Salinity effects on chloroplast PSII performance in glycophytes and halophytes

2016 ◽  
Vol 43 (11) ◽  
pp. 1003 ◽  
Author(s):  
William J. Percey ◽  
Andrew McMinn ◽  
Jayakumar Bose ◽  
Michael C. Breadmore ◽  
Rosanne M. Guijt ◽  
...  
Keyword(s):  
Critical Role ◽  
Photochemical Efficiency ◽  
Chenopodium Quinoa ◽  
Nacl Stress ◽  
Photosynthetic Performance ◽  
K Channel ◽  
Photosynthetic Parameters ◽  
Atpase Inhibitor ◽  
Mesophyll Cells ◽  
Isolated Chloroplasts

The effects of NaCl stress and K+ nutrition on photosynthetic parameters of isolated chloroplasts were investigated using PAM fluorescence. Intact mesophyll cells were able to maintain optimal photosynthetic performance when exposed to salinity for more than 24 h whereas isolated chloroplasts showed declines in both the relative electron transport rate (rETR) and the maximal photochemical efficiency of PSII (Fv/Fm) within the first hour of treatment. The rETR was much more sensitive to salt stress compared with Fv/Fm, with 40% inhibition of rETR observed at apoplastic NaCl concentration as low as 20 mM. In isolated chloroplasts, absolute K+ concentrations were more essential for the maintenance of the optimal photochemical performance (Fv/Fm values) rather than sodium concentrations per se. Chloroplasts from halophyte species of quinoa (Chenopodium quinoa Willd.) and pigface (Carpobrotus rosii (Haw.) Schwantes) showed less than 18% decline in Fv/Fm under salinity, whereas the Fv/Fm decline in chloroplasts from glycophyte pea (Pisum sativum L.) and bean (Vicia faba L.) species was much stronger (31 and 47% respectively). Vanadate (a P-type ATPase inhibitor) significantly reduced Fv/Fm in both control and salinity treated chloroplasts (by 7 and 25% respectively), whereas no significant effects of gadolinium (blocker of non-selective cation channels) were observed in salt-treated chloroplasts. Tetraethyl ammonium (TEA) (K+ channel inhibitor) and amiloride (inhibitor of the Na+/H+ antiporter) increased the Fv/Fm of salinity treated chloroplasts by 16 and 17% respectively. These results suggest that chloroplasts’ ability to regulate ion transport across the envelope and thylakoid membranes play a critical role in leaf photosynthetic performance under salinity.

Effects of Enhanced UV-B Radiation on the Drought Semi-deciduous Mediterranean Shrub Phlomis fruticosa under Field Conditions are Season-specific

1995 ◽  
Vol 22 (5) ◽  
pp. 737 ◽  
Author(s):  
D Nikolopoulos ◽  
Y Petropoulou ◽  
A Kyparissis ◽  
Y Manetas
Keyword(s):  
Developmental Stages ◽  
Stratospheric Ozone ◽  
Photochemical Efficiency ◽  
Net Photosynthesis ◽  
Experimental Period ◽  
Dry Mass ◽  
Photosynthetic Performance ◽  
Photosynthetic Parameters ◽  
Summer Drought ◽  
Total Carotenoids

The effects of enhanced UV-B radiation on Phlomis fruticosa L. were recorded during a 1- year field study. Plants received ambient or ambient plus supplemental UV-B radiation (simulating a 15% stratospheric ozone depletion over Patras, 38.3�N, 29.1�E) and only natural precipitation, i.e. they were simultaneously exposed to other natural stresses, particularly water stress during summer. Actual, biologically equivalent UV-B doses were 8.55 and 11.21 kJ m-2 day-1 during the summer maximum (14 July) and 0.85 and 1.12 kJ m-2 day-1 during the winter minimum (27 December) for control and W-B plants respectively, while intermediate values were received for the rest of the year. lho seasonally separated effects could be distinguished. The first was a growth response, observed at late spring, in the absence of any simultaneous stress and at the period most favourable for this shrub, during which it shows maximum photosynthetic performance. The effect was an inhibition of new leaf development and premature falling of old leaves, leading to lower leaf numbers and total leaf areas for the rest of the experimental period. The second effect coincided with the summer drought, during which net photosynthesis, chlorophyll content and photochemical efficiency of photosystem II decreased in the controls, but a trend towards a further decrease in W-B irradiated plants was also evident. Changes in total carotenoids were negligible, leading to higher carotenoid to chlorophyll ratios under enhanced W-B radiation. Photosynthetic parameters recovered to the same levels in control and UV-B irradiated plants after the first heavy rains in autumn. At final harvest, considerable decreases in total dry mass were evident for UV-B irradiated plants, while plant height, UV-B-absorbing compounds, relative water content and leaf specific mass were unaffected during the whole experimental period. UV-B effects may depend not only on co-occumng natural stresses, but on the specific sensitivity of individual developmental stages as well, i.e. they may be season-specific.

