Rhizophagus irregularis and biochar can synergistically improve the physiological characteristics of saline-alkali resistance of switchgrass.

Inoculation of arbuscular mycorrhizal fungi (AMF) or biochar (BC) application can improve photosynthesis and promote plant growth under saline-alkali stress. However, little is known about the effects of the two combined on growth and physiological characteristics of switchgrass under saline-alkali stress. This study examined the effects of four treatments: (1) no AMF inoculation and no biochar addition (control), (2) biochar (BC) alone, (3) AMF (Rhizophagus irregularis, Ri) alone, and (4) the combination of both (BC+Ri) on the plant biomass, antioxidant enzymes, chlorophyll, and photosynthetic parameters of switchgrass under saline-alkali stress. The results showed that the above-ground, belowground and total biomass of switchgrass in the BC+Ri treatment group was significantly higher (+136.7%, 120.2% and 132.4%, respectively) than in other treatments compared with Control. BC+Ri treatment significantly increased plant leaves' relative chlorophyll content, antioxidant enzyme activity, and photosynthesis parameters. It is worth noting that the transpiration rate, stomatal conductance, net photosynthetic rate, PSII efficiency and other photosynthetic-related indexes of the BC+Ri treatment group were the highest (38% to 54% higher than other treatments). The fitting results of light response and CO2 response curves showed that the light saturation point, light compensation point, maximum carboxylation rate and maximum electron transfer rate of switchgrass in the Ri+BC treatment group were the highest. In conclusion, biochar combined with Ri has potential beneficial effects on promoting switchgrass growth under saline-alkali stress and improving the activity of antioxidant enzymes and photosynthetic characteristics of plants.

Association of the electrical parameters and photosynthetic characteristics of the tea tree manifests its response to simulated karst drought.

Tea plantations in Karst regions suffer from the serious effects of frequent temporary karst droughts, leading to a decline in tea production and quality in the region. The close relationship between growth and electrical parameters of plants, including physiological capacitance, resistance and impedance, can be used to accurately monitor their plant water status online, quickly, accurately, timely and nondestructively. In this study, three tea tree cultivars of Zhonghuang No.2 (ZH), Wuniuzao (WNZ), and Longjing 43 (LJ) with different levels of drought resistance were selected as experimental materials, and experiments were carried out under controlled conditions according to control (soil water content of 40-45%, D0), (keeping D0 no watering to 5 days, D5), (keeping D0 no watering to 10 days, D10), (the first day after D10 is rehydrated to D0 is regarded as R1) and (the fifth day after D10 rehydration to D0 is regarded as R5), to determine intracellular water metabolism and nutrient translocation characteristics based on intrinsic electrical parameters. The photosynthetic characteristics and chlorophyll fluorescence parameters were also determined to investigate the response of water metabolism to simulated karst drought in the three tea tree cultivars. The results indicated that the water metabolism patterns responded to environmental water changes with a medium water-holding capacity, medium water transport rate, and low water-use efficiency, and the nutrient patterns in those tea tree varieties demonstrated with a high nutrient flux per unit area, low nutrient transfer rate, and high nutrient transport capacity. After rehydration, only the electrical characteristics of WNZ returned to the D0 levels, but the net photosynthetic rate of all varieties returned to or even exceeded the D0 levels. The chlorophyll fluorescence parameters could not be used to characterize the recoverability of metabolism in tea trees. The electrical characteristics quickly reflected the response of the water metabolism in plants to environmental changes, and the fusion of electrical characteristics and photosynthetic characteristics was able to more quickly, accurately, and comprehensively reflect the response of water metabolism to temporary karst drought.

Emmer wheat (Triticum dicoccum Schuebl.) favours high photosynthetic capacity adaptation to low nitrogen stress.

