научный журнал по биологии Физиология растений ISSN: 0015-3303

ALIKAMANOGLU S., SEN A. — 2014 г.

In this study, the static magnetic field (SMF) flux of 2.9–4.7 mT was applied to mature embryo explants of Tekirdag and Selimiye wheat cultivars (Triticum aestivum L.) under tissue culture conditions at three different pretreatment times of 0, 2.2, and 19.8 s, at the rate of 1 m/s with and without 60 g/L PEG 6000 or 100 mM NaCl. Changes in different biochemical parameters were investigated. SMF pretreatment with and without 60 g/L PEG 6000 or 100 mM NaCl increased chlorophyll and carotenoid contents, FRAP values, and antioxidant enzyme (SOD, CAT, POX, and APX) activities in all experimental groups except for the activities of Mn-SOD in the cv. Selimiye root samples. Among SOD isozymes, Fe-SOD was affected by SMF stronger than other izozymes. The combinations of SMF pretreatment with and without 60 g/L PEG 6000 or 100 mM NaCl differently affected SOD isozyme activities besides its effects on other biochemical parameters.

ALLAKHVERDIEV S.I., BOSA K., JADCZUK-TOBJASZ E., KALAJI H.M., MAJEWSKA M. — 2014 г.

In this experiment, leaf gas exchange, photosynthetic efficiency, area index, and chlorophyll content were measured in pear (Pyrus communis L.) trees grown on different rootstocks and potassium fertilization doses. Our results showed that trees budded on the Pyrodwarf rootstock had the biggest leaf area and the highest photosynthetic efficiency, photosynthesis rate, and chlorophyll content. There was no correlation between the applied potassium fertilization dosage and the photosynthetic efficiency of the trees. This paper is addressed to discuss various mechanisms and selected factors responsible for pear tree photosynthetic productivity.

DING L., DU C.X., FAN H.F., XU Y.L. — 2014 г.

We investigated the effects of exogenous sodium nitroprusside (SNP), a nitric oxide (NO) donor, on growth of cucumber (Cucumis sativus L., cv. Jinyou No. 1) seedlings and antioxidant enzyme activities in cucumber leaves under waterlogging stress. The growth of cucumber seedlings was significantly inhibited when plants were exposed to waterlogging, whereas shoot spraying with SNP significantly alleviated the inhibition of growth from this type of stress: height, fresh and dry weights of the flooded plants increased obviously. Waterlogging also caused the activation of the antioxidant enzymes (superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX)), the reduction of the chlorophyll content, and the accumulation of MDA and protein in leaves. It was found that SNP treatment further potentiated the antioxidant enzyme activities and maintained the chlorophyll and protein content during the entire waterlogging period; however, it reduced the MDA content. Thus, NO protects plants from oxidative damage and promotes growth by activation of antioxidant enzymes in leaves in an extent sufficient for the alleviation of membrane injury. However, exogenous NO had no significant effects on cucumber seedlings growth and antioxidant enzyme activities under nonstress conditions.

SHI W.M., YE X.Z., ZHAO S.P. — 2014 г.

OsAMT is a high-affinity ammonium transporter responsible for NH uptake by rice plants. To investigate the expression patterns of OsAMT in different genotypes in relation to nitrogen accumulation, we measured the expression of OsAMT1.1, OsAMT1.2, and OsAMT1.3 using Real-Time PCR (RT-PCR) in GD (higher N accumulation) and NG (lower N accumulation) seedlings of the Oryza sativa L. cultivar treated with 0.1 mM NH4NO3 and 2 mM NH4NO3. We found that the expression level of OsAMT1.1 was significantly higher than those of OsAMT1.2 and OsAMT1.3 in the roots treated with 0.1 mM NH4NO3, suggesting that OsAMT1.1 contributed the most to N accumulation among the three genes. In GD root, OsAMT1.1 had significantly higher expression levels when it was up-regulated by 0.1 mM NH4NO3 than when down-regulated by 2 mM NH4NO3. OsAMT1.1 was mainly found in GD roots treated with 0.1 mM NH4NO3. We conclude that the OsAMT1.1 in GD roots, which was significantly up-regulated by low N and down-regulated by high N, was the dominating factor in determining the higher N acquisition in GD than in NG at 0.1 mM NH4NO3.

