After exposing one half of a low light-adapted kidney bean (Phaseolus vulgaris) leaf to high light, parameters of chlorophyll (Chl) a fluorescence, such as PSII operating efficiency, PSII maximum efficiency under light, and photochemical quenching, decreased in the opposite half of the same leaf, whereas the capacity of the cyanide-resistant respiratory pathway significantly increased. When one half of the low light-adapted leaf was exposed to low light, the opposite half pretreated with 1 mM salicylhydroxamic acid (SHAM, an inhibitor of the cyanide-resistant respiratory pathway) did not exhibit significant changes in the Chl fluorescence values compared with the without SHAM pretreatment. However, after exposing one half of the low light-adapted leaf to high light, the opposite half pretreated with 1 mM SHAM showed lower Chl fluorescence values than that without SHAM pretreatment. Our results indicate that partial exposure of the low light-adapted leaf to high light can impose a systemic stress on the PSII photochemistry. The enhanced capacity of the cyanide-resistant respiratory pathway may be involved in the maintenance of the photosynthetic performance in the leaf tissues experiencing high light-induced systemic stress., H.-Q. Feng, S.-Z. Tang, K. Sun, L.-Y. Jia, R.-F. Wang., and Obsahuje bibliografii
The negative effects of continuous light (CL) seen in tomato plants are often claimed to be linked to effects of offsetting the diurnal rhythm. In this study we tested whether a short-term daily temperature drop prevents the decreased photosynthetic performance seen in tomato plants grown under CL. Tomato (Lycopersicon esculentum Mill.) plantlets were grown at constant temperature of 26°C under 16-h day (16D) or 24-h day (24D) at 150 μmol m-2 s-1 PPFD. Some 24D plants were treated daily by 2 h temperature drop from 26 to 10°C (24D+DROP). Physiological disorder, such as severe leaf chlorosis, a large decrease in net photosynthetic rate, maximal quantum yield of PSII photochemistry, and the effective quantum yield of PSII photochemistry were observed in 24D, but not in 16D and 24D+DROP plants. The daily 2-h drop in temperature eliminated a negative effect of CL on photosynthesis and prevented the development of leaf chlorosis in tomato plants. This could be due to a change in carbohydrate metabolism as the short drop in temperature might allow maintenance of the diurnal rhythms., E. N. Ikkonen, T. G. Shibaeva, E. Rosenqvist, C.-O. Ottosen., and Obsahuje seznam literatury
PSI trimer to monomer ratio in intact cyanobacterial cells and isolated thylakoids was analysed by two noninvasive, in vivo methods; low-temperature fluorescence emission and circular dichroism spectroscopy. We measured fluorescence emission spectra of cells upon chlorophyll (Chl, 436 nm) excitation. All three species - Synechocystis sp. PCC 6803, Anabaena sp. PCC 7120, and Spirulina platensis - showed shifted Chl peak, indicating they have different spectral properties. CD spectroscopy revealed the highest intensity at 515 nm (PSI peak) in Spirulina platensis cells, which may originate from PSI multi-oligomerisation. The most sensitive response to heat treatment in this strain was the oligomerisation of PSI RCs. PSI dimers and tetramers in Anabaena cells showed smaller changes of the CD signal upon the heat treatment compared to that of Synechocystis WT. The lack of γ-linolenic acid affected the filament morphology by the loss of the spiral shape and the PSI monomerisation in Spirulina I22., T. Zakar, L. Kovacs, S. Vajravel, E. Herman, M. Kis, H. Laczko-Dobos, Z. Gombos., and Obsahuje bibliografické odkazy
Models were developed to estimate nondestructively chlorophyll (Chl) content per unit of leaf area (Chlarea) and nitrogen content per unit of leaf area (Narea) using readings of two optical meters for five warm-temperate, evergreen, broadleaved tree species (Castanopsis sieboldii, Cinnamomum tenuifolium, Eurya japonica, Machilus thunbergii, and Neolitsea sericea). It was determined whether models should be adjusted seasonally. Readings (were obtained six times during a year period and Chlarea and Narea were determined using destructive methods. Bayesian inference was used to estimate parameters of models that related optical meter readings to Chlarea or Narea for each species. Deviance information criterion values were used to select the best among models, including the models with seasonal adjustment. The selected models were species-specific and predicted Chlarea accurately (R2 = 0.93-0.96). The best model included parameters with seasonal adjustments for one out of five species. Model-based estimates of Narea were not as accurate as those for Chlarea, but they were still adequate (R2 = 0.64-0.82). For all species studied, the best models did not include parameters with seasonal adjustments. The estimation methods used in this study were rapid and nondestructive; thus, they could be used to assess a function of many leaves and/or repeatedly on individual leaves in the field. and D. Mizusaki, K. Umeki, T. Honjo.
