Hypobaria (low total atmospheric pressure) is essential in sustainable, energy-efficient plant production systems for long-term space exploration and human habitation on the Moon and Mars. There are also critical engineering, safety, and materials handling advantages of growing plants under hypobaria, including reduced atmospheric leakage from extraterrestrial base environments. The potential for producing crops under hypobaria and manipulating hypoxia (low oxygen stress) to increase health-promoting bioactive compounds is not well characterized. Here we showed that hypobaric-grown lettuce plants (25 kPa ≈ 25% of normal pressure) exposed to hypoxia (6 kPa pO2 ≈ 29% of normal pO2) during the final 3 d of the production cycle had enhanced antioxidant activity, increased synthesis of anthocyananins, phenolics, and carotenoids without reduction of photosynthesis or plant biomass. Net photosynthetic rate (PN) was not affected by total pressure. However, 10 d of hypoxia reduced PN, dark respiration rate (RD),
PN/RD ratio, and plant biomass. Growing plants under hypobaria and manipulating hypoxia during crop production to enhance health-promoting bioactive compounds is important for the health and well-being of astronauts exposed to space radiation and other stresses during long-term habitation. and C. He ... [et al.].
Dendrobium is one of the three largest genera in the Orchidaceae and is distributed throughout various habitats. We investigated photosynthesis in seven Dendrobium species and cultivars by comparing their leaf δ13C values, titratable acidity, and CO2 exchange in well-watered and drought-stressed conditions. In addition, the leaf thickness and mesophyll succulence index (Sm) were measured in well-watered conditions. Our results indicate that Dendrobium loddigesii is a typical obligate (or constitutive) CAM plant because the leaf δ13C values were -14.47 and -14.66‰ in both conditions, respectively. Others showed the leaf thickness of 0.31-0.89 mm and their δ13C values ranged from -25.68 to -28.37‰. These are not the CAM plants but they could not be classified as obligate C3 or C3/CAM intermediate plants. Dendrobium crepidatum and Dendrobium fimbriatum were further identified as the obligate C3 plants because the net CO2 uptake was positive during daytime and negative during nighttime in both conditions. In contrast, Dendrobium chrysotoxum, Dendrobium nobile, and D. nobile ‘V1’ and ‘V4’, showed no positive net CO2 uptake and low ΔH+ values during nighttime under well-watered conditions, indicating C3 photosynthesis. However, they showed the positive net CO2 uptake and large ΔH+ values during nighttime after drought-stress (21 or 28 days without H2O), indicating CAM photosynthesis. Therefore, these four species and cultivars were identified as C3/CAM intermediate (inducible or facultative) plants. In brief, obligate CAM, C3/CAM intermediate, and obligate C3 plant types all exist in the section of Dendrobium. To the best of our knowledge, this is the first report of the obligate C3 plants in Dendrobium, and these diverse photosynthetic pathways may explain their varied environmental adaptations., S. Qiu, S. Sultana, Z. D. Liu, L. Y. Yin, C. Y. Wang., and Obsahuje bibliografii
Poplars (Populus spp.) are widely used in the pulp and paper industry and as bioenergy resources. Poplars require a large amount of water for biomass accumulation and lack of water is a limiting factor for poplar growth. Arbuscular mycorrhizal (AM) fungi have been previously reported to afford some plant species with greater resistance to drought stress. However, the effects of AM fungi on hybrid poplar under drought stress and recovery have not been studied. The main aim of this study was to evaluate the effects of the AM fungus, Rhizophagus irregularis, on the growth, water status, chlorophyll (Chl) content and fluorescence, and photosynthesis of poplar seedlings. The experiment was divided into three stages. At each stage of the experiment, the seedlings were subjected to a different watering regime: well-watered (prior stress), drought, and then rewatering (recovery). Measurements were taken at the end of each stage of the experiment. The results showed that mycorrhizal plants had a higher net photosynthetic rate and Chl fluorescence compared with nonmycorrhizal plants, regardless of the stage. Mycorrhizal and nonmycorrhizal plants showed different responses to drought stress: mycorrhizal plants showed better water-use efficiency and water uptake under drought stress conditions. In general, the poplar seedlings that formed the AM symbiosis with R. irregularis showed enhanced growth and reduced loss of biomass during the drought stress compared with the nonmycorrhizal seedlings., T. Liu, M. Sheng, C. Y. Wang, H. Chen, Z. Li, M. Tang., and Obsahuje bibliografii
