Synthesis and Crystal Structure of a Co(II) Coordination Polymer Derived from a Flexible Bipyridyl Derivative Ligand

The self-assembly of a flexible bipyridyl ligand 2,2?-bis(4-pyridylmethyle- neoxy)-1,1?-biphenylene (4,4?-bpp) with cobalt(II) center gave rise to a one-dimensional chain complex [Co(μ-4,4?-bpp)2(SCN)2?H2O]n 1 which has been characterized by single-crystal X-ray diffraction. The polymer crystallizes in monoclinic, space group C2/c with unit cell parameters: a = 13.1888(13), b = 24.230(2), c = 15.4218(17) ?, β = 93.291(6)o, V = 4920.1(8) ?3, Z = 4, C50H42CoN6O5S2, Mr = 929.95, Dc = 1.255 g/cm3, F(000) = 1932 and μ(MoKα) = 0.484 mm-1. The final R and wR are 0.0691 and 0.1670 for 3746 observed reflections with I > 2σ(I). 1 possesses an infinite 1-D polymeric chain structure consisting of the repeated basic square units Co2(μ-4,4?-bpp)2, where the Co(II) center acts as the joint of the square ring. The Co(II) center is coordinated in a slightly distorted octahedral geometry with four nitrogen atoms from four different 4,4?-bpp ligands in the equatorial plane and two trans thiocyanate ligands occupying the axial positions, preventing the formation of an extended framework.

Hydrothermal Synthesis, Crystal Structure and Thermal Analyses of Pyrazine-2,3-dicarboxylic Acid Bridged Co(II) Coordination Polymer of _∞~2[Co(phen)(μ-L)_(3/3)]·H_2O (H_2L = Pyrazine-2,3-dicarboxylic Acid)

A novel pyrazine-2,3-dicarboxylic acid bridged Co(II) phen complex 2 ∞ [Co- (phen)(μ-L)3/3]?H2O (H2L = pyrazine-2,3-dicarboxylic acid) has been hydrothermally synthesized, and X-ray single-crystal diffraction analysis shows that it crystallizes in the monoclinic system, space group P21/n with a = 11.480(2), b = 11.885(2), c = 12.939(3) ?, β = 110.55(3)°, V = 1653.1(6) ?3, Mr = 423.25, Dc = 0.425 g/cm3, Z = 4, R = 0.0361 and wR = 0.1011. The title complex consists of 2D 2 ∞ [Co(phen)(μ-L)3/3] layers and crystal water molecules. Each Co atom is octahedrally coordinated by three N atoms and three O atoms to form 2D 2 ∞ [Co(phen)(μ-L)3/3] polymeric layers. Furthermore, such 2D layers are stacked into 3D supramolecular frameworks via Van der Waals’ intermolecular forces, strong and weak hydrogen-bond interactions. The coordination phen and crystal water molecules are resided into cavities of the frameworks.

Different Effects of Malate on the Activities of Photosystem II in Detached Leaves of Maize and Tobacco

Malate is the first stable product after CO2 is fixed in NADP-dependent malic enzyme (NADP-ME) type of C4 plants, which transfers CO2 and the reducing equivalent from mesophyll cell (MC) to vascular bundle sheath cell (BSC) chloroplasts and affects the redox state of BSC. The aim of this experiment is to investigate the effect of exogenous malate on the activity of photosystem II (PS II) in C4 and C3 plants. The leaf discs from the 5th fully expanded leaves of maize (NADP-ME type C4 plants) and the 10th fully expanded leaves of tobacco (C3 plants) were treated with malate of 50, 100 μM and the chlorophyll fluorescence parameters were measured. Malate treatments decreased the photochemical reaction efficiency (FV/FM) in maize leaves, as a result of rising in initial fluorescence (FO) and decreasing in maximal fluorescence (FM). The number of active PS II reaction center (RC) per excited cross section (RC/CS) declined in malate-treated maize, suggesting that malate inactivated PS II RC. Malate treatments also increased Wk, representing the severity of oxygen-evolving complex (OEC) damage, and decreased the rate of photosynthetic oxygen evolution. We conclude that exogenous malate regulates the activity and structure of PS II in C4 plant maize. No significant changes in the activity of PS II were observed in malate-treated C3 plant tobacco. It is suggested that the short term malate treatment will inhibit PS II of leaves which have C4 anatomy and C4 enzymes.