scholarly journals Maintenance of K+/Na+ Balance in the Roots of Nitraria sibirica Pall. in Response to NaCl Stress

Forests ◽  
2018 ◽  
Vol 9 (10) ◽  
pp. 601 ◽  
Author(s):  
Xiaoqian Tang ◽  
Xiuyan Yang ◽  
Huanyong Li ◽  
Huaxin Zhang
Keyword(s):  
Plasma Membrane ◽  
Nacl Stress ◽  
K Channel ◽  
Sodium Vanadate ◽  
Atpase Inhibitor ◽  
K Channels ◽  
Non Invasive ◽  
Na Efflux ◽  
Seedling Roots ◽  
Nitraria Sibirica

Using Non-invasive Micro-test Technology (NMT), the Na+, K+ and H+ flux profiles in the root meristem regions were investigated in Nitraria sibirica Pall. seedlings under different NaCl concentrations. NaCl stress increased the K+ and Na+ contents in the roots of N. sibirica seedlings. NaCl stress significantly increased the steady Na+ efflux from the N. sibirica seedling roots. Steady K+ effluxes were measured in the control roots (without NaCl) and in the roots treated with 200 mM NaCl, and no significant differences were observed between the two treatments. The steady K+ efflux from roots treated with 400 mM NaCl decreased gradually. NaCl treatment significantly increased the H+ influx. Pharmacological experiments showed that amiloride and sodium vanadate significantly inhibited the Na+ efflux and H+ influx, suggesting that the Na+ efflux was mediated by a Na+/H+ antiporter using energy provided by plasma membrane H+-ATPase. The NaCl-induced root K+ efflux was inhibited by the K+ channel inhibitor tetraethylammonium chloride (TEA), and was significantly increased by the H+-ATPase inhibitor sodium vanadate. The NaCl-induced K+ efflux was mediated by depolarization-activated outward-rectifying K+ channels and nonselective cation channels (NSCCs). Under salt stress, N. sibirica seedlings showed increased Na+ efflux due to increased plasma membrane H+-ATPase and Na+/H+ antiporter activity. High H+ pump activity not only restricts the Na+ influx through NSCCs, but also limits K+ leakage through outward-rectifying K+ channels and NSCCs, leading to maintenance of the K+/Na+ balance and higher salt tolerance.

scholarly journals Uniform Water Potential Induced by Salt, Alkali, and Drought Stresses Has Different Impacts on the Seedling of Hordeum jubatum: From Growth, Photosynthesis, and Chlorophyll Fluorescence

2021 ◽  
Vol 12 ◽  
Author(s):  
Congcong Shi ◽  
Fan Yang ◽  
Zihao Liu ◽  
Yueming Li ◽  
Xiaolin Di ◽  
...  
Keyword(s):  
Chlorophyll Fluorescence ◽  
Water Potential ◽  
Photochemical Efficiency ◽  
Photosynthetic Performance ◽  
Photochemical Quenching ◽  
Photosynthetic Parameters ◽  
Alkali Stress ◽  
Gas Exchange Parameters ◽  
Hordeum Jubatum ◽  
Damaging Effects