We studied the developmental changes in photosynthetic and respiration rates and thermal dissipation processes connected with chloroplasts and mitochondria activity in etiolated wheat (Triticum aestivum L., var. Irgina) seedlings during the greening process. Etioplasts gradually developed into mature chloroplasts under continuous light [190 μmol(photon) m-2 s-1] for 48 h in 5-day-dark-grown seedlings. The net photosynthetic rate of irradiated leaves became positive after 6 h of illumination and increased further. The first two hours of de-etiolation were characterized by low values of maximum (Fv/Fm) and actual photochemical efficiency of photosystem II (PSII) and by a coefficient of photochemical quenching in leaves. Fv/Fm reached 0.8 by the end of 24 h-light period. During greening, energy-dependent component of nonphotochemical quenching of chlorophyll fluorescence, violaxanthin cycle (VXC) operation, and lipoperoxidation activity changed in a similar way. Values of these parameters were the highest at the later phase of de-etiolation (4-12 h of illumination). The respiration rate increased significantly after 2 h of greening and it was the highest after 4-6 h of illumination. It was caused by an increase in alternative respiration (AP) capacity. The strong, positive linear correlation was revealed between AP capacity and heat production in greening tissues. These results indicated that VXC in chloroplasts and AP in mitochondria were intensified as energy-dissipating systems at the later stage of greening (after 4 h), when most of prolamellar bodies converted into thylakoids, and they showed the greatest activity until the photosynthetic machinery was almost completely developed. and E. V. Garmash ... [et al.].
Lianas perform better than co-occurring trees in secondary forests or disturbed areas. Lianas and trees differ strikingly in water use strategy, which may result in a significant difference in photosynthetic light use between both growth forms. However, the difference in the photosynthetic efficiency and light energy dissipation between these two growth forms is poorly understood. Moreover, photorespiration is an important mechanism of photoprotection under conditions of high light. In this study, we used Bridelia stipularis (Linn.) Bl. (liana) and Strophioblachia fimbricalyx Boerl. (tree) in order to measure the response curves of the gas exchange and photosynthetic electron flow to the incident light gradients and intercellular CO2 concentration, as well as the hydraulic conductivity. We tested whether the photochemical efficiency and photorespiration differed between both growth forms. Our results clearly demonstrated that B. stipularis possessed a significantly higher stem and leaf specific hydraulic conductivity, total electron flow, and maximum rate of ribulose-1,5-bisphosphate regeneration compared to the sympatric tree S. fimbricalyx. Correspondingly, B. stipularis exhibited a significantly higher photochemical quenching coefficient and electron flow to photorespiration relative to S. fimbricalyx under saturating light levels. We suggested that photorespiration might play an important role in photoprotection for both species under high light, but particularly for B. stipularis. These findings could enrich our knowledge of the superior photosynthetic and growth performance of lianas over the co-occurring trees., S.-B. Zhang, J.-L. Zhang, K.-F. Cao., and Seznam literatury
a1_Previous studies have focused mainly on the accumulation of photosynthates and less on their distribution in sweet potato (Ipomoea batatas L.). In addition, the effect of photosynthate accumulation in root tubers on photosynthate distribution was not considered. Thus, a field experiment was carried out from May to October (2011 and 2012) to clarify the differences in photosynthate transport between high- and low-yielding sweet potato. This study mainly focused on the photosynthetic capacities of leaves, photosynthate distribution, and characteristics of photosynthate accumulation in root tubers. Results showed the high-yielding varieties displayed the higher fresh root tuber yield and the economic coefficient than the low-yielding varieties. They also showed greater net photosynthetic rate with a pronounced increase at the early and middle growth stages (8.9% and 11.4%, respectively). After the growth peak, the leaf area index (LAI) of the high-yielding varieties decreased with time and was maintained at 2~3 until harvest, whereas the LAI of the low-yielding varieties decreased slowly. The high-yielding varieties reached the 13C distribution rate ≥ 50% at the early (2011, 2012) and middle (2011) growth stages, whereas the low-yielding varieties reached it at the late (2011) or middle (2012) growth stages. At harvest, the 13C distribution rates in the branches and root tubers of the
