The photosynthetic responses to salt stress were examined in a wheat (Triticum aestivum L. cv. Asakaze)-barley (Hordeum vulgare L. cv. Manas) 7H addition line having elevated salt tolerance and compared to the parental wheat genotype. For this purpose, increasing NaCl concentrations up to 300 mM were applied and followed by a 7-day recovery period. Up to moderate salt stress (200 mM NaCl), forcible stomatal closure, parallel with a reduction in the net assimilation rate (PN), was only observed in wheat, but not in the 7H addition line or barley. Since the photosynthetic electron transport processes of wheat were not affected by NaCl, the impairment in PN could largely be accounted for the salt-induced decline in stomatal conductance (gs), accompanied by depressed intercellular CO2 concentration and carboxylation efficiency. Both, PN and nonstomatal limitation factors (Lns) were practically unaffected by moderate salt stress in barley and in the 7H addition line due to the sustained gs, which might be an efficient strategy to maintain the efficient photosynthetic activity and biomass production. At 300 mM NaCl, both PN and gs decreased significantly in all the genotypes, but the changes in PN and Lns in the 7H addition line were more favourable similar to those in wheat. The downregulation of photosynthetic electron transport processes around PSII, accompanied by increases in the quantum yield of regulated energy dissipation and of the donor side limitation of PSI without damage to PSII, was observed in the addition line and barley during severe stress. Incomplete recovery of PN was observed in the 7H addition line as a result of declined PSII activity probably caused by enhanced cyclic electron flow around PSI. These results suggest that the better photosynthetic tolerance to moderate salt stress of barley can be manifested in the 7H addition line which may be a suitable candidate for improving salt tolerance of wheat., D. Szopkó, É. Darkó, I. Molnár, K. Kruppa, B. Háló, A. Vojtkó,
M. Molnár-Láng, S. Dulai., and Obsahuje bibliografii
Two cultivars (Katy and Erhuacao) of apricot (Prunus armeniaca L.) were evaluated under open-field and solar-heated greenhouse conditions in northwest China, to determine the effect of photosynthetic photon flux density (PPFD), leaf temperature, and CO2 concentration on the net photosynthetic rate (PN). In greenhouse, Katy registered 28.3 µmol m-2 s-1 for compensation irradiance and 823 µmol m-2 s-1 for saturation irradiance, which were 73 and 117 % of those required by Erhuacao, respectively. The optimum temperatures for cvs. Katy and Erhuacao were 25 and 35 °C in open-field and 22 and 30 °C in greenhouse, respectively. At optimal temperatures, PN of the field-grown Katy was 16.5 µmol m-2 s-1, 21 % less than for a greenhouse-grown apricot. Both cultivars responded positively to CO2 concentrations below the CO2 saturation concentration, whereas Katy exhibited greater PN (18 %) and higher carboxylation efficiency (91 %) than Erhuacao at optimal CO2 concentration. Both cultivars exhibited greater photosynthesis in solar-heated greenhouses than in open-field, but Katy performed better than Erhuacao under greenhouse conditions. and F. L. Wang, H. Wang, G. Wang.
