In leaves of four tomato (Lycopersicon esculentum Mill.) cultivars (Red Cloud, Floradade, Peto 95, and Scorpio) the contents of chlorophyll (Chl) (a+b), Chl a, and β-carotene decreased due to 100 mM NaCl treatment as compared with those of controls. The contents of soluble sugars and total saccharides were significantly increased in leaves of NaCl-treated plants, but the starch content was not significantly affected. Transmission electron microscopy indicated that in leaves of NaCl-treated plants, the chloroplasts were aggregated, the cell membranes were distorted and wrinkled, and there was no sign of grana and thylakoid structures in chloroplasts. and R. A. Khavari-Nejad, Y. Mostofi.
NaCl stress (200 mM) inhibited the electron transport activity of photosystem 2 (PS2) more than that of PS1. The degree of electron transport activity inhibition was lower in the salt-tolerant cultivar Pokkali than in the salt-sensitive cultivar Peta. The polypeptide composition of the thylakoid membrane and PS2 particles did not change after NaCl treatment but there was a difference in polypeptide compositions of thylakoid membrane and PS2 particles between the two cultivars. PS2 particles of cv. Pokkali contained more 33-kDa and 43-kDa polypeptides than cv. Peta. Additionally, PS2 particles after NaCl treatment showed deficiency of 23-kDa outside polypeptides of PS2. and L. R. Wang ... [et al.].
The effects of NaCl stress on the growth and photosynthetic characters of Ulmus pumila L. seedlings were investigated under sand culture condition. With increasing NaCl concentration, main stem height, branch number, leaf number, and leaf area declined, while Na+ content and the Na+/K+ ratio in both expanded and expanding leaves increased. Na+ content was significantly higher in expanded leaves than in those just expanding. Chlorophyll (Chl) a and Chl b contents declined as NaCl concentration increased. The net photosynthetic rate, intercellular CO2 concentration, stomatal conductance, and transpiration rate also declined, but stomatal limitation value increased as NaCl concentration increased. Both the maximal quantum yield of PSII photochemistry and the effective quantum yield of PSII photochemistry declined as NaCl concentration rose. These results suggest that the accumulation of Na+ in already expanded leaves might reduce damage to the expanding leaves and help U. pumila endure high salinity. The reduced photosynthesis in response to salt stress was mainly caused by stomatal limitation., Z. T. Feng, Y. Q. Deng, H. Fan, Q. J. Sun, N. Sui, B. S. Wang., and Obsahuje bibliografii
Exposure of two-month-old seedlings of Bruguiera parviflora to NaCl stress (0 to 400 mM) for 45 d under hydroponic culture caused notable disorganisation of the thylakoid structure of chloroplasts in NaCl-treated leaves as revealed from transmission electron microscopy. The absorption spectra of treated and control thylakoid samples were similar having a red peak at 680 nm and Soret peaks at 439 and 471 nm in the blue region of the spectrum. The spectra of treated samples differed from control samples by gradual decrease in absorbance of 100, 200, and 400 mM NaCl treated samples at 471 and 439 nm, which could be due to scattering of radiation in these samples. Thus, absorption characteristics of thylakoid membranes indicated no major alterations in the structural integrity of the photosynthetic membranes during salt stress in B. parviflora. Analysis of pigment protein complexes of thylakoids on non-denaturing gel showed that CP1 complex consisting of photosystem (PS) 1 reaction centre decreased marginally by 19% and the CP47 constituting the core antenna of PS2 declined significantly by 30% in 400 mM NaCl treated samples in respect to control. This decrease in structural core antenna might cause inefficient photon harvesting capacity. However, CP43 content did not alter. An increase in CP2/CP1 ratio from 3.2 in control to 4.0 in 400 mM NaCl treated samples indicated significant structural changes in the thylakoids of salt treated plants. Haem staining of thylakoids revealed significant losses in cytochrome (Cyt)f and Cyt b 6 contents by NaCl stress. However, Cyt b 559 content remained nearly constant in both control and NaCl treated samples. SDS-PAGE of thylakoid proteins showed that the intensity of many of Coomassie stained polypeptide bands ranging from 15-22 and 28-66 kDa regions decreased significantly in NaCl treated samples as compared to control. Electron transport activity of thylakoids, measured in terms of DCPIP photoreduction, was 22% lower in 400 mM NaCl treated plants than in the control ones. Hence, NaCl induces oxidative stress in chloroplasts causing structural alterations in thylakoids. These structural alterations might be responsible for declined efficiency of photosystems and reduced electron transport activity. and A. K. Parida, A. B. Das, B. Mittra.
The presence of the parasitic copepod Neoalbionella globosa in the olfactory chamber of a specimen of the catshark Scyliorhinus canicula has been already reported in the literature, but this is the first record from the north-western Mediterranean Sea. Besides confirming this host-parasite association in the Ligurian Sea, the present study aims to describe some effects of the copepod's presence on the olfactory system of S. canicula, thus inferring potential effects of nasal parasites on olfaction. The copepod was accidentally found during a sampling campaign. The copepod, a mature female with well-developed egg sacs, parasitized the right olfactory rosette; the rosette presented visible swelling in some of the olfactory lamellae while, histologically, restricted edema was detectable close to the zone of attachment. The ipsilateral olfactory bulb, which receives the primary olfactory afferences, had a smaller number of cells and smaller neuron density compared to the contralateral bulb and to the average values for non-parasitized specimens of the same size. The results suggest that, although the olfactory rosette does not seem severely damaged, the presence of the parasite could deeply affect the highly efficient water flow within the nasal chamber, potentially causing partial olfactory impairment.
