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PubMed1980

Effect of butyl 2-hydroxy-3-butynoate on sunflower leaf photosynthesis and photorespiration.

Detached leaves and whole plants of sunflower were supplied with butyl 2-hydroxy-3-butynoate (BHB), a competitive inactivator of glycolate oxidase, to evaluate the possibility of inhibiting photorespiration and increasing photosynthetic efficiency. In all treatments in vivo and in vitro, BHB inhibited glycolate oxidase. With partially purified glycolate oxidase from spinach leaves, the apparent K(i) for BHB was 13.2 micromolar.Low concentrations of BHB neither decreased photorespiration nor increased net photosynthesis. At higher concentrations, either a proportional decrease in photosynthesis and photorespiration or an inhibition of net photosynthesis greater than photorespiration was observed. CO(2) evolution in BHB-treated leaves was O(2)-sensitive and was derived from recent photosynthate. BHB inhibited photosynthesis in 2, 21, or 50% O(2) but the ratio of the rates of photosynthesis in these O(2) concentrations was the same as in control leaves. BHB treatment resulted in a stimulation of dark respiration.As photosynthesis, photorespiration, and dark respiration were all affected by BHB, the action of BHB on whole leaf metabolism appears to be complex. Substantial inhibition of photorespiration was accompanied by inhibition of photosynthesis and increases in photosynthesis were not observed.

Journal Article↗
PubMed1985

Leaf k interaction with water stress inhibition of nonstomatal-controlled photosynthesis.

The relationship between leaf K(+) concentration, in vitro dehydration, and nonstomatal-controlled photosynthesis was investigated using leaf slices that were vacuum infiltrated with media containing varying sorbitol concentrations. The leaf slices were from plants either supplied with complete or K(+)-deficient medium throughout a 35-day growth period. During this time, leaf K(+) concentration, water potential, osmotic potential, and turgor pressure were monitored. Leaf K(+) concentration averaged 239 micomoles per gram (fresh weight) in control plants, and dropped to 74.3 micromoles per gram (fresh weight) in K(+)-deficient plants. Less negative osmotic potentials and resultant turgor loss in K(+)-deficient plants indicated that the osmotically active pool of cellular K(+) was lower in those plants.The decrease in leaf K(+) concentration enhanced the dehydration inhibition of photosynthesis. For example, increasing sorbitol from 0.33 to 0.5 molar during incubation inhibited photosynthesis in the controls by 14% or less. This same protocol resulted in an inhibition of photosynthesis by as much as 41% in K(+)-deficient tissue. In contrast to the data obtained with leaf slices, dehydration inhibition of isolated chloroplast photosynthesis was not affected by K(+) status of parent plant material. These data are consistent with the hypothesis that one effect of leaf K(+) deficiencies on photosynthetic response to dehydration may be mediated by extra-choloroplastic factors.Ammonium ions, which facilitate stromal alkalinization, reversed the increased sensitivity of K(+)-deficient leaf slice photosynthesis to cell dehydration. However, NH(4) (+) had no effect on photosynthesis of K(+)-deficient leaf slices under nonhypertonic conditions. These data suggest that endogenous extra-chloroplastic K(+) may modulate dehydration inhibition of photosynthesis, possibly by facilitating stromal alkalinization.

Journal Article↗
PubMed1986

Oxygen Stimulation of Apparent Photosynthesis in Flaveria linearis.

A plant was found in the C(3)-C(4) intermediate species, Flaveria linearis, in which apparent photosynthesis is stimulated by atmospheric O(2) concentrations. A survey of 44 selfed progeny of the plant showed that the O(2) stimulation of apparent photosynthesis was passed on to the progeny. When leaves equilibrated at 210 milliliters per liter O(2) were transferred to 20 milliliters per liter O(2) apparent photosynthesis was initially stimulated, but gradually declined so that at 30 to 40 minutes the rate was only about 80 to 85% of that at 210 milliliters per liter O(2). Switching from 20 to 210 milliliters per liter caused the opposite transition in apparent photosynthesis. All other plants of F. linearis reached steady rates within 5 minutes after switching O(2) that were 20 to 24% lower in 210 than in 20 milliliters per liter O(2). At low intercellular CO(2) concentrations and low irradiances, O(2) inhibition of apparent photosynthesis of the aberrant plant was similar to that in normal plants, but at an irradiance of 2 millimoles quanta per square meter per second and near 300 microliters per liter CO(2) apparent photosynthesis was consistently higher at 210 than at 20 milliliters per liter O(2). In morphology and leaf anatomy, the aberrant plant is like the normal plants in F. linearis. The stimulation of apparent photosynthesis at air levels of O(2) in the aberrant plant is similar to other literature reports on observations with C(3) plants at high CO(2) concentrations, high irradiance and/or low temperatures, and may be related to limitation of photosynthesis by triose phosphate utilization.

