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The effects of red/blue=3/1 [R/B=3/1(9/3), as control, CK本试验采用发光二极管(LED)精准调控光源环境,以‘改良大龙茄’为试材,在前期探明红/蓝组合光(R/B)=3/1有利于培育茄子壮苗基础上,以R/B=3/1(9/3,CK

To get optimal nitrogen (N), phosphorus (P本试验采用三因子二次饱和D-最优设计(310),以蛭石为栽培介质,建立了以氮、磷、钾浓度为变量因子,茄子产量和品质为目标函数的三元二次数学模型,以期得到茄子优质高产最优氮磷钾浓度范围.对模型解析结果表明: 氮、磷、钾浓度对茄子产量和品质均有显著影响.对产量和品质的影响程度均以钾浓度较大,对产量的影响程度以氮浓度次之,磷浓度较小,对品质则为磷浓度次之,氮浓度较小.氮磷、氮钾、磷钾浓度交互对茄子产量均有显著影响;氮钾浓度交互对茄子品质亦有显著影响.在低水平条件下,茄子产量和品质均随氮、磷、钾浓度增加而增加,但超过一定范围后,茄子产量和品质均随之降低.通过计算机模拟运算得出,本试验条件下茄子单株产量达3600 g的施肥方案为:氮16.0～20.0 mmol·L

The solution culture method was used to study the effects of sodium nitroprusside (SNP) on plant growth, nutrient uptake and antioxidant enzyme activities of tomato seedlings under iron deficiency and NO采用营养液培养方法,研究外源NO供体(硝普钠,SNP)对缺铁和硝酸盐胁迫番茄幼苗生长、养分吸收及抗氧化酶活性的影响.结果表明: 处理7 d后,缺铁使番茄幼苗生长受到抑制,叶绿素a、b、类萝卜素含量显著降低,出现明显失绿症状;降低叶片中超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)的活性,电解质渗漏率、丙二醛含量明显增加,脯氨酸和可溶性糖含量变化不显著,幼苗叶片和根中N、P、K、Ca、Mg、Fe含量比对照处理有不同程度的减少.硝酸盐和缺铁双重胁迫对番茄幼苗生长抑制加剧,叶绿素a、b、类萝卜素含量、SOD、POD和CAT活性显著降低,电解质渗漏率、脯氨酸、可溶性糖和丙二醛含量明显增加;番茄幼苗叶片和根中N、P、Mg、Fe含量显著减少,而K、Ca含量显著增加. 与不添加处理相比,添加0.1 mmol·L

'Jinyan No. 4'cucumber was used as experimental material. The growth of cucumber radicles treated with different concentrations of p-hydroxybenzoic acid (0, 2.5, 5, 7.5, 10, 12.5, 15, 17.5 and 20 mmol·L以‘津研四号’黄瓜为试材,分别用0、2.5、5、7.5、10、12.5、15、17.5、20 mmol·L

To investigate the effect of calcium and ABA on photosynthesis and the activities of antioxidant enzymes in cucumber seedlings under drought stress, the cucumber was used as the expe-riment materials, normal nutrient solution culture was considered as the control, and PEG-6000 application in the nutrient solution simulated the drought stress. There were five different treatments which were spraying water, ABA, CaCl为探讨在干旱胁迫下钙与脱落酸对黄瓜幼苗光合作用及相关酶活性的影响,以黄瓜为试材,正常营养液栽培为对照,利用PEG-6000(聚乙二醇)营养液添加模拟干旱胁迫,设干旱胁迫条件下幼苗叶片喷施清水、脱落酸(ABA)、CaCl

The effects of white light, red light, blue light, yellow light, red+blue light and red+blue+yellow light on the growth and quality of Gynura bicolor were investigated under the same light intensity (350±5 μmol·m以紫背天葵为供试材料,采用LED灯精量调控光质和光强,研究相同光照强度(350±5 μmol·m

The effects of red light, blue light, red+blue light and white light (control) generated by LED on the quality and antioxidation capacity of fruit and yield of ' Brita' eggplants were stu died. The results showed that under blue LED, the soluble protein, free amino acids contents o eggplant pulps and the anthocyanin content of eggplant peels were significantly higher by 15.1%, 27.2% and 73.6% than control respectively, but flavonoid and phenolic contents of pulps and the yield were significantly lower than those of the other treatments. Under red LED, the eggplant peels flavonoid was remarkably increased, but vitamin C (Vc) and soluble protein contents were consi derably decreased. Under red+blue LED, the soluble sugar of pulps and phenolic, red pigment yellow pigment contents, total antioxidation capacity (TAG) of peels and the yield were significantly higher than those of the other treatments, in which, the TAC of peels and the yield increased by 43.5% and 43.4% compared with control, respectively. Vc, flavonoid and phenolic contents and TAC of eggplant pulps were the highest under white LED. There was significant positive correlation between the phenol content of peels and Vc content of pulps with TAC. Under the protected cultivation condition, an appropriate amount of blue or red LED could improve the quality of eggplant fruit, and red+blue LED was more beneficial to promote the quality of eggplant peels and the yield.

