Photosynthesis In Spinach Research Articles

Gibberellic acid application on biomass, oxidative stress response, and photosynthesis in spinach (Spinacia oleracea L.) seedlings under copper stress.

The mechanism of Cu tolerance in plants and its control measures are of considerable significance for the remediation of Cu-contaminated soils. Gibberellic acid (GA3) is involved in plant growth and development and in the response to heavy metal stress. In the present study, changes in the biomass, oxidative stress response responses, and photosynthesis of spinach seedlings were examined under Cu stress with exogenous GA3 applied at concentrations of 0, 3, 5, 10, 20, 40, 60, or 80 mg L-1. Under Cu stress, the plant Cu concentration and oxidative damage were greater, photosynthetic parameters and biomass declined, and antioxidant enzyme activities and the proline concentration increased. However, spinach growth did not terminate, indicating that spinach seedlings had strong Cu tolerance. When low concentrations of GA3 (3-5 mg L-1) were added to Cu-stressed spinach seedlings, the damage caused by Cu stress to spinach seedlings was reduced, and the Cu tolerance of spinach seedlings was enhanced, which mainly manifested as reduced oxidation damage, an increased proline concentration, elevated antioxidant enzyme activities, decreased Cu concentration in leaves, and increased Cu concentration in roots, increased photosynthetic parameters, and an increased in the total biomass. In contrast, additions of GA3 at concentrations higher than 40 mg L-1 intensified oxidative damage and decreased the activities of antioxidant enzymes, photosynthetic parameters, and biomass. Additionally, the Cu concentration increased in leaves and decreased Cu concentration in roots, indicating that high concentrations of GA3 aggravated stress damage and severely influenced physiological functions in spinach seedlings. In summary, the application of 3-5 mg L-1 GA3 to spinach seedlings in Cu-contaminated soil can be used to reduce Cu toxicity to plants and increase Cu tolerance.

Real-Time Imaging of Oxygenic Photosynthesis in Spinach Using Bio-LSI

In the present study, we used a large-scale integration (LSI)-based amperometric sensor array system, designated Bio-LSI, to image in-vivo light-induced oxygen release from Spinach Leaves. The Bio-LSI device consists of 400 sensor electrodes with a pitch of 250 μm for rapid electrochemical imaging of large areas. Fig.1 shows schematic diagram for detection of oxygen production from Spinach leaves during photosynthesis using Bio-LSI. The imaging of oxygen production from Spinach leaves using Bio-LSI was also measured at light intensities of 20 and 30 klx (Fig 2, A3; a and b) which was found to be considerably higher as compared to the dark control (Fig 2, A2). The real-time monitoring of oxygen reduction current in control and light illuminated samples has also been presented (Fig. 2B). The results shows almost no changes in oxygen reduction current in non-illuminated Spinach leaves while a considerable changes have been observed in leaves illuminated with intensities of either 20 klx and 30 klx which was found to drop immediately at the switching off of the light source. Our results show that light induced oxygen release can be monitored using the device, suggesting that the Bio-LSI is a promising tool for real time imaging of oxygen release and the effects of stresses in whole Spinach leaf under in-vivo conditions. To the best of our knowledge, this report is the first to describe real time electrochemical imaging of light induced oxygen release in Spinach leaves using LSI-based amperometric sensors. References (1) T. Yasukawa, et al., Chem. Lett., 28,975-976, 1999. (2) K.Y.Inoue, et al. Lab Chip. 5, 848-856, 2015. Figure 1

Untangling metabolic and spatial interactions of stress tolerance in plants. 1. Patterns of carbon metabolism within leaves

