Thanks Ed! This is extremely useful.
While common knowledge for ENTS, I feel the nuances of these cycles are not part of the general public's knowledge bank (certainly weren't part of mine until just now). I look forward to shedding light on photorespiration but comparing it to our own daily and yearly cycles. Cheers! Karl Karl Cronin dry earth e: [email protected] p: (718)916-3528 w: dryearth.org face: http://tinyurl.com/dryearth tweet: dryearth Check out our new website! www.dryearth.org //////////////////////////////////////////////////// On Mar 18, 2009, at 9:32 PM, Edward Frank wrote: > Karl, > > During the daylight the plant takes in carbon dioxide through he > leaves. and through the process of photosynthesis produces sugars, > and expels oxygen. Also during the same time as photosynthesis is > taking place is the reverse process of respiration in which some of > the oxygen and sugar is burned to produce energy and carbon > dioxide.- an indirect method to convert light energy from the sun to > chemical energy. Plants can only perform photosynthesis during the > daytime. At night the trees at a slower rate absorb oxygen from the > leaves and burns sugars producing energy and carbon dioxide that is > expelled from the leaves. In the fall deciduous trees drop their > leaves in the autumn in temperate climates, so they are unable to > perform photosynthesis in the winter. They still perform respiration > in order to use stored energy and survive during these times. > > So there is a day/night cycle involved and a spring through fall > versus winter cycle. > > Ed > > --------------------------------------- > http://www.sciencedaily.com/releases/2004/07/040723093305.htm > ScienceDaily (July 26, 2004) — A biological process in plants, > thought to be useless and even wasteful, has significant benefits > and should not be engineered out -- particularly in the face of > looming climate change, says a team of UC Davis researchers. > > The researchers have found that the process, photorespiration, is > necessary for healthy plant growth and if impaired could inhibit > plant growth, particularly as atmospheric carbon dioxide rises as it > is globally. Their findings are published this week in the > Proceedings of the National Academy of Sciences. > > Over the past two hundred years, scientists have come to understand > that plants are amazing biochemical factories that harness energy > from sunlight to convert water and carbon dioxide into sugars that > fuel the plant, while giving off oxygen. > > Though elegantly simple in concept, this process, known as > photosynthesis, is remarkably complex in detail. And for years, > researchers have been puzzled by another process, photorespiration, > which seems to have annoyingly associated with photosynthesis down > the evolutionary pathway. > > Photorespiration has appeared to be downright wasteful because it > virtually undoes much of the work of photosynthesis by converting > sugars in the plant back into carbon dioxide, water and energy. > > Believing that photorespiration is a consequence of the higher > levels of atmospheric carbon dioxide in long past ages, many > scientists concluded that photorespiration is no longer necessary. > Some have even set about to genetically engineer crop plants so that > the activity of the enzyme that initiates both the light-independent > reactions of photosynthesis and photorespiration would favor > photosynthesis to a greater extent and minimize photorespiration. > > The result, they have thought, would be more productive crop plants > that make more efficient use of available resources. > > But the new UC Davis study suggests that there is more to > photorespiration than meets the eye and any attempts to minimize its > activity in crop plants would be ill advised. > > "Photorespiration is a mysterious process that under present > condition dissipates about 25 percent of the energy that a plant > captures during photosynthesis," said Arnold Bloom, a professor in > UC Davis' vegetable crops department and lead researcher on the > study. "But our research has shown that photorespiration enables the > plant to take inorganic nitrogen in the form of nitrate and convert > it into a form that is useful for plant growth." > > The UC Davis team used two different methods to demonstrate in both > wheat and Arabidopsis, a common research plant, that when plants are > exposed to elevated levels of atmospheric carbon dioxide or low > levels of oxygen -- both conditions that inhibit photorespiration -- > nitrate assimilation in the plant's shoot slows down. Eventually, a > shortage of nitrogen will curtail the plant's growth. > > "This explains why many plants are unable to sustain rapid growth > when there is a significant increase in atmospheric carbon dioxide," > said Bloom. "And, as we anticipate a doubling of atmospheric carbon > dioxide associated with global climate change by the end of this > century, our results suggest that it would not be wise to decrease > photorespiration in crop plants." > > The UC Davis study was supported by the National Science Foundation, > the U.S. Department of Agriculture and an Israel Binational > Agricultural Research and Development Fund fellowship. > > -------------------------------------------------------------- > > > > > Breathing, the inspiration and expiration of air by animals, is not > the same as respiration. Both animals and plants respire, but plants > neither breathe nor have specialized respiratory systems as do > animals. In plants, gases diffuse passively into the plant (through > the stomata or directly into the epidermal cells) where they come > into contact with the moist cellular membranes and then move in > water along diffusion gradients between and within cells. No special > carriers (such as the hemoglobin of human blood) or organs (such as > lungs or gills) aid in the diffusion. > > Glucose is the originating molecule for respiration; other reserve > foods either follow different utilization pathways or, in the case > of complex carbohydrates, are broken down to glucose before > undergoing respiratory oxidation. > > > > --~--~---------~--~----~------------~-------~--~----~ Eastern Native Tree Society http://www.nativetreesociety.org Send email to [email protected] Visit this group at http://groups.google.com/group/entstrees?hl=en To unsubscribe send email to [email protected] -~----------~----~----~----~------~----~------~--~---