Effects of drought treatment on photosystemⅡactivity in the ephemeral plant Erodium oxyrhinchum

Drought is a critical limiting factor affecting the growth and development of plants in arid and semi-arid areas.Photosynthesis,one of the most important physiological processes of plants,can be significantly inhibited by drought.PhotosystemⅡ(PSⅡ)is considered the main attack target when photosynthesis is affected by drought.To clarify how PSⅡcomponents of the ephemeral plant Erodium oxyrhinchum(grown in the Gurbantunggut Desert,China)respond to drought treatment,we evaluated the functional activity of PSII by determining chlorophyll fluorescence and gas exchange parameters under different drought treatment levels(control(400 mL),moderate drought(200 mL),and severe drought(100 m L)).Under moderate drought treatment,significant decreases were found in net photosynthetic rate(Pn),effective quantum yield of PSII(Y(Ⅱ)),relative electron transfer rate of PSII(rETR(Ⅱ)),oxygen-releasing complex,probability of an absorbed exciton moving an electron into the electron transport chain beyond primary quinone receptor Q_(A)-(Φ(E_(o))),probability of a trapped exciton moving an electron into the electron transport chain beyond primary quinone receptor Q_(A)-(ψ(E_(o))),and performance index of PSⅡ(PI_(abs)).Compared to control treatment,marked increases were observed in water use efficiency(WUE),relative variable fluorescence at the J step(V_(J)),initial fluorescence(F_(o)),and dissipated energy per active reaction center(DI_(o)/RC)under moderate drought treatment,but there were no substantial changes in semi-saturated light intensity(I_(K)),active reaction centers per cross-section(RC/CS),and total performance index of PSII and PSI(PI_(total),where PSI is the photosystemⅠ).The changes of the above parameters under severe drought treatment were more significant than those under moderate drought treatment.In addition,severe drought treatment significantly increased the absorbed energy per active reaction center(ABS/RC)and trapping energy per active reaction center(TR_(o)/RC)but decreased the energy transmission connectivity of PSⅡcomponents,RC/CS,and PI_(total),compared to moderate drought and control treatments.Principle component analysis(PCA)revealed similar information according to the grouping of parameters.Moderate drought treatment was obviously characterized by RC/CS parameter,and the values of F_(o),V_(J),ABS/RC,DI_(o)/RC,and TR_(o)/RC showed specific reactions to severe drought treatment.These results demonstrated that moderate drought treatment reduced the photochemical activity of PSII to a certain extent but E.oxyrhinchum still showed strong adaptation against drought treatment,while severe drought treatment seriously damaged the structure of PSⅡ.The results of this study are useful for further understanding the adaptations of ephemeral plants to different water conditions and can provide a reference for the selection of relevant parameters for photosynthesis measurements of large samples in the field.

Blue light is more essential than red light for maintaining the activities of photosystem Ⅱ and Ⅰ and photosynthetic electron transport capacity in cucumber leaves

Blue and red lights differently regulate leaf photosynthesis. Previous studies indicated that plants under blue light generally exhibit better photosynthetic characteristics than those under red light. However, the regulation mechanism of related photosynthesis characteristics remains largely unclear. Here, four light qualities treatments （300 μmol m-2 s-1） including white fluorescent light （FL）, blue monochromatic light （B, 440 nm）, red monochromatic light （R, 660 nm）, and a combination of red and blue light （RB, R：B=8：1） were carried out to investigate their effects on the activity of photosystem II （PSII） and photosystem I （PSI）, and photosynthetic electron transport capacity in the leaves of cucumber （Cucumis sativus L.） seedlings. The results showed that compared to the FL treatment, the R treatment significantly limited electron transport rate in PSII （ETR11） and in PSI （ETR1） by 79.4 and 66.3%, respectively, increased non-light induced non-photochemical quenching in PSII （q^No） and limitation of donor side in PSI （φND） and reduced most JIP-test parameters, suggesting that the R treatment induced suboptimal activity of photosystems and inhibited electron transport from PSII donor side up to PSI. However, these suppressions were effectively alleviated by blue light addition （RB）. Compared with the R treatment, the RB treatment significantly increased ETR, and ETR1 by 176.9 and 127.0%, respectively, promoted photosystems activity and enhanced linear electron transport by elevating electron transport from QA to PSI. The B treatment plants exhibited normal photosystems activity and photosynthetic electron transport capacity similar to that of the FL treatment. It was concluded that blue light is more essential than red light for normal photosynthesis by mediating photosystems activity and photosynthetic electron transport capacity.

