Chlorophyll Fluorescence Responses Research Articles

Characterization of Low-Temperature Sensitivity and Chlorophyll Fluorescence in Yellow Leaf Mutants of Tomato

Leaf color mutants serve as valuable models for studying the regulation of plant photosynthesis, alternations in chloroplast structure and function, and the analysis of associated gene functions. A yellow leaf mutant, ylm, was separated from the wild tomato M82, with its yellowing intensity influenced by low temperature. To assess the low-temperature sensitivity of this mutant, the photosynthetic and chlorophyll fluorescence responses of ylm and M82 were examined under different temperature conditions. In this study, the ylm mutant and its wild type, M82, were exposed to three temperature levels, 16, 25, and 30 °C, for 48 h. The impact of these temperature treatments on leaf color change, chlorophyll content, photosynthetic performance, and chlorophyll fluorescence characteristics of mutant ylm was investigated. The results revealed the following: (1) After exposure to 16 °C, the ylm mutant exhibited significant yellowing, a marked reduction in chlorophyll content, and a notable increase in carotenoid content. At 25 °C, the differences were less pronounced, and at 30 °C, the differences between ylm and M82 were minimal. (2) The photosynthetic rate of the ylm mutant was lower than that of M82 at 16 °C, with the gap narrowing as temperature increased, eventually converging at higher temperatures. (3) The fluorescence transient curve (OJIP) of the ylm mutant differed significantly from that of M82 at 16 °C, with higher fluorescence intensity at the O point and lower intensity at the J, I, and P points. This difference was decreased at 25 °C and nearly disappeared at 30 °C. Additionally, the Fv/Fm, Fv/Fo, PIabs, PItotal, ABS/CSm, TRo/CSm, and ETo/CSm values of ylm were lower than those of M82 at 16 °C, while the ABS/RC and DIo/RC values were higher, with no significant differences observed at 30 °C. These findings suggest that the ylm mutant is highly sensitive to low temperature, with pronounced yellowing, reduced light energy absorption and capture efficiency, and impaired electron transport at lower temperature.

Effect of arbuscular mycorrhizal symbiosis on growth and biochemical characteristics of Chinese fir (Cunninghamia lanceolata) seedlings under low phosphorus environment.

The continuous establishment of Chinese fir (Cunninghamia lanceolata) plantations across multiple generations has led to the limited impact of soil phosphorus (P) on tree growth. This challenge poses a significant obstacle in maintaining the sustainable management of Chinese fir. To investigate the effects of Arbuscular mycorrhizal fungi (AMF) on the growth and physiological characteristics of Chinese fir under different P supply treatments. We conducted an indoor pot simulation experiment in the greenhouse of the Forestry College of Fujian Agriculture and Forestry University with one-and-half-year-old seedlings of Chinese fir from March 2019 to June 2019, with the two P level treatment groups included a normal P supply treatment (1.0 mmolL-1 KH2PO4, P1) and a no P supply treatment (0 mmolL-1 KH2PO4, P0). P0 and P1 were inoculated with Funneliformis mosseae (F.m) or Rhizophagus intraradices (R.i) or not inoculated with AMF treatment. The AMF colonization rate in the root system, seedling height (SH), root collar diameter (RCD) growth, chlorophyll (Chl) photosynthetic characteristics, enzyme activities, and endogenous hormone contents of Chinese fir were estimated. The results showed that the colonization rate of F.m in the roots of Chinese fir seedlings was the highest at P0, up to 85.14%, which was 1.66 times that of P1. Under P0 and P1 treatment, root inoculation with either F.m or R.i promoted SH growth, the SH of R.i treatment was 1.38 times and 1.05 times that of F.m treatment, respectively. In the P1 treatment, root inoculation with either F.m or R.i inhibited RCD growth. R.i inhibited RCD growth more aggressively than F.m. In the P0 treatment, root inoculation with F.m and R.i reduced the inhibitory effect of phosphorus deficiency on RCD. At this time, there was no significant difference in RCD between F.m, R.i and CK treatments (p < 0.05). AMF inoculation increased Fm, Fv, Fv/Fm, and Fv/Fo during the chlorophyll fluorescence response in the tested Chinese fir seedlings. Under the two phosphorus supply levels, the trend of Fv and Fm of Chinese fir seedlings in different treatment groups was F.m > R.i > CK. Under P0 treatment, The values of Fv were 235.86, 221.86 and 147.71, respectively. The values of Fm were 287.57, 275.71 and 201.57, respectively. It increased the antioxidant enzyme activity and reduced the leaf's malondialdehyde (MDA) content to a certain extent. It is concluded that AMF can enhance the photosynthetic capacity of the host, regulate the distribution of endogenous hormones in plants, and promote plant growth by increasing the activity of antioxidant enzymes. When the P supply is insufficient, AMF is more helpful to plants, and R.i is more effective than F.m in alleviating P starvation stress in Chinese fir.

