B14 Flashcards
What is photosynthesis?
Process that converts light energy into biochemical energy which is then used to drive the assimilation of low energy inorganic carbon into high energy organic biochemicals.
What is the photosynthesis equation?
6CO2 + 6H20 -> C6H1206 + 6O2
What are the two phases of photosynthesis?
Light phase (grana) which is a physical phase
Dark phase (stroma) which is a chemical phase
What happens in the light phase?
Light energy absorbed by pigments is funnelled to reaction centres and used to drive the production of ATP (metabolic energy) and NADPH (reducing energy). Oxygen is also formed during the light phase
What happens in the dark phase?
Uses ATP and NADPH formed in the light phase in a series of enzyme catalysed reactions to assimilate CO2 into high energy organic form
What is climate change?
Large-scale, long-term shift in the planets weather patterns or average temperatures. Earth has had tropical climates and ice ages many times in its 4.5billion years.
How much did the ice shelf reduce by?
12%
What other changing weather patterns are there?
Rainfall, storms, hurricanes, typhoons, tornados, hurricanes. These create knock on effects and unpredictable patterns
What causes greater damage by floods and rainfall?
Compounded changes in land use
What are hurricanes and cyclones?
A hurricane is a tropical cyclone that occurs in the Atlantic Ocean and northeastern Pacific Ocean. A cyclone is a large scale air mass that rotates around a strong centre of low atmospheric pressure.
What is happening to crop yields due to climate change?
Decrease in some yields.
What factors limit photosynthesis?
Light, CO2, Temperature, mineral deficiencies, herbicides, pollutants
What does the light saturation curve show
Below compensation point is the dark respiration rate. At low PAR, photosynthesis is masked by respiration. The PAR level where CO2 uptake is equal to CO2 output is called the compensation point. During the light limitation phase, photosynthesis is limited by the light phase. At light saturation, photosynthesis is limited by the dark phase.
What is the light saturation curve for a C3 plant?
The carboxylation reaction limits photosynthesis under high light conditions. Photorespiration occurs under low CO2 levels, as stomata close and O2 is added to RuBP instead.
What happens in photoinhibition?
A decrease in photosynthesis induced by high fluxes of PAR. Caused by an excess of PAR quanta absorbed due to exposure to excess irradiance, exposure to chilling under normal radiance, exposure to conditions that decrease CO2 fixation under normal irradiance.
What follows photoinhibition?
Photo-oxidation
What is photo-oxidation?
Bleaching of photosynthetic pigments, unless there is prolonged stress resulting in photodamage, photoinhibition is reversible and there is no permanent damage to thylakoid membranes
When considering responses of plants to climate change ; what factors need to be considered?
Change in temp and climate, change in the CO2 conc, mineral availability.
In biomes what determines the distribution of vegetation?
Climate
What ecosystems have the highest productivity?
Tropical rainforest, fresh water wetland, saltwater wetland
What provide data on past climatic conditions?
Ice cores they contain CO2 bubbles which are formed as snow falls and traps air between flakes
What effects does anthropogenic activity have on climate change?
Unprecedented increases in atmospheric CO2.
In what form is CO2 available to terrestrial and aquatic plants?
CO2 to terrestrial, HCO3- to aquatic.
How does CO2 diffuse into plants?
Via stomata
What does the rate of CO2 uptake equate to and how is it measured?
It equates to rate of photosynthesis and is measured by infra red gas analysis.
What is the equation for CO2 uptake?
[CO2]ext - [CO2]int / Ra + Rs + Rm. R = resistance to diffusion offered by boundary layer (a) stomata (s) and mesophyll (m)
What effects does the CO2 saturation curve show on CO2 concentration on net photosynthesis?
Current atmospheric CO2 is approx 411ppm, a doubling of CO2 in the atmosphere is widely predicted.
What effect does increasing CO2 on vegetation have for C3 plants?
An increase in the rate of net photosynthesis, at least in the short term, because : increase in CO2 as substrate for photosynthesis, decrease in photorespiration. Also an increased water use efficiency.
What effect does increasing CO2 on vegetation have for C4 plants?
Saturated at current CO2 concentration
How does CO2 enrichment experiments compare biomass?
Compare biomass production at 35Pa and 70Pa in growth chambers. This gives a biomass enhancement ratio.
What are some experimental issues related to studying the effect of increasing CO2 on vegetation?
Data available for <1% of world higher plant flora. Large variation, inter-specific differences. Some species show a negative response. Length of experiment is important, short term experiments, many C3 plants show a significant stimulation in net CO2 assimilation.
What is the free-air CO2 enrichment (FACE)?
Opportunity to make long term observation of forests under elevated CO2 in realistic forest stand conditions.
What is the effect if CO2 in water use efficiency?
CO2 affects stomatal conductance, decreases stomatal aperture, decreased number of stomata per unit area.
What do studies on the effect of CO2 on water use efficiency show?
Average reduction in stomatal density with CO2 enrichment. Also, decreased stomatal conductance. CO2 enrichment will increase water use efficiency by decreasing transpiration.
What are carbon:nitrogen ratios?
Plants must maintain C:N ratios within certain limits. Above these, C accumulates as carbohydrate and C-fixation is down-regulated, plants become N deficient. CO2 fertilisation may be limited by availability of nitrogen and more significant where there is nitrogen pollution
What do in situ studies into CO2 enrichment find?
Enriching CO2 alone does not stimulate enough long-term fertilisation. If CO2 concentration is doubled and temperature is raised by 4 degrees, CO2 fertilisation is sustained and there is increased carbon storage. Warmer temp may have stimulated extra mineralisation in tundra soils.
What have studies found about the effects of invasive species and global climate change?
Responses of 6 invasive weedy plants, 46% stimulation in biomass with CO2 fertilisation from current to future levels. Biggest stimulation was in the 20th century so therefore those changes may have played a significant role in selecting invasive species.
How does climate change affect plants?
Temperature has great effects, some species are cold intolerant. Boundaries between vegetation types are generally determined by summer warmth.
How does rainfall affect plants?
It affects the balance of grasses to woody vegetation. Other factors such as soil type of herbivory may also be affected by climate change.
How is plant biodiversity affected by climate change?
Species left behind, as they cannot change distribution fast enough. Species with long life cycles and/or slow dispersal are particularly vulnerable. Isolated or disjunct species are particularly vulnerable. Invasive species most successful.
What is phenology?
The study of the timing of events in the natural calendar. Mismatch between timing of lifecycles between animals and plants
