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Overwintering and spring recovery of pine needles have important ecological significance. The natural changes in physiological state, photosynthetic function, and material metabolism in needles of Pinus densiflora Siebold & Zucc. from the autumn of 2020 to the spring of 2021 were assessed. The photosynthetic rate (Pn) of P. densiflora needles decreased first and then increased, with the maximum Pn observed in the autumn. After experiencing sub-zero temperatures in the winter, needles of P. densiflora still performed weak photosynthesis at a temperature above zero. In the spring, the Pn gradually recovered but could not recover to the maximum. Under sub-zero temperatures in the winter of 2020, the plasma membrane permeability and MDA content of needles increased, whereas the chlorophyll content and Fv/Fm decreased significantly. The needles showed obvious characteristics of freezing injury. During the whole process, the water content of needles remained at a low level (about 60%), which gradually decreased with the increase of leaf age. The cell sap concentration and soluble sugar content of needles decreased with the decrease in air temperature and recovered in spring. Therefore, P. densiflora needles do not improve frost resistance through osmotic adjustment. However, the increasing carotenoid content is helpful for needles to tide over the winter. The soluble sugar and protein contents increased, implying they are important for the recovery of needles in spring. This study expands our understanding of the mechanism and ecological contribution of overwintering and spring recovery of pine needles.

Plants produce reactive oxygen species (ROS) to defend pathogens. To counteract this attack, certain pathogens express superoxide dismutases (SODs) to scavenge host-derived ROS. However, the roles of SODs in Verticillium dahliae, an important vascular pathogen, are not clear. Our previous study has shown that a putative extracellular SOD (VdSOD5) of V. dahliae is significantly induced by culturing in cotton tissues, suggesting that VdSOD5 may play an important role in host–pathogen interactions and virulence. Here, we showed that VdSOD5 encoded a superoxide dismutase with a cofactor copper-binding site and a functional signal peptide that can conduct protein secretion in an invertase-mutated yeast strain. The mutations in VdSOD5 (ΔVdSOD5) did not change the normal vegetative growth and conidial production but reduced the virulence of V. dahliae on susceptible host cotton. Further studies showed that the transcription of VdSOD5 was significantly up-regulated during the early stage of infection, and the loss-of-function of VdSOD5 decreased culture filtrate and fungal tissue SOD activities of V. dahliae by 74 and 28%, respectively. Compared to the wild-type strain Vd991, the ΔVdSOD5 showed the same sensitivity to the intracellular ROS generator menadione. Furthermore, nitroblue tetrazolium (NBT) staining demonstrated that VdSOD5 functioned in the detoxification of superoxides generated by host roots during infection. These results suggest that VdSOD5 of V. dahliae is an important virulence factor, secreted out of cells to combat host-derived ROS.

Plant pathogens generally employ superoxide dismutase (SOD) to detoxify host defense reactive oxygen species (ROS), and to scavenge ROS derived from their own metabolism. However, the roles of SODs in an important vascular pathogen, Verticillium dahliae, are unclear. Our previous study has shown that a putative signal-peptide-lacking manganese superoxide dismutase (VdSOD3) is present in the exoproteome of V. dahliae cultured in tissues of host cotton, suggesting that VdSOD3 may be exported out of the fungal cells and contribute to the SOD activity extracellularly. Here, we confirm that the N-terminal of VdSOD3 is not a functional signal peptide by yeast signal trap assay. Despite lacking the signal peptide, the extracellular distribution of VdSOD3 was observed in planta by confocal microscopy during infection. Loss-of-function of VdSOD3 decreased extracellular and intracellular SOD activities of V. dahliae by 58.2% and 17.4%, respectively. Deletion mutant of VdSOD3 had normal growth and conidiation but showed significantly reduced virulence to susceptible hosts of cotton and Nicotiana benthamiana. Our data show that signal-peptide-lacking VdSOD3 is a dual function superoxide dismutase, localizing and functioning intracellularly and extracellularly. Whereas nonessential for viability, VdSOD3 plays a vital role in the virulence of V. dahliae.