Journal Article↗
PubMed1986

Photosynthesis of F(1) Hybrids between C(4) and C(3)-C(4) Species of Flaveria.

Photosynthetic characteristics were studied in several F(1) hybrids between C(4) and C(3)-C(4) species of Flaveria. Stable carbon isotope ratios, O(2) inhibition of apparent photosynthesis, and phosphoenolpyruvate carboxylase activities in the hybrids were similar to the means for the parents. Values of CO(2) compensation concentrations were nearer to those of the C(4) parent and apparent photosynthesis was below that of both parents, being only 60 and 74% of that of the lowest (C(3)-C(4)) parent in two experiments. Reductions of CO(2) compensation concentration and O(2) inhibition of apparent photosynthesis as well as increases in carbon isotope ratios and phosphoenolpyruvate carboxylase activities compared to values in C(3)-C(4) species suggest transfer of a limited degree of C(4) photosynthesis to the F(1) hybrids. However, the lower apparent photosynthesis of the hybrids suggests that transfer of C(4) characteristics to non-C(4) species is detrimental unless characteristics associated with C(4) photosynthesis are fully developed. There was a highly significant negative correlation (r = -0.90) between CO(2) compensation concentration and the logarithm of phosphoenolpyruvate carboxylase activity in the parents and hybrids, suggesting involvement of this enzyme in controlling the CO(2) compensation concentration. Although bundle-sheath cells were more developed in leaves of hybrids than in C(3)-C(4) parents, they appeared to contain lower quantities of organelles than those of the C(4) parent. Reduced quantities of organelles in bundle-sheath cells could indicate incomplete compartmentation of partial pathways of the C(4) cycle in the hybrids. This may mean that the reduction of CO(2) compensation and O(2) inhibition of apparent photosynthesis relative to the C(3)-C(4) parents is less dependent on fully developed Kranz anatomy than is increased apparent photosynthesis.

Journal Article↗
PubMed1987

Modulation of water stress effects on photosynthesis by altered leaf k.

Wheat irrigated with nutrient solutions containing 0, 0.2, 0.5, 1, 2, or 6 millimolar K(+) had maximum photosynthetic rates at 1 to 2 millimolar K(+) concentrations. Rates in the 6 millimolar K(+)-grown plants were not higher than the 2 millimolar K(+)-grown wheat, and rates were inhibited below 0.5 millimolar K(+). Photosynthesis was measured by both attached whole leaf CO(2) uptake and by (14)CO(2) fixation of leaf slices in solution. Exposure of leaf slices from 0.2, 2, and 6 millimolar K(+)-grown wheat to various assay media water potentials showed that photosynthesis of the 0.2 millimolar K(+)-grown wheat decreased from control (high water potential) rates by 35%, that of the 2 millimolar K(+)-grown wheat by 20.4%, and that of the 6 millimolar K(+)-grown wheat by only 8.3% at -3.11 megapascals. Also, photosynthesis of the 6 millimolar K(+)-grown wheat was enhanced by 28% over that of the 2 millimolar K(+) wheat at the most severe water stress (-3.11 megapascals), indicating that the excess leaf K(+) in the 6 millimolar K(+)-grown wheat partially reversed dehydration effects on photosynthesis. Oligomycin eliminated the protective effects of high K(+) on photosynthesis in dehydrated leaf slices. These results suggest that the protective effect of high K(+) under water stress may involve the exchange of K(+) in the cytoplasm for stroma H(+), thus altering stromal pH and restoring photosynthesis. The protective effect of high K(+) was also observed in attached whole leaf photosynthesis of in situ water-stressed wheat grown on 0.2, 2, and 6 millimolar K(+). Under water stress, rates of the 6 millimolar K(+)-grown wheat were enhanced by 66.2% and 113.9% over that of 2 millimolar K(+)-grown wheat in two separate experiments. Internal CO(2) concentration of the 6 millimolar K(+)-grown wheat was lower than that of the 0.2 and 2 millimolar K(+)-grown wheat. These results suggest that the high K(+) effects on chloroplast photosynthesis seen in leaf slices also occur at the whole plant level.

