Main Photosynthetic Parameters Research Articles

Photosynthetic and antioxidant activity in the sex-related heat stress response of the dioecious species Rumex thyrsiflorus Fingerh.

Rumex thyrsiflorus Fingerh. is a dioecious species with heteromorphic sex chromosomes. Due to sexual dimorphism and the content of bioactive constituents used in pharmacology, this species is an interesting object of study. A complex analysis of selected physiological and biochemical aspects of the sex-related response to heat stress in vitro and in vivo was carried out. The experiment included in vitro regenerated plants and plants obtained from seeds. Regenerants were obtained from hypocotyls on Murashige and Skoog (MS) medium supplemented with 2.27 μM thidiazuron (TDZ). The sex of the plants was determined by molecular analysis based on genetic sex markers. Analysis of the main photosynthetic parameters indicated that in vitro regenerated plants showed a decrease in photosystem II (PSII) activity when directly exposed to a stressor. However, in contrast to the seed-derived plants, they adapted efficiently to the recovery conditions within 1 week after the stress was terminated. Furthermore, in vitro regenerated male and female plants acclimatised well to field conditions and showed greater stress tolerance based on better efficiency of the photosynthetic apparatus and the highest chlorophyll a/b ratio. In case of plants derived from seeds, male plants were less sensitive to heat stress and showed greater stability of PSII at high temperatures compared to female plants. The results showed that the response to high-temperature stress depends on the sex and the origin of the plants, i. e. in vitro regenerated plants versus plants obtained from seeds. Even short-term heat stress resulted in differences in photosynthetic efficiency. Biochemical analysis of antioxidant activity in response to heat stress, carried out for the first time in Rumex thyrsiflorus, has allowed the identification of the following forms of superoxide dismutase (SOD): manganese (MnSOD), iron (FeSOD) and two copper-zinc isoforms (Cu/ZnSOD I and Cu/ZnSOD II).

Effects of CO2 on transplantation of grape plantlets cultured in vitro by promoting photosynthesis

Plantlet in vitro is an indispensable step in micropropagation and breeding of grape (Vitis vinifera L.). However, the plantlets rely on the artificially controlled micro-environment, which is difficult to adapt to the field acclimation and transplantation, resulting in low survival rate and qualified plantlets rate. Studying the photosynthetic and growth characteristics of plantlets cultured with CO2 and sucrose as carbon sources presents important references for the acclimation and transplantation. In this context, "Pinot Noir" plantlets in vitro were cultured with S1: medium with 2% sucrose, normal carbon dioxide (CO2) concentration (380 μmol•mol−1), CS: medium with 2% sucrose, high CO2 concentration (1000 μmol•mol−1), C0: medium without sucrose, high CO2 concentration (1000 μmol•mol−1) and S0: medium without sucrose, normal CO2 concentration (380 μmol•mol−1). The results indicated that the growth status and survival rate (an average increase of 19.4%) of plantlets were significantly improved by high concentration CO2 treatments. The photosynthetic parameters of high-concentration CO2 treatments had a positive effect on photosynthetic products, which were consistent with the up-regulated trend of the relative expression of related synthesis and transport genes. Interestingly, the sugar content of photosynthetic products in leaves showed a trend from high to low at different carbon treatment stages, but the opposite trend was observed in stems. What's more, the main photosynthetic parameters of high concentration CO2 treatments were significantly increased, especially the photosynthetic fluorescence parameters of CS were the highest, and the relative expression of photosynthesis related genes were significantly up-regulated during acclimation and transplantation. Comprehensive principal component analysis method speculated that exogenous CO2 mainly laid a good foundation for the acclimation and transplantation by promoting the photosynthesis of plantlets and adjusting the source-sink relationship of leaf and stem photosynthetic products.

Antioxidative response and photosynthetic regulatory mechanisms in common fig leaves after short‐term chilling stress