The accumulation of reactive oxygen species (ROS) is a widespread defence mechanism in higher plants against pathogen attack and sometimes is the cause of cell death that facilitates attack by necrotrophic pathogens. Plant pathogens use superoxide dismutase (SOD) to scavenge ROS derived from their own metabolism or generated from host defence. The significance and roles of SODs in the vascular plant pathogen Verticillium dahliae are unclear. Our previous study showed a significant upregulation of Cu/Zn‐SOD1 (VdSOD1) in cotton tissues following V. dahliae infection, suggesting that it may play a role in pathogen virulence. Here, we constructed VdSOD1 deletion mutants (ΔSOD1) and investigated its function in scavenging ROS and promoting pathogen virulence. ΔSOD1 had normal growth and conidiation but exhibited significantly higher sensitivity to the intracellular ROS generator menadione. Despite lacking a signal peptide, assays in vitro by western blot and in vivo by confocal microscopy revealed that secretion of VdSOD1 is dependent on the Golgi reassembly stacking protein (VdGRASP). Both menadione‐treated ΔSOD1 and cotton roots infected with ΔSOD1 accumulated more O2‐ and less H2O2 than with the wildtype strain. The absence of a functioning VdSOD1 significantly reduced symptom severity and pathogen colonization in both cotton and Nicotiana benthamiana. VdSOD1 is nonessential for growth or viability of V. dahliae, but is involved in the detoxification of both intracellular ROS and host‐generated extracellular ROS, and contributes significantly to virulence in V. dahliae., Verticillium dahliae Cu/Zn superoxide dismutase detoxifies self‐ and host‐generated ROS to maximize virulence.

MYB-type transcription factors are known to participate in the response of plants to a number of stress agents. MsMYB2L is an alfalfa member of this large gene family. Its transcription in alfalfa seedlings was found to be rapidly and strongly induced by salinity, moisture deficiency and exogenously supplied abscisic acid. An analysis based on a yeast one hybrid assay indicated that its product is able to activate transcription, consistent with its function as a transcription factor. When the gene was constitutively expressed in Arabidopsis thaliana, both germination and seedling growth were more sensitive to ABA treatment than wild type, and growth was less strongly compromised by salinity and moisture deficiency stress, presumably as a result of the induction of certain stress-related genes active in ABA-dependent pathways. The transgenic seedlings' enhanced the synthesis of many osmotic regulatory substances such as proline and soluble sugar, and decreased the lipid peroxidation. In all, MsMYB2L represents a potential candidate gene for manipulating the salinity and drought tolerance of alfalfa.

Summary • Here, the effects of salinity (0–400 mM NaCl) on photosynthesis, photosystem II (PSII) efficiency and the xanthophyll cycle were investigated in the halophyte Atriplex centralasiatica grown under outdoor conditions. • Leaf sodium and chloride in leaves increased considerably whereas CO2 assimilation rate decreased. PSII efficiency (ΦPSII) and the efficiency of excitation energy capture by open PSII reaction centres decreased whereas nonphotochemical quenching (NPQ) increased significantly. There was no change in photochemical quenching (qP) in salt-adapted plants. Salinity induced no changes in the maximum efficiency of PSII photochemistry (Fv/Fm) measured either at midday or at predawn. However, Fv/Fm values were c. 20% lower at midday than at predawn. • Contents of chlorophyll (a + b), neoxanthin, lutein and β-carotene were unchanged with increasing salt concentration, but zeaxanthan increased significantly, at the expense of violaxanthin. There was a linear relationship between the de-epoxidation state of the xanthophyll cycle and ΦPSII, , and NPQ. • Our results suggest that A. centralasiatica shows high tolerance to both high salinity and photoinhibition and that the xanthophyll cycle played an important role in protecting photosynthetic apparatus from photoinhibitory damage. Tolerance of PSII to salinity and photoinhibition can be viewed as an important strategy for A. centralasiatica to grow in very high saline soil during the summer season with high irradiance.