Gas exchange and chlorophyll fluorescence responses of Camellia sinensis grown under various cultivations in different seasons

Sod culture (SC) and conventional agriculture (CA) represent two distinct field management approaches utilized in the cultivation of tea plants in Taiwan. In this study, we employed gas exchange and chlorophyll fluorescence techniques to assess the impact of SC and CA methods on the photosynthetic machinery of Camellia sinensis cv. TTES No.12 (Jhinhsuan) in response to variable light intensities across different seasons. In spring, at photosynthetic photon flux densities (PPFD) ranging from 800 to 2,000 μmol photon m-2 s-1, the net photosynthesis rate (Pn, 10.43 μmol CO2 m-2 s-1), stomatal conductance (Gs, 126.11 mmol H2O m-2 s-1), electron transport rate (ETR, 137.94), and ΔF/Fm’ and Fv/Fm (50.37) values for plants grown using SC were comparatively higher than those cultivated under CA. Conversely, the non-photochemical quenching (NPQ) values for SC-grown plants were relatively lower (3.11) compared to those grown under CA at 800 to 2,000 PPFD in spring. Additionally, when tea plants were exposed to PPFD levels below 1,500 μmol photon m− 2 s− 1, there was a concurrent increase in Pn, Gs, ETR, and NPQ. These photosynthetic parameters are crucial for devising models that optimize cultivation practices across varying seasons and specific tillage requirements, and for predicting photosynthetic and respiratory responses of tea plants to seasonally or artificially altered light irradiances. The observed positive impacts of SC on maximum photosynthetic rate (Amax), Fv/Fm, Gs, water-use efficiency (WUE), and ETR suggest that SC is advantageous for enhancing the productivity of tea plants, thereby offering a more adaptable management model for tea gardens.

Integrating SWAP and SIF anomaly to assess the responses of vegetation to the drought-flood abrupt alternation in the middle and lower reaches of the Yangtze River basin, China

Study regionThe middle and lower reaches of the Yangtze River basin, China. Study focusUnder the background of global warming, drought-flood abrupt alternation (DFAA) events are occurred frequently, with substantial impact on ecosystems and water resources. Therefore, this study calculated the Standard Weighted Average Precipitation (SWAP) based on daily precipitation to verify the applicability of SWAP in the middle and lower reaches of the Yangtze River basin (MLRYRB). The response of Solar-Induced Chlorophyll Fluorescence (SIF) anomaly to DFAA events was determined based on lagged time correlation coefficients. Finally, based on Partial Wavelet Coherence (PWC), the impact of atmospheric circulation factors on the response relationship between DFAA events and vegetation was analyzed. New hydrological insights for the regionThe results indicate that: (1) the evolutionary characteristics of DFAA events determined by SWAP were consistent with historical records. (2) the DFAA events frequency with most regions experiencing 8–11 events during 2001–2019, with intensity of 2–3, and in the northern and southwestern Jiangxi and southeastern Hubei regions were more intensive and frequently. (3) the stronger correlations were mainly in eastern Guizhou and eastern Jiangxi, with SIF anomaly more sensitive to SWAP at 2-month lag time. (4) The El Niño-Southern Oscillation (ENSO) and sunspots have a significant influence on the response relationship between DFAA events and vegetation anomaly. This research can provide a scientific basis for the integrated response to DFAA events and ecological management in the MLRYRB.

