Photochemical Efficiency Of PS Research Articles

Effects of exponential N fertilization on the growth and nutrient content in clonal Cunninghamia lanceolata seedlings

A pot experiment was conducted in a greenhouse on one-year-old clonal seedlings of Cunninghamia lanceolata. Five treatments were designed including control, conventional fertilization and three exponential fertilization treatments, with N application rates of 0, 0.5, 0.5, 1.0 and 2.0 g·seedling-1, with N applied at 20 times at 10-day interval. The height, ground diameter, biomass, chlorophyll fluorescence and N absorption were measured after 210 days of N application. The results showed that fertilization significantly promoted the seedling height, ground diameter and biomass with the optimal values of 59.0 cm, 6.0 mm, 52.99 g·seedling-1, in exponential fertilization treatment of 1.0 g N·seedling-1. Chlorophyll fluorescence in exponential fertilization treatments was significantly higher than that in conventional fertilization. The photochemical quenching, PS2 electron transport rate and photochemical efficiency of PS2 in exponential fertilization treatments increased first and then decreased, with the optimal values of 0.89, 35.79 and 0.71 in 1.0 g N·seedling-1 treatment. N contents in different organs of C. lanceolata clonal seedlings were in the order of leaf > root > stem. Compared with the CK, the N contents in root, stem and leaf increased by 39.6%, 16.6% and 41.1% in the conventional fertilization treatment, and by 22.6%-81.4%, 27.3%-152.6% and 73.6%-135.5% in exponential fertilization treatments. N contents in root, stem and leaf in the exponential fertilization treatments of 1.0 and 2.0 g N·seedling-1 were significantly higher than those in the conventional fertilization treatment. P and K contents were not significantly different among the different organs. Considering the characteristics of seedling growth, chlorophyll fluorescence, the contents of N, P and K, the exponential fertilization treatment of 1.0g N· seedling-1 was the best in cultivating C. lanceolata clonal seedlings in this experiment.

Leaf economics spectrum among different plant functional types in Beijing Botanical Garden, China.

We measured leaf photosynthetic and chlorophyll fluorescence parameters as well as leaf area, dry biomass, and nitrogen content of different plant functional types (PFTs) at the Beijing Botanical Garden, and analyzed the leaf economics spectrum (LES) among different PFTs. The results showed that the plants with the life form of grasses, those with an annual type of life history, and with a C4 photosynthetic pathway might provide a quick return on investment for the species located at one end of the LES. Similarly, the plants with a life form of trees and shrubs, with a perennial type of life history, and with a C3 photosynthetic pathway might provide a slower return on investment for the species located at the other end of the LES. This indicated that plants with different PFTs might have diverse strategies that allowed them to adapt to the environment through a trade-off among leaf traits. The results showed that the LES existed among different PFTs. Remarkable diffe-rences were observed in most of the leaf traits among different PFTs. The various life forms analyzed here were ranked in the order of grasses > vines > shrubs > trees based on specific leaf area (SLA), mass-based nitrogen concentration (Nmass), mass-based photosynthetic capacity (Amass), and photosynthetic nitrogen use efficiency (PNUE). Among the different life histories, SLA, Nmass, Amass, and PNUE in annual species were significantly higher than those in perennial species. In addition, Amass, PNUE, and the quantum yield of PS2 electron transport (ΦPS2) were higher in C4 species than in C3 species. Nmass, Amass, and SLA were significantly positively correlated with each other. SLA was significantly negatively correlated with the photochemical efficiency of PS2 in the light (Fv'/Fm'), whereas it was significantly positively correlated with PNUE.

Effect of extreme temperatures at different stages during grain filling on rice seed weight and germination and its regulations

A series of studies were carried out in chamber room to investigate the injury mechanism under extreme temperature and at different grain filling stages with foliar application of plant growth regulators (Abscisic acid-ABA and salicylic acid-SA) on the rice cultivar Huanghuazhan. Grain filling rate and grain weight were measured as yield components, while seed germination rate, germination index and seed vigour index were measured as seed quality indices. Chlorophyll fluorescence parameters and active oxygen resistance activity were also analyzed. The results showed that the rate of grain filling and grain weight were significantly reduced under the extreme temperature conditions and at higher concentrations of the plant growth regulators. Superoxide dismutase (SOD) activity increased and decreased among treatments, while malondialdehyde (MDA) content was significantly high. Maximal photochemical efficiency of PS II (Fv/Fm) and the potential photochemical efficiency of PS II (Fv/Fo) also decreased under high temperature stress, whilst it increased and decreased under low temperature stress among treatments.