Journal Article↗
PubMed1992

Control of Photosynthesis and Stomatal Conductance in Ricinus communis L. (Castor Bean) by Leaf to Air Vapor Pressure Deficit.

Castor bean (Ricinus communis L.) has a high photosynthetic capacity under high humidity and a pronounced sensitivity of photosynthesis to high water vapor pressure deficit (VPD). The sensitivity of photosynthesis to varying VPD was analyzed by measuring CO(2) assimilation, stomatal conductance (g(s)), quantum yield of photosystem II (phi(II)), and nonphotochemical quenching of chlorophyll fluorescence (q(N)) under different VPD. Under both medium (1000) and high (1800 micromoles quanta per square meter per second) light intensities, CO(2) assimilation decreased as the VPD between the leaf and the air around the leaf increased. The g(s) initially dropped rapidly with increasing VPD and then showed a slower decrease above a VPD of 10 to 20 millibars. Over a temperature range from 20 to 40 degrees C, CO(2) assimilation and g(s) were inhibited by high VPD (20 millibars). However, the rate of transpiration increased with increasing temperature at either low or high VPD due to an increase in g(s). The relative inhibition of photosynthesis under photorespiring (atmospheric levels of CO(2) and O(2)) versus nonphotorespiring (700 microbars CO(2) and 2% O(2)) conditions was greater under high VPD (30 millibars) than under low VPD (3 millibars). Also, with increasing light intensity the relative inhibition of photosynthesis by O(2) increased under high VPD, but decreased under low VPD. The effect of high VPD on photosynthesis under various conditions could not be totally accounted for by the decrease in the intercellular CO(2) in the leaf (C(i)) where C(i) was estimated from gas exchange measurements. However, estimates of C(i) from measurements of phi(II) and q(N) suggest that the decrease in photosynthesis and increase in photorespiration under high VPD can be totally accounted for by stomatal closure and a decrease in C(i). The results also suggest that nonuniform closure of stomata may occur in well-watered plants under high VPD, causing overestimates in the calculation of C(i) from gas exchange measurements. Under low VPD, 30 degrees C, high light, and saturating CO(2), castor bean (C(3) tropical shrub) has a rate of photosynthesis (61 micromoles CO(2) per square meter per second) that is about 50% higher than that of tobacco (C(3)) or maize (C(4)) under the same conditions. The chlorophyll content, total soluble protein, and ribulose-1,5-bisphosphate carboxylase/oxygenase level on a leaf area basis were much higher in castor bean than in maize or tobacco, which accounts for its high rates of photosynthesis under low VPD.

Journal Article↗
PubMed2004

A novel method for measuring photosynthesis using delayed fluorescence of chloroplast.

Photosynthesis is the most important chemical reaction in the world. The measurement of plant photosynthesis rate plays an important role in agriculture. Light-induced delayed fluorescence (DF) in plants is an intrinsic label of the efficiency of charge separation at P680 in photosystem II (PS II). In this paper, we have developed a biosensor that can accurately measure the plant photosynthesis ability by means of DF. Compared with common methods for measuring the photosynthesis rate based on consumption of CO2, the proposed technique can quantify the plant photosynthesis ability with less influence of the environment. The biosensor is an all-weather measuring instrument, it has its own illumination power and utilizes intrinsic DF as the measurement marker. The current investigation has revealed that, there is a good correspondence between the results measured by the biosensor and that by commercially available portable photosynthesis system under controlled conditions. We thus conclude that DF is an excellent marker for evaluating plant photosynthesis ability under its biological status with less interferences of the environment.

Biosensing Techniques↗
PubMed2002

Characteristics of C4 photosynthesis in stems and petioles of C3 flowering plants.

