Photosynthesis – Limiting Factors

pic Photosynthesis Outline Terms and diction Autotroph Photosynthesis Photon Pigment Chloroplast Reaction Center Electron Donor pinch Electron Transport System Ferredoxin NADPH RuBP PGA Cuticle Stomata Rubisco Photorespiration C4 Pathway Concepts 1. What be twain Adaptations of plant leaves for capturing devolve? 2. diagnose the properties of Light Energy in ground of energy and wavelength. 3. Why are Pigments important for Photosynthesis? 4. What two types of reactions take drift during photosynthesis? 5. Summarize the results of Light dependent Reactions. . Summarize the results of Light-Independent Reactions. 7. Where are the pigments for the twinkle-dependent reactions located in the tack? 8. What is the function of a photosystem? 9. What is the function of water in the airyly-dependent reactions? 10. Describe the similarities and differences of Photosystems I & II 11. What are the modifyation factor outs to photosynthesis? 12. Describe adaptations that allow the leaf to retain water. 13. Explain how photorespiration reduces production of glucose. Look at the graphs below. A pic B pic C pic D pic 1. Which graph best shows the onus of augment liberal intensity on the deem of photosynthesis? 2. 3. Which graph best shows the effect of adjoin cytosine dioxide concentration on the rate of photosynthesis? 4. Which graph best shows the effect of increasing temperature if light and carbon dioxide are not restrict (i. e. he levels of light and carbon dioxide are high). If you plot the rate of photosynthesis a recognisest the levels of these three limiting factors you get graphs like the ones below. pic Limiting Factor In biology, agricultural science, physiology, and ecology, a limiting factor is one that controls a process, such as beingness growth or species population size or distri simplyion. The concept is found upon Liebigs Law of the Minimum put forth by German geochemist, Justus von Liebig, in 1840. It can be easy to conceive how a limiting imaging (say, food) controls a process (say, growth) by cartroad low or running out.However, some biological and ecological processes are controlled by too often of a factor (such as set off) rather than too little. Or, processes may be controlled by complex interactions of factors (Shelford, 1952). At any given moment, the rate of a physiological process is limited by the one factor which is in the shortest supply. (Toole pg 273) The factor which is nearest its minimum value determines the rate of the reaction. Changing the levels of this factor will change the rate of the reaction. Changing the levels of the other factors will nurse no effect on the rate of the reaction. Example pic pic 1. Up to A1, A2 and A3 the concentrations of carbonic acid gas is the limiting factor for the respective light intensities. 2. Low Light saturation beyond A1 light intensity is the limiting factor because increasing the light intensity (medium value) increases the rate of photos ynthesis. 3. Medium Light Intensity beyond A2 light intensity is the limiting factor because increasing the light intensity (high value) increases the rate of photosynthesis. . High Light Intensity beyond A3 the limiting factor could be light intensity, chlorophyll content, temperature or the enzyme system. It cannot be carbon dioxide concentration because increase in carbonic acid gas concentration does not lead to an increase in photosynthesis. pic 1. Up to A1, A2 and A3 the light intensity is the limiting factor for the respective carbon dioxide concentrations. 2. Low carbon dioxide concentration beyond A1 CO2 concentration is the limiting factor because increasing the CO2 concentration (medium value) increases the rate of photosynthesis. . Medium CO2 concentration beyond A2 CO2 concentration is the limiting factor because increasing the CO2 concentration (high value) increases the rate of photosynthesis. 4. High CO2 concentration beyond A3 the limiting factor could be CO2 con centration, chlorophyll content, temperature or the enzyme system. It cannot be light intensity because increase in light intensity does not increase photosynthesis. pic In commercial greenhouses horticulturists try to maximise productivity by maximising the rate of photosynthesis.How do they achieve this? Clear glass maximizes light intensity Extra lighting in winter Glass traps heat energy from solar radiation Heaters raise night time temperature drift and oil heaters put extra carbon dioxide into the air. pic Photosynthesis and productivity carbon gain by the plant (biomass) is dependent on the balance between carbon uptake by photosynthesis and carbon loss by respiration factors influencing productivity include light, CO2, temperature, environmental factors light at low fluence levels, there is a net loss of CO2 light compensation point is where CO2 uptake and exchange equal zero (equivalent to an office or room) as fluence rate increases above compensation point , so does photosynthesis (C3 plants) until light saturation is reached (1/4 to ? full sun) light saturation occurs because CO2 is limiting C4 plants dont achieve light saturation as rapidly as C3 plants CO2 CO2 content in atmosphere is about 0. 035% by wad ( puff up below CO2 saturation point in plants) at high fluence rates when CO2 is not imiting, photosynthesis increases some commercial growers practice CO2-enrichment to increase yield and biomass temperature temperature response is influenced by temperature dependence of enzymes and chemical reactions cardinal points are used to describe temperature minimum maximum, and optimal of a reaction legion(predicate) reaction rates tend to decline sharply following optimum due to enzyme denaturation for photosynthesis, temperature response curves represent the average of many different enzymes, but are dominated by rubisco (C3 plants) and PEPcase (C4 plants) water water tenseness causes a decline in photosynthesis water s tress triggers stomatal closure and attendant decrease in CO2 levels turgor pressure reduces leaf expansion change magnitude photosynthetic surface area even mild water stress causes decrease in net photosynthesis nutrients, pathology, and pollutants photosynthetic capacity is especially stark naked to nitrogen rubisco accounts for 50% of total leaf nitrogen pathogen stress reduces photosynthetic capacity environmental pollutants (sulpher dioxide, ozone, heavy metals) also reduce capacity eaf factors distrust Which has a higher photosynthetic rate a pine corner needle or a maple tree leaf? Why power needles be favored over leaves on pine trees? productivity of plants is wedge by leaf canopy canopy is determined by age, morphology, list and spacing of individual leaves in older plants, lower leaves may be shaded and fall below light compensation point (negative carbon gain) and are a burden to the plant many annuals undergo sequential ageing to avoid the burden som e leaves change with the angle of the sun pic pic pic A plant in the dark does not photosynthesize. pic Increasing the amount of light increases the amount of photosynthesis. pic Even if a plant in the dark is well watered and given increasing amounts of carbon dioxide it will not photosynthesize. only a change in light intensity will alter the rate. Light is the limiting factor.