Although tetraploid wheat has rich genetic variability for cultivar improvement, its physiological mechanisms associated with photosynthetic productivity and resilience under nitrogen (N) deficit stress have not been investigated. In this study, we selected emmer wheat (Kronos, tetraploid), Yangmai 25 (YM25, hexaploid), and Chinese Spring (CS, hexaploid) as materials and investigated the differences in net photosynthetic rate (Pn), carboxylation capacity, electron transfer capacity, photosynthetic product output, and photosynthetic N allocation under normal N (CK) and low N (LN) through hydroponic experiments. Tetraploid emmer wheat (Kronos) had a stronger photosynthetic capacity than hexaploid wheat (YM25, CS) under low N stress, which mainly associated with the higher degree of PSII opening, electron transfer rate, Rubisco content and activity, ATP/ADP ratio, Rubisco activase (Rca) activity and Rubisco activation state, and more leaves N allocation to the photosynthetic apparatus, especially the proportion of N allocation to carboxylation under low N stress. Moreover, Kronos reduced the feedback inhibition of photosynthesis by sucrose accumulation through higher sucrose phosphate synthetase (SPS) activity and triose phosphate utilization rate (VTPU). Overall, Kronos could allocate more N to the photosynthetic components to improve Rubisco content and activity to maintain photosynthetic capacity under low N stress while enhancing triose phosphate output to reduce feedback inhibition of photosynthesis. This study reveals the physiological mechanisms of emmer wheat that maintain the photosynthetic capacity under low N stress, which will provide indispensable germplasm resources for elite low-N-tolerant wheat improvement and breeding.

Individual architecture and photosynthetic performance of the submerged form of Drosera intermedia Hayne.

Drosera intermedia grows in acidic bogs in parts of valleys that are flooded in winter, and that often dry out in summer. It is also described as the sundew of the most heavily hydrated habitats in peatlands, and it is often found in water and even underwater. This sundew is the only one that can tolerate long periods of submersion, and more importantly produces a typical submerged form that can live in such conditions for many years. Submerged habitats are occupied by D. intermedia relatively frequently. The aim of the study was to determine the environmental conditions and architecture of individuals in the submerged form of D. intermedia. The features of the morphological and anatomical structure and chlorophyll a fluorescence of this form that were measured were compared with analogous ones in individuals that occurred in emerged and peatland habitats. The submerged form occurred to a depth of 20 cm. Compared to the other forms, its habitat had the highest pH (4.71-4.92; Me = 4.71), the highest temperature and substrate hydration, and above all, the lowest photosynthetically active radiation (PAR; 20.4-59.4%). This form differed from the other forms in almost all of the features of the plant's architecture. It is particularly noteworthy that it had the largest main axis height among all of the forms, which exceeded 18 cm. The number of living leaves in a rosette was notable (18.1 ± 8.1), while the number of dead leaves was very low (6.9 ± 3.8). The most significant differences were in the shape of its submerged leaves, in which the length of the leaf blade was the lowest of all of the forms (0.493 ± 0.15 mm; p < 0.001) and usually the widest. The stem cross-sectional area was noticeably smaller in the submerged form than in the other forms, the xylem was less developed and collaterally closed vascular bundles occurred. Our analysis of the parameters of chlorophyll fluorescence in vivo revealed that the maximum quantum yield of the primary photochemistry of photosystem II is the highest for the submerged form (Me = 0.681), the same as the maximum quantum yield of the electron transport (Me φE0 = 0.183). The efficiency of energy use per one active reaction center of photosystem II (RC) was the lowest in the submerged form (Me = 2.978), same as the fraction of energy trapped by one active RC (Me = 1.976) and the non-photochemical energy dissipation (DI0/RC; Me = 0.916). The ET0/RC parameter, associated with the efficiency of the energy utilization for electron transport by one RC, in the submerged plant reached the highest value (Me = 0.489). The submerged form of D. intermedia clearly differed from the emerged and peatland forms in its plant architecture. The submerged plants had a thinner leaf blade and less developed xylem than the other forms, however, their stems were much longer. The relatively high photosynthetic efficiency of the submerged forms suggests that most of the trapped energy is utilized to drive photosynthesis with a minimum energy loss, which may be a mechanism to compensate for the relatively small size of the leaf blade.

Accurate photosynthetic parameter estimation at low stomatal conductance: effects of cuticular conductance and instrumental noise.