2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) is one of the most toxic polybrominated diphenyl ethers (PBDEs). The toxic effects of BDE-47 on Chinese cabbage seedlings were analyzed in this study. After a 30-day hydroponic exposure to BDE-47 at different concentrations (25, 50, 75, and 100 µg·L−1), the fresh weight of Chinese cabbage seedlings was significantly decreased, whereas their root:shoot ratio was increased, indicating that BDE-47 inhibited the growth of the plant, especially the overground parts. The water content, chlorophyll content, and protein content of Chinese cabbage leaves also markedly decreased with the increase of the BDE-47 concentration. In addition, BDE-47 weakened the photosynthetic capacity of the leaves, which was supported by the decreased photosynthetic parameters [net photosynthetic rate (Pn) and stomatal conductance (gS)]. Although the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in the leaves were enhanced after exposure to BDE-47, the increased malondialdehyde (MDA) content attested to the existence of membrane lipid peroxidation. The increased plasma membrane permeability and the decreased chlorophyll fluorescence parameters [the maximum quantum yield of PSII photochemistry at t = 0 (Fv/Fm), photosystem II (PSII) reaction centers (RCs) per cross section (CS) (RC/CS), absorption energy flux per CS (ABS/CS), trapped energy flux per CS (TRo/CS), electron transport flux per CS (ETo/CS), performance index on the absorption basis (PIabs), and driving force for photosynthesis (DF)] further proved that the plasma membrane and photosynthetic membrane were damaged by BDE-47. Our study demonstrated the phytotoxicities of BDE-47 to Chinese cabbage, which can provide valuable information for understanding the toxicity of BDE-47 on vegetables.

The AINTEGUMENTA-like (AIL) family plays a central role in regulating the growth and development of organs in many plants. However, little is known about the characteristics and functions of the AIL family in Chinese cabbage (Brassica rapa L. ssp. pekinensis). In this study, a genome-wide analysis was performed to identify the members of the AIL family in Chinese cabbage. We identified three ANT genes and six ANT-like genes of Chinese cabbage, most of which were differentially expressed in different organs or tissues. Furthermore, compared with the wild-type line, the size of different organs in the 35S-BrANT-1 line was significantly increased by promoting cell proliferation. Meanwhile, over-expression of BrANT-1 also increases the stomatal number and delays the leaf senescence. Transcriptome analyses revealed that a set of cell proliferation and stoma development genes were up-regulated, while the senescence-associated genes were down-regulated, suggesting these genes may be involved in BrANT-1 regulated processes for controlling organ size, stomatal density and leaf senescence. In summary, this study offers important insights into the characteristics and functions of the ANT genes in Chinese cabbage, and provides a promising strategy to improve yield or head size in Chinese cabbage breeding programs.

To investigate the toxic effect and mechanism of 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) in aquatic plants, in vivo and in vitro exposure to BDE-47 were conducted. After 14-d exposure to 5–20 μg/L BDE-47, the growth of Lemna minor plants was significantly suppressed, and the chlorophyll and soluble protein contents in fronds markedly decreased. Accordingly, the photosynthetic efficiency (Fv/Fm, PI) decreased. When the thylakoid membranes isolated from healthy fronds was exposed to 5–20 mg/L BDE-47 directly in vitro for 1 h, the photosynthetic efficiency also decreased significantly. In both the in vitro (5–20 μg/L) and in vivo (5–20 mg/L) experiments, BDE-47 led to an increased plasma membrane permeability. Hence, we concluded that BDE-47 had a direct toxicity to photosynthetic membranes and plasma membranes. However, direct effects on the activities of peroxidase (POD), malate dehydrogenase (MDH) and nitroreductase (NR) were not observed by adding 5–20 mg/L BDE-47 into crude enzyme extracts. The malondialdehyde (MDA) and superoxide anion radical (O2− ) contents in the BDE-47 treated fronds were higher than those in the control fronds, suggesting that L. minor can not effectively relieve reactive oxygen species (ROS). The data above indicates that BDE-47 is toxic to L. minor through acting directly on biomembranes, which induces the production of ROS and thus causes remarkable oxidative damage to cells.

Abiotic stresses such as drought and salinity are major environmental factors that limit crop yields. Unraveling the molecular mechanisms underlying abiotic stress resistance is crucial for improving crop performance and increasing productivity under adverse environmental conditions. Zinc finger proteins, comprising one of the largest transcription factor families, are known for their finger-like structure and their ability to bind Zn2+. Zinc finger proteins are categorized into nine subfamilies based on their conserved Cys and His motifs, including the Cys2/His2-type (C2H2), C3H, C3HC4, C2HC5, C4HC3, C2HC, C4, C6, and C8 subfamilies. Over the past two decades, much progress has been made in understanding the roles of C2H2 zinc finger proteins in plant growth, development, and stress signal transduction. In this review, we focus on recent progress in elucidating the structures, functions, and classifications of plant C2H2 zinc finger proteins and their roles in abiotic stress responses.