The localization of the key photoreductive and oxidative processes and some stress-protective reactions within leaves of mesophytic C(3) plants were investigated. The role of light in determining the profile of Rubisco, glutamate oxaloacetate transaminase, catalase, fumarase, and cytochrome-c-oxidase across spinach leaves was examined by exposing leaves to illumination on either the adaxial or abaxial leaf surfaces. Oxygen evolution in fresh paradermal leaf sections and CO(2) gas exchange in whole leaves under adaxial or abaxial illumination was also examined. The results showed that the palisade mesophyll is responsible for the midday depression of photosynthesis in spinach leaves. The photosynthetic apparatus was more sensitive to the light environment than the respiratory apparatus. Additionally, examination of the paradermal leaf sections by optical microscopy allowed us to describe two new types of parenchyma in spinach-pirum mesophyll and pillow spongy mesophyll. A hypothesis that oxaloacetate may protect the upper leaf tissue from the destructive influence of active oxygen is presented. The application of mathematical modeling shows that the pattern of enzymatic distribution across leaves abides by the principle of maximal ecological utility. Light regulation of carbon metabolism across leaves is discussed.

Cerium relieving the inhibition of photosynthesis and growth of spinach caused by lead

Chloroplasts were isolated from spinach cultured in lead chloride-present, Ce 3+-administered, cerium chloride-administered lead chloride-present Hoagland's media or that of Hoagland's media. The experimental study demonstrated the effects of cerium (Ce) on distribution of light energy and photochemical activities of spinach chloroplast grown in lead (Pb)-present media. It was observed that Pb 2+ significantly inhibited photosynthesis in spinach, including light absorption, energy transfer from LHCII to photosystem II, excitation energy distribution from photosystem I to photosystem II, and transformation from light energy to electron energy and oxygen evolution of chloroplasts, and decreased spinach growth. However, Ce 3+ treatment to Pb 2+-present chloroplasts could obviously improve light absorption and excitation energy distribution in both photosystems and increase activity of photochemical reaction and oxygen evolution of chloroplasts. The results suggested that Ce 3+ under Pb 2+ stress could maintain the stability of chloroplast membrane, and improve photosynthesis of spinach chloroplast, thus promote spinach growth.

Temperature acclimation of photosynthesis in spinach leaves: analyses of photosynthetic components and temperature dependencies of photosynthetic partial reactions

ABSTRACTSpinach (Spinacia oleracea) plants were grown under the day/night temperature regime of 15/10 °C (LT) or 30/25 °C (HT). The plants were also transferred from HT to LT when the sample leaves were at particular developmental stages (HL‐transfer). With fully mature leaves, the light‐saturated photosynthetic rate (A) at the ambient CO2 concentration (Ca) of 1500 µL L−1 (A1500) and the initial slope of A versus intercellular CO2 concentration (Ci) at low Ci region (IS) were obtained to assess capacities of RuBP regeneration and carboxylation. Photosynthetic components including Rubisco and cytochrome f (Cyt f) were also determined. The optimum temperatures for A at Ca of 360 µL L−1 (A360), A1500 and IS in HT leaves were 27, 36 and 24 °C, whereas those in LT leaves were 18, 30 and 18 °C. The optimum temperatures in HL‐transfer leaves approached those of LT leaves with the increase in the duration at LT. The shift in the optimum temperature was greater and quicker for IS than A1500. By the HL‐transfer, the maximum values of A1500 and IS also increased. The maximum A1500 and Cyt f content increased more promptly than IS and Rubisco content. Changes in the Cyt f/Rubisco ratio were reflected to those in the A1500/IS ratio. Taken together, photosynthetic acclimation to low temperature in spinach leaves was due not only to the change in the balance of the absolute rates of RuBP regeneration and carboxylation but also to the large change in the optimum temperature of RuBP carboxylation.