Seedlings of Chrysanthemum, cultivar 'Puma Sunny', were grown under a range of shading regimes (natural full sunlight, 55, 25, and 15% of full sunlight) for 18 days. Here, we characterized effects of varying light regimes on plant morphology, photosynthesis, chlorophyll fluorescence, anatomical traits, and chloroplast ultrastructure. We showed that leaf color was yellowish-green under full sunlight. Leaf area, internode length, and petiole length of plants were the largest under 15% irradiance. Net photosynthetic rate, water-use efficiency, PSII quantum efficiency, and starch grain were reduced with decreasing irradiance from 100 to 15%. Heavy shading resulted in the partial closure of PSII reaction centers and the CO₂ assimilation was restricted. The results showed the leaves of plants were thinner under 25 and 15% irradiance with loose palisade tissue and irregularly arranged spongy mesophyll cells, while the plants grown under full sunlight showed the most compact leaf palisade parenchyma. Irradiance lesser than 25% of full sunlight reduced carbon assimilation and led to limited plant growth. Approximately 55% irradiance was suggested to be the optimal for Chrysanthemum morifolium., S. Han, S. M. Chen, A. P. Song, R. X. Liu, H. Y. Li, J. F. Jiang, F. D. Chen., and Obsahuje bibliografii
This study aimed to determine the photosynthetic performance and differences in chlorophyll fluorescence (ChlF) parameters between Eulophia dentata and its companion species Bletilla formosana and Saccharum spontaneum when subjected to different photosynthetic photon flux density (PPFDs). Leaf surfaces were then illuminated with 50, 100 (low PPFDs), 300, 500, 800 (moderate PPFDs); 1,000; 1,500; and 2,000 (high PPFDs) μmol m-2.s-1, and the ChlF parameters were measured during the whole process. Increasing nonphotochemical quenching of ChlF and decreasing potential quantum efficiency of PSII, actual quantum efficiency of PSII, and quantum efficiency ratio of PSII in dark recovery from 0-60 min were observed in all leaves. A significant and negative relationship was detected between energy-dependent quenching (qE) and photoinhibition percent in three species under specific PPFD conditions, whereas a significant and positive relationship was detected between photoinhibitory quenching (qI) and photoinhibition percent. The qE and qI can be easily measured in the field and provide useful ecological indexes for E. dentata species restoration, habitat creation, and monitoring.
The effects of shade on the gas exchange of four Hosta cultivars were determined under differing irradiances (5, 30, 50, and 100 % of full irradiance) within pots. Irradiance saturation ranged between 400-800 μmol m-2 s-1 among the four cultivars, of which H. sieboldiana cv. Elegans and H. plantagenea cv. Aphrodite exerted the lowest saturation and compensation irradiances. The maximal photosynthetic rate (Pmax) was significantly higher in shade than in full irradiance in Elegans and Aphrodite, and was at maximum in seedlings grown in 30 % of full irradiance. The best shade treatment for cvs. Antioch and Golden Edger was 50 % of full irradiance. The diurnal gas exchange patterns in four cultivars were greatly influenced by the irradiance. Single-peak patterns of net photosynthetic rate (PN) and stomatal conductance (gs) were observed under 5 and 30 % full irradiance for all the cultivars while Elegans and Aphrodite suffered from midday depression in 50 % of full irradiance. Under open sky, all four cultivars showed two-peak patters in their diurnal gas exchange, but the midday depression was less in Antioch and Golden Edger than in Elegans and Aphrodite. According to their photosynthetic responses to shade, the shade tolerance of the four cultivars was in the order: Elegans>Aphrodite>Antioch>Golden Edger. and J. Z. Zhang ... [et al.].
Peanut plants were adapted to drought. Due to parahelionastic leaf movements under water stress they decreased heat load and transpiring area, Folding of leaflets minimised damage to photosynthetic apparatus by high temperatoe. A positive correlation between transpiration rate (E) and leaf water potential indicated the dependence of the latter on E. Phosphoenolpyruvate carboxylase (PEPC) activity progressively increased with increased period of stress, whereas activities of ribulose-l,5-bisphosphate carboxylase (RuBPC) and NADP-glyceraldehyde-3- phosphate dehydrogenase (NADP-G-3-PDH) decreased gradually.