The Difference between the Responses of Gross Primary Production and Sun-Induced Chlorophyll Fluorescence to the Environment Based on Tower-Based and TROPOMI SIF Data

The strong correlation between gross primary production (GPP) and sun-induced chlorophyll fluorescence (SIF) has been reported in many studies and is the basis of the SIF-based GPP estimation. However, GPP and SIF are not fully synchronous under various environmental conditions, which may destroy a stable GPP–SIF relationship. Therefore, exploring the difference between responses of GPP and SIF to the environment is essential to correctly understand the GPP–SIF relationship. As the common driver of GPP and SIF, the incident radiation could cause GPP and SIF to have similar responses to the environment, which may obscure the discrepancies in the responses of GPP and SIF to the other environmental variables, and further result in the ambiguity of the GPP–SIF relationship and uncertainties in the application of SIF. Therefore, we tried to exclude the dominant role of radiation in the responses of GPP and SIF to the environment based on the binning method, in which continuous tower-based SIF, satellite SIF, and eddy covariance GPP data from two growing seasons were used to investigate the differences in the responses of GPP and SIF to radiation, air temperature (Ta), and evaporation fraction (EF). We found that the following: (1) At both the site and satellite scales, there were divergences in the light response speeds between GPP and SIF which were affected by Ta and EF. (2) SIF and its light response curves were insensitive to EF and Ta compared to GPP, and the consistency in GPP and SIF light responses was gradually improved with the improvement of Ta and EF. (3) The dynamic slope values of the GPP–SIF relationship were mostly caused by the different sensitivities of GPP and SIF to EF and Ta. Our results highlighted that GPP and SIF were not highly consistent, having differences in environmental responses that further confused the GPP–SIF relationship, leading to complex SIF application.

Exploring Physiological and Nonphysiological Responses of Sun-Induced Chlorophyll Fluorescence to Different Levels of Water Stress in Winter Wheat

Exploring Physiological and Nonphysiological Responses of Sun-Induced Chlorophyll Fluorescence to Different Levels of Water Stress in Winter Wheat

Effects of biofertilizers on the growth, leaf physiological indices and chlorophyll fluorescence response of spinach seedlings.

Chemcial fertilizer as the main strategy for improving the vegetable yields was excessively applied in recent years which led to progressively serious soil problems such as the soil acidification. According the situation, five different biofertilizer treatments [no fertilizer (CK), inoculations of Bacillus subtilis (Bs, T1), combination of Bs and Bacillus mucilaginosus (Bs+Bm, T2), Bs and Bacillus amyloliquefaciens (Bs+Ba, T3), and Bm+Ba (T4)] were conducted to investigate the effect of the growth, leaf physiological indices, and chlorophyll fluorescence of spinach seedlings in the growth chamber. The growth and physiological indices of the spinach seedlings attained a maximum under the T2 treatments. Under the T2 treatment, the ABS/RC (Absorption flux per RC), TR0/RC (Trapping flux per RC), and ET0/RC (Electron transport flux per RC) was significantly increased, while the DI0/RC [Dissipated energy flux per RC (at t = 0)] was decreased. The OJIP curve was improved under of the inoculations of fertilizers, and the increasing range was the largest under the T2 treatment. The leaf light response curve (LC) was also significantly increased under the T2 treatment. The plant growth characteristics [leaf length (LL), leaf weight (LW), plant height (PH)] were positively correlated with the J-I-P test chlorophyll fluorescence parameters [PIABS (Performance index for energy conservation from exciton to the reduction of intersystem electron acceptors), φP0 (Maximum quantum yield of primary photochemistry), φE0 (Quantum yield of electron transport), ψ0 (The probability that a trapped exciton moved an electron in electron transport chain further than QA-), TR0/RC, and ET0/RC] while negatively correlated with φD0 (Quantum yield of energy dissipation) and DI0/RC. The leaf physiological characteristics [SP (soluble protein concentrations), SC (soluble carbohydrate concentrations), Chl a (chlorophyll a), Chl b (chlorophyll b), Chl a+b, Chl a/b, and WP (water potential)] were positively correlated with the J-I-P test chlorophyll fluorescence parameters (PIABS, φP0, φE0, ψ0, ABS/RC, TR0/RC, and ET0/RC) while negatively correlated with φD0 and DI0/RC. These results indicated that the combination of Bs+Bm inoculations promoted the growth of the spinach and improved the adaptability of the vegetable to acid soil while Ba inoculation didn't have any effects to plants.