Accurate estimation of photosynthetic parameters is essential for understanding plant physiological limitations and responses to environmental factors from the leaf to the global scale. Gas exchange is a useful tool to measure responses of net CO2 assimilation (A) to internal CO2 concentration (Ci), a necessary step in estimating photosynthetic parameters including the maximum rate of carboxylation (Vcmax) and the electron transport rate (Jmax). However, species and environmental conditions of low stomatal conductance (gsw) reduce the signal-to-noise ratio of gas exchange, challenging estimations of Ci. Previous works showed that not considering cuticular conductance to water (gcw) can lead to significant errors in estimating Ci, because it has a different effect on total conductance to CO2 (gtc) than does gsw. Here we present a systematic assessment of the need for incorporating gcw into Ci estimates. In this study we modeled the effect of gcw and of instrumental noise and quantified these effects on photosynthetic parameters in the cases of four species with varying gsw and gcw, measured using steady-state and constant ramping techniques, like the rapid A/Ci response method. We show that not accounting for gcw quantitatively influences Ci and the resulting Vcmax and Jmax, particularly when gcw exceeds 7% of the total conductance to water. The influence of gcw was not limited to low gsw species, highlighting the importance of species-specific knowledge before assessing A/Ci curves. Furthermore, at low gsw instrumental noise can affect Ci estimation, but the effect of instrumental noise can be minimized using constant-ramping rather than steady-state techniques. By incorporating these considerations, more precise measurements and interpretations of photosynthetic parameters can be obtained in a broader range of species and environmental conditions.

Investigating the Balance between Structural Conservation and Functional Flexibility in Photosystem I.

Photosynthesis, as the primary source of energy for all life forms, plays a crucial role in maintaining the global balance of energy, entropy, and enthalpy in living organisms. Among its various building blocks, photosystem I (PSI) is responsible for light-driven electron transfer, crucial for generating cellular reducing power. PSI acts as a light-driven plastocyanin-ferredoxin oxidoreductase and is situated in the thylakoid membranes of cyanobacteria and the chloroplasts of eukaryotic photosynthetic organisms. Comprehending the structure and function of the photosynthetic machinery is essential for understanding its mode of action. New insights are offered into the structure and function of PSI and its associated light-harvesting proteins, with a specific focus on the remarkable structural conservation of the core complex and high plasticity of the peripheral light-harvesting complexes.

Effects of different light conditions on morphological, anatomical, photosynthetic and biochemical parameters of Cypripedium macranthos Sw.

In this study, the morphological (plant height, leaf length and width, stem diameter and leaf number), anatomical (epidermal cell density and thickness, Stomatal length and width), photosynthetic (net photosynthetic rate, transpiration rate, stomatal conductance, intercellular CO2 concentration, relative humidity, leaf temperature and chlorophyll fluorescence parameters) and biochemical parameters (the content of soluble sugar, soluble protein, proline, malondialdehyde and electrical conductivity) of Cypripedium macranthos Sw. in Changbai Mountain were determined under different light conditions (L10, L30, L50, L100). The results showed that morphological values including plant height, leaf area, stem diameter and leaf number of C. macranthos were smaller under the condition of full light at L100. The epidermal cell density and epidermal thickness of C. macranthos were the highest under L30 and L50 treatments, respectively. It had the highest net photosynthetic rate (Pn) and chlorophyll content under L50 treatment. Meanwhile, correlation analysis indicated that photosynthetically active radiation (PAR) and water use efficiency (WUE) were the main factors influencing Pn. C. macranthos accumulated more soluble sugars and soluble proteins under L100 treatment, while the degree of membrane peroxidation was the highest and the plant was severely damaged. In summary, the adaptability of C. macranthos to light conditions is ranked as follows L50 > L30 > L10 > L100. Appropriate light conditions for C. macranthos are 30%-50% of full light, which should be taken into account in protection and cultivation.

Latitudinal variation in thermal performance of the common coral Pocillopora spp.

Understanding how tropical corals respond to temperatures is important to evaluating their capacity to persist in a warmer future. We studied the common Pacific coral Pocillopora over 44° of latitude, and used populations at three islands with different thermal regimes to compare their responses to temperature using thermal performance curves (TPCs) for respiration and gross photosynthesis. Corals were sampled in the local autumn from Moorea, Guam and Okinawa, where mean±s.d. annual seawater temperature is 28.0±0.9°C, 28.9±0.7°C and 25.1±3.4°C, respectively. TPCs for respiration were similar among latitudes, the thermal optimum (Topt) was above the local maximum temperature at all three islands, and maximum respiration was lowest at Okinawa. TPCs for gross photosynthesis were wider, implying greater thermal eurytopy, with a higher Topt in Moorea versus Guam and Okinawa. Topt was above the maximum temperature in Moorea, but was similar to daily temperatures over 13% of the year in Okinawa and 53% of the year in Guam. There was greater annual variation in daily temperatures in Okinawa than Guam or Moorea, which translated to large variation in the supply of metabolic energy and photosynthetically fixed carbon at higher latitudes. Despite these trends, the differences in TPCs for Pocillopora spp. were not profoundly different across latitudes, reducing the likelihood that populations of these corals could better match their phenotypes to future more extreme temperatures through migration. Any such response would place a premium on high metabolic plasticity and tolerance of large seasonal variations in energy budgets.