The control effects of Eupolyphaga (Eupolyphaga sinensis Walker) frass and its extracts on Meloidogyne incognita were studied through laboratory assays and pot experiments, and the organic volatile compounds and oligochitosan contents in the frass were analyzed. The results indicated that the nematode immobility and mortality was significantly increased with increasing the extract concentration and treatment time. Compared with the control, egg hatching was significantly inhibited when the extract concentration was beyond 20%. Pot experiment indicated that root galling of tomato seedlings was reduced and the relative control effect was significantly improved with the increasing frass application. Meanwhile, plant height, stem diameter and leaf number of tomato increased with the increasing dosage of eupolyphaga frass. The ingredients analysis showed that the content of oligochitosan was about 4.35% and there were 9 categories and 110 kinds of volatile compounds in the frass.

In order to explore the effects of NO3- stress on photosynthetic characteristics and nitrogen metabolism, strawberry seedlings were grown in sand culture condition under different concentrations of NO3- (64, 112 and 160 mmol · L(-1)) with the control of 16 mmol NO3- · L(-1). The results indicated that at the 8th day after treatment, with the increased NO3- concentration, the strawberry leaf net photosynthetic rate (Pn), stomatal conductance (g(s)), PS II actual photochemical efficiency (ΦPS II), PS II maximum photochemical efficiency (Fv/Fm), and photochemical quenching coefficient (q(P)) significantly decreased, and decreased by 67.7%, 68.4%, 35.7%, 23.2% and 26.9%, respectively, when NO3- concentration reached 160 mmol · L(-1) compared with the control. The non-photochemical quenching coefficient (q(N)) increased by 4.4%, 10.9% and 75.8% respectively in the treatments of 64, 112 and 160 mmol NO3- · L(-1) compared with the control. The intercellular CO2 concentration (Ci) decreased under low NO3- concentration stress and then increased under high NO3- concentration stress, while the stomatal limitation (Ls) was vice versa. With the increased NO3- concentration, the nitrate nitrogen, ammonia nitrogen, total nitrogen and Kjeldahl nitrogen contents in the strawberry leaves and roots increased, but the protein nitrogen content decreased. The activities of nitrate reductase (NR) , glutamine sybthetase (GS), glutamate synthase (GOGAT) and glutamate dehydrogenase (GDH) increased at low NO3- concentration and then decreased at high NO3 concentration. Consequently, the net photosynthetic rate of strawberry seedling leaves decreased, the PS II electron transfer was blocked, the nitrogen accumulated with the increasing NO3- concentration, and the nitrogen metabolism enzyme activity decreased at high NO3- concentrations. When the NO3- concentration reached 64 mmol · L(-1) or higher in the nutrient solution, the growth of strawberry seedlings were inhibited significantly.

The effects of NO3- stress on the growth and the magnesium absorption of cucumber seedlings were investigated after 1 and 14 d of suboptimal temperature [18 °C/12 °C (day/night)] treatment. The results indicated that the growth, net photosynthetic rate, transpiration rate, Fv/Fm and ΦPSII of cucumber seedlings were significantly inhibited by NO3- stress under suboptimal temperature. The magnesium content of cucumber seedlings was also significantly decreased compared with control treatment, especially in the IV treatment (suboptimal temperature +140 mmol · L(-1) NO3- + 1 mmol · L(-1) Mg2+), and the antagonistic impact of magnesium ion absorption on the absorption of potassium and calcium ion was observed. The magnesium deficiency symptom of cucumber seedlings could be partly alleviated by increasing the concentration of magnesium ion in the nutrient solution.