Tomato meets the dietary nutrient and antioxidant requirements of diverse populations. Being a C3 crop and an important vegetable, it is likely to be influenced by increased CO2 concentrations under climate change situation. This study was conducted to investigate the effects of elevated CO2 on overall physiology, water relations, growth, yield, and fruit quality of tomato (Lycopersicon esculentum Mill) cv. Arka Ashish. Plants were grown at elevated CO2 [550 (EC550) and 700 (EC700) ppm of CO2] in open top chambers. Increased assimilation rate, decreased stomatal conductance and transpiration rate were observed at elevated CO2 (EC) concentrations. Reduced leaf osmotic potential and increased water potential were observed at EC compared with the control (380 ppm of CO2) in flowering and fruiting stages. Lower total chlorophyll content was recorded at EC700. Plant height was significantly higher at EC550 compared with EC700. Higher number of branches was observed at EC700 as compared with plants grown at EC550 and the control. Leaf area was lower at EC700 compared with EC550 but specific leaf mass was higher at EC700. Due to higher leaf dry mass and root dry mass, the plants grown at EC700 exhibited higher total dry mass compared to EC550 and the control. Increased number of flowers and fruits together with higher fruit set led to higher fruit yield at both EC concentrations. The highest yield increase was observed at EC700. The fruits showed a lower content of phenols, flavonoids, ferric reducing antioxidant potential, total soluble solids, and titratable acidity in plants grown at EC as compared with the control. The ascorbic acid content was high at both EC700 and EC550. Carotenoids and lycopene content was low at EC700 compared to higher content observed at EC550 and the control., H. Mamatha, N. K. Srinivasa Rao, R. H. Laxman, K. S. Shivashankara, R. M. Bhatt, K. C. Pavithra., and Obsahuje bibliografii
Light-emitting diodes (LEDs) are a promising technology with a potential to improve the irradiance efficiency, light quality, and the light spectrum for increasing plant yield and quality. In this experiment, we investigated the impacts of various LED light qualities, including 100% red, 100% blue, 70% red + 30% blue, and 100% white, on the growth and photosynthesis, phytochemical contents, and mineral element concentrations in lettuce (Lactuca sativa L. cv. 'Grizzly') in comparison to normal greenhouse conditions. Photon flux of 300 µmol m-2 s-1 was provided for 14 h by 120 LEDs set on a 60 cm × 60 cm sheet of aluminum platform in the growth chambers, where plants were grown for 60 d. Fresh mass per plant was significantly higher when grown under 100% blue and 70% red + 30% blue LEDs compared to the other environments including greenhouse conditions. Phytochemical concentrations and a nutritive value of lettuce were also significantly affected by the light treatments. Chlorophyll and carotenoid concentrations increased in the plants grown under 70% red + 30% blue LEDs compared to those grown in the greenhouse. Vitamin C content was 2.25-fold higher in the plants grown under 100% blue LEDs compared to those grown in the greenhouse. Higher photosynthesis and maximal quantum yield of PSII photochemistry were also observed in the plants treated with LED lights. The application of LED light led to the elevated concentrations of macro-and micronutrients in lettuce possibly because of the direct effect of LED light and lower stress conditions in the growth chambers compared to the greenhouse. Although the mechanism of the changes in lettuce grown under LED is not well understood, the results of this study demonstrated that LED light could be used to enhance the growth and nutritional value of lettuce in indoor plant production facilities., A. Amoozgar, A. Mohammadi, M. R. Sabzalian., and Obsahuje bibliografii
Plant cells plastically change their functions according to the environment. Although Arabidopsis roots are heterotrophic organs, they increase photosynthetic capacity after shoot removal. Transcription factors regulating chloroplast development are involved in this response downstream of positive cytokinin and negative auxin regulation. To dissect the crosstalk of these regulators after shoot removal, we analyzed photosynthetic parameters in roots with chloroplast development enhanced by shoot removal, overexpression of transcription factors, or hormonal treatment. Our data suggest that shoot removal improves electron transfer downstream of PSII in roots, with a decrease in nonregulated energy dissipation. Cytokinin, auxin, and transcription factors affect the photosynthetic capacity of roots in a highly complex manner. Overexpression of two different types of transcription factors (GOLDEN 2-LIKE 1 and class-B GATAs) synergistically increased root chlorophyll content while maintaining high photosynthetic efficiency. Our data demonstrate the flexible regulation of the photosynthetic machinery by hormone signaling and downstream transcription factors., A. Ohnishi, H. Wada, K. Kobayashi., and Obsahuje bibliografické odkazy