Nitrogen-fixing and non-nitrogen-fixing legume plants differ in leaf nutrient concentrations and relationships between photosynthetic and hydraulic traits.

Legumes account for a significant proportion of plants in the terrestrial ecosystems. Nitrogen (N)-fixing capability of certain legumes is a pivotal trait that contributes to their ecological dominance. Yet, the functional traits and trait relationships between N-fixer and non-N-fixer legumes are poorly understood. Here, we investigated 27 functional traits associated with morphology, nutrients, hydraulic conductance and photosynthesis in 42 woody legumes (19 N-fixers and 23 non-N-fixers) in a common garden. Our results showed that N-fixers had higher specific leaf area, photosynthetic phosphorus (P)-use efficiency, leaf N, and iron concentrations on both area and mass basis, N/P ratio, and carbon (C) to P ratio, but lower wood density, area-based maximum photosynthetic rate (Aa), photosynthetic N-use efficiency, leaf mass- and area-based P and molybdenum and area-based boron concentrations, and C/N ratio, compared with non-N-fixers. The mass-based maximum photosynthetic rate (Am), stomatal conductance (gs), intrinsic water-use efficiency (WUEi), mass- and area-based leaf potassium and mass-based boron concentrations, leaf hydraulic conductance (Kleaf), and whole-shoot hydraulic conductance (Kshoot) showed no difference between N-fixers and non-N-fixers. Significant positive associations between all hydraulic and photosynthetic trait pairs were found in N-fixers, but only one pair (Kshoot-Aa) in non-N-fixers, suggesting that hydraulic conductance plays a more important role in mediating photosynthetic capacity in N-fixers compared with non-N-fixers. Higher mass-based leaf N was linked to lower time-integrated gs and higher WUEi among non-N-fixer legumes or all legumes pooled after phylogeny was considered. Moreover, mass-based P concentration was positively related to Am and gs in N-fixers, but not in non-N-fixers, indicating that the photosynthetic capacity and stomatal conductance in N-fixers were more dependent on leaf P status than in non-N-fixers. These findings expand our understanding of the trait-based ecology within and across N-fixer and non-N-fixer legumes in tropics.

The combined effect of diffuse radiation and leaf wetness on functional traits and transpiration efficiency on a cloud forest species.

Cloud forests are unique biomes that thrive in foggy environments for a substantial part of the season. Fog in cloud forests plays two critical roles: it reduces incoming radiation and creates a humid environment, leading to the wetting of the canopy. This paper aims to investigate the combined effect of both radiation and wetness on Myrica faya Wilbur-a cloud forest species present in subtropical regions-both directly in plants and through simulations. Experiments consisted of a controlled environment with two levels of radiation and leaf wetness: low radiation/wet conditions, and high radiation/no-wetness; and three treatments: continuous low radiation and wetness, continuous high radiation and no wetness and alternate high low radiation and alternate wetness. The results revealed that a combination of low radiation and leaf wetness significantly improves leaf stomata conductance and increases the specific leaf area (SLA). Changes in SLA were driven by leaf size changes. However, the minimum leaf conductance (gmin) did not respond to any of the treatments. The simulations focused on exploring the impact of radiation and canopy wetness on transpiration efficiency (TE), i.e. the ratio between photosynthesis (An) and transpiration (Tc). The simulations demonstrated that TE increased exponentially as the canopy was gradually wetted, regardless of the radiation environment. This increase in TE results from Tc approaching zero while An maintains positive values. Overall, this study provides an integrated understanding of how fog alters M. faya functioning and, potentially, other cloud forest tree species.

Potassium deficiency enhances imbalances in rice water relations under water deficit by decreasing leaf hydraulic conductance.