Changes in chlorophyll content and fluorescence and fruit yield contributing traits in different genotypes of strawberry (Fragaria x ananassa DUCH.)

Analysis of changes in chlorophyll fluorescence parameters in strawberry leaves was based on a field experiment performed in the years 2009–2010. Ten genotypes including 5 cultivars: ‘Kent’, ‘Teresa’, ‘Senga Sengana’, ‘Chandler’ and the breeding clone 1387 as well as their inbred progeny, were the object of the study. During the experiment the following indicators were evaluated: chlorophyll a and b content in fresh leaf mass as well as fluorescence parameters: minimum (F0) and maximum fluorescence yield (Fm), photochemical efficiency of PS II (Fv/Fm), actual quantum yield of PSII photochemistry (Y), minimum (F0’) and maximum efficiency of fluorescence (Fm’) in the light, coefficient of photochemical (qP) and non-photo- chemical (qN) fluorescence quenching. In this work, we also examined the effect of repeated inbreeding on strawberry fruit yield and yield components. The analysis of changes of these parameters showed that inbreeding caused a reaction in all tested cultivars. In all inbred progeny, chlorophyll a and b content decreased compared to the cultivars. Generally, the photoche- mical efficiency of photosystem II (Fv/Fm) and the parameter ΔF/ Fm’ were not affected by strong inbreeding. In analyzing the values of the coefficients qP and qN, it has been observed that changes in their values depend on the sensitivity of the examined genotypes to self-pollination. The functioning of PS II is the most sensitive indicator of the effect of various factors on plants and is useful, among others, in breeding to select plants with a required genotype. The yield – determining features such as: fruit yield per plant, weight of single fruit, number of fruit per plant and weight of leaves per plant in S3 generation, were lower as compared with parental forms.

Mechanism associated with nonstructural carbohydrate accumulation in submergence tolerant rice (Oryza sativa L.) cultivars

Nonstructural carbohydrate (NSC) accumulation in submergence tolerant rice cultivars (cv) was studied in six Indica rice [Oryza sativa (L.)] cv under control and simulated submerged conditions. Tolerant cultivars accumulated greater contents of NSC compared to the susceptible cultivars. Starch and total NSC content showed significant positive association with survival percentage. On the other hand, elongation due to submergence was significantly a negative association with survival. The CO2 photosynthetic rate, chlorophyll content, maximum photochemical efficiency of PS II (Fv/Fm), and activities of Rubisco were not significantly different between tolerant and susceptible cv under control condition. The ADP glucose pyrophosphorylase (AGPPase) activity was significantly higher in the tolerant cv and was a positive association with starch/NSC, whereas Fructose 1,6-diphosphatase (FDPase) activity was significantly higher in susceptible cv compared to tolerant cv and was a negative association with starch/NSC. Greater activities of AGPPase along with lower activities of FDPase might facilitate greater accumulation of NSC in tolerant rice cultivars.

Interactive effects of simultaneous ozone and fluoranthene fumigation on the eco-physiological status of the evergreen conifer, Japanese red pine (Pinus densiflora Sieb et. Zucc.)