Monitoring low O2 stress in apples – What we can learn from chlorophyll fluorescence and respiratory characteristics

Dynamic controlled atmosphere (DCA) is becoming a storage method of choice for apple producers seeking to store long-term. There is limited prior work comparing DCA monitoring chlorophyll fluorescence yield (DCA-CF) and respiratory characteristics (DCA-RQ), particularly for the popular UK-grown apple cultivars ‘Gala’ and ‘Braeburn’. However, these techniques can give an insight into the physiological response of apples to low O2 storage, which could help to design more efficient and sustainable storage regimes. In this study the chlorophyll fluorescence (CF) and respiratory quotient (RQ) responses of ‘Gala’ and ‘Braeburn’ are compared in typical and exaggerated DCA conditions. Results show that not only do the two techniques differ in their detection of low O2 stress but the two cultivars studied also differ noticeably in their behaviour. CF increase was confirmed to be a reaction to a stress signal from inside the fruit. Respiration rate curves were found to reflect the internal structure of the fruit, with ‘Gala’’s more homogeneous tissues and greater gas permeability resulting in a strongly bimodal O2 consumption rate where the change in rate hypothetically corresponds with the majority of the fruit tissue switching to anaerobic respiration at the same time. CF and RQ showed noticeable differences between cultivars, agreeing with previous observations that ‘Braeburn’ is less tolerant of low O2 and elevated CO2 than ‘Gala’ (CF Lower O2 Limit (LOL) for Braeburn of approximately 0.75 kPa O2 relative to 0.5 kPa O2 for Gala). Additionally, the CF and RQ responses indicated different LOLs for ‘Gala’, at approximately 0.5 kPa O2 for CF and 0.25 kPa O2 for RQ. Elevated CO2 depressed both the CF and RQ response, with a strong depressive effect on the rate of CO2 evolution but little effect on the rate of O2 consumption.

Fight against cold: photosynthetic and antioxidant responses of different bell pepper cultivars (Capsicum annuum L.) to cold stress

The special metabolites of bell pepper (Capsicum annuum L.) leaves can protect the plant under possibly damaging circumstances, such as high light, UV, unfavorable temperatures, or other environmental effects. In this study, we examined the cold stress tolerance of three different Hungarian pepper varieties (Darina, Édesalma, Rekord), focusing on the antioxidant and photosynthetic responses. The plants were developed in growth chambers under optimal temperature conditions (day/night 25 °C/20 °C) until the leaves on the fourth node became fully developed, then half of the plants received a cold treatment (day/night 15 °C/10 °C). Via a detailed pigment analysis, the PS II chlorophyll fluorescence responses, gas exchange parameters and total antioxidant capacities, leaf acclimation to low temperatures has been characterized. Our results display some of the developing physiological and antioxidant properties, which are among the main factors in monitoring the damaging effects of cold temperatures. Nevertheless, despite their differences, the tested pepper varieties did not show different cold responses.

Evaluation of Growth, Flowering, and Chlorophyll Fluorescence Responses of &amp;lt;italic&amp;gt;Viola cornuta&amp;lt;/italic&amp;gt; cv. Penny Red Wing according to Spectral Power Distributions