Potassium (K+) is an essential macronutrient for appropriate plant development and physiology. However, little is known about the mechanisms involved in the regulation of leaf water relations by K under water deficit. A pot experiment with two K supplies of 0.45 and 0 g K2O per pot (3 kg soil per pot) and two watering conditions (well-watered and water-deficit) was conducted to explore the effects of K deficiency on canopy transpiration characteristics, leaf water status, photosynthesis, and hydraulic traits in two rice genotypes with contrasting resistance to drought. The results showed that K deficiency reduced canopy transpiration rate by decreasing stomatal conductance, which led to higher canopy temperatures, resulting in limited water deficit tolerance in rice. In addition, K deficiency led to further substantial reductions in leaf relative water content and water potential under water deficit, which increased the imbalance in leaf water relations under water deficit. Notably, K deficiency limited leaf gas exchange by reducing leaf hydraulic conductance, but decreased the intrinsic water use efficiency under water deficit, especially for the drought-resistant cultivar. Further analysis of the underlying process of leaf hydraulic resistance revealed that the key limiting factor of leaf hydraulic conductance under K deficiency was the outside-xylem hydraulic conductance rather than the xylem hydraulic conductance. Overall, our results provide a comprehensive perspective for assessing leaf water relations under K deficiency, water deficit, and their combined stresses, which will be useful for optimal rice fertilization strategies.

The role of leaf superoxide dismutase and proline on intra-specific photosynthesis recovery of Schima superba following drought.

Understanding the physiological and biochemical responses of tree seedlings under extreme drought stress, along with recovery during rewatering, and potential intra-species differences, will allow us to more accurately predict forest responses under future climate change. Here, we selected seedlings from four provenances (AH (Anhui), JX (Jiangxi), HN (Hunan) and GX (Guangxi)) of Schima superba and carried out a simulated drought-rewatering experiment in a field-based rain-out shelter. Seedlings were progressively dried until they reached 50% and 88% loss of xylem hydraulic conductivity (PLC) (i.e. P50 and P88), respectively, before they were rehydrated and maintained at field capacity for 30 days. Leaf photosynthesis (Asat), water status, activity of superoxide dismutase (SOD), and proline (Pro) concentration were monitored and their associations were determined. Increasing drought significantly reduced Asat, relative water content (RWC) and SOD activity in all provenances, and Pro concentration was increased to improve water retention; all four provenances exhibited similar response patterns, associated with similar leaf ultrastructure at pre-drought. Upon rewatering, physiological and biochemical traits were restored to well-watered control values in P50-stressed seedlings. In P88-stressed seedlings, Pro was restored to control values, while SOD was not fully recovered. The recovery pattern differed partially among provenances. There was a progression of recovery following watering, with RWC firstly recovered, followed by SOD and Pro, and then Asat, but with significant associations among these traits. Collectively, the intra-specific differences of S. superba seedlings in recovery of physiology and biochemistry following rewatering highlight the need to consider variations within a given tree species coping with future more frequent drought stress.

Unveiling the ecological resilience and industrial potential of Skeletonema marinoi through mixotrophic cultivation in Nordic winter condition.

Mixotrophy, the concurrent use of inorganic and organic carbon in the presence of light for microalgal growth, holds ecological and industrial significance. However, it is poorly explored in diatoms, especially in ecologically relevant species like Skeletonema marinoi. This study strategically employed mixotrophic metabolism to optimize the growth of a strain of Skeletonema marinoi (Sm142), which was found potentially important for biomass production on the west coast of Sweden in winter conditions. The aim of this study was to discern the most effective organic carbon sources by closely monitoring microalgal growth through the assessment of optical density, chlorophyll a fluorescence, and biomass concentration. The impact of various carbon sources on the physiology of Sm142 was investigated using photosynthetic and respiratory parameters. The findings revealed that glycerol exhibited the highest potential for enhancing the biomass concentration of Sm142 in a multi-cultivator under the specified experimental conditions, thanks to the increase in respiration activity. Furthermore, the stimulatory effect of glycerol was confirmed at a larger scale using environmental photobioreactors simulating the winter conditions on the west coast of Sweden; it was found comparable to the stimulation by CO2-enriched air versus normal air. These results were the first evidence of the ability of Skeletonema marinoi to perform mixotrophic metabolism during the winter and could explain the ecological success of this diatom on the Swedish west coast. These findings also highlight the importance of both organic and inorganic carbon sources for enhancing biomass productivity in harsh winter conditions.

Using leaf economic spectrum and photosynthetic acclimation to evaluate the potential performance of wintersweet under future climate conditions.