Distribution of lanthanum among the chloroplast subcomponents of spinach and its biological effects on photosynthesis: location of the lanthanum binding sites in photosystem II

The effects of lanthanum at different concentrations on the related photosynthetic activities of Hill reaction, Mg2+-ATPase and Ca2+-ATPase in spinach chloroplast were studied. Experimental results showed that lanthanum can increase all the activities at suitable concentration (15–30 mg · L−1), however, it behaves toxically on them when over used (60 mg · L−1). To get an improved understanding of the mechanism of lanthanum effects on the photosynthesis of spinach, the different subcomponents in the chloroplast of the cultured spinach were isolated, and the content of lanthanum in each subcomponent was determined by ICP-MS. The results obtained indicated that among these different subcomponents, about 90% out of the total chloroplast lanthanum was located in photosystem II (PS II) while there was little lanthanum in photosystem I (PS I). Moreover, size exclusion high performance liquid chromatography (SE-HPLC) coupled with online UV and ICP-MS detections was novelly used for locating lanthanum binding sites in PS II proteins for the first time. It was found that lanthanum has two binding sites in PS II: La associates with chlorophyll together with magnesium in PS II by partly replacing magnesium and also shares the common binding sites of PS II proteins together with the inorganic cofactors of calcium and manganese, influencing the process of photosynthesis.

Interactive Effects of Sodium and Potassium on the Growth and Photosynthesis of Spinach and Komatsuna

Two cultivars of spinach and one cultivar of komatsuna were sand cultured using a nutrient solution with Na and K in various combinations. The growth (fresh weight of shoot) of spinach cv. Atlas was significantly increased when 1.4 mM KC1 of the 7 m M KO was replaced with 1.4 mM NaCl, although the growth was reduced when more KC1 was replaced with NaCl. In another spinach cv. All Right, however, NaCl substituting for 20% of KC1 showed no significant effects. In komatsuna, Na used in place of K at any ratio reduced the growth. The growth of spinach cv. Atlas was increased by applying 20 mM NaCl, irrespective of K dose (480 - 2400 mg K2O per 1/2000 a Wagner pot). The growth of spinach cv. All Right was also increased by 20 mM NaCl when K was at a deficient level (480 - 960 mg K20 per pot), but was not when K was at: an excessive level (1920 - 2400 mg K2O per pot). In komatsuna, 20 mM NaCl reduced the growth. In spinach, Na prevented the decrease of the photosynthetic rate and stomatal conductance caused by K deficiency.

An evaluation of direct and indirect mechanisms for the ?sink-regulation? of photosynthesis in spinach: Changes in gas exchange, carbohydrates, metabolites, enzyme activities and steady-state transcript levels after cold-girdling source leaves

Mature source leaves of spinach (Spinacia oleracea L.) plants growing hydroponically in a 9 h light (350 μmol photons·m−2 · s−1)/15 h dark cycle at 20° C in a climate chamber were fitted with a cold girdle around the petiole, 2 h into the light period. Samples were taken 1, 3 and 7 h later, and at the end of the photoperiod for the following 4 d. Control samples were taken from ungirdled leaves. In the first 7 h after fitting the cold girdle there was (compared to the control leaves) a two to five-fold accumulation of sucrose, glucose, fructose and starch, a 40–50% increase of hexose-phosphates and ribulose-1,5-bisphosphate, a decrease of glycerate-3-phosphate, a small decrease in sucrose-phosphate synthase activation, an increase of fructose-2,6-bisphosphate, increased activation of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), but no significant change in photosynthetic rate or stomatal conductance. Steady-state transcript levels for rbcS (small subunit of Rubisco) and atp-D (D-subunit of the thylakoid ATP synthase) decreased 30%, cab (chlorophyll-a-binding protein) decreased by 15% and agp-S (S-isoenzyme of ADP-glucose pyrophosphorylase) and nra (nitrate reductase) rose twofold. On the following days, levels of carbohydrates continued to rise and the changes of metabolites were maintained. Transcripts for rbcS, cab and atpD declined to 20, 70 and 25% of the control values. From day 3 onward the maximum activity of Rubisco declined. This was accompanied by a further increase of Rubisco activation to over 90% and, from day 4 onwards, an inhibition of photosynthesis which was associated with high internal CO2 concentration (ci), high ribulose-1,5-bisphosphate, and low glycerate-3-phosphate. When the cold-girdle was removed on day 5 there was a gradual recovery of photosynthesis and decline of ci over the next 2 d. Hexose-phosphates levels and transcripts for rbcS, cab and atp-D completely recovered within 2 d, even though the levels of carbohydrates had not fully recovered. Activity of Rubisco only reverted partly after 2 d, and Rubisco activation state and the ribulose-1,5-bisphosphate/glycerate-3-phosphate ratio were still higher than in control leaves. Transcripts for nra and agp-S were also still higher than in control leaves. It is concluded (i) that a reversible modulation of gene expression in response to the export rate plays a central role in the mid-term feedback “sink” regulation of photosynthesis, and (ii) that feedback regulation of CO2 fixation by changes of Pi are of little importance in spinach under these conditions. Further (iii) the rapid and reciprocal changes in nra and agpS transcripts, compared to rbcS, provide evidence that gene expression could also contribute to the modulation of nitrate assimilation and carbohydrate storage in conditions of decreased sink demand.