Background and objective: The genus &lt;i&gt;Viola&lt;/i&gt;, a member of the Violaceae family, is renowned for its ornamental flower crops. Additionally, &lt;i&gt;Viola&lt;/i&gt; species are relatively pest-resistant and easy to manage. They are widely used in gardens, and some of their flowers are even edible. In this study, our focus was on &lt;i&gt;V. cornuta&lt;/i&gt; cv. Penny Red Wing (hereinafter referred to as ‘Penny Red Wing’), an experimental plant chosen for its high ornamental value and rapid growth.Methods: We applied a purple light-emitting diode (LED) and three types of white LEDs with varying color temperatures: 3000, 4100, and 6500 K, respectively, as artificial light sources. Notably, a purple LED has a far-red wavelength (700-800 nm) ratio of approximately 17.6% in their spectral power distribution.Results: The findings indicated that several parameters exhibited higher values under purple LED: shoot size parameters, shoot biomass, moisture content of shoots and roots, photochemical reflectance index (PRI), modified chlorophyll absorption ratio index (MCARI), total number of flowers, flower size parameters, scent score, F&lt;sub&gt;v&lt;/sub&gt;/F&lt;sub&gt;m&lt;/sub&gt;, and PI&lt;sub&gt;ABS&lt;/sub&gt;. However, the 6500 K white LED led to higher evaluations of root length, number of shoots and leaves, root biomass, moisture content of shoots and roots, F&lt;sub&gt;v&lt;/sub&gt;/F&lt;sub&gt;m&lt;/sub&gt;, and PI&lt;sub&gt;ABS&lt;/sub&gt;. Nevertheless, it was observed that shoot growth was relatively hindered, and the flowering responses were inadequate under the 6500 K white LED, suggesting their unsuitability for the mass production of ‘Penny Red Wing’. Furthermore, the 3000 and 4100 K white LEDs were also deemed unsuitable for cultivating ‘Penny Red Wing’ due to their lower cultivation efficiency.Conclusion: ‘Penny Red Wing’ was evaluated as having superior growth, flowering, and chlorophyll fluorescence responses under purple LED, indicating that the far-red wavelength had a more pronounced effect compared to the green wavelength (500-600 nm). Therefore, we recommend cultivating this cultivar under purple LED, which include the far-red wavelength.

Plants cope with fluctuating light by frequency-dependent nonphotochemical quenching and cyclic electron transport.

In natural environments, plants are exposed to rapidly changing light. Maintaining photosynthetic efficiency while avoiding photodamage requires equally rapid regulation of photoprotective mechanisms. We asked what the operation frequency range of regulation is in which plants can efficiently respond to varying light. Chlorophyll fluorescence, P700, plastocyanin, and ferredoxin responses of wild-types Arabidopsis thaliana were measured in oscillating light of various frequencies. We also investigated the npq1 mutant lacking violaxanthin de-epoxidase, the npq4 mutant lacking PsbS protein, and the mutants crr2-2, and pgrl1ab impaired in different pathways of the cyclic electron transport. The fastest was the PsbS-regulation responding to oscillation periods longer than 10 s. Processes involving violaxanthin de-epoxidase dampened changes in chlorophyll fluorescence in oscillation periods of 2 min or longer. Knocking out the PGR5/PGRL1 pathway strongly reduced variations of all monitored parameters, probably due to congestion in the electron transport. Incapacitating the NDH-like pathway only slightly changed the photosynthetic dynamics. Our observations are consistent with the hypothesis that nonphotochemical quenching in slow light oscillations involves violaxanthin de-epoxidase to produce, presumably, a largely stationary level of zeaxanthin. We interpret the observed dynamics of photosystem I components as being formed in slow light oscillations partially by thylakoid remodeling that modulates the redox rates.

Effects of Drip Irrigation-Fertilization on Growth, Flowering, Photosynthesis and Nutrient Absorption of Containerized Seedlings of Hibiscus syriacus L. (Haeoreum).

The amount of irrigation and fertilization should be considered first for the production and standardization of high-quality H. syriacus L. seedlings using container seedlings. This study was conducted to investigate the optimal conditions suitable for container cultivation of hibiscus by analyzing growth and physiological responses according to the control of irrigation and fertilization. Therefore, in this study, H. syriacus L. for. Haeoreum (3-year-old hardwood cutting propagation), a fast-growing, was transplanted into a 40 L container. The irrigation amount per container was adjusted (0.2, 0.3 and 0.4 ton/yr/tree), and the amount of fertilizer applied (0, 69.0, 138.0 and 207.0 g/yr/tree). The growth rate according to the irrigation-fertilization treatment was higher in the 0.3 ton-138.0 g/yr/tree irrigation-fertilization treatment (p < 0.001). Total biomass yield and seedling quality index (SQI) were highest in the 0.3 ton-138.0 g/yr/tree irrigation-fertilization treatment (p < 0.001). The higher the fertilization concentration, the faster the flowering and the longer the flowering. The photosynthetic capacity of H. syriacus L. was reduced in bare root seedling cultivation and container-non-fertilized treatment. The chlorophyll fluorescence response was also affected by bare root cultivation and containerized seedling cultivation fertilization. Nutrient vector diagnosis showed "nutritional suitability" in the 0.3 ton-138.0 g/yr/tree treatment. Overall, containerized seedling cultivation was superior in growth, photosynthetic performance, photochemical efficiency, and nutrient storage capacity compared to bare root cultivation. These results be expected to contribute not only to the industrial production of excellent container seedlings of H. syriacus L. but also to the production of other woody plants.