The function of landscape plants on the ecosystem can alleviate environmental issues of urbanization and global change. Global changes due to elevated CO2 affect plant growth and survival, but there is a lack of quantitative methods to evaluate the adaptability of landscape plants to future climate conditions. Leaf traits characterized by leaf economic spectrum (LES) are the universal currency for predicting the impact on plant ecosystem functions. Elevated CO2 usually leads to photosynthetic acclimation (PC), characterised by decreased photosynthetic capacity. Here, we proposed a theoretical and practical framework for the use of LES and PC to project the potential performance of landscape plants under future climatic conditions through principal component analysis, structural equation modelling, photosynthetic restriction analysis and nitrogen allocation analysis. We used wintersweet (an important landscaping species) to test the feasibility of this framework under elevated CO2 and different nitrogen (N) supplies. We found that elevated CO2 decreased the specific leaf area but increased leaf N concentration. The results suggest wintersweet may be characterized by an LES with high leaf construction costs, low photosynthetic return, and robust stress resistance. Elevated CO2 reduced photosynthetic capacity and stomatal conductance but increased photosynthetic rate and leaf area. These positive physio-ecological traits, e.g., larger leaf area (canopy), higher water use efficiency and stress resistance, may lead to improved performance of wintersweet under the predicted future climatic conditions. The results suggest planting more wintersweet in urban landscaping may be an effective adaptive strategy to climate change.

Response of carbon fixation, allocation, and growth to source-sink manipulation by defoliation in vegetative citrus trees.

Source-sink balance in plants determines carbon distribution, and altering it can impact carbon fixation, transport, and allocation. We aimed to investigate the effect of altered source-sink ratios on carbon fixation, transport, and distribution in 'Valencia' sweet orange (Citrus x sinensis) by various defoliation treatments (0%, 33%, 66%, and 83% leaf removal). Gas exchange parameters were measured on 0 and 10 days after defoliation using A/Ci response curves, and leaf export was measured two days after defoliation using radioisotope tracer techniques. Greater defoliation increased the maximum rate of carboxylation (Vcmax), electron transport rate (J1200), and triose-phosphate utilization rate (TPU). Leaf export was unaffected by defoliation but increased in leaves closer to the shoot apex. Basipetal translocation velocity in the trunk remained unaltered, indicating that more photosynthates remained in the shoot rather than being transported directly to the root sink. Defoliated plants initiated more new flush shoots but accumulated less shoot biomass per plant after 8 weeks. Carbon allocation to fine roots was smaller in defoliated plants, suggesting defoliation led to retention of carbohydrates in aboveground organs such as the trunk and other shoots from previous growing cycles. In conclusion, the low source-sink ratio increased carbon fixation without impacting individual leaf export in citrus. The results suggest that intermediate sinks such as the aboveground perennial organs play a role in mediating the translocation velocity. Further research is necessary to better understand the dynamics of source-sink regulation in citrus trees.

Light Response Curves in Land Plants.

Light is the driving force for photosynthesis. Two techniques are commonly employed to help characterize the relationship between the light environment and photosynthesis in plants.Chlorophyll a fluorescence analysis is used to examine both the capacity for and the efficiency of the conversion of absorbed light into energy for photosynthesis. Additionally, gas exchange analysis is used to assess the utilization of that energy for carbon fixation. These techniques are used either in isolation or in combination to acquire light response curves that measure the response of the plant to sequential changes in irradiance. Light response curves can help users understand photosynthetic mechanisms, evaluate how plants respond to light conditions, or assess the extent of physiological plasticity within plants. In this chapter, we provide a generalized method for acquiring light response curves suitable for both chlorophyll a fluorescence and gas exchange techniques using commercially available apparatus. Depending on the equipment available, these methods can be applied individually or combined to acquire data simultaneously. The methods are broadly applicable to most land plants but are ideally suited to help those that are unfamiliar with these techniques.

Measuring Canopy Gas Exchange Using CAnopy Photosynthesis and Transpiration Systems (CAPTS).

