Xylem: vessel which transports water and dissolved minerals and has lignified walls made of cellulose
Phloem: vessel which transports nutrients
Stomata: little holes that opens and closes to allow gaseous exchange to take place.
how does stomata work
The stomata close to prevent water loss and open to let gases come in and out. When guard cells lose water, the stoma close (at night), while the stoma open when guard cells gain water & swell (during the day).
Xylem function and characteristics
Unidirectional vessel which transports water and dissolved minerals.
Walls are made out of waterproof lignin.
Water moves up due to transpiration and osmosis
phloem function and characteristics
Bidirectional vessel
Contains sieve elements which allow sugars to pass from one cell to next downwards
Contains companion cells which provide energy for active transport of sugars all over plant.
Translocation moves organic molecules (sugars, amino acids) from source to sink.
Phloem vessels still have cross walls called sieve plates that contain pores.
Companion cells actively load sucrose into the phloem.
Water follows high solute in phloem by osmosis. A positive pressure potential develops moving mass of phloem sap forward.
Phloem still contains small amount of cytoplasm along the walls but the organelle content is greatly reduced.
Companion cells actively unload (ATP used) the organic molecules
mineral requirements of plants
- nitrogen
- magnesium
nitrogen purpose for plants
Needed for protein synthesis `
Deficiency: small plant, slow growth, top leaves pale, bottom leaves dead and roots slightly affected
magnesium purpose for plants
Needed for chlorophyll synthesis
Deficiency: plant lack chlorophyll, leaves yellow but normal roots
what are nitrogen fertilizers
provide nitrogen in the form of nitrate ions, nitrite ions or ammonium ions. But using fertilisers can lead to eutrophication, which is when the fertiliser is transported by rain and leaches into stagnant water e.g. pond or river
