Applying ultra-violet visible spectrophotometry and various types of chromatography to compare the amounts of certain photosynthetic pigments in fresh, frozen, and canned phaseolus vulgaris and spinacia olercea.
The Effects of Elevated Carbon Dioxide Levels on the Transpiratoin Rates of Zonal Geranium PlantsHow Does the Introduction of NaF Affect the Rate of Photosynthesis in Isolated Chloroplasts?
Jan van Helmont began the research of the process in the mid-17th century when he carefully measured the mass of the soil used by a plant and the mass of the plant as it grew.
In the light reactions, one molecule of the pigment chlorophyll absorbs one photon and loses one electron. This electron is passed to a modified form of chlorophyll called pheophytin, which passes the electron to a quinonemolecule, allowing the start of a flow of electrons down an electron transport chain that leads to the ultimate reduction of NADP to NADPH. In addition, this creates a proton gradient across the chloroplast membrane; its dissipation is used by ATP synthase for the concomitant synthesis of ATP. The chlorophyll molecule regains the lost electron from a water molecule through a process called photolysis, which releases a dioxygen (O2) molecule. The overall equation for the light-dependent reactions under the conditions of non-cyclic electron flow in green plants is:
evolution of the CAM photosynthetic pathway and the ensuing colonization of arid and other extreme environments, has promoted taxonomic diversification in the Bromeliaceae.
In an attempt to explain the CAM photosynthetic pathway in mostly layman's terms (some technical terms are unavoidable), the article comprises information from the following scientific articles and internet pages.
Appropriate because the plant may have evolutionary implications, and remarkable because it has an intermediate photosynthetic pathway between C3 and CAM Idling.
The table highlights which broms are CAM within the family.
There may well be some alterations/additions to this list as time passes, however because of the fairly clear determination process of whether a plant is C3 or CAM, they are unlikely to be numerous.Note that the Orchidaceae has more CAM species than any other plant family.
Most are angiosperms (flowering plants), and CAM species are five times more numerous than C4 species.
There are a number of factors which influence the degree of CAM photosynthetic pathway, and these include salinity; pollutants, these decrease the nocturnal CO uptake; nutrient availability; increased CO, which increases the malate; the light level; oxygen; air vapour pressure; temperature; water stress, which influences the enzyme type and volume; nitrogen etc.
Often the benefit of continued metabolism (survival) is at the expense of quantum yield (growth).
Plants which can switch photosynthetic pathways between CAM and C3 depend on environmental factors for the switch e.g.
The CO concentrates around the enzyme RuBisCo and photosynthesis via the Calvin cycle results.Day Malic acid --> Malate decarboxylated --> PEP + CO (for Calvin cycle)In the late afternoon the stomata open and this day/night cycle repeats.The water efficiency of this process is demonstrated by the fact that C3 plants lose 97% of their water by transpiration whereas CAM plants loose little to none.
Imagine what that might do for rice production and the worlds food problems.References: As with Photosynthesis 1, this presentation was gleaned from the following scientific articles and internet pages:
Sage et al, 2011, The C4 plant lineages of planet Earth.
Under these conditions C4 photosynthesis has developed a number of times in a number of plant lines in the 25-30 million years since the late Oligocene, getting to todays numbers by the end of the Miocene.Assuming that low CO is a pre-condition for the development of C4 plants, paramaters such as increasing aridity, high light habitats, increasing temperature and seasonality, fire, and the distribution of grazing animals, are all thought to play an important part in this evolutionary trend.At temperatures 22C - 30C, Quantum yields for C3 and C4 plants are the same
Temperatures above 30C, quantum yields are greater in C4 plants
Temperatures below 22C, quantum yields are greater in C3 plants.
Note that photorespiration which is in general caused by the uptake of O (oxygen) instead of CO by the RuBisCo enzyme, undoes the good work of photosynthesis in the C3 plant.