JIANG Q., LIAN J.P., LIU Z.L., SUN J.L., WANG Q., XU H., YANG Y.Q., ZHAO H.X. — 2014 г.

Very long chain fatty acids (VLCFAs) are essential lipid components in many plants. 3-Ketoacyl-CoA synthase (KCS) catalyzes the condensation reaction to form 3-ketoacyl-CoA in VLCFA synthesis. AtELO4 has been reported to be involved in VLCFA synthesis, functioning as a KCS in Arabidopsis. However, no studies on other three AtELO members have been reported. Here, we initially found by real-time PCR in Arabidopsis thaliana (L.) Heynh., that AtELO1, AtELO3, and AtELO4 displayed characteristic expression patterns, but AtELO2 was nearly expressed in any organ. Then the transient expression of ELO-like-eGFP fusions in Arabidopsis green leaf protoplasts showed that AtELO1, AtELO3, and AtELO4 were localized in ER, where VLCFA synthesis took place. Finally, we found that the contents of all fatty acids were decreased by 10–20% in seeds of atelo1 T-DNA insertion mutants. In seeds of Pro35S:AtELO1 plants, the levels of all remaining components, except C20:0 and C20:3, were significantly increased. Taken together, our study revealed biological functions of AtELO members and may lay the foundation for further genetic manipulations to generate oil crops with the high oil content.

HUANG A.X., LIU Y.E., SHE X.P., SONG X.G., WANG Y.X., YUE M., ZHU X. — 2014 г.

Ethylene promotes stomatal closure via inducing hydrogen peroxide (H2O2) generation. H2O2 can be catalytically synthesized by several enzymes in plants. Here, by means of stomatal bioassay, the analysis of enzyme activity and using laser-scanning confocal microscopy based on the H2O2-sensitive probe 2,7-dichlorodihydrofluorescein diacetate (H2DCF-DA), the roles of copper amine oxidase (CuAO) in ethylene-induced H2O2 production in guard cells and stomatal closure in Vicia faba L. were investigated. 1-aminocyclopropane-1-carboxylic acid (ACC), an immediate precursor of ethylene synthesis, and ethylene gas significantly activated CuAO in intercellular washing fluid (IWF) from leaves, the production of H2O2 in guard cells, and stomatal closure. These effects of ACC and ethylene gas were largely prevented by both aminoguanidine (AG) and 2-bromoethylamine (BEA), which are irreversible inhibitors of CuAO. Among major catalyzed and metabolized products of CuAO, only H2O2 could markedly promote stomatal closure and evidently reversed the effect of CuAO inhibitor on stomatal closure by ACC and ethylene gas. The data described above show that CuAO-mediated H2O2 production is involved in ethylene-induced stomatal closure.

CHEN X., HAO J., LI N.N., LIN X.F., QI F., YU C.R., ZHANG W.B. — 2014 г.

Caragana is a native desert shrub with high forage values and stress tolerance, as well as sand-fixing capabilities. Some Caragana species, including C. korshinskii, C. microphylla, and C. intermedia, are commonly used for vegetation restoration programs in the Loess Plateau region of northwestern China and are known to have ecological benefits and high commercial value. In this study, full-length sequences of Cu/Zn-SOD genes were isolated from three Caragana species using degenerate polymerase chain reaction (PCR) and rapid amplification of cDNA ends (RACE) techniques, and their expression under drought stress conditions were investigated. The cloned SOD cDNAs contained a predicted open reading frame of 459 bp encoding a polypeptide of 152 amino acids with a theoretical molecular weight of 15.2 kD. Cu/Zn-SOD cDNA of C. korshinskii and C. intermedia shared 100% sequence identity, implying a close relationship. A 24-bp specific sequence was found in the 3-UTR region of C. microphylla Cu/Zn SOD-cDNA, and reverse transcription RT-PCR and genomic PCR confirmed the feasibility of the 24-bp sequence as a DNA marker for rapid variety identification of C. microphylla. RT-PCR revealed that the expression of the Caragana Cu/Zn-SOD genes was induced by PEG-simulated drought stress and ABA. The three Caragana Cu/Zn-SOD genes showed similar expression patterns, and no significant difference in transcriptional level was observed among the three genes. These results increase our understanding of the molecular mechanism of drought tolerance and can be used to improve vegetation restoration programs of Caragana plants.