It is difficult to determine the photosynthetic parameters of non-flat leaves/green stems using photosynthetic instruments, due to the unusual morphology of both organs, especially for Suaeda salsa and Salicornia bigelovii as two seawater-tolerant vegetables. To solve the problem, we developed a simple, practical, and effective method to measure and calculate the photosynthetic parameters (such as PN, gs, E) based on unit fresh mass, instead of leaf area. The light/CO2/temperature response curves of the plants can also be measured by this method. This new method is more effective, stable, and reliable than conventional methods for plants with non-flat leaves. In addition, the relative notes on measurements and calculation of photosynthetic parameters were discussed in this paper. This method solves technical difficulties in photosynthetic parameter determination of the two seawater-tolerant vegetables and similar plants.

Salt stress is one of the major abiotic stresses that severely impact plant growth and development. In this study, we investigated the physiological and transcriptomic responses of Chinese cabbage "Qingmaye" to salt stress, a main variety in North China. Our results showed that the growth and photosynthesis of Chinese cabbage were significantly inhibited by salt treatment. However, as a glycophyte, Chinese cabbage could cope with high salinity; it could complete an entire life cycle at 100 mM NaCl. The high salt tolerance of Chinese cabbage was achieved by accumulating osmoprotectants and by maintaining higher activity of antioxidant enzymes. Transcriptomic responses were analyzed using the digital gene expression profiling (DGE) technique after 12 h of treatment by 200 mM NaCl. A total of 1235 differentially expressed genes (DEGs) including 740 up- and 495 down-regulated genes were identified. Functional annotation analyses showed that the DEGs were related to signal transduction, osmolyte synthesis, transcription factors, and antioxidant proteins. Taken together, this study contributes to our understanding of the mechanism of salt tolerance in Chinese cabbage and provides valuable information for further improvement of salt tolerance in Chinese cabbage breeding programs.

Algae collection and chlorophyll extraction are two troublesome steps in the traditional methods used for the determination of chlorophyll concentration in natural water. A new method was established in this study for fast collection and extraction of chlorophyll. Based on our results, the optimum centrifugation condition for collecting algae was determined as: 5000 g for 15 min at 4 °C, and the optimum dilution ratio of dimethyl sulfoxide: 90% acetone was 1:4. The specific steps were as follows: the algae in water samples were collected by centrifugation at 5000 g at 4 °C for 15 min. The precipitated algae were suspended with 2 mL DMSO. Then the sample was transferred to a 15 mL centrifuge tube, and the tube was incubated at 65 °C for 1–2 h in the dark until the sample turned white. After cooling, the chlorophyll extract was diluted with 8 mL 90% acetone, before centrifugation at 5000 g for 5 min. The absorbance values of the supernatants at 750, 664, 647 and 630 nm were used for the calculation of chlorophyll concentrations by the trichromatic equations. This new method saved the filter cost, simplified the extraction process, improved the algae acquisition efficiency, and accelerated the chlorophyll extraction rate.

The strategy of Suaeda salsa adaptation to high salinity was shown in this study. Our results firstly demonstrated that Na+ was a beneficial element rather than toxic ion for S. salsa plants. The biomass of S. salsa seedlings increased significantly after salt-treatment (100–400 mmol/L NaCl). Secondly, S. salsa had strong ability to accumulate Na+ under saline condition. Ninety-four percent of Na+ absorbed by salt-treated S. salsa plant accumulated in the shoot, especially in the leaves, and 98% of Na+ in the leaves accumulated in leaf symplast. Thirdly, measurement on isolated tonoplast-enriched membrane vesicles derived from the leaves of S. salsa showed that increased V-H+-ATPase hydrolytic activity, V-H+-ATPase proton pump activity and the tonoplast Na+/H+ antiport activity were found in salt-treated leaves compared with the control leaves. Up-regulation of the tonoplast Na+/H+ antiport activity was due to increase of both transcription and translation. These results suggested that coordinate up-regulation of V-H+-ATPase activity and Na+/H+ antiporter activity play a pivotal role in Na+ sequestering into vacuoles of S. salsa.