On the Function of Mitochondrial Metabolism during Photosynthesis in Spinach (Spinacia oleracea L.) Leaves (Partitioning between Respiration and Export of Redox Equivalents and Precursors for Nitrate Assimilation Products).

The functioning of isolated spinach (Spinacia oleracea L.) leaf mitochondria has been studied in the presence of metabolite concentrations similar to those that occur in the cytosol in vivo. From measurements of the concentration dependence of the oxidation of the main substrates, glycine and malate, we have concluded that the state 3 oxidation rate of these substrates in vivo is less than half of the maximal rates due to substrate limitation. Analogously, we conclude that under steady-state conditions of photosynthesis, the oxidation of cytosolic NADH by the mitochondria does not contribute to mitochondrial respiration. Measurements of mitochondrial respiration with glycine and malate as substrates and in the presence of a defined malate:oxaloacetate ratio indicated that about 25% of the NADH formed in vivo during the oxidation of these metabolites inside the mitochondria is oxidized by a malate-oxaloacetate shuttle to serve extramitochondrial processes, e.g. reduction of nitrate in the cytosol or of hydroxypyruvate in the peroxisomes. The analysis of the products of the oxidation of malate indicates that in the steady state of photosynthesis the activity of the tricarboxylic acid cycle is very low. Therefore, we have concluded that the mitochondrial oxidation of malate in illuminated leaves produces mainly citrate, which is converted via cytosolic aconitase and NADP-isocitrate dehydrogenase to yield 2-oxoglutarate as the precursor for the formation of glutamate and glutamine, which are the main products of photosynthetic nitrate assimilation.

Effect of long‐term H2S fumigation on photosynthesis in spinach. Correlation between CO2 fixation and chlorophyll a fluorescence

Spinach plunts (Spinacia oleracea L. cv. Monosa) were exposed to air with and without 0.25 μl l‐1 H2S. Effects of H2S exposure for up to 18 days on photosynthesis, dark respiration and on chlorophyll a fluorescence were studied. Dark respiration was not affected by H2S fumigation. Photosynthetic CO2 fixation decreased linearly with time in both control and fumigated plants. The rate of decrease in CO2 fixation was faster in the fumigated plants; after 14 days of exposure the fumigated plants showed a decrease in CO2 fixation of 23%äs compared with the control plants. The H2S‐induced decrease in CO2 fixation was accompanied by a decrease in quenching of the chlorophyll fluorescence. The most characteristic change in chlorophyll fluorescence was a decreased difference between maximum and steady‐state fluorescence [(P‐T)/P), suggesting a reduced efficiency in the use of photochemical energy in photosynthesis. Differences in CO2 fixation were more pronounced whcn measured at high light intensity; the maximum rate of CO2 fixation at light saturation decreased significantly with time in the H2S‐exposed plants; after 14 days of H2S exposure a decrease of more than 70% was noted. The decrease in CO2 fixation could not be attributed to a decreased chlorophyll content; on the contrary, chlorophyll content even slightly increased during fumigation. The initial increase in CO2 fixation rate with increasing light intensity was also reduced by prolonged H2S fumigation, indicating an effect of H2S fumigation on photosynthetic electron transport.Finally, the phytotoxicity of H2S is discusscd in relation to the H2S‐induced changes in photosynthetic CO2 fixation and chlorophyll a fluorescence, and the effect of H2S on leaf development observed in earlier studies.