AbstractCommon fig (Ficus carica L.) is widely cultivated Mediterranean species. Such warm‐climate species are adapted to elevated temperatures and are susceptible to chilling stress (0–12°C). However, occasional short chilling periods are common during growing season in temperate areas that can affect functionality of the plant. The aim of this work was to investigate influence of short‐term chilling stress on antioxidative response and PSII photochemistry in developing leaves of two common fig varieties: Zamorčica and Green matalon. Leaves were detached from the trees, acclimated at room temperature in dark for 16 hr and then exposed to low temperature (10°C) at low irradiation (50 μmol m−2 s−1) for 4 hr. Dark adapted leaves were considered as the control. The damage to the membranes was determined as lipid peroxidation (thiobarbituric acid reactive substances) while the antioxidative response was evaluated by determining activities of the selected antioxidative enzymes. Photosynthetic performance was analysed by measuring in vivo chlorophyll a fluorescence (ChlF) increase. Relative accumulation of the main photosynthetic proteins (D1 and Rubisco LSU) was determined, as well. Due to efficient antioxidative activity, neither of investigated variety showed damage of the membrane lipids. Both varieties revealed functional antennae and its good connectivity to their reaction centres shown as negative L and K bands as well as stable D1 protein accumulation suggesting functional electron transport through photosystem II (PSII) and efficient primary photochemistry. Blocked electron flow further than QA resulted in limitation of the Photosystem I (PSI) functionality in both varieties. Due to differential relative accumulation of D1 and Rubisco LSU proteins upon the chilling stress, Zamorčica revealed greater decrease of the main photosynthetic parameters derived from in vivo ChlF induction (PItotal, PIABS and φP0) in comparison to Green matalon. In addition, increased specific energy fluxes through PSII in Zamorčica suggested its higher susceptibility to photoinhibition caused by chilling stress in comparison to Green matalon.

Photosynthesis-related protein expression in sugarcane during sugarcane–Fusarium verticillioides interaction revealed by iTRAQ

Pokkah boeng disease (PBD) is mainly caused by Fusarium verticillioides and F. proliferatum, and it substantially reduces sugarcane yield and quality in China. Sugarcane proteins play important roles in defense against these fungal infections. This study aimed to explore the photosynthesis-related proteins involved in PBD resistance in resistant (R) and susceptible (S) sugarcane materials. The main photosynthetic parameters were measured with the LI-6400 photosynthesis system, fluorescence measurements were acquired via saturation pulse, and an isobaric tags for relative and absolute quantification (iTRAQ) and low PH nano-HPLC–MS–MS-based proteomic techniques were used to assess photosynthesis-related proteome changes 14 days after inoculation with F. verticillioides between inoculated and control leaves of YT94-128 (R) and GT37 (S) plants. The net photosynthetic rate (Pn), stomatal conductance (gs), and transpiration rate (E) of sugarcane plants were significantly reduced as pathogen stress increased, and the intercellular CO2 concentration (Ci) was significantly elevated compared to that in the control plants. In addition, 29 proteins involved in photosynthesis were found to be differentially expressed following pathogen inoculation, including six proteins that were differentially expressed in both sugarcane varieties. These results indicate that complex photosynthesis-related proteins are involved in the sugarcane–F. verticillioides interaction and provide novel insights into the molecular mechanisms underlying sugarcane response to PBD pathogen infection.

Tree growth and leaf gas exchange variability of three Mediterranean Pinus spp. growing in a common garden in Northeastern Tunisia

A dendrochronological approach and gas exchange techniques were used to study the adaptation of Pinus halepensis, Pinus pinea, and Pinus brutia growing in a 47-year-old common garden experiment to the local subhumid climate in Northeastern Tunisia. P. pinea showed the highest survival rate, the greatest height, the widest diameter at breast height, and the largest specific leaf area. The lowest values were recorded for P. halepensis. Ring width data showed that P. pinea had the highest radial growth, which was correlated to the lowest mean sensitivity and the first-order autocorrelation coefficient. The highest values of the abovementioned parameters were recorded for P. halepensis. CO2 response curves of net leaf photosynthesis were used to directly calculate the main photosynthetic parameters, including the CO2-saturated net photosynthesis rate, stomatal limitation, and carboxylation efficiency. At the natural ambient CO2 concentration, P. brutia presented the lowest net photosynthesis, P. pinea exhibited the highest water-use efficiency, and the highest stomatal conductance was recorded for P. halepensis. Furthermore, at a high concentration of CO2, the highest stomatal limitation was recorded for P. brutia, which may partially explain why it presented the lowest net CO2-saturated photosynthesis rate; the highest net CO2-saturated photosynthesis rate was observed for P. halepensis. The response of the growth pattern to the climate was found to depend on the species. P. pinea showed the highest radial growth and water-use efficiency, implying that this species is the best suited of the three species investigated to the pedoclimatic conditions in the studied area.

Photosynthetic limitations in two Antarctic vascular plants: importance of leaf anatomical traits and Rubisco kinetic parameters.