The effects of high salinity (up to 400 mM NaCI) on photosystem II (PSII) photochemistry, photoinhibition and the xanthophyll cycle were investigated in the halophyte Artimisia anethifolia grown under outdoor conditions. In order to examine the changes in PSII photochemistry, photoinhibition, thermal dissipation associated with the xanthophyll cycle in salt-acclimated plants, the experiments were conducted at midday on a clear day (maximal irradiance 1500 μmol m -1 s -1 ) and on a cloudy day (maximal irradiance 700 μmol m -1 s -1 ), respectively. With increasing salt concentration, the accumulation of sodium and chloride in leaves increased considerably while the relative growth rate and CO 2 assimilation rate decreased significantly. Salinity induced no effects on PSII photochemistry, thermal energy dissipation, and the contents of the xanthophyll cycle pigments either on a clear day or on a cloudy day. However, when compared with those on a cloudy day, PSII photochemistry decreased and thermal energy dissipation increased significantly in both control and salt-acclimated plants on a clear day. The levels of zeaxanthin and antheraxanthin at the expense of violaxanthin were higher on a clear day than on a cloudy day. The results suggest that photoinhibition and the xanthophyll cycle were not induced by high salinity but by high light only in A. anethifolia plants. The results also suggest that A. anethifolia showed high resistance not only to high salinity, but also to photoinhibition even when it was treated with high salinity and exposed to full sunlight.

Kalanchoe daigremontiana, a CAM plant grown in a greenhouse, was subjected to severe water stress. The changes in photosystem II (PSII) photochemistry were investigated in water-stressed leaves. To separate water stress effects from photoinhibition, water stress was imposed at low irradiance (daily peak PFD 150 μmol m -2 s -1 ). There were no significant changes in the maximal efficiency of PSII photochemistry (F y /F m ), the traditional fluorescence induction kinetics (OIP) and the polyphasic fluorescence induction kinetics (OJIP), suggesting that water stress had no direct effects on the primary PSII photochemistry in dark-adapted leaves. However, PSII photochemistry in light-adapted leaves was modified in water-stressed plants. This was shown by the decrease in the actual PSII efficiency (Φ PSII ), the efficiency of excitation energy capture by open PSII centres (F' v /F' m ), and photochemical quenching (qp), as well as a significant increase in non-photochemical quenching (NPQ) in particular at high PFDs. In addition, photoinhibition and the xanthophyll cycle were investigated in water-stressed leaves when exposed to 50% full sunlight and full sunlight. At midday, water stress induced a substantial decrease in F v /F m which was reversible. Such a decrease was greater at higher irradiance. Similar results were observed in Φ PSII , q P , and F' v /F' m . On the other hand, water stress induced a significant increase in NPQ and the level of zeaxanthin via the de-epoxidation of violaxanthin and their increases were greater at higher irradiance. The results suggest that water stress led to increased susceptibility to photoinhibition which was attributed to a photoprotective process but not to a photodamage process. Such a photoprotection was associated with the enhanced formation of zeaxanthin via de-epoxidation of violaxanthin. The results also suggest that thermal dissipation of excess energy associated with the xanthophyll cycle may be an important adaptive mechanism to help protect the photosynthetic apparatus from photoinhibitory damage for CAM plants normally growing in arid and semi-arid areas where they are subjected to a combination of water stress and high light.

Salicornia bigelovii is an unusually salt-tolerant plant species and is able to continue to photosynthesize and grow in saline conditions. There is an interest in understanding the mechanisms of this salt tolerance. In this study, S. bigelovii plants grown under 400 mM NaCl had higher growth and higher photosynthetic capacity than those not grown with salt. The intensities of the fluorescence emission peaks in the thylakoid membrane spectra in the salt treatment were higher than in the control. PSII and PSI peaks of the control were blue-shifted, indicating that salt deficiency affects energy transfer and structural stability in PSII and PSI. Both SDS-PAGE and western blot illustrated that the PSI proteins PsaA and PsaB and the PSII proteins CP47 and CP43 were upregulated with salt treatment, which might partly explain the change in the energy transfer process. Furthermore, Lhcb1 was also stimulated by salt treatment while Lhcb2 and Lhcb3 did not show noticeable changes. This demonstrated that salt is important in the maintenance of photosynthesis. In summary, treatment with salt led to an increased amount of PsaA/B, CP47, CP43, and Lhcb1 with a concurrent increase in antennae size. These photosystem changes may be responsible for the adaptation of S. bigelovii to saline conditions.