Gas exchange, chlorophyll (Chl) fluorescence, and contents of photosynthetic pigments, soluble proteins (ribulose-1,5-bisphosphate carboxylase/oxygenase, RuBPCO), and antioxidant enzymes were characterized in the fully expanded 6th leaves in rice seedlings grown on either complete (CK) or on nitrogen-deficient nutrient (N-deficiency) solutions during a 20-chase period. Compared with the control plants, the lower photosynthetic capacity at saturation irradiance (Pmax) was accompanied by an increase in intercellular CO2 concentration (Ci), indicating that in N-deficient plants the decline in Pmax was not due to stomatal limitation but due to the reduced carboxylation efficiency. The fluorescence parameters ΦPS2, Fv'/Fm', electron transport rate (ETR), and qP showed the same tendency as Pmax in N-deficient plants. Correspondingly, a higher qN paralleled the rise of the ratio of carotenoid (Car) to Chl contents. However, Fv/Fm was still diminished, suggesting that photoinhibition did occur in the photosystem 2 (PS2) reaction centres. In addition, the activities of antioxidant enzymes on a fresh mass basis were gradually lowered, leading to the aggravation of membrane lipid peroxidation with the proceeding N-deficiency. The accumulation of malonyldialdehyde resulted in the lessening of Chl and soluble protein content. Analyses of regression showed PS2 excitation pressure (1 - qP) was linearly correlated with the content of Chl and inversely with soluble protein (particularly RuBPCO) content. There was a lag phase in the increase of PS2 excitation pressure compared to the decrease of RuBPCO content. Therefore, the increased excitation pressure under N-deficiency is probably the result of saturation of the electron transport chain due to the limitation of the use of reductants by the Calvin cycle. Rice plants responded to N-deficiency and high irradiance by decreasing light-harvesting capacity and by increasing thermal dissipation of absorbed energy. and Z.-A. Huang ... [et al.].
The UNECE-ICP Integrated Monitoring site Zöbelboden in the Northern Alps of Austria was established to assess the effects of air pollutants on forest ecosystems. Changes in recruitment of the dominant tree species may be among these effects but there is little information on how germination and juvenile growth of these species respond to changes in nutrient supply. This study focused on the effects of nitrogen availability on the performance of the early life history stages of Picea abies, Fagus sylvatica, Fraxinus excelsior and Acer pseudoplatanus based on measured soil variables and Ellenberg indicator values. For 106, 0.5 × 0.5 m plots, the pH-value, NH4+, NO3–, gross and net N mineralization and C:N ratio ot the top mineral soil were analyzed. Additionally, incoming solar radiation and estimated number of seeds arriving in each plot were recorded. Recruitment and juvenile growth rates of the tree species were related to these variables and to mean Ellenberg indicator values calculated from the vascular plant species composition of the plots, respectively, using linear or generalized linear mixed models. Despite the relatively high correlations of Ellenberg indicator values with the three measured soil variables, namely pH, ammonium, and, in particular, gross N mineralization, models using measured variables and Ellenberg indicator values produced inconsistent results in most cases. In general, closer correlations were obtained between measured soil variables and tree performance than between Ellenberg indicator values and tree performance. Measured nitrogen variables had a significant effect on the recruitment and growth of Fagus sylvatica and Acer pseudoplatanus. However, whereas the growth of both species was similarly greater where NH4 contents and gross mineralization rates were higher, their responses to soil nitrogen were clearly distinct in terms of recruitment. Finally, neither recruitment nor growth of Fraxinus excelsior are significantly correlated with any of the measured nitrogen variables. Partitioning of regeneration niches in terms of different nitrogen sources and supply rates might hence contribute to the co-existence of different tree species in such mixed mountain forests.
We investigated the responses of photon-saturated photosynthesis rate (Psat) and its simultaneous acclimation of anatomy and nitrogen use patterns of current needles of Korean pine (Pinus koraiensis) seedlings grown under factorial combinations of two nitrogen levels and irradiances. Although N supply resulted in a significant increase of N content in needles under both irradiances, the increase of P sat tended to be suppressed only in shade (S). The significant increase of P sat in full sunlight (O) was associated with the increase of ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) and chlorophyll (Chl) contents. In contrast, small increase of Chl content and no increase of RuBPCO content were found in S (90 % cut of full irradiance), which would result in a small increase of Psat. This result suggests that extra N is stocked in needles under shade for the growth in next season. With N supply, a significant decrease of specific leaf area (SLA) was detected only in O. This decrease of SLA was due to the increase of density of needle. Furthermore, the increase of needle density was not due to the increased number and size of mesophyll cells, but the increased density of each mesophyll cell. Therefore, although SLA changed in O, the change did not involve anatomical adaptation to use increased N effectively, at least observable by light microscopy. Hence, even though the SLA would change, N deposition will improve the photosynthetic capacity of Korean pine seedlings, not through the development of needle anatomy but through improvement of the allocation of N in both irradiances. and K. Makoto, T. Koike.