CUI Y.Y., LAI Q.X., LIN F.F., QIN Q.P., ZHANG L.L. — 2014 г.

Fructose is essential for plant development as well as for fruit sugar composition and fruit quality. Fructose is one of the major sugars in the mature loquat (Eriobotrya japonica Lindl.) fruit, which is popular because of its flavor and availability in early summer. The elucidation of the mechanism of fructose metabolism is of great importance for fruit quality improving. Fructose is primarily phosphorylated by fructokinase (FRK). In order to understand the fructose metabolism in the loquat fruit, a putative loquat FRK full-length cDNA designated as EjFRK was isolated in this study. The EjFRK encoding FRK possesses conserved regions inherent to plant FRKs. Transient expression of 35S:EjFRK-GFP fusion protein in onion epidermal cells showed that EjFRK was mainly expressed in the cytosol. The real-time RT-PCR analysis indicated that EjFRK was expressed in all loquat tissues. Monitoring the dynamic changes of EjFRK transcripts and FRK enzymatic activities demonstrated that EjFRK expression was at a relative high level during early fruit developmental stages and dropped to the lower level during maturation, similar with the changes in FRK activity, which was opposite to the fructose levels during fruit development. The results indicated that the high FRK enzymatic activity was not conducive to fructose accumulation in loquat fruit. The EjFRK transcript level in leaves of loquat seedlings was significantly enhanced after 6 h of treatment with 10 and 100 mM fructose or glucose, which indicates that EjFRK is modulated by fructose and glucose in vivo.

HAO J.H., LI T.L., WANG J.L., YANG R., ZHANG Q. — 2014 г.

Low night temperatures seriously affect plant growth and fruit quality. To investigate the effect of low night temperatures on the expression of galactinol synthase genes (GOLS) and phloem loading of raffinose family oligosaccharides, particular stachyose and raffinose (RFO represents stachyose and raffinose in this paper) and to gain a better understanding of the relationship between the phloem loading of RFO and fruit development, melon (Cucumis melo L.) plants at the fruit development stage were treated with temperatures of 28/12°C or 28/9°C (day/night) with 28/15°C as the control. Both the CmGOLS1 and CmGOLS2 gene expression and the activity of galactinol synthase were clearly repressed after treatments with 9 and 12°C at night, and the effect of 9°C was more obvious. Furthermore, low night temperatures inhibited photosynthesis and caused the lower amounts of sucrose to supply the RFO synthesis. However, the total soluble sugar, RFO, and sucrose contents were increased in leaves subjected to low night temperatures. It is supposed that low night temperature blocked symplastic phloem loading, which led to the accumulation of RFO in the leaf cells. With increasing content of RFO in the leaves, the expression of GOLS genes was inhibited according to the principle of feedback, and therefore the decreased expression of GOLS limited RFO synthesis and was indirectly harmful to phloem loading, thereby affecting fruit development.

ARCHBOLD D.D., DUAN W., FAN P.G., LI S.H., MA L., WANG L.J., WU B.H., XU M. — 2014 г.

Low sink demand provided by pod removal and stem girdling of beans (Vicia faba, cv. Daqingshan) (–Sink) induced a significantly lower net photosynthetic rate (Pn), stomatal conductance (gs), internal CO2 concentration (Ci), and transpiration rate (E) compared with pod and root sink retention (CK). This depression in Pn was due to stomatal limitation. Low sink demand of –Sink plants resulted in a higher leaf sucrose content, but a lower sucrose content in guard cells. Moreover, the significant accumulation of H2O2 and ABA were observed in both leaves and guard cells of –Sink plants. The most intensive electron dense deposit of cerium perhydroxides, produced by H2O2 reaction with cerium chloride, was present in the cell walls, especially the dorsal walls of guard cells. Immunogold electron-microscopy localization of ABA showed that ABA was distributed in ventral walls of guard cells and the intercellular space of mesophyll cells of –Sink leaves in contrast to CK plants. Application of exogenous sucrose to isolated bean leaves increased H2O2 and ABA contents. H2O2 and ABA in leaves was likely generated by two independently regulated pathways, each affected by the high sucrose concentration induced by low sink demand. Increased sucrose in leaves in response to low sink demand may have caused the increase of H2O2 and ABA, and their accumulation in mesophyll cells and guard cells was likely the primary cause for stomatal closure under low sink demand.