Forest decline has long been attributed to air pollution and acid rain/fog, with ozone having a record for damaging trees. This study investigated eco-physiological changes on Japanese red pine caused by simultaneous fumigation of O(3) (O) and fluoranthene (F) over a 90 day period. Seedlings were exposed individually or in combinations to 10 muM fluoranthene and O(3) (3 ppm and 6 ppm in 60 days and 90 days, respectively) inside growth chambers. Eco-physiological parameters monitored included gas exchange, chlorophyll fluorescence, needle chlorophyll content, and visual appearance. After 90 days, O + F treatment showed deleterious effects on visual needle appearance and the net photosynthesis rate near saturated irradiance. In addition, decreased levels in stomatal conductance, photochemical efficiency of PS II in the dark, and total chlorophyll and Chl a: Chl b were observed. F only treatment showed similar results but in lesser magnitude compared with F + O treatment. O treatment alone showed no significant negative effect, probably due to its low concentration in the 60 day treatment. The addition of mannitol (OH radical scavenger) mitigated O + F and F negative effects. Fluoranthene deposited on Japanese red pine presents great eco-physiological damage risk, even at low O(3) concentration. Furthermore, the effects of O(3) assisted phyto-toxicity of fluoranthene on red pine may have relevance to other plant species.

Calcium protection of PS2 complex of Phaseolus coccineus from cadmium toxicity: In vitro study

The action of 10 and 20 mM Ca against harmful Cd effect on PS2 complex isolated from leaves of Phaseolus coccineus L. cv. Piękny Jaś was studied. The changes in fast chlorophyll a fluorescence induction kinetics and protein composition of PS2 complex were the symptoms of Cd toxicity and Ca protection of PS2 complex. Calcium applied at 10 mM concentration prevented F 0 reduction caused by the presence of 250–1000 μM Cd in the incubation mixture, but that of (the variable chlorophyll a fluorescence) F v, F m, F v/ F 0, and F v/ F m only at 250 μM Cd. Ca concentration doubling in the incubation mixture resulted in complete overcoming the toxicity of 250–1000 μM Cd to F v and F m. However, the protection of F v/ F 0 and the photochemical efficiency of PS2 ( F v/ F m) from 1000 μM Cd was only partial even at 20 mM Ca. A protective effect of 10 mM Ca on D1, D2 and 17 kDa proteins was found in PS2 complex exposed to 250 μM Cd, and on 43 kDa protein in the complex treated with 500 μM Cd. However, 20 mM Ca counteracted the toxicity of 500 μM Cd to the 43, 47 and 17 kDa proteins, as well as the harmful effect of 1000 μM Cd on 47 and 17 kDa ones.

Salinity reduced growth PS2 photochemistry and chlorophyll content in radish

When plants are grown under saline conditions, photosynthetic activity decreases leading to reduced plant growth, leaf area, chlorophyll content and chlorophyll fluorescence. Seeds and seedlings of radish (Raphanus sativus L.) were grown in NaCl solutions under controlled greenhouse conditions. The NaCl concentrations in complete nutrient solutions were 0 (control), 4.7, 9.4 and 14.1 dS m-1. The salinity reduced germination percentage and also delayed the germination rate as the salt level increased. Lengths and fresh weights of root and shoot decreased with the increasing salt concentration. Furthermore, photochemical efficiency of PS2 (Fv/Fm), photochemical quenching coefficient (qP), non photochemical quenching coefficient (qN), leaf area and chlorophyll content (SPAD value) were also reduced (P < 0.001) by salt stress. In contrast, the Fo/Fm ratio increased with increasing salt concentration while salinity showed no effect on the efficiency of excitation captured by open PS2 (Fv'/Fm'), electron transport rate (ETR), and leaf water content. Linear regression shows that the photochemical efficiency of PS2 (Fv/Fm) had a positive relationship with the photochemical quenching coefficient (qP), leaf area and chlorophyll content but had no relation with Fv'/Fm', Fo/Fm, and qN.

Carbon assimilation characteristics of plants in oasis-desert ecotone and their response to CO2 enrichment