The photosynthetic response of spectral chlorophyll fluorescence differs across species and light environments in a boreal forest ecosystem

Chlorophyll fluorescence can serve as a proxy of photosynthesis in boreal forests. When sustained non-photochemical quenching (NPQS) relaxes towards summer, leaf chlorophyll fluorescence (ChlF) emission increases along with photosynthesis. Yet, other physical and physiological factors can also leave a measurable imprint on the fluorescence emission spectra, and disrupt this relationship.We measured spectral ChlF in leaves of three dominant evergreen species in the boreal ecosystem (Scots pine, Norway spruce and lingonberry) growing under contrasting light environments and throughout the spring recovery of photosynthesis. We also measured photosynthetic, biochemical and morphological traits. Correlations between traits and ChlF spectral components were analyzed to identify the mechanisms underlying both the spatial variation found between species and light environments, and the temporal variation along the spring recovery of photosynthesis.Spatially, we found evidence of baseline differences in leaf-level ChlF magnitude, which we attribute to species- and light environment-specific changes in leaf morphology. Temporally, ChlF magnitude followed the relaxation of NPQS towards summer, but only in upper canopy foliage and lingonberry, suggesting a seasonal compensation effect between sustained photochemical quenching (PQS) and NPQS, potentially decoupling the seasonal relationship between ChlF and photosynthesis in shaded foliage. Finally, we show subtle changes in the shape of the ChlF spectra that took place independently of chlorophyll concentration dynamics, pointing to the complexity of NPQS which could reflect structural rearrangements in the thylakoids and changes in the relative contribution of PSI to emitted ChlF.We conclude that the diversity of species and light environments found within an ecosystem generates a baseline level of variation in leaf spectral ChlF as well as contrasting seasonal photosynthetic acclimation patterns. These sources of variability should be taken into account when developing quantitative models for the interpretation of ChlF data, in particular for applications involving high resolution SIF imaging systems capable of resolving different plant individuals and their parts.

Contrasting responses of two C4 desert shrubs to drought but consistent decoupling of photosynthesis and stomatal conductance at high temperature

How desert shrubs respond to drought and heat remains poorly understood. We investigated how drought affected the morphology and physiology of two C4 species with different root architecture, Calligonum arborescens and Haloxylon ammodendron, in the Taklamakan Desert. We measured leaf traits, chlorophyll fluorescence and temperature responses of photosynthesis after ∼3 years of experimental drought and asked: (1) Do both species adjust similarly to drought? (2) Does transpirational cooling increase at high temperature, and if so, how is this affected by drought? Drought plants of H. ammodendron had shorter and thinner leaves than controls, and lower chlorophyll content, photochemical efficiency, and electron transport rate. In contrast, C. arborescens leaves became shorter and thicker. Drought reduced maximum photosynthesis by 63 % and 21 % in H. ammodendron and C. arborescens, respectively. The optimum temperature did not change significantly in H. ammodendron and decreased by ∼2 °C in C. arborescens. Surprisingly, above 40–45 °C, stomatal conductance (gsw) and transpiration increased—even under drought stomata partially reopened. This consistent uncoupling of photosynthesis and gsw suggests that widely-implemented stomatal optimization models may poorly reflect high-temperature behaviors in dryland ecosystems. Our study established the basis for predicting the eco-physiological responses of C4 species in hyper-arid ecosystems to climate change.