HAN M.M., HU F., REN J., WANG X., ZHANG S.Y., ZHAO F.Y. — 2014 г.

Previously, we have reported the role of MAPKs (mitogen-activated protein kinases) under cadmium stress. This work continue to explore the relationship between MAPKs, H2O2, auxin signaling, and OsHMA and OsZIP gene expression in rice (Oryza sativa L.) roots under combined cadmium (Cd) and zinc (Zn) stress. Compared with Cd, Cd+Zn reduced Cd levels but increased Zn accumulation in the roots. Three OsMAPK genes were negatively regulated, while two OsHMA and two OsZIP genes were positively regulated by MAPK pathways under Cd+Zn stress. Transgenic rice expressing DR5-GUS exhibited enhanced GUS activity in H2O2-, PD (MAPKK inhibitor PD98059)-, or (Cd+Zn)-treated roots, which also exhibited increased H2O2 concentrations, whereas GUS staining decreased in roots in response to Cd+Zn+PD, DMTU (N,N-dimethylthiourea, a H2O2 scavenger), or Cd+Zn+DMTU treatment, with reduced H2O2 levels. GUS levels were consistent with H2O2 levels, suggesting that MAPK pathway-mediated auxin redistribution occurs via H2O2, and H2O2 functions downstream of MAPK but upstream of auxin signaling pathways. Furthermore, MAPK pathways serve specific functions in regulating the expression of some key genes of auxin signaling (OsYUCCA, OsPIN, OsARF, and OsIAA) under Cd+Zn stress. Overall, MAPK cascades function in the integration of metal transport, H2O2 generation, and auxin signaling in rice seedlings grown under Cd+Zn stress.

LIU F., LIU H., ZHAO P. — 2014 г.

The functions of microRNA399 (miR399) in response to phosphate (Pi) deficiency have been extensively studied in Arabidopsis; however, previous studies have focused on relatively late responses of seedlings. In this study, the expression profiles of five miR399 primary transcripts (pri-miR399s) and mature miR399 were investigated in seedlings, calli, and mesophyll protoplasts. Pi deficiency rapidly stimulated the accumulation of pri-miR399s in the seedlings except pri-miR399b at 1 day; the amount of pri-miR399a decreased at 3 and 5 days. pri-miR399c and pri-miR399e/f showed continuously increasing patterns; the greatest accumulation of pri-miR399d was observed at 3 days. The expression of pri-miR399b, c, and f was significantly induced in the callus after 15 days of exposure to Pi deficiency. In protoplasts, the expression patterns of five pri-miR399s were comparable to those in seedlings at 1 day of Pi deficiency. Mature miR399 accumulated in the treated seedlings; and more than 460-fold of induction was observed in the calli without Pi. The expression profiles of pri-miR399s suggest that these primary transcripts are temporally and tissue-specific regulated in plant responses to Pi deficiency. Moreover, fresh isolated protoplasts could be used to study physiological perception and local signaling of Pi deficiency during early stages.

ALLAKHVERDIEV S.I., BORAWSKA-JARMULOWICZ B., CARPENTIER R., KALAJI M.H., MASTALERCZUK G., PIETKIEWICZ S. — 2014 г.

Resistance to low temperature is crucial for overwintering crops. In this work we compared the resistance to low temperature treatment of some varieties of two forage grass species Dactylis glomerata L. and Lolium perenne L. in order to elucidate the reason for the better resistance found in some species. The variety Amila of D. glomerata and Diament of L. perenne were more tolerant to low temperature stress during the emergence and tillering phases as compared to the varieties Amera and Gagat. The improved tolerance and ability for recovery after stress were associated with better recovery of photosynthetic efficiency of these varieties and better survival of their shoots after low temperature stress.

BOZKURT H., CELEKLI A., DONMEZ G. — 2014 г.

Predictive modeling of ?-carotene accumulation by Dunaliella salina as a function of NaCl, pH, and irradiance was studied. Modified Logistic, Gompertz, Schnute, Richards, and Stannard models were fitted to describe ?-carotene accumulation by the alga under various environmental conditions. Lag time ( , days), maximum accumulation (A, pg/cell), and the maximum production rate ( , 1/day) for ?-carotene accumulation were calculated by modified Logistic and Gompertz models. Values of , A, and for ?-carotene accumulation varied between 0.26 and 20.14 days, 57.48 to 198.76 pg ?-carotene/cell, and 1.80 to 3.68 1/day, respectively. Results revealed that Logistic and Gompertz models could be used to describe the accumulation of ?-carotene by D. salina as a function of salt concentrations, pH, and irradiance. The highest asymptotic value was predicted from Logistic and Gompertz models at pH 9.0, 48 kerg/(cm2 s) light intensity, and 20% NaCl concentration.