The spider mite Tetranychus urticae Koch is emerging as a major problem in Jatropha curcas cultivation. The goal of this study was to investigate the photosynthetic responses of Jatropha to spider mite infestation. Leaf CO2 assimilation rate, stomatal conductance, transpiration, intracellular CO2 concentration, and instantaneous carboxylation efficiency significantly decreased in mite-infested leaves compared with controls. Lower water content and specific leaf area of the mite-infested leaves were positively related to symptoms of wrinkling and curling. Leaf electrolyte leakage remained unchanged in the mite-infested leaves, revealing no effect on leaf membrane integrity. Leaves exhibited reductions in soluble protein and soluble sugar in association with photosynthetic impairment. Although decreases in photochemical activity and chlorophyll fluorescence parameters suggested damage to the photosynthetic apparatus, although there were no measurable reductions in chlorophyll or carotenoid contents associated with photosynthetic apparatus impairment. The decrease in the leaf CO2 assimilation rate was partially attributed to stomatal and metabolic limitations in the mite-infested leaves., M.-H. Hsu, C.-C. Chen, K.-H. Lin, M.-Y. Huang, C.-M. Yang, W.-D. Huang., and Obsahuje seznam literatury
Cuttings of P. przewalski were exposed to two different watering regimes which were watered to 100 and 25 % of field capacity (WW and WS, respectively). Drought stress not only significantly decreased net photosynthetic rate (PN), transpiration rate (E), stomatal conductance (gs), efficiency of photosystem 2 (PS2) (Fv/Fm and yield), and increased intrinsic water use efficiency (WUEi) under controlled optimal conditions, but also altered the diurnal changes of gas exchange, chlorophyll fluorescence, and WUEi. On the other hand, WS also affected the
PN-photosynthetically active radiation (PAR) response curve. Under drought stress, PN peak appeared earlier (at about 10:30 of local time) than under WW condition (at about 12:30). At midday, there was a depression in PN for WS plants, but not for WW plants, and it could be caused by the whole microclimate, especially high temperature, low relative humidity, and high PAR. There were stomatal and non-stomatal limitations to photosynthesis. Stomatal limitation dominated in the morning, and low PN at midday was caused by both stomatal and non-stomatal limitations, whereas non-stomatal limitation dominated in the afternoon. In addition, drought stress also increased compensation irradiance and dark respiration rate, and decreased saturation irradiance and maximum net photosynthetic rate. Thus drought stress decreased plant assimilation and increased dissimilation through affected gas exchange, the diurnal pattern of gas exchange, and photosynthesis-PAR response curve, thereby reducing plant growth and productivity. and C. Y. Yin, F. Berninger, C. Y. Li.
Plant growth, chlorophyll (Chl) content, photosynthetic gas exchange, ribulose-1,5-bisphosphate carboxylase (RuBPCO) enzyme activity, and Chl fluorescence in radish (Raphanus sativus var. longipinnatus) plants were examined after turnip mosaic virus (TuMV) infection. Plant fresh mass, dry mass, Chl content, net photosynthetic rate (PN), transpiration rate (E), stomatal conductance (gs), and RuBPCO activity were significantly lower in infected plants after 5 weeks of virus infection as compared to healthy plants. The 5-week virus infection did not induce significant differences in intercellular CO2 concentration (Ci, photochemical efficiency of photosystem 2, PS2 (Fv/Fm), excitation capture efficiency of open PS2 reaction centres (Fv'/Fm'), effective quantum efficiency of photosystem 2 (ΔF/Fm'), and photochemical quenching (qP), but non-photochemical quenching (qN) and alternative electron sink (AES) were significantly enhanced. Thus the decreased plant biomass of TuMV-infected plants might be associated with the decreased photosynthetic activity mainly due to reduced RuBPCO activity. and Y.-P. Guo ... [et al.].
Sargassum fusiforme, a species of brown seaweed with economic importance, inhabits lower intertidal zones where algae are often exposed to various stresses. In this study, changes in the photosynthetic performance of S. fusiforme under saline stress were investigated. The PSII performance in S. fusiforme significantly improved, when the thalli were exposed to 0% salinity, and remained high with prolonging treatment time. In contrast, the PSII activity declined considerably under salinities of 4.5 and 6%. The PSI activity did not change remarkably under saline stress, thus demonstrating higher tolerance to saline stress than PSII. In addition, the PSI activity could be also restored after saline treatments, when PSII was inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea. It might be as a result of changes in the NAD(P)H content in the thalli under saline stress. Our results suggested that PSI was much more tolerant to different saline stress than PSII in S. fusiforme. We demonstrated that S. fusiforme was much more tolerant to hyposaline than to hypersaline stress., S. Gao, L. Huan, X.-P. Lu, W.-H. Jin, X.-L. Wang, M.-J. Wu, G.-C. Wang., and Seznam literatury