Particular physiological traits allow the vascular plants Deschampsia antarctica Desv. and Colobanthus quitensis (Kunth) Bartl. to inhabit Antarctica. The photosynthetic performance of these species was evaluated in situ, focusing on diffusive and biochemical constraints to CO2 assimilation. Leaf gas exchange, Chl a fluorescence, leaf ultrastructure, and Rubisco catalytic properties were examined in plants growing on King George and Lagotellerie islands. In spite of the species- and population-specific effects of the measurement temperature on the main photosynthetic parameters, CO2 assimilation was highly limited by CO2 diffusion. In particular, the mesophyll conductance (gm)-estimated from both gas exchange and leaf chlorophyll fluorescence and modeled from leaf anatomy-was remarkably low, restricting CO2 diffusion and imposing the strongest constraint to CO2 acquisition. Rubisco presented a high specificity for CO2 as determined in vitro, suggesting a tight co-ordination between CO2 diffusion and leaf biochemistry that may be critical ultimately to optimize carbon balance in these species. Interestingly, both anatomical and biochemical traits resembled those described in plants from arid environments, providing a new insight into plant functional acclimation to extreme conditions. Understanding what actually limits photosynthesis in these species is important to anticipate their responses to the ongoing and predicted rapid warming in the Antarctic Peninsula.

Collaborative application of BEPS at different time steps.

BEPSHourly is committed to simulate the ecological and physiological process of vegetation at hourly time steps, and is often applied to analyze the diurnal change of gross primary productivity (GPP), net primary productivity (NPP) at site scale because of its more complex model structure and time-consuming solving process. However, daily photosynthetic rate calculation in BEPSDaily model is simpler and less time-consuming, not involving many iterative processes. It is suitable for simulating the regional primary productivity and analyzing the spatial distribution of regional carbon sources and sinks. According to the characteristics and applicability of BEPSDaily and BEPSHourly models, this paper proposed a method of collaborative application of BEPS at daily and hourly time steps. Firstly, BEPSHourly was used to optimize the main photosynthetic parameters: the maximum rate of carboxylation (Vc max) and the maximum rate of photosynthetic electron transport (Jmax) at site scale, and then the two optimized parameters were introduced into BEPSDaily model to estimate regional NPP at regional scale. The results showed that optimization of the main photosynthesis parameters based on the flux data could improve the simulate ability of the model. The primary productivity of different forest types in descending order was deciduous broad-leaved forest, mixed forest, coniferous forest in 2011. The collaborative application of carbon cycle models at different steps proposed in this study could effectively optimize the main photosynthesis parameters Vc max and Jmax, simulate the monthly averaged diurnal GPP, NPP, calculate the regional NPP, and analyze the spatial distribution of regional carbon sources and sinks.

Parameter optimization of BEPS model based on the flux data of the temperate deciduous broad-leaved forest in Northeast China.

Keeping other parameters as empirical constants, different numerical combinations of the main photosynthetic parameters Vc max and Jmax were conducted to estimate daily GPP by using the iteration method in this paper. To optimize Vc max and Jmax in BEPSHourly model at hourly time steps, simulated daily GPP using different numerical combinations of the parameters were compared with the flux tower data obtained from the temperate deciduous broad-leaved forest of the Maoershan Forest Farm in Northeast China. Comparing the simulated daily GPP with the observed flux data in 2011, the results showed that optimal Vc max and Jmax for the deciduous broad-leaved forest in Northeast China were 41.1 μmol·m-2·s-1 and 82.8 μmol·m-2·s-1 respectively with the minimal RMSE and the maximum R2 of 1.10 g C·m-2·d-1 and 0.95. After Vc max and Jmax optimization, BEPSHourly model simulated the seasonal variation of GPP better.

Comparison of drought stress response and gene expression between a GM maize variety and a near-isogenic non-GM variety.

Maize MON810, grown and commercialised worldwide, is the only cultivated GM event in the EU. Maize MON810, variety DKC6575, and the corresponding near-isogenic line Tietar were studied in different growth conditions, to compare their behaviour in response to drought. Main photosynthetic parameters were significantly affected by drought stress in both GM and non-GM varieties to a similar extent. Though DKC6575 (GM) had a greater sensitivity in the early phase of stress response as compared with Tietar (non-GM), after six days of stress they behaved similarly, and both varieties recovered from stress damage. Profiling gene expression in water deficit regimes and in a generalised drought stress condition showed an up-regulation of many stress-responsive genes, but a greater number of differentially expressed genes was observed in Tietar, with genes belonging to transcription factor families and genes encoding heat shock proteins, late embryogenesis abundant proteins and detoxification enzymes. Since induction of these genes have been indicated from the literature as typical of stress responses, their activation in Tietar rather than in DKC6575 may be reminiscent of a more efficient response to drought. DKC6575 was also analysed for the expression of the transgene CryIAb (encoding the delta-endotoxin insecticidal protein) in water deficit conditions. In all the experiments, the CryIAb transcript was not influenced by drought stress, but was expressed at a constant level. This suggests that though possessing a different pattern of sensitivity to stress, the GM variety maintains the same expression level for the transgene.