EXCITATION ENERGY TRANSFER IN VITRO BETWEEN PHYCOBILIPROTEINS AND THYLAKOID PHOTOSYSTEM Ⅱ OF HIGHER PLANTS

The excitation energy transfer from phycobiliproteins to thylakoid PSII of higher plants was investigated. When incubated with spinach thylakoids, phycobiliproteins isolated from red and blue- green algae transferred light energy absorbed to spinach PSII. The efficiency of energy transfer was dependent on the kind of phycobiliproteins used. If spinach thylakoids were replaced by the thylakoids of Brassica chinensis, R phycoerythin or C- phycocyanin did not transfer their excitation energy to PSII of Brassica chinensis unless allophycocyanin was present.

A Novel 3D Cd(II) Coordination Polymer with an Unusual 3-Connected(8~2·10) Lig Net: Synthesis, Crystal Structure and Luminescent Properties

A new 3D Cd(II) coordination polymer, [Cd(Hpidc)]n(1, H3 pidc = 2-(pyrid-2-yl)-1H-imidazole-4,5-dicarboxy acid), has been prepared and characterized by elemental analysis, IR spectra, PXRD, and single-crystal X-ray diffraction. Compound 1 crystallizes in orthorhombic, space group Fdd2 with a = 22.833(9), b = 25.536(9), c = 7.437(3) A, V = 4336(3) A3, Z = 16, Dc = 2.105 Mg·m-3, μ = 2.025 mm-1, F(000) = 2656, and the final R = 0.0261 and w R = 0.0636. The structure determination reveals that 1 exhibits a rare 3D 3-connected lig net with a point symbol of(82·10). In addition, the solid state properties such as thermogravimetric analysis and luminescence of 1 were also studied.

Solvothermal Synthesis and Crystal Structure of a 1D Helical-chain Cobalt(II) Complex Containing (Quinolin-8-yloxy)acetate

The cobalt（II） complex with （quinolin-8-yloxy）acetate, [CoCl（C11H8NO3）]n （1）, has been prepared via the solvothermal method and characterized by IR, elemental analysis, UV- Vis diffuse-reflection spectra and single-crystal X-ray diffraction analysis. Complex 1 is a novel carboxylate-bridged one-dimensional helical cobalt（II） polymer, and the Co（II） centre exhibits an approximately square pyramidal CoClNO3 coordination geometry. It crystallizes in monoclinic, space group P21/n, with a = 9.1594（10）, b = 6.8864（7）, c = 17.290（2） , β = 102.629（3）o, C11H8ClCoNO3, Mr = 296.56, V = 1064.2（2） 3, Z = 4, Dc = 1.851 g/cm3, F（000） = 596, μ = 1.856 mm-1, the final R = 0.0308 and wR = 0.0807. Interestingly, the chain complexes are assembled to form two-dimensional networks through intermolecular face-to-face π-π stacking interactions with the centroid-to-centroid distance of 3.559（1） and the dihedral angle of 8.4（1）° between the aromatic rings.

Hydrothermal Synthesis and Crystal Structure of One 3D Coordination Polymer of Nickel(Ⅱ) Achieved from 5-Iodo-isophthalic Acid Ligand

A new coordination polymer [Ni（L）（m-bix）（H2O）]n （1, H2L = 5-iodo-isophthalic acid, m-bix=1,3-bis（imidazol-1-ylmethyl）-benzene） has been synthesized by the hydrothermal method and characterized by IR, elemental analysis, powder XRD and single-crystal X-ray analysis. The crystal is of triclinic, space group Pī with a = 9.1638（3）, b = 10.2319（3）, c = 13.2463（4） ？, α = 80.1710（10）, β = 83.671（2）, γ = 70.3790（10）o,C22H19NiIN4O5, Mr = 605.02, V = 1150.85（6） ？3, Dc = 1.746 g/cm3, F（000） = 600, μ = 2.225 mm-1, S = 1.045 and Z = 2. The final R = 0.0388 and wR = 0.1257 for 5089 observed reflections with I 〉 2σ（I）. In the title complex, the M and P layers are arranged alternately to give a double-layer structure by the symmetry related hydrogen bonds, and these double-layers are further joined together to achieve a 2D supramolecular architecture through I···π interaction involving iodine atoms and imidazole rings. The thermal stability of the title complex was studied by thermal gravimetric （TG） and differential thermal analysis （DTA）.