Transcriptome modulation by endophyte drives rice seedlings response to Pb stress

This study investigated the growth, SPAD value, chlorophyll fluorescence and transcriptome response of endophyte uninoculated and inoculated rice seedlings under Pb stress after treatment of 1 d and 5 d. Inoculation of endophytes significantly improved the plant height, SPAD value, Fv/F0, Fv/Fm and PIABS by 1.29, 1.73, 0.16, 1.25 and 1.90 times on the 1 d, by 1.07, 2.45, 0.11, 1.59 and 7.90 times on the 5 d, respectively, however, decreased the root length by 1.11 and 1.65 times on the 1 d and 5 d, respectively under Pb stress. Analysis of rice seedlings leaves by RNA-seq, there were 574 down-regulated and 918 up-regulated genes after treatment of 1 d, 205 down-regulated and 127 up-regulated genes after treatment of 5 d, of which 20 genes (11 up-regulated and 9 down-regulated) exhibited the same changing pattern after treatment of 1 d and 5 d. Using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) to annotate these DEGs, and it was found that many of DEGs involved in photosynthesis, oxidative detoxification, hormone synthesis and signal transduction, protein phosphorylation/kinase and transcription factors. These findings provide new insights into the molecular mechanism of interaction between endophyte and plants under heavy metal stress, and contribute to agricultural production in limited environments.

Responses of photosynthesis and chlorophyll fluorescence during light induction in different seedling ages of Mahonia oiwakensis

BackgroundThe aim of this study was to determine the actual state of the photosynthetic apparatus and exhibit distinguishable differences in the chlorophyll fluorescence (ChlF) components in different seedling ages of M. oiwakensis plants subjected to different light intensity (LI). Potted 6-month-old greenhouse seedlings and field collected 2.4-year-old seedlings with 5 cm heights were selected and randomly separated into seven groups for photosynthesis measurements illuminated with 50, 100 (assigned as low LI), 300, 500, 1,000 (as moderate LI), 1,500 and 2,000 (as high LI) μmol m–2 s–1 photosynthetic photon flux density (PPFD) treatments.Resultsn 6-month-old seedlings, as LI increased from 50 to 2,000 PPFD, the values of non-photochemical quenching and photo-inhibitory quenching (qI) increased but potential quantum efficiency of PSII (Fv/Fm) and photochemical efficiency of photosystem II (ΦPSII) values decreased. High electron transport rate and percentage of actual PSII efficiency by Fv/Fm values were observed in 2.4-year-old seedlings at high LI conditions. Furthermore, higher ΦPSII was detected under low LI conditions, with lower energy-dependent quenching (qE) and qI values and photo-inhibition % decreased as well. However, qE and qI increased as ΦPSII decreased and photo-inhibition% increased under high LI treatments.ConclusionsThese results could be useful for predicting the changes in growth and distribution of Mahonia species grown in controlled environments and open fields with various combinations of varying light illuminations, and ecological monitoring of their restoration and habitat creation is important for provenance conservation and helps to formulate better conservation strategies for the seedlings.

Responses of Leaf Ion Content, Photosynthesis and Chlorophyll Fluorescence to Nacl Stress in Soybean

Responses of Leaf Ion Content, Photosynthesis and Chlorophyll Fluorescence to Nacl Stress in Soybean

Response of Fluorescence and Chlorophyll Physiological Characteristics of Typical Urban Trees to Ozone Stress

In this study, four typical urban landscaping tree species were selected, three open top air chambers with different ozone concentrations were set, and the responses of chlorophyll fluorescence, chlorophyll content and relative conductivity of the trees to ozone stress were studied. The results showed that with the increase in ozone concentration, the maximum photochemical efficiency, electron transfer quantum yield, electron transfer rate (ETR) and chlorophyll content of the different tree species decreased significantly, while the relative conductivity of the different tree species increased significantly. Compared with the ozone concentration of NF, under an ozone concentration of nf40 and nf80, the decline in the rate of Fv/Fm of Koelreuteria paniculata and Ginkgo biloba was 2.47 and 2.28 times that of Pinus bungeana and Platycladus orientalis, respectively, and the increase in the rate of relative conductivity of K. paniculata and G. biloba was 2.11 and 1.28 times that of P. bungeana and P. orientalis, respectively. Under different ozone concentrations, the photochemical efficiency, electron transfer rate, chlorophyll content and relative conductivity of P. bungeana and P. orientalis were higher than those of Ginkgo biloba and K. paniculata, indicating that K. paniculata and G. biloba were more sensitive to ozone. This study is of great significance for improving urban environmental quality and ozone control and also provides a basis for selecting tree species with strong ozone tolerance.

