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Topic: Photorespiration

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CAM plants

Carbon fixation

Peroxisome

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	Plant respiration not just an evolutionary leftover, study shows
		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.
		"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.
	www.eurekalert.org /pub_releases/2004-07/uoc--prn072104.php (552 words)

	Re: photorespiration
		Photorespiration is favored under high light and high O2/low CO2 level.
		Photorespiration should be low or insignificant at this stage.
		In short, it seems that photorespiration is high in initial stage; low when photosynthesis is activated due to depletion of sucrose; but slowly increase again when the O2/CO2 ration is increased some time after activation of photosynthesis.
	plant-tc.coafes.umn.edu /listserv/2000/log0004/msg00159.html (474 words)

	Photorespiration -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-10-17)
		Photorespiration is an alternate pathway for (Click link for more info and facts about rubisco) rubisco, the main enzyme of (Synthesis of compounds with the aid of radiant energy (especially in plants)) photosynthesis (specifically, the (Click link for more info and facts about Calvin cycle) Calvin cycle).
		This usually occurs when oxygen levels are high; for example, when the (Click link for more info and facts about stomata) stomata (tiny pores on the underside of the (The main organ of photosynthesis and transpiration in higher plants) leaf) are closed to prevent water loss.
		Photorespiration is a wasteful process because no (Click link for more info and facts about PGAL) PGAL is created.
	www.absoluteastronomy.com /encyclopedia/p/ph/photorespiration.htm (168 words)

	Question 5.16 (Site not responding. Last check: 2007-10-17)
		The 2 carbon glycolate produced by photorespiration in the chloroplast is converted to glycine in the peroxisome.
		Glycine from the peroxisome is transferred to the mitochondria where it is the immediate source of photorespired CO The 3 carbon glycerate is exported from the peroxisome and picked up by the chloroplast to be converted into ribulose 1,5-bisphosphate.
		For each carbon lost during photorespiration one nitrogen atom is released in the form of ammonia.
	www.mta.ca /~rthompso/Hopkins1/Chapt5H/quest5,16.html (101 words)

	Is photorespiration an effective mechanism for protecting against photoinhibition?
		They hypothesised that an increase of GS2 leading to an increase in photorespiration flux would lead to an increase in the flux of metabolites through the Calvin cycle, burning more energy and protecting the plant from photoinhibition.
		Those with a reduced amount of GS2 had a diminished capacity for photorespiration and were photoinhibited more severely by high intensity light compared with control plants.
		However altering a specific enzyme in the middle of the photorespiratory pathway may not be the most accurate way of determining the contribution to protection against photoinhibition.
	www.coursework.info /i/12510.html (839 words)

	What happens during photorespiration. (Site not responding. Last check: 2007-10-17)
		It is believed that photorespiration in plants has increased over geologic time and is the result of increasing levels of O
		The appearance of C4-type plants appears to be an evolutionary mechanism by which photorespiration is suppressed.
		It has long been the dream of biologists to increase the production of certain crop plants, such as wheat, that carry on C3-type photosynthesis by genetically re-engineer them to perform C4-type photosynthesis.
	www.marietta.edu /~spilatrs/biol103/photolab/photresp.html (162 words)

	The Mystery of Photorespiration
		One hypothesis is that photorespiration had a role in early evolution, when there was more carbon dioxide in the air.
		Another explanation is that plants use photorespiration to slow down photosynthesis under certain stressful conditions, like intense light, so that the photosynthetic apparatus doesn't get damaged.
		Researchers at UC Davis showed that photorespiration enables a plant to convert inorganic nitrogen into a form of nitrate that's needed for plant growth.
	amos.indiana.edu /library/scripts/photorespiration.html (235 words)

	Arabidopsis thaliana photorespiration (Site not responding. Last check: 2007-10-17)
		Photorespiration involves three organelles: the chloroplast, the peroxisome, and the mitochondria.
		The outcome of photorespiration is loss of CO and energy in photosynthetic cells.
		One possibility is that photorespiration is necessary under conditions of high light intensity and low CO concentration (i.e.
	aracyc.stanford.edu:1555 /ARA/new-image?type=PATHWAY&object=PWY-181 (243 words)

	Untitled (Site not responding. Last check: 2007-10-17)
		Both photosynthesis and photorespiration are initiated by the same enzyme.
		Photorespiration salvages 3 of 4 carbons that would otherwise be lost due to the oxygenase activity of RUBISCO and recycles them back into the Calvin Cycle.
		This occurs by the condensation of 2 2-C compounds into a 4 C compound followed by its breakdown to form a 3C sugar that can enter the Calvin cycle (in the cascade to regenerate RuBP).
	www.cofc.edu /~tomlinsn/QUIZ4.htm (110 words)