Green photosynthetic stems are often responsible for photosynthesis due to the reduction of leaves in arid and hot climates. We studied the response of PSII activity to high irradiance in the photosynthetic stems of Hexinia polydichotoma in the Taklimakan Desert by analysis of the fast fluorescence transients (OJIP). Leaf clips of a chlorophyll fluorometer were used in conjunction with a sponge with a 4-mm-width groove to prevent light leakage for precise in vivo measurements. High irradiance reduced performance indices, illustrating the photoinhibition of PSII to some extent. However, the decrease in active reaction centers (RC) per PSII absorption area and maximum quantum yield indicated a partial inactivation of RCs and an increase in excitation energy dissipation, resulting in downregulation of photosynthetic excitation pressure. In addition, the increased efficiency of electron transport to PSI acceptors alleviated overexcitation energy pressure on PSII. These mechanisms protected the PSII apparatus as well as PSI against damages from excessive excitation energy. We suggested that H. polydichotoma exhibited rather photoadaptation than photodamage when exposed to high irradiance during the summer in the Taklimakan Desert. The experiment also demonstrated that the modified leaf clip can be used for studying dark adaptation in a photosynthetic stem., L. Li, Z. Zhou, J. Liang, R. Lv., and Obsahuje seznam literatury
The principal function of the thylakoid membrane depends on the integrity of the lipid bilayer, yet almost half of the thylakoid lipids are of non-bilayer-forming type, whose exact functions are not fully understood. Non-bilayer lipids can be extruded from the membrane in the presence of high concentrations of co-solutes. We applied 2 M sucrose to induce lipid phase separation in isolated thylakoid membranes, following consequent structural and physiological effects. Circular dichroism spectroscopy indicated significant changes in the chiral macro-arrangement of the pigment-protein complexes, which were reversed after washing out the co-solute. Similarly, merocyanine-540 fluorescence suggested reversible changes in the lipid phases. The PSII function, as tested by chlorophyll fluorescence induction transients and time-resolved fluorescence, was almost unaffected. However, the presence of sucrose dramatically increased the PSII thermostability, which can partly be explained by a direct osmolyte effect and partly by the lipid phase separation stabilizing the stacked membrane., C. Kotakis, P. Akhtar, O. Zsiros, G. Garab, P. H. Lambrev., and Obsahuje bibliografické odkazy
We studied the effect of arbuscular mycorrhizal (AM) fungus, Glomus constrictum (Trappe), and soil phosphorus (P) on
gas-exchange parameters, growth, and nutrition of soybean plants grown in pots with sterilized soil. Two contrasting concentrations of KH2PO4, i.e. no added and 0.5 g(P) kg-1(soil), were used. Addition of soluble phosphate increased all growth parameters, P and N concentrations, and most of the studied photosynthetic parameters of both the mycorrhizal and nonmycorrhizal plants. The mycorrhizal inoculation significantly increased plant growth responses, P and N concentrations in shoot and root tissues, acid and alkaline phosphatase activities, and total soluble proteins in root tissues compared with the nonmycorrhizal plants. The stimulations were related to the level of the mycorrhizal colonization in the root tissues. The mycorrhizal plants showed significantly higher net photosynthetic rate, stomatal conductance, and transpiration rate than those of nonmycorrhizal plants, especially in soil without added P. The phosphate addition to soil reduced generally the percentage of the mycorrhizal colonization in the root tissues, and consequently the mycorrhizal benefits. In general, growth, nutrition, and photosynthetic parameters of the soybean plants showed a high degree of dependency on the mycorrhizal fungus in nonfertilized soil when compared with the soil fertilized with P. This study confirmed that AM colonization could improve growth and nutrition of the soybean plant through increasing photosynthesis in leaves, particularly at low P in soil., G. M. Abdel-Fattah, A. A. Asrar, S. M. Al-Amri, E. M. Abdel-Salam., and Obsahuje bibliografii
In order to elucidate the drought resistance and high-yield mechanism of hybrid millet, we studied the influence of drought stress on the photosynthetic characteristics and dry matter accumulation. Our results revealed that drought stress caused lesser reduction in the net photosynthetic rate, maximal quantum yield of PSII photochemistry, excitation energy capture efficiency of PSII reaction centers and in the yield of hybrid millet compared to normal millet. When drought stress occurred in the jointing stage, the percentage decrease of PN, Fv/Fm, Fv′/Fm′, and the yield of Zhangzagu3 cultivar compared to control were 27.9%, 2.6%, 25. 5%, and 1.9%, respectively, the percentage decrease of Zhangzagu5 were 37.6%, 3.9%, 28.3%, and 16.7%, respectively, the decrease percentage of Datong29 were 60.1%, 6.4%, 4%, and 23.4%, respectively. Hybrid millet showed the similar reduction in the parameters referred above, when drought stress occurred at the heading stage, but the percentage decrease was much higher than that at the jointing stage. We concluded that hybrid millet showed higher drought resistance than normal millet., H. B. Lu, Y. M. Qiao, X. C. Gong, H. Q. Li, Q. Zhang, Z. H. Zhao, L. L. Meng., and Obsahuje bibliografii