Synthesis and Crystal Structure of a 1D Coordination Polymer:{[Cu(HSSA)(py)_3]·H_2O}_n (H_3SSA =5-Sulfosalicylic Acid,py = Pyridine)

The title compound [Cu（HSSA）（py）3H2O]n （H3SSA = 5-sulfosalicylic acid, py = pyridine） I has been synthesized and structurally determined by single-crystal X-ray diffraction. I was further characterized by elemental analyses, thermogravimetric analyses, IR and UV-visible spectroscopy. The crystal belongs to the monoclinic system, space group P21/c with a = 9.4564（10）, b = 18.2679（19）, c = 15.7284（12） A,β= 126.045（4）°, V= 2196.9（4）A^3, Z= 4, Dc = 1.618 g/cm^3, Mr = 535.02,μ = 1.141 mm^-1, F（000） = 1100, 2（MoKα） = 0.71073 A, the final R = 0.0429 and wR = 0.1044 for all observed reflections. In the structure, every two Cu（II） atoms are bridged by a bivalent 5-sulfosalicylic anion to form a 1D chain-like coordination polymer. Lattice waters between chains link them to form 2D layers which are further linked by C-H…O hydrogen bonds to form a three-dimensional supramolecular network.

Crystal Structure and Thermal Stability Properties of a New 1D Chain Cu(Ⅱ)Coordination Polymer with2,3-Pyridinedicarboxylic Acid as the Ligand

A new 1D chain copper coordination polymer [CuE（H2L）2（C10HsN2）（HEO）2]n＇3n（H20） with 2,3-pyridinedi carboxylic acid （H2L） and 2,2＇-bipyridine （2,2＇-bipy） as ligands has been synthesized in the mixed ethanol and water solvents. Crystal data for this complex are as follows： monoclinic, space group P2Jc, a = 7.7713（7）, b = 27.478（3）, c = 13.2621（13）/1,, fl = 100.6940（10）, V= 2782.8（5） A3, Dc = 1.722 g/cm3, Z = 4, p = 1.61 mm-1, F（000） = 1472, the final R = 0.0363 and wR = 0.0933. In the crystal structure, the whole molecule consists of two cooper ions, two H2L, one 2,2＂-bipy molecule and six water molecules. Each central copper ion is coordinated with three oxygen atoms from two H2L and one water molecule, two nitrogen atoms from one 2,2＇-bipy molecule and two H2L, giving a distorted tetragonal pyramidal geometry. Thermal stability properties of the complex were investigated.

Hydrothermal Synthesis and Crystal Structure of a New 2D Zinc(Ⅱ) Coordination Polymer with 2-Aminoethanesulfonic Acid

A new 2D Zn（Ⅱ） coordination polymer [Zn（TAU）2]n （1, HTAU=2-aminoethane- sulfonic acid） constructed by 2-aminoethanesulfonic acid ligand has been hydrothermally synthesized by the reaction of Zn（CH3COO）2 and 2-aminoethanesulfonic acid with a 1：2 mole ratio and characterized by single-crystal X-ray diffraction, elemental analysis, infrared spectroscopy and thermogravimetric analysis. Crystal structural analysis reveals it crystallizes in monoclinic, space group P21/c with a=8.672（4）, b=6.523（3）, c=9.134（5） , β=115.441（5）°, V=466.6（4） 3, Mr=313.65, Z=2, Dc=2.232 Mg·m-3, F（000） =320, μ（MoKα）=3.091 mm-1, the final R=0.0358 and wR=0.0919 for 2026 observed reflections with Ⅰ 〉 2σ（Ⅰ）. In the structure, each zinc（Ⅱ） ion is coordinated in a slightly distorted octahedron, and each μ3-TAU– acts as a bridge to bond three neighboring Zn（Ⅱ） ions to form an infinite 2D network structure.

Synthesis and Crystal Structure of a Three-dimensional Mn(Ⅱ) Coordination Polymer with 3-(Pyrazin-2-yloxy)-pyridine and Azide Anion as Mixed Bridge Ligand

A three-dimensional coordination polymer [Mn2（μ1.3-N3）4（μ-PP）2]n （PP = 3-（pyrazin-2-yloxy）-pyridine） has been synthesized with 3-（pyrazin-2-yloxy）-pyridine and azide anion as mixed bridge ligand, and its crystal structure was determined by X-ray crystallography. The crystal data： triclinic system, space group P1, with a = 6.794（4）, b = 9.885（6）, c = 9.947（6） A, α = 64.170（6）, β= 84.190（8）, γ= 85.319（8）°, V = 597.7（6）A^3, Z = 1, C18H14Mn2N18O2, Mr = 624.35, Dc = 1.735 g/cm^3, F（000） = 314 and μ = 1.117 mm^-1. In the crystal, the azide anion acts as a bridge ligand and makes adjacent Mn（Ⅱ） ions connect into a two-dimensional sheet on the ab plane, then 3-（pyrazin-2-yloxy）-pyridine serves as a bidentate bridge ligand to connect neighboring sheets along