A modified rectangular hyperbola to describe the light-response curve of photosynthesis of Bidens pilosa L. grown under low and high light conditions

The light-response curve of leaf net photosynthesis is an important tool for understanding the photochemical efficiency of the photosynthetic process. We measured the light-response of the photosynthetic rate of Bidens pilosa L., when grown under high light of 100% full sunlight (HL) and low light of 50% full sunlight (LL) using a gas analyzer Li-6400. The measured data were simulated by a modified rectangular hyperbola. The fitted results showed that the modified rectangular hyperbola described the part of the curve up to the light saturation and the range of levels above the saturation light intensity in Bidens pilosa L. well. It was used to directly calculate the main photosynthetic parameters, including the lightsaturated net photosynthetic rate (P max), saturation light intensity (I m), light compensation point (I c), dark respiration rate, and the initial slope of curve without any additional hypotheses. Good agreement was obtained between the modified rectangular hyperbola estimates and observations of P max and I m of B. pilosa under LH and LL conditions. Furthermore, the modified rectangular hyperbola provided a very easy and simple method for simultaneously simulating the data on the light-response curve of photosynthesis at low irradiances, saturating irradiances, photoacclimation and photoinhibition.

Light acclimatisation of Elodea nuttallii grown under ambient DIC conditions

Light acclimatisation capabilities of Elodea nuttallii at nearly ambient DIC conditions were investigated by determining growth characteristics, main photosynthetic parameters and pigmentation of plants incubated at 5 different irradiances (10–146 μmol photons m−2 s−1). Positive net growth was observed under all light treatments tested. Maximum ratio root versus shoot (r:s) of 1.86 was achieved at medium irradiances (72–94 μmol photons m−2 s−1), whereas at low (10 μmol photons m−2 s−1) and high irradiances (146 μmol photons m−2 s−1) r:s was significantly lower (0.39 and 1.05, respectively). With respect to main photosynthetic parameters, an increase of light compensation points (Ec), attended by decreasing ratios of light saturation points of photosynthesis (Ek)/irradiance were observed. Ec values were comparable to other low-light adapted macrophytes, which indicate that E. nuttallii can be regarded as a low-light adapted plant, under photorespiratory conditions. This was also confirmed by maximum Ek values of just 73 μmol photons m−2 s−1. Further support was achieved from pigmentation and non-photochemical quenching (NPQ) data, both indicating rather limited acclimatisation ability at light treatments above 90 μmol photons m−2 s−1. These results are discussed with respect to the competitive abilities of E. nuttallii under nearly ambient (photorespiratory) DIC conditions, especially in dense stands and turbid phytoplankton-dominated waters.

Investigation on dynamic changes of photosynthetic characteristics of 10 wheat ( Triticum aestivum L.) genotypes during two vegetative-growth stages at water deficits

Drought is a worldwide problem, seriously influencing plant (crop) productivity. Wheat is a stable food for 35% of the world population, and moreover, about 60% of land area on the globe belongs to arid and semiarid zone. Wheat drought resistance is a multi-gene controlling quantitative character and wheat final production in field is realized mainly by physiological regulation under the condition of multi-environmental factor interaction. Exploring drought resistance physiological mechanisms for different wheat genotypes is of importance to finding new drought resistance gene resources and conventional breeding, and the basis for wheat drought resistance biotechnological breeding and platform. Photosynthesis is the main component for physiological machinery of wheat assimilates conversion and wheat production. Investigation on photosynthetic characteristics of different wheat genotypes at soil water deficits also has other implications for refine physiological regulation of photosynthesis in fields and field management of crops in arid and semiarid areas. By pot-cultivating experiments, investigation of photosynthesis for 10 wheat genotypes at seedling stage and tillering stage at soil water deficits (75%FC, 55%FC and 45%FC, respectively) was conducted. The main results were as followed: developmental stages influenced wheat photosynthesis greatly and tillering stage played more roles; there were significant difference in the main photosynthetic parameters, photosynthesis rate (Photo), stomatal conductance (Cond) and transpiration rate (Tr), among 10 wheat genotypes; general photosynthesis and drought resistance in different wheat genotypes was related much to their domesticated origin soil water environment and selected generations and there was a photosynthetic threshold effect in terms of different wheat genotypes at soil water deficits.