	Photorespiration - Wikipedia, the free encyclopedia
		Although Rubisco favors carbon, it can also use oxygen, producing a glycolate and a glycerate.
		The phosphoglycolate is salvaged by a series of reactions in the peroxisome and mitochondria whereby it is converted into serine and later glycerate and enters the Calvin cycle, at a cost of 1 ATP, by conversion to 3-phosphoglycerate within the chloroplast.
		Photorespiration is a wasteful process because PGAL is created at a reduced rate and higher metabolic cost compared to RuBP carboxylase activity.
	en.wikipedia.org /wiki/Photorespiration (176 words)

	Biology 2402 Lecture Notes - Photosynthesis Part 2. The Dark Reactions
		It is caused by a fundamental "inefficiency" of Rubisco.
		A significant portion (25%) of the carbon in phosphoglycolate is lost as CO Plants must use energy to "recover" the remaining 75% of this carbon, which further limits the efficiency of photosynthesis.
		The importance of photorespiration is easily demonstrated by the fact that nearly all plants grow better under high CO versus low CO Conditions that favor carboxylation (photosynthesis) over oxygenation (photorespiration) include high CO, moderate light intensities, and moderate temperatures.
	www.ualr.edu /~botany/darkrxns.html (1802 words)

	References - photorespiration or photorespiratory - HORT640 - Metabolic Plant Physiology - Department of Horticulture ...
		Edwards JW, Coruzzi GM 1989 Photorespiration and light act in concert to regulate the expression of the nuclear gene for chloroplast glutamine synthetase.
		Hanson KR, Peterson RB 1985 The stoichiometry of photorespiration during C3-photosynthesis is not fixed: evidence from combined physical and stereochemical methods.
		Hanson KR, Peterson RB 1986 Regulation of photorespiration in leaves: evidence that the fraction of ribulose bisphosphate oxygenated is conserved and stoichiometry fluctuates.
	www.hort.purdue.edu /rhodcv/hort640c/referen/presp.htm (6154 words)

	Azerbaijan:Head of National Program
		It is believed that the high intensity of observable photosynthesis of high-productive genotypes with a great intensity of photorespiration is supported at the expense of a greater true photosynthesis.
		The relation of true photosynthesis to photorespiration in ontogenesis is rather constant and is equal in the average 3:1 with an increase of the given relation at intensive genotypes, and losses of assimilated carbon at photorespiration is about 30%.
		In opponent to the usual earlier assumption of some authors about dissipation of photorespiration J. Aliyev has proved by versatile experiments, that the idea to low photorespiration with the purpose of increasing of a plant’s productivity is incorrect because the high productivity is characterized by a high intensity both of photosynthesis and photorespiration.
	www.cac-biodiversity.org /aze/aze_head.htm (1973 words)

	Learn more about Photosynthesis in the online encyclopedia. (Site not responding. Last check: 2007-10-17)
		Rather, it results in the loss of both CO and nitrogen (in the form of ammonia, NH) from the plant, in a process known as photorespiration.
		While some evidence indicates that photorespiration can help protect plants from damage due to very high light intensities, it is generally considered a wasteful process, in which as much as 50% of the plant's fixed carbon can be lost to the atmosphere.
		Some plants have evolved strategies to minimize photorespiration; these plants are grouped into C4 plants and CAM plants.
	www.onlineencyclopedia.org /p/ph/photosynthesis.html (882 words)

	Jillian Lang
		Chapter 14 is titled "Respiration and Photorespiration", and sections 14.7, 14.8 and 14.9 all have photorespiration in the title.
		Photorespiration protects C3 plants from Photooxidation: This article states that photorespiration is a defense from photoinhibition.
		Reduced photorespiration and increased energy-use efficiency in young CO sub(2)-enriched sorghum leaves also seemed to be an article of interest dealing with a specific organism.
	home.wlu.edu /~langj/bio182/log.html (1867 words)

	W0408 (Site not responding. Last check: 2007-10-17)
		Photorespiration is a metabolite salvage pathway resulting in the light-dependent consumption of O
		Moreover, since photorespiration is temperature sensitive, slight changes in temperature caused by global warming may have a great effect on photorespiration rates and consequences for the planet's O
		Thus efforts to understand the biochemistry and regulatory mechanisms involved in photorespiration are of global importance.
	www.hwi.buffalo.edu /ACA/ACA03/abstracts/text/W0408.html (426 words)