Synthesis and Crystal Structure of a Three-dimensional Cobalt Coordination Polymer Assembled by Ozagrel Ligands

A three-dimensional cobalt coordination polymer [Co（IMPAA）2]n（1, HIMPAA =（2E）-3-[4-（1H-imidazol-1-ylmethyl）phenyl]acrylic acid） was synthesized with ozagrel and structurally characterized by element analysis, IR, PXRD, TGA and X-ray diffraction. Complex 1 is of monoclinic system, space group P21 with a = 5.136（4）, b = 25.577（19）, c = 8.174（6） A, V = 1078.6（14） A3, Mr = 513.41, Z = 2, Dc = 1.581 g/cm3, F（000） = 686, μ = 0.840 mm-1, S = 1.119, Rint = 0.0637 and w R = 0.1456. In complex 1, four IMPAA- and four Co（II） ions form a S-shaped 52-membered macrocycle [Co4（IMPAA）4]4＋. Two carboxlate oxygen atoms link the macrocycles to form a one-dimensional chain. IMPAA- ligands bridge one-dimensional chains to yield a novel three-dimensional metal-organic framework（MOFs）. The complex is stable up to 350 ℃.

Optimum Dark Adaptation Period for Evaluating the Maximum Quantum Efficiency of Photosystem II in Ozone-Exposed Rice Leaves

Because the transient O3 injury of leaves is lost with time, the evaluation of O3 effect on the maximum quantum efficiency of PSII (Fv/Fm) is difficult. Thus, the authors examined Fv/Fm in rice leaves exposed to different O3 concentrations (0, 0.1, and 0.3 cm3·m-3, expressed as O0, O0.1, and O0.3) under different dark adaptation periods (0, 1, 5, 10, 20, and 30 min, expressed as D0, D1, D5, D10, D20, and D30) to ascertain its optimum time span. Fv/Fm was inhibited by O3;however in the O0 and O0.1 plants, it recovered during dark adaptation. In the O0.3 plants, Fv/Fm decreased gradually with time. F0 was found to be increased by O3, and it increased further in the O0.3 plants during dark adaptation. Under a high light intensity, Fm was decreased by O3, and the O3-induced damage to Fv/Fm was therefore more pronounced. However, the sensitivity of

Effects of Direction of Bridging of Thiocyanato on the Dimension of Coordination Polymers: Synthesis, Characterization and Single-crystal X-ray Structure Determination of [Cd(4,4'-dm-2,2'-bpy)(NCS)_2]_n and [Cd(4,4'-dmo-2,2'-bpy)(NCS)_2]_n Coordination Pol

Two new cadmium（II）-thiocyanato coordination polymers with 4,4＇-dimethyl-2,2＇-bipyridine（4,4＇-dm-2,2＇-bpy） and 4,4＇-dimethoxy-2,2＇-bipyridine（4,4＇-dmo-2,2＇-bpy） as chelating ligands were synthesized and characterized by elemental analysis, IR and 1H NMR spectroscopy and X-ray crystallography. Thermal properties were also studied as well. These complexes have formed as [Cd（4,4＇-dm-2,2＇-bpy）（NCS）2]n（1） and [Cd（4,4＇-dmo-2,2＇-bpy）（NCS）2]n（2）. The coordination numbers of CdII in 1 and 2 are six（Cd N4S2）. Direction of bridging of thiocyanato anions in 1 and 2 created one- and two-dimensional coordination polymers, respectively. The supramolecular features in these complexes were guided and controlled by weak directional intermolecular interactions.

Preparation, Crystal Structure and Thermal Behaviour of a One-dimensional Coordination Polymer [Mn(m-CPOAH)_2(H_2O)_2]_n

The coordination polymer of [Mn(m-CPOAH)2(H2O)2]n (m-CPOAH– = 3-carboxyl- phenoxyacetate) has been synthesized and characterized by elemental analyses, IR, TG and single- crystal X-ray diffraction. The title complex crystallizes in the triclinic system, space group P1 with a = 4.7013(9), b = 5.6822(11), c = 17.758(4) ?, α = 87.39(3), β = 85.39(3), γ = 85.76(3)o, V = 471.18(17) ?3, Z = 1, Mr = 481.26, Dc = 1.696 g/cm3, μ = 0.770 mm-1, F(000) = 247, R = 0.0385 and wR = 0.1015. The Mn(II) atom assumes a distorted octahedral geometry, involving four carboxyl oxygen atoms from different m-CPOAH– ligands and two coordinated water molecules. The Mn(II) atoms are linked by the m-CPOAH– ligand to form a one-dimensional chain structure along the a axis. The shortest Mn…Mn separation within the polymer is 7.401(4) ?. A three- dimensional supramolecular network is constructed by O–H…O hydrogen bonding interactions.