Most plants are known as C3 plants because the first product of photosynthetic CO2 fixation is a three-carbon compound. C4 plants, which use an alternative pathway in which the first product is a four-carbon compound, have evolved independently many times and are found in at least 18 families. In addition to differences in their biochemistry, photosynthetic organs of C4 plants show alterations in their anatomy and ultrastructure. Little is known about whether the biochemical or anatomical characteristics of C4 photosynthesis evolved first. Here we report that tobacco, a typical C3 plant, shows characteristics of C4 photosynthesis in cells of stems and petioles that surround the xylem and phloem, and that these cells are supplied with carbon for photosynthesis from the vascular system and not from stomata. These photosynthetic cells possess high activities of enzymes characteristic of C4 photosynthesis, which allow the decarboxylation of four-carbon organic acids from the xylem and phloem, thus releasing CO2 for photosynthesis. These biochemical characteristics of C4 photosynthesis in cells around the vascular bundles of stems of C3 plants might explain why C4 photosynthesis has evolved independently many times.

Carbon↗
PubMed2001

Sink regulation of photosynthesis.

The concept that photosynthetic flux is influenced by the accumulation of photo-assimilate persisted for 100 years before receiving any strong experimental support. Precise analysis of the mechanisms of photosynthetic responses to sink activity required the development of a battery of appropriate molecular techniques and has benefited from contemporary interest in the effects of elevated CO2 on photosynthesis. Photosynthesis is one of the most highly integrated and regulated metabolic processes to maximize the use of available light, to minimize the damaging effects of excess light and to optimize the use of limiting carbon and nitrogen resources. Hypotheses of feedback regulation must take account of this integration. In the short term, departure from homeostasis can lead to redox signals, which cause rapid changes in the transcription of genes encoding photosystems I and II. End-product synthesis can exert short-term metabolic feedback control through Pi recycling. Beyond this, carbohydrate accumulation in leaves when there is an imbalance between source and sink at the whole plant level can lead to decreased expression of photosynthetic genes and accelerated leaf senescence. In a high CO2 world this may become a more prevalent feature of photosynthetic regulation. However, sink regulation of photosynthesis is highly dependent on the physiology of the rest of the plant. This physiological state regulates photosynthesis through signal transduction pathways that co-ordinate the plant carbon : nitrogen balance, which match photosynthetic capacity to growth and storage capacity and underpin and can override the direct short-term controls of photosynthesis by light and CO2. Photosynthate supply and phytohormones, particularly cytokinins, interact with nitrogen supply to control the expression of photosynthesis genes, the development of leaves and the whole plant nitrogen distribution, which provides the dominant basis for sink regulation of photosynthesis.

Arabidopsis↗
PubMed2001

Importance of needle age and shoot structure on canopy net photosynthesis of balsam fir (Abies balsamea): a spatially inexplicit modeling analysis.

We have developed a spatially inexplicit model of canopy photosynthesis for balsam fir (Abies balsamea (L.) Mill.) that accounts for key processes of light-shoot interaction including irradiance interception by the shoot, spatial aggregation of shoots into branches and crowns, the differential propagation of diffuse and direct light within the canopy, and an ideal representation of penumbra. Also accounted for in the model are the effects of the average radiative climate and shoot age on needle retention, light interception, and photosynthetic capacity. We used reduced versions of this model to quantify the effects of simplifying canopy representation on modeled canopy net photosynthesis. Simplifications explored were the omission of direct beam transformation into penumbral light and the use of different constant shoot properties throughout the canopy. The model was parameterized for a relatively dense balsam fir stand (leaf area index of 5.8) north of Québec City, Canada, and run using hourly meteorological data obtained at the site. The overall performance of the complete model was satisfactory, with maximum values of canopy net photosynthesis of 23 micromol (m(2) ground)(-1) s(-1) (83 mmol m(-2) h(-1)), and a near-saturation of the canopy at a photosynthetically active radiation photon flux density of about 750 micromol m(-2) s(-1) (2.7 mol m(-2) h(-1)). The omission of penumbral effects through the use of unattenuated direct (beam) radiation at all layers of the canopy, as used for broad-leaved species, reduced canopy net photosynthesis by 3.7%. Analysis of the results show that the small impact of penumbra on canopy net photosynthesis stems from the high proportion of diffuse radiation (73%) estimated from our meteorological data set; single-hour results under clear sky conditions approach theoretical bias values of about 30%. Use of mean shoot photosynthetic, light capture and light transmission properties throughout the canopy biased canopy net photosynthesis by less than 3%. However, simulations carried out based on properties of 1-year-old shoots throughout the canopy overestimated canopy net photosynthesis by 9%. Use of the shoot as our smallest functional unit was a potential source of bias because the differential absorption of direct and diffuse radiation within the shoot could not be factored into the model. Other sources of potential bias are discussed.