YANG X.E., ZHANG M. — 2014 г.

The effects of Cd on the chlorophyll fluorescence parameters of hyperaccumulating ecotype (HE) and non-hyperaccumulating ecotype (NHE) of Sedum alfredii Hance were studied. The photosystem II (PSII) photochemical efficiency of HE plants was not affected, and the non-photochemical quenching (NPQ) value was significantly increased under Cd treatment. In the NHE plants, Cd treatment caused significant loss in PSII photochemical efficiency and NPQ value. Gene expression analysis showed that both ecotypes of S. alfredii accumulated more than twofold higher PsbS (PSII subunit S) transcript levels than control plants after exposure to Cd. Overexpression of PsbS gene isolated from HE plants (SaPsbS) enhanced tobacco growth. The transgenic tobacco possessed greater NPQ capacity in the presence of 100 Cd and accumulated the significantly higher Cd content in shoots than the wild-type plants. These data indicate that the SaPsbS may function in NPQ capacity and protect the PSII reaction center in HE plants.

HASI A., HE Y., KANG Y., MA C., REN X., SUN H., WANG H., ZHANG Y. — 2014 г.

In nature, the phytopathogen usually initiates its infection on the leaf surface before moving into the internal space through natural openings. Little is known about immediate response of the leaf to the surface-colonizing phytopathogen and its correlation with individual microbe-associated molecular patterns (MAMPs). In this study, we monitored the dynamic changes in the cytosolic Ca2+ concentration ([Ca2+]cyt) in the Arabidopsis leaf expressing luminescence protein aequorin as the response to the surface-inoculating Pseudomonas syringae DC3000 (Pst DC3000) with a touching-free system. The significant [Ca2+]cyt transient rise was evoked in the leaf right after inoculation, and its magnitude was correlated with the pathogen concentration. Pharmacological studies revealed that the rising [Ca2+]cyt occurs primarily from the cAMP-mediated Ca2+ mobility pathway, but not Gd3+-sensitive Ca2+ influx channel in the plasma membrane, which was distinct from those induced by individual MAMPs (lipopolysaccharide, flagellin, and elongation factor Tu). Pretreating the leaf with Pst DC3000 or MAMPs significantly attenuated its responses to subsequent treatments of any of them, which indicates that the leaf has the convergent mechanism of sensitivity to the pathogen and MAMPs. Furthermore, Pst DC3000 mutants defective in flagellum, type III secretion apparatus, and phytotoxin coronine production significantly lost their multiplication ability in the leaf apoplast, but evoked [Ca2+]cyt responses comparable with that of the wild type. Taken together, these data indicates that the [Ca2+]cyt in the leaf has the sensitive response to the surface-inoculating phytopathogen, which was distinct from those of individual MAMPs and had no correlation with the pathogen pathogenesis capacity.

DENG M., LI W., LIU C., LIU L., PAN K., SHEN X., WANG Y., ZHANG L. — 2014 г.

The responses of the antioxidant defense system in plant species to drought stress are still relatively unknown. In order to further understand how the system responds to drought stress, the leaves of Fargesia denudata seedlings were investigated. Antioxidant enzyme activities, antioxidant contents, hydrogen peroxide (H2O2), superoxide anion (O ) and MDA contents in the seedling leaves were measured under well-watered (WW), moderate drought-stressed (MD), and severe drought-stressed (SD) treatments. Although drought stress significantly increased H2O2 and O levels in F. denudata leaves, only weak lipid peroxidation was observed. This is attributed to the higher superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), and dehydroascorbate reductase (DHAR) activities in F. denudata leaves during the entire drought period. Reduced and oxidized ascorbate (AsA and DHA) contents were almost not affected by drought except that DHA under SD showed an obvious increase on day 30. Furthermore, reduced glutathione (GSH) content under drought stress significantly decreased, while oxidized glutathione (GSSG) markedly increased under SD on days 30 and 45 as well as under MD on day 30; as a result, the ratio GSH/GSSG declined considerably. These results indicated that GSH was involved in scavenging H2O2 and O under drought stress and it was more sensitive to drought stress in scavenging H2O2 and O than AsA. As a result, a highly efficient antioxidant defense system in drought-stressed F. denudata leaves operated mainly through the synergistic functioning of SOD, CAT, APX, MDHAR, DHAR, GR, and GSH against oxidative damage.