The effects of salt stress (0–400 mM NaCl) on PSII photochemistry, photoinhibition and photosynthetic pigment composition were investigated in the halophyte Suaeda salsa grown under outdoor conditions and exposed to full sunlight. Salt stress resulted in a growth stimulation which was optimal at 200 mM NaCl. With increasing salt concentration, leaf water potential and evaporation rate decreased significantly while there were no changes in leaf relative water content. Salt stress also resulted in a significant accumulation of sodium and chloride in leaves. Salt stress induced neither effects on the maximal efficiency of PSII photochemistry measured either at predawn or at midday nor effects on the actual PSII efficiency ( Φ PSII ), the efficiency of excitation energy capture by open PSII reaction centres, photochemical quenching, and non-photochemical quenching (NPQ) at midday. No significant changes were observed in the contents of neoxanthin, lutein, β-carotene, violaxnthin, antheraxthin, zeaxanthin, chlorophyll a and b in salt-stressed plants. Our results suggest that S. salsa showed high resistance not only to salinity stress but also to photoinhibition even when treated with high salinity as high as 400 mM NaCl and exposed to full sunlight. The results indicate that tolerance of PSII to high salinity stress and high light stress can be viewed as an important strategy for S. salsa to grow in very high saline soil.

Background Growth regulating factors (GRFs) have been shown to play important roles in plant growth and development. GRF genes represent a large multigene family in plants. Recently, genome-wide structural and evolutionary analyses of the GRF gene families in Arabidopsis, rice, and maize have been reported. Chinese cabbage (Brassica rapa L. ssp. pekinensis) is one of the most important vegetables for agricultural production, and a full genome assembly for this plant has recently been released. However, to our knowledge, the GRF gene family from Chinese cabbage has not been characterized in detail. Results In this study, genome-wide analysis was carried out to identify all the GRF genes in Chinese cabbage. Based on the complete Chinese cabbage genome sequence, 17 nonredundant GRF genes, named BrGRFs, were identified and classified into six groups. Phylogenetic analysis of the translated GRF protein sequences from Chinese cabbage, Arabidopsis, and rice indicated that the Chinese cabbage GRF proteins were more closely related to the GRF proteins of Arabidopsis than to those of rice. Expression profile analysis showed that the BrGRF genes had uneven transcript levels in different organs or tissues, and the transcription of most BrGRF genes was induced by gibberellic acid (GA3) treatment. Additionally, over-expression of BrGRF8 in transgenic Arabidopsis plants increased the sizes of the leaves and other organs by regulation of cell proliferation. Conclusions The data obtained from this investigation will contribute to a better understanding of the characteristics of the GRF gene family in Chinese cabbage, and provide a basis for further studies to investigate GRF protein function during development as well as for Chinese cabbage-breeding programs to improve yield and/or head size. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-807) contains supplementary material, which is available to authorized users.

Thermotolerance of photosystem II (PSII) in leaves of salt-adapted Artemisia anethifolia L. plants (100-400 mM NaCl) was evaluated after exposure to heat stress (30-45 degrees C) for 30 min. After exposure to 30 degrees C, salt adaptation had no effects on the maximal efficiency of PSII photochemistry (F(v)/F(m)), the efficiency of excitation capture by open PSII centers (F(v)'/F(m)'), or the actual PSII efficiency (Phi(PSII)). After pretreatment at 40 degrees C, there was a striking difference in the responses of F(v)/F(m), F(v)'/F(m)' and Phi(PSII) to heat stress in non-salt-adapted and salt-adapted leaves. Leaves from salt-adapted plants maintained significantly higher values of F(v)/F(m), F(v)'/F(m)' and Phi(PSII) than those from non-salt-adapted leaves. The differences in F(v)/F(m), F(v)'/F(m)' and Phi(PSII) between non-salt-adapted and salt-adapted plants persisted for at least 12 h following heat stress. These results clearly show that thermotolerance of PSII was enhanced in salt-adapted plants. This enhanced thermotolerance was associated with an improvement in thermotolerance of the PSII reaction centers, the oxygen-evolving complexes and the light-harvesting complex. In addition, we observed that after exposure to 42.5 degrees C for 30 min, non-salt-adapted plants showed a significant decrease in CO(2) assimilation rate while in salt-adapted plants CO(2) assimilation rate was either maintained or even increased to some extent. Given that photosynthesis is considered to be the physiological process most sensitive to high-temperature damage and that PSII appears to be the most heat-sensitive part of the photosynthetic apparatus, enhanced thermotolerance of PSII may be of significance for A. anethifolia, a halophyte plant, which grows in the high-salinity regions in the north of China, where the air temperature in the summer is often as high as 45 degrees C.