Effects of Nitrogen Nutrition on Electron Transport Components and Photosynthesis in Spinach

Spinach plants (Spinacia oleracea L.) were grown in hydroponic culture in a glasshouse under full sunlight. They were supplied with different concentrations of nitrate nitrogen in solution, ranging from 1 to 12 mM, in order to produce leaves with different nitrogen contents. Oxygen evolution at CO2 saturation was measured as a function of absorbed irradiance in leaf discs with an oxygen electrode. Electron transport activities, reaction centre densities, cytochrome f and plastoquinone contents, RuP2 carboxylase and coupling factor activities and soluble protein content were measured in similar material. Although nitrogen and chlorophyll contents per unit leaf area were reduced by 60% by nitrogen deficiency, when expressed on a chlorophyll basis, thylakoid components, electron transport activities and the rate of oxygen evolution at CO2 saturation were similar between nitrogen treatments. In contrast, the content of soluble protein and RuP2 carboxylase expressed on a chlorophyll basis was greater the greater the nitrogen content per unit leaf area. Therefore the ratio of RuP2 carboxylase activity to electron transport activity increased in leaves having greater nitrogen content.

Response of Photosynthesis and Dark-CO2-Fixation to Light, CO2and Temperature in Leaf Slices under Osmotic Stress

Photosynthesis and dark-CO2-fixation were measured in vacuum-infiltrated leaf slices from the mesophyte Spinacia oleracea and the Mediterranean xerophyte Arbutus unedo under hypertonic stress as a function of light-intensity, CO2-concentration and temperature, in the absence of stomatal control. Under hypertonic stress, photosynthesis and dark-CO2-fixation were inhibited in leaf tissue from both plants. 50% inhibition of photosynthesis in spinach occurred at about −3.0 MPa, and of dark-CO2-fixation at about −3.5 MPa. 50% inhibition of photosynthesis in Arbutus unedo was reached at about −4.0 MPa (sorbitol as osmoticum). In both plants, osmotic dehydration decreased the slope and the maximum of the CO2- and light-response curves. The slope of the CO2-response curve of dark-CO2-fixation was also decreased under hypertonic stress, but the inhibition of the maximal fixation rate was less obvious than for photosynthesis. Photosynthesis and dark-CO2-fixation differed significantly in their response to high temperature: under light- and CO2-saturation, photosynthesis of spinach leaf slices had a temperature optimum at about 37 °C, and it was nearly completely inhibited at 45 °C. The rate of dark-CO2-fixation, however, increased continuously up to 45 °C. Osmotic dehydration increased the resistance of photosynthesis to high temperatures.

Effect of BASF 13-338, a Substituted Pyridazinone, on Lipid Metabolism in Leaf Tissue of Spinach, Pea, Linseed, and Wheat