high-yielding varieties were 6.0-20.3% and 73.7-91.2%, respectively, whereas those of the low-yielding varieties were 29.6-34.7% and 60.7-63.5%, respectively. The high-yielding varieties showed the remarkable initial potential in root tubers, which was much better than that of the low-yielding varieties. The high-yielding varieties also produced heavier root tubers and the higher number of root tubers per plant at the early bulking stage., a2_The root tubers also attained the greater content of soluble sugar and starch. The high-yielding varieties formed root tubers earlier, showed strong abilities to transport photosynthates into the root tubers, and exhibited a higher mean accumulation rate. These varieties could also reduce the photosynthate consumption in branch leaves and stems. Therefore, the high-yielding varieties established growth advantage for the root tubers earlier. It contributed to a reasonable distribution structure of photosynthates that led to the high root tuber yield. Based on our results, effective agricultural measures can be chosen to improve the root tuber yield of sweet potato., H. J. Liu, S. S. Chai, C. Y. Shi, C. J. Wang, G. B. Ren, Y. Jiang, C. C. Si., and Obsahuje seznam literatury
Photosynthetic light curve, chlorophyll (Chl) content, Chl fluorescence parameters, malondialdehyde (MDA) content, phosphoenolpyruvate carboxylase (PEPC) activity and reactive oxygen metabolism were studied under drought stress in two autotetraploid rice lines and corresponding diploid rice lines. Net photosynthetic rate decreased dramatically, especially under severe drought stress and under high photosynthetic active radiation in diploid rice, while it declined less under the same conditions in autotetraploid lines. Compared with the corresponding diploid lines, the Chl content, maximum photochemical efficiency of photosystem (PS) II, and actual photochemical efficiency of PSII were reduced less in autotetraploid lines. PEPC activities were higher in autotetraploid rice lines. PEPC could alleviate inhibition of photosynthesis caused by drought stress. The chromosome-doubling enhanced rice photoinhibition tolerance under drought stress. The lower MDA content and superoxide anion production rate was found in the autotetraploid rice indicating low peroxidation level of cell membranes. At the same time, the superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities were higher in autotetraploid rice lines. SOD, POD, and CAT could effectively diminish the reactive oxygen species and reduced the membrane lipid peroxidation., P.-M. Yang, Q.-C. Huang, G.-Y. Qin, S.-P. Zhao, J.-G. Zhou., and Obsahuje bibliografii
Carbonic anhydrase (CA) catalyzes reversible hydration of CO2 and it can compensate for the lack of H2O and CO2 in plants under stress conditions. Antioxidative enzymes play a key role in scavenging reactive oxygen species and in protecting plant cells against toxic effects. Tomato represents a stress-sensitive plant while violet orychophragmus belongs to adversity-resistant plants. In order to study the drought responses in tomato and violet orychophragmus plants, CA and antioxidative enzyme activities, photosynthetic capacity, and water potential were determined in plants under drought stress. We found that there were similar change trends in CA activity and drought tolerance in violet orychophragmus, and in antioxidative enzymes and drought tolerance in tomato plants. Basic mechanisms of drought resistance should be identified for understanding of breeding measures in plants under stress conditions., W. H. Sun, Y. Y. Wu, X. Y. Wen, S. J. Xiong, H. G. He, Y. Wang, G. Q. Lu., and Obsahuje seznam literatury