Six species of more than 20-year-old desert woody plants in the oasis-desert ecotone were selected for study. The results showed that: (1) in different growing seasons δ13C values of assimilating organ varied between -14%. and -16%. for Haloxylon ammodendron (HA),-14%. - -15%. for Calligonum mongolicum (CM) and -25%. - -28%. for Caragana korshinskii (CK), Nitraria sphaerocarpa (NS) and Hedysarum scoparium (HS). (2) The net photosynthetic rate (Pn) of HA and CM was significantly higher than those of the other species. With the decrease in Pn for the six species, their intercellular CO2 concentration increased, but stomatal limitation value decreased under the intensive light. At the same time, the photochemical efficiency of PS II dropped to different degrees. (3) The CO2 enrichment experiment demonstrated that, Pn of HA and CM increased to different extent under 450 μmol/mol, but their Pn reduced or approximated to the current condition under 650 μmol/mol. Under 450 μmol/mol the efficiency for solar energy utilization of CK and HS significantly reduced and under 650 μmol/mol their respiration rate exceeded photosynthesis rate. It can be concluded that HA and CM have some function of pathway for C4 but the other three species have the function for C3. The decline in their Pn is mainly caused by non-stomatal factors. HA, CM, CK and HS exhibited photoinhibition, which disappeared in a short time. This is a kind of positive readjustment to adapting to the desert environment. HA and CM can adapt to the high CO2 environment, but CK and HS cannot. With the rise in atmospheric CO2 concentration and climate warming, the latter two species in the oasis-desert ecotone may be gradually degraded or even disappear.

Modifications in Photosynthetic Pigments and Chlorophyll Fluorescence in 20-Year-Old Pine Trees after a Four-Year Exposure to Carbon Dioxide and Temperature Elevation

Changes in pigment composition and chlorophyll (Chl) fluorescence parameters were studied in 20 year-old Scots pine (Pinus sylvestris L.) trees grown in environment-controlled chambers and subjected to ambient conditions (CON), doubled ambient CO2 concentration (EC), elevated temperature (ambient +2-6 °C, ET), or a combination of EC and ET (ECT) for four years. EC did not significantly alter the optimal photochemical efficiency of photosystem 2 (PS2; Fv/Fm), or Chl a+b content during the main growth season (days 150-240) but it reduced Fv/Fm and the Chl a+b content and increased the ratio of total carotenoids to Chl a+b during the 'off season'. By contrast, ET significantly enhanced the efficiency of PS2 in terms of increases in Fv/Fm and Chl a+b content throughout the year, but with more pronounced enhancement in the 'off season'. The reduction in Fv/Fm during autumn could be associated with the CO2-induced earlier yellowing of the leaves, whereas the temperature-stimulated increase in the photochemical efficiency of PS2 during the 'off season' could be attributed to the maintenance of a high sink capacity. The pigment and fluorescence responses in the case of ECT showed a similar pattern to that for ET, implying the importance of the temperature factor in future climate changes in the boreal zone.

Photoinhibition of Photosynthesis in Vitis berlandieri and Vitis rupestris Leaves under Field Conditions

Photoinhibition of photosynthesis was investigated in Vitis berlandieri and Vitis rupestris leaves under field conditions at different sampling time in a day. The degree of photoinhibition was determined by means of the ratio of variable to maximum chlorophyll fluorescence (Fv/Fm) and photosynthetic electron transport measurements. When the photochemical efficiency of PS2, Fv/Fm, markedly declined, F0 increased significantly in leaves of V. berlandieri, while F0 did not increase in V. rupestris leaves. Isolated thylakoids of leaves of V. berlandieri showed significant inhibition of whole chain and PS2 activities at midday. A smaller inhibition was observed for V. rupestris. Later, the leaves reached maximum PS2 efficiencies similar to those observed early in the morning during sampling at evening. The artificial exogenous electron donor Mn2+ failed to restore PS2 activity in both species, while DPC and NH2OH significantly restored PS2 activity in V. rupestris midday leaf samples. Quantification of the PS2 reaction centre protein D1 and 33 kDa protein of water splitting complex following midday exposure of leaves showed pronounced differences between V. berlandieri and V. rupestris leaves. The marked loss of PS2 activity noticed in midday samples was mainly due to the marked loss of D1 protein in V. berlandieri while in V. rupestris it was the 33 kDa protein.