HUANG J., LIU X.H., LU Y.M., WANG J.M. — 2014 г.

Flowering is a critical step in plant reproduction. Oriental lily (Lilium) characterized by showy flowers is increasingly used; however, the blossom period is an important limiting factor influencing the value of lily. Improving the flowering of lily by molecular breeding technology has limitless applications, but the mechanism of the regulation of lily flowering remains to be studied. Transcriptomes providing comprehensive sequence profiling data of transcription variation during flowering process in Oriental hybrids lily cv. Sorbonne were assembled from RNA-Seq data. Approximately 124.16 million 90 bp paired-end clean reads were assembled into 66 327 unigenes and compared with the UniProt databases. There are 30 254 unigenes that have significant hits to the sequences in the UniProt database, 60 738, 16 601, and 12 494 unigenes have similarity to the GO, KEGG, and COG databases, respectively. By analyzing dynamic changes in the transcriptome of lily flowering based on our RNA sequencing (RNA-Seq) data, some genes involved in floral induction were found, which revealed the complicated flower regulation network at the transcriptome level during lily flowering. Moreover, 12 DEGs related to flowering including LoLFY, LoMAF, LoFT, LoAG, LoCBF, LoAGL6a, LoSOC1, LoSEP1, LoNAC1, LoAPX, LoARF10, and LoICE were identified with real-time quantitative RT-PCR analysis. The results suggested that the flower of Oriental lily possessed a high proportion of flowering genes active at different stages of flowering. According to the results of the present study, we predicted that they would play an important role during flowering process; these data provided the foundation for future studies of metabolism during flowering of Oriental lily.

PANG Q.Y., WANG Y., WU Y., XIE G.E., YAN X.F., YU Y. — 2014 г.

Camptotheca acuminate plant is an important phytomedicinal species that contains camptothecin (CPT), a natural pentacyclic indole alkaloid. This study was aimed at the effect of arbuscular mycorrhiza (AM) development on the accumulation and location of this metabolite in C. acuminate seedling roots. Autofluorescence of CPT shows the localization of CPT in mycorrhizal roots. We examined CPT level in response to AM development in C. acuminate roots by the combination of confocal laser scanning microscopy and spontaneous fluorescence of CPT. CPT was specifically localized around AM fungi in AM roots of C. acuminate, and the level of CPT rose with increasing colonization of roots with AM fungi. The accumulation and localization of CPT was directly correlated with the formation and development of AM in C. acuminate roots.

OSMAN M.E.H. — 2014 г.

Thylakoids were isolated from the leaves of three different plants (Pisum sativum L., Lactuca sativa L., Raphanus sativus L.). The addition of HCO to a suspension of salt- and HCO -depleted thylakoids (suspended in salt-free medium) raised the rate of O2 evolution up to fourfold. This stimulation could be partially replaced by the addition of chloride or nitrate ions. However, the addition of HCO in the presence of Cl- or NO resulted in a higher stimulation of O2 evolution (sixfold in the presence of nitrate and sevenfold in the presence of chloride). On the other hand, the addition of HCO to the thylakoids depleted from salt only raised the rate of O2 evolution by 10–15%, whereas 40–70% was obtained by the addition of nitrate or chloride ions. The fluorescence induction studies indicated a significant decrease in the yield of the variable fluorescence of the salt- and HCO -depleted thylakoids. A partial increase in the fluorescence yield was obtained by the addition of HCO alone. A typical fluorescence induction curves were obtained by the addition of HCO in the presence of Cl- or NO ions. The obtained data suggest a similar role for chloride and nitrate ions in O2 evolution in the Hill reaction, which is restricted at the donor side of photosystem II, whereas bicarbonate plays its role at both sides (acceptor and donor sides). The presented data are those obtained for the thylakoids of P. sativum, which were more or less similar to those obtained for L. sativa and R. sativus.