Canopy photosynthesis (Ac), rather than leaf photosynthesis, is critical to gaining higher biomass production in the field because the daily or seasonal integrals of Ac correlate with the daily or seasonal integrals of biomass production. The canopy photosynthesis and transpiration measurement system (CAPTS) was developed to enable measurement of canopy photosynthetic CO2 uptake, transpiration, and respiration rates. CAPTS continuously records the CO2 concentration, water vapor concentration, air temperature, air pressure, air relative humidity, and photosynthetic photon flux density (PPFD) inside the chamber, which can be used to derive CO2 and H2O fluxes of a canopy covered by the chamber. This system can also be used to measure the fluxes of greenhouse gases when integrating with CH4 and N2O analyzers. Here, we describe the protocol for using CAPTS to perform experiments on rice (Oryza sativa L.) in paddy field, wheat (Triticum aestivum L.) in upland field, and tobacco (Nicotiana tabacum L.) in pots.

Shining Light into a "Black Box": Essential Rationale Underlying Multiphase Flash Methodology.

The world we live in is very fragile. Sustainable food production is increasingly under intense pressure due to changing environmental conditions on many levels. Understanding the complexities of how to optimize food production under increasingly deleterious environmental conditions is dependent upon accurate and detailed analyses of plant productivity from the molecular-to-the-remote scales. One method that can link many of these scales has been around for decades, namely, pulse amplitude modulation (PAM) chlorophyll a fluorescence. This technique is used to measure an assortment of important parameters based on chlorophyll a fluorescence. One of the parameters measured by this method is termed the steady state maximum fluorescence yield ( Φ Fm ' ). This parameter, while extremely informative when used to quantify an assortment of processes of intense scientific interest, is nonetheless subject to intrinsic underestimation. A clever approach has evolved over several decades to more accurately estimate Φ Fm ' . The underlying rationale of the methodology requires a thorough and nuanced explanation, which is lacking in the literature. Herein, we systematically develop the essential rationale for accurately measuring Φ Fm ' based on the latest evolution of this approach, called multiphase flash (MPF) methodology.

ChloroSpec: A new in vivo chlorophyll fluorescence spectrometer for simultaneous wavelength- and time-resolved detection.

Chlorophyll fluorescence is a ubiquitous tool in basic and applied plant science research. Various standard commercial instruments are available for characterization of photosynthetic material like leaves or microalgae, most of which integrate the overall fluorescence signals above a certain cut-off wavelength. However, wavelength-resolved (fluorescence signals appearing at different wavelengths having different time dependent decay) signals contain vast information required to decompose complex signals and processes into their underlying components that can untangle the photo-physiological process of photosynthesis. Hence, to address this we describe an advanced chlorophyll fluorescence spectrometer - ChloroSpec - allowing three-dimensional simultaneous detection of fluorescence intensities at different wavelengths in a time-resolved manner. We demonstrate for a variety of typical examples that most of the generally used fluorescence parameters are strongly wavelength dependent. This indicates a pronounced heterogeneity and a highly dynamic nature of the thylakoid and the photosynthetic apparatus under actinic illumination. Furthermore, we provide examples of advanced global analysis procedures integrating this three-dimensional signal and relevant information extracted from them that relate to the physiological properties of the organism. This conveniently obtained broad range of data can make ChloroSpec a new standard tool in photosynthesis research.

Ecotoxicological assessment of cigarette butts on morphology and photosynthetic potential of Azolla pinnata.

Cigarette butts (CBs) have become the most ubiquitous form of anthropogenic litter globally. CBs contain various hazardous chemicals that persist in the environment for longer period. These substances are susceptible to leaching into the environment through waterways. The recent study was aimed to evaluate the effects of disposed CBs on the growth and development of Azolla pinnata, an aquatic plant. It was found that after a span of 6 days, the root length, surface area, number of fronds, and photosynthetic efficacy of plant were considerably diminished on the exposure of CBs (concentrations 0 to 40). The exposure of CBs led to a decrease in the FM, FV/F0, and φP0, in contrast, the φD0 increased in response to CBs concentration. Moreover, ABS/CSm, TR0/CSm, and ET0/CSm displayed a negative correlation with CB-induced chemical stress. The performance indices were also decreased (p-value ≤ 0.05) at the highest concentration of CBs. LD50 and LD90 represent the lethal dose, obtained value for LD50 is 20.30 CBs and LD90 is 35.26 CBs through probit analysis. Our results demonstrate that the CBs cause irreversible damage of photosynthetic machinery in plants and also reflect the efficacy of chlorophyll a fluorescence analysis and JIP test for assessing the toxicity of CBs in plants.