	Forest Biology and Ecology for Educators
		In a sense the PEPcarboxylase functions as a highly efficient CO pump which captures carbon and moves it into the bundle sheath cells where it is incorporated into sugars by the Calvin cycle.
		Any CO that may be released by photorespiration in the bundle sheath cells would quickly be recaptured by PEPcarboxylase in the surrounding mesophyll cells.
		Photorespiration, growth respiration and maintenance respiration are responsible for carbon outputs or withdraws.
	www.fw.vt.edu /DENDRO/forbioeco/htmltext/chapter3.htm (3574 words)

	c4
		Because the CO2 collected in the many mesophyll cells is being concentrated into a few bundle sheath cells, the plants can keep a higher concentration of CO2 in the bundle sheath cells (where the dark reactions and photosythesis are occurring) than it can elsewhere in the leaf.
		This higher concentration of CO2 prevents photorespiration and allows the plant to close its stomata during the hot hours of the day.
		For this reason C4 plants are thought to have evolved in places where photorespiration was a serious problem for plants.
	www2.mcdaniel.edu /Biology/botf99/photodark/c4.htm (257 words)

	Photorespiratory NH4+ Production in Leaves of Wild-Type and Glutamine Synthetase 2 Antisense Oilseed Rape -- Husted et ...
		The marked increase in photorespiration at increasing leaf temperatures was not followed by a concomitant increase in NH concentration in any of the plant tissues analyzed, namely bulk
		Photorespiration increased 5-fold when the leaf temperature was raised from 15°C to 25°C (Table I).
		The rate of photorespiration was determined at leaf temperatures of 15°C, 20°C, and 25°C in the Global genotype.
	www.plantphysiol.org /cgi/content/full/130/2/989 (5149 words)

	Aboveground Respiration
		Photorespiration may not be considered by ecosystem modelers (see Stand-level models), but it is worthwhile to understand the process.
		The products of photorespiration are 3-phosphoglyceric acid which enters the Calvin cycle, and glycolate which is quickly broken down to release CO Photorespiration represents a carbon loss to the plant, and many plants have developed the alternate C
		Dark respiration is a misnomer; whereas it is best measured in the dark in the absence of photorespiration, it occurs all the time in living plants.
	www.biology.duke.edu /bio265/zhangmin/Aboveground.htm (698 words)

	Welcome to Adobe GoLive 6
		However, one of every four carbons that enters the photorespiratory pathway is used to produce CO2, and the conversion of glycine to serine results in the formation of NH3.
		Thus, photorespiration may play a key role in mediating the release of fixed carbon and nitrogen from cells under conditions of high light or high O2.
		We are collaborating with scientists in the UW School of Oceanography's Marine Molecular Biology Laboratory and at Florida A and M University to investigate glycolate cycling in the upper ocean.
	depts.washington.edu /aog/glycolate.html (568 words)

	Drought and Oxidative Load in the Leaves of C3 Plants: a Predominant Role for Photorespiration? -- NOCTOR et al. 89 ...
		The utilization of electrons associated with photorespiration and CO fixation was calculated as described for Fig.
		Gross CO assimilation, photorespiration, and mitochondrial respiration in the light in tomato under drought stress.
		The role of photorespiration during drought stress: an analysis utilizing barley mutants with reduced activities of photorespiratory enzymes.
	aob.oxfordjournals.org /cgi/content/full/89/7/841 (6103 words)

	The long-term effects of nitrogen on phosphoenolpyruvate carboxylase activity and photorespiration in in vitro ...
		To investigate the impact of sucrose and N on photorespiration of potato (Solanum tuberosum, cv.
		Plants cultivated with +N and 2% sucrose exhibited higher phosphoenolpyruvate carboxylase activities accompanied with elevated photorespiration rate and low root values of soluble sugars, compared to plants grown with reduced amount of N while the highest sucrose content were found in N-starved plants.
		No different of PEPC activity and photorespiration rate was found in plants grown with 0% sucrose.
	abstracts.aspb.org /pb2000/public/P42/0974.html (293 words)

	photosynthesis
		Photorespiration is probably a metabolic relic from a much earlier time when the atmosphere had less O
		Now, it is considered to be wasteful, since photorespiration drains away as much as 50% of the carbon fixed by the Calvin cycle.
		If photorespiration could be reduced in certain plant species, without affecting photosynthetic productivity, crop yields and food supplies would increase.
	www.bio.umass.edu /biology/conn.river/photosyn.html (1366 words)

	photoresp (Site not responding. Last check: 2007-10-17)
		In C-3 plants photorespiration can result in significant loss of CO that is fixed by photosynthesis.
		The CO compensation point is the CO concentration reached when a plant is kept in a closed system in the light.
		The difference is due to higher rates of photorespiration in soybean.
	sunflower.bio.indiana.edu /~rhangart/courses/b373/lecturenotes/photosyn/photoresp/photoresp.html (261 words)

	PHOTORESPIRATION (Site not responding. Last check: 2007-10-17)
		If atmospheric concentrations of carbon dioxide are low (normal [CO2] = ______%), plants may photorespire
		During photorespiration, oxygen competes with CO2 for _____ and forms _____ and PGA is not formed
		Photorespiration _________ efficiency of photosynthesis and accounts for the low (ə%) efficiency
	www.auburn.edu /academic/classes/biol/1000/photo2/sld003.htm (43 words)

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