Effects of Severe Drought and Glyphosate Stress on Physiological Characteristics and Protein Expression of Photosystem Ⅱ in Genentically Modified Soybean

[Objective] The paper was to investigate effects of glyphosate stress on physiological characteristics and protein expression of photosystem Ⅱ(PSⅡ) in genentically modified soybean GTS 40-3-2 seedlings under severe drought condition. [Method] A pot experiment was carried out in growth chamber to determine the response of genetically modified soybean treated by severe drought stress and different concentrations of glyphosate at the third compound leaf stage. [Result] Severe drought treatment increased the electrolyte leakage(EL), superoxide dismutase(SOD) and peroxidase(POD) activities, and decreased the relative water content(RWC), chlorophyll content, and catalase(CAT) activity. The EL, SOD and POD activities were significantly increased in severe drought and glyphosate treatments, which were related to glyphosate concentrations. The chlorophyll content decreased, which was also related to glyphosate concentrations. But the BWC and CAT activity were not affected by glyphosate concentrations. Western blot displayed that PSⅡ protein Lhcb2 was not affected by stress conditions and stably expressed. D1, D2 and Lhcb4 protein level decreased, and there was no significant change in Lhcb1 expression under severe drought stress. The protein levels of D1, D2, Lhcb1 and Lhcb4 decreased with the increase of glyphosate concentrations under severe drought and glyphosate stress. When the glyphosate concentrations were 0.92 and 1.84 kg·ai/hm^2, the protein levels of D1, D2 and Lhcb4 were slightly higher than those in severe drought stress. When the glyphosate concentrations were 3.68 and 7.36 kg·ai/hm^2, the protein level of D1, D2, Lhcb1 and Lhcb4 decreased sharply. [Conclusion] This research provides a theoretical basis for production of genetically modified soybean.

Identification and Quantification of Intracoordination Water in Insoluble Pectinates Cu²⁺and Pb²⁺

By derivatography in insoluble pectins Cu2+ (РCu2+) and Pb2+ (РPb2+), the presence of “a high-temperature component” (150°C- 165°C) is established. During potentiometric alkalimetric titration of РCu2+ and РPb2+, endpoints are established at рН accordingly 4.87 and 4.95, proving acid properties of PM. Obtained data show the presence of water in the internal sphere of PM. Considering the loss of this water and the known ratio of metal cations and monomers of pectin (L-), the simplest formulas of pectins are established: [Cu(L-)2(H2O)2], [Pb(L-)2(H2O)4].

Comparative Analysis of Photosynthetic Activity and PSII Protein Profiles of Some Plants Grown under Enhanced Solar UV-B Radiation

The deleterious effects of ultraviolet B(UV-B)radiation on photosynthesis and photosynthetic proteins of tropical and temperate plants have been studied.Like tropical plants(black gram and green gram),the temperate plants(carrot and radish)also successfully grown in the tropical region.They were exposed to enhanced UV-B radiation under field condition.Comparative studies show that under enhanced UV-B radiation photosynthetic activity was increased in black gram.In green gram and radish the UV-B radiation slightly enhanced the photosynthetic activity,but it inhibited the photosynthetic activity in carrot.The comparative results showed changes in contents of thylakoid 55,47,43,33,29,27-25,23 and 17 kDa polypeptides that were significantly lowered in UV-B treated carrot plant when compared to other plants.The PSII protein profile results showed a strong correlation between the presence of a membrane polypeptide and photosynthetic activity.In black gram and green gram the UV-B radiation did not produce any significant difference in the PSII polypeptides.As in the case of radish the UV-B radiation increased the accumulation of 33-28 kDa protein and affected expression of the 63 kDa protein.In the case of carrot,severe degradation of 32 kDa and 33 kDa,corresponding to D1 and D2 core proteins of PSII,was observed.It could be concluded that the ability of plants to tolerate increased levels of UV-B radiation,relative to photosynthetic capacity,depends on acclimation processes of the plant in the growing region.