S3 - Plant Nutrition and Transport Flashcards
photosynthesis:
-photosynthesis is the process of making glucose from sunlight in the leaves of the plant
-it is an endothermic reaction in which light energy is converted into chemical energy within the chloroplasts
word equation for photosynthesis:
carbon dioxide + water (light)-> glucose + oxygen
CO2 + H20 -> C6H12O6 + O2
balanced: 6CO2 + 6H02 -> C6H12O6 + 602
factors affecting photosynthesis: temperature
-with an increase in temperature, the rate of photosynthesis increases
-however, as the reaction is controlled by enzymes, this trend only continues up to certain temperature until the enzymes begin to denature and the rate of reaction decreases
factors affecting photosynthesis: light intensity
-for most plants, the higher the light intensity, the rate of photosynthesis increases
-as the distance between the light source and the plant increases, the light intensity decreases, i.e. it is inversely proportional to the square of the distance: light intensity∝ 1/distance^2
-this means that if a lamp is 2 metres away from a plant, then light intensity of the lamp is a 1/4 of its original value -> 1/2^2 = 1/4
factors affecting photosynthesis: carbon dioxide concentration
-carbon dioxide is also needed to make glucose
-as the concentration of carbon dioxide increases, the rate of reaction increases
structure of a leaf:
-waxy cuticle: helps to reduce water loss by evaporation and is a protective layer found at the top of a leaf
-upper epidermis: very thin and transparent in order to let light in to the palisade mesphyll
-palisade mesophyll: contain lots of chloroplasts so that photosynthesis can happen rapidly
-spongy mesophyll: have lots of air spaces to allow gases to diffuse in and out of cells faster, as it increases the surface area : volume ratio
-lower epidermis: contains guard cells and stomata (gaps)
-guard cell: kidney-shaped cells that open and close the stomata by absorbing or losing water. When lots of water is available, the cells fill and open stomata
-stomata: where gas exchange and loss of water by evaporation takes place- opens during the day and closes at night
plants require 2 main types of mineral ions:
-mineral ions: for growth
-magnesium: required for chlorophyll production, deficiency -> causes leaves to turn yellow
-nitrate: required to produce amino acids, deficiency
-> causes stunted growth and turns leaves yellow
practicals investigating photosynthesis:
-use water plants, such as Elodea which release bubbles of oxygen when photosynthesising
-a lamp with an LED bulb is set up beside the beaker of water containing the water plant. An LED is best as it will not raise the temperature of the water
-sodium hydrogen carbonate (NaHCO3) is added to the water to supply carbon dioxide
-this can set up can be used to investigate the evolution of oxygen from a water plant
practical: investigating the effect of light intensity:
1) place pondweed in water and set up a desk lamp next to alongside a ruler so that you can measure the distance between the light and the beaker
2) move a lamp away by 10 cm
3) leave for 5 minutes to allow for the pondweed to adapt
4) count the number of bubbles given off in 1 minute and record
5) repeat steps 2-4
practical: investigating the effect of carbon dioxide:
-complete the experiment of light but instead of testing the variable of light intensity using a lamp, use different concentrations of sodium hydrogen carbonate solution, whilst keeping the other variables the same
practical: investigating starch production:
1) cover half of a small leaf with foil
2) place the plant on a windowsill for 48 hours so that ligh can reach it
3) put the leaf into boiling water to kill and preserve it
4) put the leaf in a boiling tube containing hot ethanol for 10 minutes (this removes the chlorophyll pigment)
5) dip the leaf in boiling water to soften it
6) put lead in a Petri dish and cover with iodine solution
7) the covered half of the leaf will remain orange-brown, whereas the exposed half will change to blue-black (as iodine solution changes colour in the presence of starch, as photosynthesis tuned the glucose into starch for storage)
experiment provide photosynthesis require chlorophyll:
-repeat the experiment of starch production but with a variegated leaf
-variegated plants are white and green and only contain chlorophyll in the green parts, therefore only the green areas of the plant will test positive for starch (i.e. turn blue-black) as a result of photosynthesis occuring
-the white areas that do not contain chlorophyll remain an orange-brown colour
transporting substances in plants: phloem adaptations
-transport surcrose and amino acids between leaves and other parts of plants (translocation)
-found in the roots, stems and leaves
-elongated cells with holes in the cell walls (the end walls are called sieve plates)
-many organelles from the cells are removed so cell sap can move through -> however, there are many mitochondria in companion cells which provide the energy the cells require
-food substances can be moved in both directions (translocation), from the leaves where they are made for use, or from storage (underground) to parts of the plant that need it
transporting substances in plants: xylem adaptations
water travels up the xylem from the roots into the leaves of the plant to replace the water that has been lost due to transpiration, xylem is adapted in many ways:
-a chemical called lignin is deposited which causes the cells to die
-these cells then become hollow and join end-to-end to form a continuous tube for water and mineral ions to travel through from the roots
-water molecules are attracted to each other by hydrogen bonding-creating a continuous column of water up the plant
-the water evaporates from the leaves of the plant, creating the transpiration stream
-lignin strengthens the plant to help it withstand the pressure of the water movement
-lignin contains bordered pits, which are holes to allow specific areas for water and therefore minerals to enter the plant