Abies↗
PubMed2003

C4 photosynthesis at low temperature. A study using transgenic plants with reduced amounts of Rubisco.

C(4) plants are rare in the cool climates characteristic of high latitudes and elevations, but the reasons for this are unclear. We tested the hypothesis that CO(2) fixation by Rubisco is the rate-limiting step during C(4) photosynthesis at cool temperatures. We measured photosynthesis and chlorophyll fluorescence from 6 degrees C to 40 degrees C, and in vitro Rubisco and phosphoenolpyruvate carboxylase activity from 0 degrees C to 42 degrees C, in Flaveria bidentis modified by an antisense construct (targeted to the nuclear-encoded small subunit of Rubisco, anti-RbcS) to have 49% and 32% of the wild-type Rubisco content. Photosynthesis was reduced at all temperatures in the anti-Rbcs plants, but the thermal optimum for photosynthesis (35 degrees C) did not differ. The in vitro turnover rate (kcat) of fully carbamylated Rubisco was 3.8 mol mol(-)(1) s(-)(1) at 24 degrees C, regardless of genotype. The in vitro kcat (Rubisco Vcmax per catalytic site) and in vivo kcat (gross photosynthesis per Rubisco catalytic site) were the same below 20 degrees C, but at warmer temperatures, the in vitro capacity of the enzyme exceeded the realized rate of photosynthesis. The quantum requirement of CO(2) assimilation increased below 25 degrees C in all genotypes, suggesting greater leakage of CO(2) from the bundle sheath. The Rubisco flux control coefficient was 0.68 at the thermal optimum and increased to 0.99 at 6 degrees C. Our results thus demonstrate that Rubisco capacity is a principle control over the rate of C(4) photosynthesis at low temperatures. On the basis of these results, we propose that the lack of C(4) success in cool climates reflects a constraint imposed by having less Rubisco than their C(3) competitors.

Carbon Dioxide↗
PubMed2006

Regulation of photosynthesis and oxygen consumption in a hypersaline cyanobacterial mat (Camargue, France) by irradiance, temperature and salinity.

Short-term effects of irradiance (0-1560 micromol photons m(-2) s(-1)), temperature (10-25 degrees C), and salinity (40-160) on oxygenic photosynthesis and oxygen consumption in a hypersaline mat (Salin-de-Giraud, France) were investigated with microsensors under controlled laboratory conditions. Dark O(2) consumption rates were mainly regulated by the mass transfer limitations imposed by the diffusive boundary layer. Areal rates of net photosynthesis increased with irradiance and saturated at irradiances >400 micromol photons m(-2) s(-1). At low irradiances, oxygen consumption increased more strongly with temperature than photosynthesis, whereas the opposite was observed at saturating irradiances. Net photosynthesis vs. irradiance curves were almost unaffected by decreasing salinity (100 to 40), whereas increasing salinities (100 to 160) led to a decrease of net photosynthesis at each irradiance. Dark O(2) consumption rates, maximal gross and net photosynthesis at light saturation were relatively constant over a broad salinity range (60-100) and decreased at salinities above the in situ salinity of 100. Within the range of natural variation, temperature was more important than salinity in regulating photosynthesis and oxygen consumption. At higher salinities the inhibitory impact of salinity on these processes and therefore the importance of salinity as a regulating environmental parameter increased, indicating that in more hypersaline systems, salinity has a stronger limiting effect on microbial activity.

Adaptation, Physiological↗
PubMed2003

[Experimental study on crop photosynthesis, transpiration and high efficient water use].