Cucumber cultivar 'Jinyan 4' was subjected to suboptimal temperature treatment of 18/12 degrees C (day/night) in the growth chambers. A solution culture experiment was conducted to study the effect of exogenously spraying 5 mg x L(-1) chlorophyllin-iron solution on plant growth, the content of proline, soluble sugar, MDA and activity of peroxidase in the leaves of cucumber seedling under suboptimal temperature. Application of chlorophyllin-iron showed prominent effects on mitigating the stress of suboptimal temperature on growth of the cucumber seedlings, significantly increasing the plant height, leaf area, shoot dry mass, the contents of soluble sugar and proline and the activities of SOD, POD, CAT and APX. Exogenously spraying chlorophyllin-iron could promote the accumulation of proline and soluble sugar, raise the activities of antioxidant enzymes, decrease the membrane lipid peroxidation and improve the adaptability of cucumber seedlings under suboptimal temperature.

The effects of spraying exogenous silicon (Si) (0, 1, 2, 3, 4 and 5 mmol L(-1)) on the growth, photosynthetic characteristics and activity of antioxidant enzymes in continuous-cropped 'Jinyan No. 4' cucumber seedlings were studied. The results showed that with the application of 1-3 mmol x L(-1) Si, electrolyte leakage (EL) and malondialdehyde (MDA) content in leaves were significantly decreased, while the contents of chlorophyll a (Chl a), chlorophyll b (Chl b), carotenoids (Car), chlorophyll (a+b) and photosynthetic rate (Pn) in leaves were significantly improved, the activities of superoxidase (SOD), peroxidase (POD), catalase (CAT) and ascorbic acid peroxidase (APX) were significantly increased, and the plant height, stem diameter and dry mass accumulation of cucumber seedlings were promoted. Compared with the low Si concentrations, excessive Si (4-5 mmol x L(-1)) resulted in higher EL and MDA, which were still lower than that in control, decreased the antioxidant enzymes activity and photosynthesis, and inhibited the growth of cucumber seedlings. These findings indicated that exogenous Si could enhance the capacity of scavenging active oxygen species and improve photosynthesis, protect cucumber seedlings from the lipid peroxidation, and increase the resistance to continuous-cropped cucumber obstacle. The optimal silicon concentration was 2 mmol x L(-1).

The effects of different NO3- concentrations (CK, 16 mmol x L(-1) NO3-; T1, 48 mmol x L(-1) NO3-; T2, 96 mmol x L(-1) NO3-; T3, 144 mmol x L(-1) NO3-) on the growth properties and antioxidant enzymes activities of strawberry seedlings were studied by sand culture. The results indicated that the plant height, leaf area, dry matter accumulation and root/shoot ratio of strawberry seedlings in T1, T2 and T3 were significantly decreased compared to the control (CK) after 15 days of treatment. The plant heights in T1, T2 and T3 decreased by 16.1%, 36.8% and 43.9%, and the areas of functional leaf decreased by 19.7%, 34.3% and 47.5% respectively, compared to the control. With the increasing NO3- concentration, the malondialdehyde (MDA), proline, soluble protein content and relative electronic leakage of the strawberry seedlings first increased and then decreased, but all those parameters in T1, T2 and T3 were higher than in the control. The activities of antioxidant enzymes, superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX) in both root and leaf, and catalase (CAT) in the root first increased and then decreased, but the CAT activity in the leaf gradually decreased with the increasing NO3 concentration. In T3, the activity of SOD in both root and leaf, APX in the root were lower than in the control. In sum, the osmolytes of strawberry seedlings increased and the plants become weaker under nitrate stress, and some antioxidant enzymes in strawberry seedlings increased at the low level of nitrate stress and decreased at the high level. The strawberry plants were stunted when growing under 48 mmol x L(-1) NO(3-) condition.

From December 2011 to March 2012, a consecutive test was conducted on the temperature and heat flux of different thickness of the soil backwall of sunken solar greenhouse in Shouguang of Shandong Province, East China, aimed to analyze the variation patterns of soil wall temperature and heat flux of the sunken solar greenhouse and to confirm the suitable wall thickness. In winter, the temperature and heat flux of the wall inner surface and outer surface varied over a wide range, which was in accordance with the variation trend of indoor and outdoor air temperature. Overall, the wall temperature decreased from the inner to the outer surface, and the layers of the inner wall with higher variation range of temperature and heat flux were more than those of the outer wall. The variation range of temperature and heat flux decreased gradually from the shallow layers to deep layers of the wall. In successive cloudy days, the temperature of each layer of inner wall decreased to different degrees, and the layers releasing heat to the indoor deepened constantly, whereas the heat in the layers of outer wall was mainly released to the outdoor. According to the variation patterns of temperature and heat flux in the wall, the wall from inside to outside could be divided into heat storage layer, transitional layer, and cold resistant layer, and their thickness was 0.8-1.0 m, 2.2-2.6 m, and 0.4-0.6 m, respectively, under the condition of the outer surface being covered. Without considering the transitional layer, the suitable thickness of the soil wall in Shouguang solar greenhouse would be 1.4-1.6 m.