Hordeum jubatum is a halophyte ornamental plant wildly distributed in the Northeast of China, where the low water potential induced by various abiotic stresses is a major factor limiting plant growth and development. However, little is known about the comparative effects of salt, alkali, and drought stresses at uniform water potential on the plants. In the present study, the growth, gas exchange parameters, photosynthetic pigments, and chlorophyll fluorescence in the seedlings of H. jubatum under three low water potentials were measured. The results showed that the growth and photosynthetic parameters under these stresses were all decreased except for carotenoid (Car) with the increasing of stress concentration, and alkali stress caused the most damaging effects on the seedlings. The decreased net photosynthetic rate (Pn), stomatal conductance (Gs), and intercellular CO2 concentrations (Ci) values under salt stress were mainly attributed to stomatal factors, while non-stomatal factors were dominate under drought and alkali stresses. The reduced chlorophyll and slightly increased Car contents occurred under these stresses, and most significant changed under alkali stress. In addition, the maximum photochemical efficiency (Fv/Fm), actual photochemical efficiency (ΦPSII), and photochemical quenching coefficient (qP) under the stresses were all decreased, indicating that salt, alkali, and drought stresses all increased susceptibility of PSII to photoinhibition, reduced the photosynthetic activity by the declined absorption of light for photochemistry, and increased PSII active reaction centers. Moreover, the non-photochemical quenching coefficient (NPQ) of alkali stress was different from salt and drought stresses, showing that the high pH of alkali stress caused more damaging effects on the photoprotection mechanism depending on the xanthophyll cycle. The above results suggest that the H. jubatum has stronger tolerance of salt than drought and alkali stresses, and the negative effects of alkali stress on the growth and photosynthetic performance of this species was most serious.

scholarly journals THE GROWTH, PHOTOSYNTHETIC PARAMETERS AND NITROGEN STATUS OF BASIL, CORIANDER AND OREGANO GROWN UNDER DIFFERENT LED LIGHT SPECTRA

2021 ◽  
Vol 20 (2) ◽  
pp. 13-22
Author(s):  
Bożena Matysiak ◽  
Artur Kowalski
Keyword(s):  
Blue Light ◽  
Red Light ◽  
Photochemical Efficiency ◽  
Photosynthetic Performance ◽  
Photosynthetic Parameters ◽  
Nitrogen Status ◽  
White Leds ◽  
Light Spectra ◽  
Plant Level ◽  
Led Lights

Growth, morphological parameters, photosynthetic performance and nitrogen status were investigated in leafy herbs grown in light-limited time in a greenhouse under different light spectra emitted by LEDs. Fluorescence-based sensors that detect crop N status and maximum photochemical efficiency of photosystem II were used in this study. Four light treatments with the ratio of Red, Blue and White LEDs including 1) R40 + B50 + W10, 2) R70 + B20 + W10, 3) R70 + B20 + W10 + Far-Red and 4) White LEDs as control were used in this study. Dominant red light and/or white LED lights at 200 µmol m–2 s–1 at plant level and a 12 h photoperiod provided the most favourable conditions for plant growth and development compared to a high proportion of blue light (R40 + B50 + W10). However, plants grown under a high proportion of blue light had a higher chlorophyll index and nitrogen balance index (NBI) than under dominant red light treatments. Our study indicates the significant potential of fluorescence-based sensors in photobiology research as well as in the production of leafy herbs under LED lights.

scholarly journals The Class II Phosphatidylinositol 3 kinase C2β Is Required for the Activation of the K+ Channel KCa3.1 and CD4 T-Cells

2009 ◽  
Vol 20 (17) ◽  
pp. 3783-3791 ◽  
Author(s):  
Shekhar Srivastava ◽  
Lie Di ◽  
Olga Zhdanova ◽  
Zhai Li ◽  
Santosha Vardhana ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
T Cell Activation ◽  
Cd4 T Cells ◽  
Critical Role ◽  
Class Ii ◽  
K Channel ◽  
Channel Activity ◽  
Phosphatidylinositol 3 Kinase ◽  
Phosphatidylinositol 3

The Ca2+-activated K+ channel KCa3.1 is required for Ca2+ influx and the subsequent activation of T-cells. We previously showed that nucleoside diphosphate kinase beta (NDPK-B), a mammalian histidine kinase, directly phosphorylates and activates KCa3.1 and is required for the activation of human CD4 T lymphocytes. We now show that the class II phosphatidylinositol 3 kinase C2β (PI3K-C2β) is activated by the T-cell receptor (TCR) and functions upstream of NDPK-B to activate KCa3.1 channel activity. Decreased expression of PI3K-C2β by siRNA in human CD4 T-cells resulted in inhibition of KCa3.1 channel activity. The inhibition was due to decreased phosphatidylinositol 3-phosphate [PI(3)P] because dialyzing PI3K-C2β siRNA-treated T-cells with PI(3)P rescued KCa3.1 channel activity. Moreover, overexpression of PI3K-C2β in KCa3.1-transfected Jurkat T-cells led to increased TCR-stimulated activation of KCa3.1 and Ca2+ influx, whereas silencing of PI3K-C2β inhibited both responses. Using total internal reflection fluorescence microscopy and planar lipid bilayers, we found that PI3K-C2β colocalized with Zap70 and the TCR in peripheral microclusters in the immunological synapse. This is the first demonstration that a class II PI3K plays a critical role in T-cell activation.