It is well known that the development of water-saving agriculture is a strategic choice for getting rid of the crisis of water shortage. In this paper, the crop photosynthesis, transpiration, stomatic behavior, and their affecting factors were studied in view of increasing the crop water use efficiency. The experimental results showed that there was a parabola relationship between photosynthesis and transpiration. The transpiration at the maximum photosynthesis was a critical value, above which, transpiration was the luxurious part. The luxurious transpiration could be controlled without affecting photosynthetic production. It is possible that the measures for increasing stomatic resistance and preventing transpiration could save water, and improve photosynthesis and yield as well. The photosynthesis rate increased with photosynthetic active radiation, and the light saturation point for photosynthesis existed. The light saturation point of dry treatment was much lower than that of wet treatment, and the relationship between transpiration and radiation was linear. When the photosynthetic active radiation was bigger than 1,000 mumol.m-2.s-1, some treatments could be carried out for decreasing transpiration and improving photosynthesis.

Crops, Agricultural↗
PubMed2006

[Physiology and ecology of Pometia tomentosa photosynthesis in tropical seasonal rain forest].

Pometia tomentosa is a dominant uppermost canopy tree in Xishuangbanna tropical seasonal rain forest. In this paper, the photosynthetic characteristics of the three layers of P. tomentosa canopy were measured with Li-6400 portable photosynthesis system, and the results showed that P. tomentosa had the characteristics of high light saturation point (1 000 - 1 500 micromol x m(-2) x s(-1)) and low compensation point (7.7 - 15.3 micromol x m(-2) x s(-1)). Its leaf photosynthesis had the adaptive responses when the high irradiance changed. PAR was the main factor affecting the diurnal changes of net photosynthesis. In December, the leaf grew well, and had a high ability of photosynthesis, with the diurnal change of P. for upper layer exhibiting single-peaked pattern and the maximum value being 8.9 micromol CO2 x m(-2) x s(-1). April was the alternative period of old and young leaves, and the ability of photosynthesis was dropped, with the diurnal change of P(n) for upper layer following double-peaked curve and the maximum value being 4.3 micromol CO2 x m(-2) x s(-1). The highest net photosynthesis rate was observed in July, with the diurnal change of P. for upper and middle layers exhibiting single-peaked pattern and that for lower layers being double-peaked. Short-term enriched CO2 concentration could evidently increase the photosynthesis of P. tomentosa, while the stomatic conductance and transpiration would be inhibited. When the CO, concentration increased from 400 micromol x mol(-1) to 800 micromol x mol(-1), water use efficiency (WUE) was increased by 50% - 100% in dry season, but rather low in wet season.

Adaptation, Physiological↗
PubMed2001

Increased heat sensitivity of photosynthesis in tobacco plants with reduced Rubisco activase.

High temperature inhibits photosynthesis by several mechanisms including deactivation of Rubisco. The inhibition of photosynthesis by high temperature and its relationship to Rubisco deactivation was studied using tobacco (Nicotiana tabaccum L. cv W38) transformed with a Rubisco activase gene inserted in the antisense orientation and untransformed controls. High temperature (42 degrees C) reduced photosynthesis in both lines of plants. However, photosynthesis recovered nearly completely in wild-type plants and very little in plants lacking Rubisco activase. The F(0)' level of chlorophyll fluorescence decreased and q(N) increased in the control plants during heating. In the antisense plants, q(N) was always high and F(0)' increased slightly during heat stress. NADP-malate dehydrogenase activation was unaffected by heat stress in control plants but was increased in the transgenic plants, consistent with a high redox status in the chloroplast. In wild-type plants, the inhibition of photosynthesis could be explained by a reversible decarbamylation of Rubisco and an acceptor-side limitation imposed on photosynthetic electron transport. However, in the anti-activase plants, carbamylation was low and constant and could not explain how photosynthesis was reduced at high temperature. Because ribulose bisphosphate was saturating at high temperature, the reduction in photosynthesis must have been caused by some impairment of Rubisco function not reflected in measurements of activation state or carbamylation status. This in vivo Rubisco impairment was not relieved upon return to lower temperature. We speculate that the reversible decarbamylation of Rubisco at moderately high temperature may be a protective mechanism by which the plant avoids more serious effects on Rubisco and the rest of the photosynthetic apparatus.

Journal Article↗
PubMed2002

A list of personal perspectives with selected quotations, along with lists of tributes, historical notes, Nobel and Kettering awards related to photosynthesis.