A substituted pyridazinone (BASF 13-338) inhibited photosynthesis in spinach (Spinacia oleracea, Hybrid 102 Arthur Yates Ltd.) leaf discs and reduced the incorporation of [1-(14)C]acetate into trienoic acids of diacylgalactosylglycerol while causing radioactivity to accumulate in diacylgalac-tosylglycerol dienoic acids. Although BASF 13-338 inhibited photosynthesis in isolated spinach chloroplasts, it did not prevent dienoate desaturation. In discs, the labeling of fatty acids was affected by the inhibitor only in diacylgalactosylglycerol. Very little radioactivity was incorporated into trienes of phosphatidylcholine and the proportion of the label recovered in the fatty acids of phosphatidylcholine was not changed by BASF 13-338. The herbicides caused an increase in the proportion of the lipid (14)C incorporated into diacylgalactosylglycerol and a decrease in labeling of phosphatidylcholine, whereas the proportion of (14)C recovered in other lipids remained unchanged. Similar results were obtained with pea (Pisum sativum cv. Victory Freeze), linseed (Linum usitatissimum cv. Punjab), and wheat (Triticum aestivum cv. Karamu). With these species, a greater proportion of the label was incorporated into phosphatidylcholine and less into diacylgalactosylglycerol than with spinach. The data indicate that trienoate synthesis uses diacylgalactosylglycerol as substrate. BASF 13-338 appears to act at that step, and seems to cause in spinach a shift in polyenoate synthesis from the pathway involving microsomal phosphatidylcholine to the pathway operating inside the chloroplast.

Effects of pH and other factors on the phosphate dependence of photosynthesis in spinach chloroplasts

Chloroplast stromal volume and pH influenced the phosphate (Pi)-dependence of photosynthesis of spinach (Spinacia oleracea L.) chloroplasts. Decreasing the sorbitol concentration in the reaction mixture from 0.35 to 0.25 M, or decreasing the external pH from 8.3 to 7.3, extended the induction period of photosynthesis and decreased both the optimal [Pi] and the minimal [Pi] required to inhibit O2 evolution completely. At least part of the effect of external pH was attributable to changes in stromal pH on the basis of effects of NH4Cl and sodium acetate at a constant external pH. When the external pH was increased from 7.3 to 8.3, the stromal pH changed only about 0.6 pH units. Hence, the pH gradient across the envelope was diminished and the efflux of phosphoglycerate relative to dihydroxyacetone phosphate was enhanced.Calvin-cycle activity, varied with light intesity or electron transport inhibitors, affected the rate of photosynthesis but not the induction period or the Pi optimum for photosynthesis. Relatively low Calvin-cycle activity was apparently sufficient to fill metabolite pools and thus terminate the induction period. The results indicate that pH does not affect the Pi dependence of photosynthesis by reducing Calvin-cycle activity. Rather, it is postulated that at low stromal pH, larger metabolic pools are required to maintain maximum rates of photosynthesis because of changes in substrate affinity of some Calvin-cycle enzymes. Consequently, chloroplast photosynthesis would be more sensitive to exogenous Pi.

Influence of Post-action of High Temperatures on Photosynthetic Activity, Composition of Lamellar Proteins and Spectral Characteristics of Pigment Systems I and II )

Summary Post-action on photosynthesis in spinach leaves after heat-treatment for 5 min at 25, 40, 45 and 50 °C was studied. Samples for analyses were taken at 0, 24 and 48 h after treatment. It was found that the inhibitory action after 5 min treatment of the leaves at 40 and 45 °C was most strongly expressed immediately after the treatment. 24 h after treatment the variant at 40 °C almost restored its photosynthetic activity close to that of the control (25 °C). Restoration, though inconsiderable, was observed with the variant at 45 °C too, while at 50 °C the inhibition of photosynthesis was irreversible. The heat-treatments did not lead to significant changes in the composition of the structural proteins in chloroplast, including those which are components of pigment systems I and II. Even 48 h after leaf treatment at 45 and 50 °C (of which the first temperature very strongly inhibits and the second one completely eliminates photosynthesis) the electrophoretic profile of the structural proteins remained almost unchanged. No significant changes in spectral characteristics of the second derivate of the absorption function and the fluorescence spectra of photosystems I and II were observed. This indicates considerable stability of the bonds between pigment + pigment and pigment + protein.