scholarly journals The  -subunit of a heterotrimeric G-protein from tobacco, NtGP 1, functions in K+ channel regulation in mesophyll cells

1999 ◽  
Vol 50 (330) ◽  
pp. 53-61
Author(s):  
G. Saalbach ◽  
G. Natura ◽  
W. Lein ◽  
P. Buschmann ◽  
I. Dahse ◽  
...  
Keyword(s):  
G Protein ◽  
K Channel ◽  
Mesophyll Cells ◽  
Heterotrimeric G Protein ◽  
Channel Regulation

Dynamic regulation of the voltage-gated Kv2.1 potassium channel by multisite phosphorylation

2007 ◽  
Vol 35 (5) ◽  
pp. 1064-1068 ◽  
Author(s):  
D.P. Mohapatra ◽  
K.-S. Park ◽  
J.S. Trimmer
Keyword(s):  
Neuronal Excitability ◽  
Critical Role ◽  
Functional Characterization ◽  
K Channel ◽  
Delayed Rectifier ◽  
Dynamic Regulation ◽  
Voltage Gated ◽  
Voltage Dependent ◽  
Specific Regulation

Voltage-gated K+ channels are key regulators of neuronal excitability. The Kv2.1 voltage-gated K+ channel is the major delayed rectifier K+ channel expressed in most central neurons, where it exists as a highly phosphorylated protein. Kv2.1 plays a critical role in homoeostatic regulation of intrinsic neuronal excitability through its activity- and calcineurin-dependent dephosphorylation. Here, we review studies leading to the identification and functional characterization of in vivo Kv2.1 phosphorylation sites, a subset of which contribute to graded modulation of voltage-dependent gating. These findings show that distinct developmental-, cell- and state-specific regulation of phosphorylation at specific sites confers a diversity of functions on Kv2.1 that is critical to its role as a regulator of intrinsic neuronal excitability.

Cell-type specific calcium signalling in a Drosophila epithelium

1997 ◽  
Vol 110 (15) ◽  
pp. 1683-1692 ◽  
Author(s):  
P. Rosay ◽  
S.A. Davies ◽  
Y. Yu ◽  
A. Sozen ◽  
K. Kaiser ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Critical Role ◽  
Cell Signalling ◽  
Calcium Signalling ◽  
Malpighian Tubule ◽  
Fluid Secretion ◽  
Cell Types ◽  
Cytosolic Calcium ◽  
Atpase Inhibitor ◽  
Principal Cells

Calcium is a ubiquitous second messenger that plays a critical role in both excitable and non-excitable cells. Calcium mobilisation in identified cell types within an intact renal epithelium, the Drosophila melanogaster Malpighian tubule, was studied by GAL4-directed expression of an aequorin transgene. CAP2b, a cardioactive neuropeptide that stimulates fluid secretion by a mechanism involving nitric oxide, causes a rapid, dose-dependent rise in cytosolic calcium in only a single, genetically-defined, set of 77 principal cells in the main (secretory) segment of the tubule. In the absence of external calcium, the CAP2b-induced calcium response is abolished. In Ca2+-free medium, the endoplasmic reticulum Ca2+-ATPase inhibitor, thapsigargin, elevates [Ca2+]i only in the smaller stellate cells, suggesting that principal cells do not contain a thapsigargin-sensitive intracellular pool. Assays for epithelial function confirm that calcium entry is essential for CAP2b to induce a physiological response in the whole organ. Furthermore, the data suggest a role for calcium signalling in the modulation of the nitric oxide signalling pathway in this epithelium. The GAL4-targeting system allows general application to studies of cell-signalling and pharmacology that does not rely on invasive or cytotoxic techniques.