The history of photosynthesis research can be found in original papers and books. However, a special history is available from the prefatory chapters and the personal perspectives of various researchers who published them in several journals over the last 40 years. We have compiled a list of such perspectives published since 1964. Selection is not easy, especially of authors who were not directly engaged in photosynthesis research; some are included for their special insights related to central issues in the study of photosynthesis. Our journal, Photosynthesis Research, contains other valuable historic data in the occasional tributes, obituaries and historical notes, that have been published. Lists of these items are included. This article ends by listing the Nobel prizes related to photosynthesis and the Kettering Awards for Excellence in Photosynthesis Research. Wherever possible, a web page address is provided. The web page addresses have been taken from the article 'Photosynthesis and the Web: 2001' by Larry Orr and Govindjee, available at http://www.life.uiuc.edu/govindjee/photoweb and at http://photoscience.la.asu.edu/photosyn/ photoweb/default.html.When I find a bit of leisureI trifle with my papers.This is one of the lesserfrailities.'- Horace, Satires I, IV.

Journal Article↗
PubMed2003

Photosynthesis research in India: transition from yield physiology into molecular biology.

Photosynthesis research in India can be traced back several thousand years, with the mention of the Sun energizing the plants, which form food for all living creatures on the earth (from the Mahabharata, the great epic, ca. 2600 B.C.) and the report of Sage Parasara (ca. 100 B.C.) on the ability of plants to make their own food, due to their pigments. With the pioneering studies by Sir Jagdish Chandra Bose, work on photosynthesis proceeded steadily during the first half of the 20th century. Some of the classic reports during this period are: malate metabolism in Hydrilla, spectrophotometric estimation of chlorophylls, importance of spectral quality for photosynthesis - an indication of two photosystems, photoinactivation of photosynthesis, and importance of flag leaf photosynthesis to grain yield. After the 1960s, there was a burst of research in the areas of physiology and biochemistry of carbon assimilation and photochemistry. A significant transition occurred, before the beginning of new millennium, into the area of molecular biology of chloroplasts, regulation of photosynthesis and stress tolerance. Future research work in India is geared to focus on the following aspects of photosynthesis: elucidation/analysis of genes, molecular biology/evolution of enzymes, development/use of transgenics and modeling.

Journal Article↗
PubMed1998

Seedlings of five boreal tree species differ in acclimation of net photosynthesis to elevated CO(2) and temperature.

Biochemical models of photosynthesis suggest that rising temperatures will increase rates of net carbon dioxide assimilation and enhance plant responses to increasing atmospheric concentrations of CO(2). We tested this hypothesis by evaluating acclimation and ontogenetic drift in net photosynthesis in seedlings of five boreal tree species grown at 370 and 580 &mgr;mol mol(-1) CO(2) in combination with day/night temperatures of 18/12, 21/15, 24/18, 27/21, and 30/24 degrees C. Leaf-area-based rates of net photosynthesis increased between 13 and 36% among species in plants grown and measured in elevated CO(2) compared to ambient CO(2). These CO(2)-induced increases in net photosynthesis were greater for slower-growing Picea mariana (Mill.) B.S.P., Pinus banksiana Lamb., and Larix laricina (Du Roi) K. Koch than for faster-growing Populus tremuloides Michx. and Betula papyrifera Marsh., paralleling longer-term growth differences between CO(2) treatments. Measures at common CO(2) concentrations revealed that net photosynthesis was down-regulated in plants grown at elevated CO(2). In situ leaf gas exchange rates varied minimally across temperature treatments and, contrary to predictions, increasing growth temperatures did not enhance the response of net photosynthesis to elevated CO(2) in four of the five species. Overall, the species exhibited declines in specific leaf area and leaf nitrogen concentration, and increases in total nonstructural carbohydrates in response to CO(2) enrichment. Consequently, the elevated CO(2) treatment enhanced rates of net photosynthesis much more when expressed on a leaf area basis (25%) than when expressed on a leaf mass basis (10%). In all species, rates of leaf net CO(2) exchange exhibited modest declines with increasing plant size through ontogeny. Among the conifers, enhancements of photosynthetic rates in elevated CO(2) were sustained through time across a wide range of plant sizes. In contrast, for Populus tremuloides and B. papyrifera, mass-based photosynthetic rates did not differ between CO(2) treatments. Overall, net photosynthetic rates were highly correlated with relative growth rate as it varied among species and treatment combinations through time. We conclude that interspecific variation may be a more important determinant of photosynthetic response to CO(2) than temperature.

Journal Article↗