Photosynthetic pigments and gas exchange during ex vitro acclimation of tobacco plants as affected by CO2 supply and abscisic acid

Nicotiana tabacum L. plantlets were grown in glass vessels or in Magenta boxes with better CO2 supply. To improve the ex vitro transfer we tested application of abscisic acid and elevated CO2 concentration. In the first two weeks after transfer, net photosynthetic rate, chlorophyll a+b content, and Chl a/b ratio were higher, and content of xanthophyll cycle pigments lower in M-plants than in G-plants, but during further growth the differences almost disappeared. ABA application alleviated the risk of wilting because it decreased stomatal conductance. The effect of ABA was enhanced under CE (28 days after transfer). In situ, PN was always higher at CE than at CA, but when measured under CA, positive effect of CE was found 2 and 16 days after transfer in M-plants and only 16 days after transfer in G-plants. Slightly increased Chl a content was found in all ABA-treated plants, and in M-plants grown under CE. The content of xanthophyll cycle pigments was lower under CE compared to CA, and the lowest one was found in ABA-treated M-plants grown under CE. On the contrary, the degree of their deepoxidation (DEPS) was slightly higher in plants grown under CE. No significant effects of ABA-treatment or growth under CE on fluorescence kinetic parameters were found and inconsistent effects on photochemical activities. The photochemical efficiency of PS2 (variable to maximum fluorescence ratio, Fv/Fm) after ex vitro transfer was similar to that in in vitro grown plants. This together with the values of DEPS indicated that no photodamage during ex vitro transfer occurred.

Cold Acclimation and Photoinhibition of Photosynthesis Accompanied by Needle Color Changes in Cryptomeria japonica during the Winter

This study focused on the physiological changes in Cryptomeria japonica accompanied by needle color changes during the winter. The physiological measurements include gas exchange, chlorophyll fluorescence, pigments, active oxygen scavenging enzymes, and several proteins in the photosynthetic apparatus. The light-saturated photosynthesis decreased during the winter. Total chlorophyll content and chlorophyll a/b ratio decreased; meanwhile xanthophyll cycle pigments and lutein contents increased significantly. These results indicate that cold acclimation had occurred. Photoinhibition was also observed in C. japonica which can be determined from the decreases in photochemical efficiency of PS II and the partial closure of PS II reaction centers. Small and large subunits of Rubisco and LHC II in the needles of C. japonica showed only a slight decrease during the winter, indicating that photoinhibition in C. japonica probably reflects a protective process to prevent more severe damage to the photosynthetic apparatus during low-temperature stress.

In Vicia faba leaves Photoinhibition from Ozone Fumigation in Light Precedes a Decrease in Quantum Yield of Functional PSII Centres

Summary Treatment with a single pulse of O3 (150 ppb, 4 h) on Vicia faba (cv. Gigante d’Ingegnoli) plants induced a decrease in photosynthetic rate at light saturation level but only slight changes in stomatal conductance and transpiration rate. The increase in intercellular CO2 concentration implied that the predominant factor responsible for the reduction in light-saturated CO2 uptake was a decrease in the carboxylation efficiency. A slight change in the photochemical efficiency of PS2 (Fv/Fm) that decreased in treated plants more than did the quantum yield of functional centres (ΔF/F′m) lasted hours after treatment termination; photosynthetic efficiency decrease occurred after an increase in F0. Thermal dependence of fluorescence yield of open PS2 reaction centres was modified by O3. This eventually led to photosensitizing these leaves to photoinhibition but quantum yield of functional centres was again less sensitive to this combination. Increase in electrolyte leakage kinetics in distilled water indicated that, in the stressed plants, damage at the membrane level was occurring and this was confirmed also by the thiobarbituric reactive substance increase in ozonated leaves, taken as indicators of membrane lipid peroxidation.

The influence of membrane localized protons on energy utilization at the reaction centres of Photosystem II in isolated thylakoids

We have investigated the steady-state photochemical efficiency of PS II under modulated actinic illumination, and the effect of Δψ and ΔpH on it. Nigericin, valinomycin, nonactin and NH4Cl were added to suppress Δψ and / or ΔpH. A correlation between an increase of PS II photochemical efficiency and the suppression of 9-aminoacridine fluorescence quenching, in the presence of the lipophilic ionophores, was found. No effect of NH4 Cl on PS II activity was observed. The enhancement of PS II photochemical efficiency by the ionophores had its maximum at low light intensity and disappeared when it approached saturation. We conclude that electron transport dependent localization of protons in intramembrane domains lowers the efficiency of light energy utilization at the PS II reaction centre.