Stimulation of total CO2 flux by 10% CO2 in rabbit CCD: role of an apical Sch-28080- and Ba-sensitive mechanism

1994 ◽  
Vol 267 (1) ◽  
pp. F114-F120 ◽  
Author(s):  
X. Zhou ◽  
C. S. Wingo
Keyword(s):  
Collecting Duct ◽  
Co2 Flux ◽  
K Channel ◽  
Co2 Absorption ◽  
Cortical Collecting Duct ◽  
Atpase Inhibitor ◽  
Contrast Exposure ◽  
Stimulation Of

These studies examine the effect of ambient PCO2 on net bicarbonate (total CO2) absorption by the in vitro perfused cortical collecting duct (CCD) from K-replete rabbits and the mechanism responsible for this effect. Exposure to 10% CO2 increased net bicarbonate flux (total CO2 flux, JtCO2) by 1.8-fold (P < 0.005), and this effect was inhibited by luminal 10 microM Sch-28080, an H-K-adenosinetriphosphatase (H-K-ATPase) inhibitor. In contrast, exposure to 10% CO2 significantly decreased Rb efflux, and this decrement in Rb efflux was blocked by luminal 2 mM Ba, a K channel blocker. Thus transepithelial tracer Rb flux did not increase upon exposure to 10% CO2 as we have observed in this segment under K-restricted conditions. The observation that 10% CO2 increased net bicarbonate absorption without a change in absorptive Rb flux suggested that 10% CO2 increased apical K recycling. To test this hypothesis, we examined whether luminal Ba inhibited the stimulation of luminal acidification induced by 10% CO2. If apical K exit were necessary for full activation of proton secretion, then inhibiting K exit should indirectly affect the stimulation of JtCO2 by 10% CO2. In fact, the effect of 10% CO2 on JtCO2 in the presence of 2 mM luminal Ba was quantitatively indistinguishable from the effect of 10% CO2 on JtCO2 in the presence of 10 microM luminal Sch-28080.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Tolerance of Three Quinoa Cultivars (Chenopodium quinoa Willd.) to Salinity and Alkalinity Stress During Germination Stage

Agronomy ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 287
Author(s):  
Vasile Stoleru ◽  
Cristina Slabu ◽  
Maricel Vitanescu ◽  
Catalina Peres ◽  
Alexandru Cojocaru ◽  
...  
Keyword(s):  
Nutritional Value ◽  
Abiotic Stress Tolerance ◽  
Germination Rate ◽  
Chenopodium Quinoa ◽  
Nacl Stress ◽  
Alkali Stress ◽  
Productivity Losses ◽  
Biometric Measurements ◽  
Global Food ◽  
Germination Stage

Salinity and alkalinity are two of the main causes for productivity losses in agriculture. Quinoa represents a better alternative for global food products such as rice and wheat flour due to its high nutritional value and abiotic stress tolerance. Three cultivars of quinoa seeds (Titicaca, Puno and Vikinga) originating from Denmark were used in the experiments. The seeds were germinated under the action of three different salts (NaCl, Na2SO4, Na2CO3) at 0–300 mM for five days and the germination rate was calculated. Biometric measurements (radicle and hypocotyls lengths) andbiochemical determinations (proline) were performed in order to quantify the tolerance and the effects of salt and alkali stresses on the three quinoa cultivars. The germination rates showed that all cultivars were affected by the presence of salts, especially at 300 mM. The most sensitive cultivar to salts was Titicaca cultivar which evinced the lowest germination rate, regardless of the salt and the concentration used. On the other hand, Puno and Vikinga cultivars showed the best tolerance to the saline and alkaline stresses. Among the salts used, Na2CO3 had the most detrimental effects on the germination of quinoa seeds inhibiting the germination by ~50% starting with 50 mM. More affected was the growth of hypocotyls in the presence of this salt, being completely inhibited for the seeds of the Puno and Titicaca cultivars. Vikinga cultivar was the only one able to grow hypocotyls at 50 and 100 mM Na2CO3. Also, this cultivar had a high adaptability to NaCl stress when significant differences were observed for the germination rates at 200 and 300 mM as compared to 0 mM NaCl, due to the proline production whose content was significantly greater than that of the untreated seeds. In conclusion, the tolerance of the three quinoa cultivars to saline and alkali stress varied with the salt type, salt concentration and tested cultivar, with the Vikinga and Puno cultivars showing the best potential for growing under saline conditions.

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