Limited effects of shade on physiological performances of cocoa (Theobroma cacao L.) under elevated temperature

Shade is one of the recommended management solutions to mitigate the effects of heat stress, which is a major challenge for cocoa production globally. Nevertheless, there are limited studies to verify this hypothesis. Here, we evaluate the effects of heat and shade on cocoa physiology using experimental plots with six-month old potted seedlings in a randomized complete block design. Infrared heaters were applied for one month to increase leaf temperatures by an average of 5–7 ºC (heat treatment) compared with no heat (unheated treatments), and shaded plants were placed under a shade net removing 60% of the light compared with no shade (sun treatments). Plants under heat treatments in sun and in shade showed severe reduction in photosynthesis. Measurements of chlorophyll fluorescence and photosynthetic light response curves indicated that heat caused damages at photosystem II and additionally resulted in lower rates of maximal photosynthesis. Temperature optima for photosynthesis were at 31–33 ºC with only small differences between treatments, and as light saturation was reached at low PAR levels of 325 – 380 µmol m −2 s −1 in shade and 427 – 521 µmol m −2 s −1 in sun, ambient rates of photosynthesis were comparable between sun and shade treatments. Heat treatments resulted in decreased concentrations of chlorophyll and changed pigment composition, reduced specific leaf areas, and plant biomass. While shade may benefit cocoa seedlings, our results indicate that the positive effects may not be sufficient to counteract the negative effects of increased temperatures on cocoa physiology. • Heat is imposed on six-month old cocoa seedlings and shade is provided. • Heat treated plants show severe reduction in photosynthesis and damages at photosystem II. • Heat decreases chlorophyll concentrations and pigment composition. • Shade improves cocoa physiology but has limited effects on heat.

Responses of chlorophyll fluorescence and non-structural carbohydrate accumulation of Castanopsis kawakamii seedlings to seed dispersal positions

When seeds fallen from the mother trees, their initial contact physical environment was litter or soil. The dispersal positions of seeds (seeds positioned on top of the litter, the soil surface and beneath the litter) determine the process of their natural regeneration. We simulated three different dispersal positions of Castanopsis kawakamii, including seeds positioned on top of the litter (2 and 4 cm litter was placed below the seed layer), soil surface (without litter), and seeds beneath the litter (2, 4, 6 and 8 cm litter covers in the upper layer of seeds). We examined the effects of seed dispersal position on the chlorophyll fluorescence characteristics, non-structural carbohydrate, specific leaf area, leaf dry matter content and nutrient content of seedlings. The results showed that leaf nitrogen content per area of seedlings had significantly positive correlation with soluble sugar content, non-structural carbohydrate content, and negative correlation with specific leaf area across different dispersal positions. Seedlings of the moderate litter cover (2 and 4 cm) adopted resource acquisitive strategies by increasing relative chlorophyll content, soluble sugar content, non-structural carbohydrate content, leaf dry matter content, leaf nitrogen content and phosphorus contents per area, and decreasing specific leaf area to achieve their demands for rapid growth. Seedlings grew on soil surface and beneath the deep litter (6 and 8 cm) adopted the resource conservative strategies with higher leaf nitrogen content per mass and specific leaf area, lower leaf dry matter content, and non-structural carbohydrate content to intercept more effective light resources to compensate for the shady environment brought by deep litter. This would further decrease the probability of seedling mortality due to 'carbon starvation'. Seedlings under litter layer stored starch in leaf, and reduced the energy consumption of photosynthetic tissues (low PSⅡ maximum photochemical efficiency) to maintain seedling growth. Comprehensive analysis of entropy method indicated that low amount of litter cover (2 cm) significantly promoted seedling growth of C. kawakamii. In the future, we could regulate the thickness of litter layer to promote the growth and regeneration of C. kawakamii seedlings in natural forest.