By using solution culture method, this paper studied the effects of exogenous nitric oxide (NO) on the antioxidants and antioxidases in the ascorbate-glutathione (AsA-GSH) cycle in tomato (Lycopersicon esculentum Mill. ) seedling roots under copper stress.Exogenous NO could affect the metabolic cycle of AsA-GSH in tomato roots under copper stress. Applying appropriate amount of exogenous NO increased the AsA and GSH contents, AsA/DHA and GSH/GSSG ratios, and decreased the DHA and GSSG contents in tomato roots under copper stress. With the addition of 100 micro mol L-1 of BSO, exogenous NO increased the AsA content, AsA/DHA ratio, and the AAO, MDHAR, and DHAR activities, and decreased the DHA, GSH, and GSSG contents and the APX and GR activities. When 250 micro mol L-1 of BSO was added, exogenous NO increased the contents of AsA, GSH, and GSSG, AsA/DHA ratio, and the activities of APX and GR, and decreased the DHA content and the AAO, DHAR and MDHAR activities. It was suggested that exogenous NO could affect the metabolic cycle of AsA-GSH in tomato roots under copper stress, and mitigate the damage of copper stress to tomato roots via regulating the AsA/DHA and GSH/GSSG ratios to alleviate oxidative stress.

A nutrient solution culture experiment was conducted to study the effects of exogenous NO donor (sodium nitroprusside) on the subcellular distribution and chemical form of copper (Cu) in tomato seedlings under the stress of 50 micromol x L(-1) of Cu2+ (CuCl2). Under this stress, the biomass and plant height of tomato seedlings decreased by 33.7% and 23.1%, respectively. Exogenous NO alleviated this inhibition effect significantly, but the Cu concentration and accumulation in the seedling organs still had a significant increase. Under the Cu stress, the Cu concentration and accumulation in the seedling organs were in the order of rootleafstempetiole. Exogenous NO limited the absorbed Cu transferred from root to shoot, but could not remove this translocation. Exogenous NO increased the Cu concentration in vacuole and cell wall significantly, and decreased the Cu concentration in organelle, which lessened the damage of Cu on the regular metabolic balance in cytoplasm and increased the tolerance of organelle against Cu. Exogenous NO increased the acetic acid-extractable Cu (F(HAc)) in root, sodium chloride-extractable Cu (F(NaCl)) in stem, F(HAc) in petiole, and ethanol-extractable Cu (F(E)) and F(NaCl) in leaf, while decreased the concentration and distribution of water-extractable Cu (F(W)) in different organs, which efficiently reduced the bio-toxicity of excessive copper.

This paper explored the main driving forces and stresses contributing to the eco-environmental changes of Baishan City in Jilin Province, through the analysis of the ecological security problems in the City. The framework of DPSIR was applied to establish an ecological security assessment index system, and further, to create an ecological security assessment model suitable for mountain areas. By using the 1989, 1999, and 2006 TM images, and in combining with the DEM data and field survey data, the interpretation of the land cover in Baishan City was conducted, and the landscape classification was carried out. With the support of Fragstats, the important ecological indicators were extracted. Then, the situations of ecological security in various districts and counties of Baishan City were assessed. The results indicated that there was an obvious regional difference in the ecological security of Baishan City, with a deteriorating trend of the overall ecological security situation. Human activities had deeper influence on the land cover pattern and species habitat distribution, and even, became the main driving force of the pattern changes in ecological security.

This paper studied the effects of Ca(2+) -carrier A23187 and Ca(2+) -chelator EGTA on the bud differentiation of cut flower chrysanthemum (Dendranthema grandiflorium 'Shenma') under photoperiodic induction, as well as the Ca2+ distribution and the sucrose, soluble sugar, and starch contents in 'Shenma' leaves during the differentiation. In the control, the leaf Ca2+ content was lower at the vegetative stage of apical bud (I), increased rapidly and reached a peak at the stage of initial differentiation (II), and decreased then. At stage I, the Ca2+ was mainly allocated in vacuole, cell wall, and cell lacuna; while at stage II, it was more in cytoplasm. Compared with the control, the leaf Ca2+ content of A23187-treated plants increased significantly, and the days of initiation and ending of bud differentiation were advanced by 2 days and 3 days, respectively. On the other hand, the leaf Ca2+ content of EGTA-treated plants decreased significantly, and the days of initiation and ending of bud differentiation were postponed by 4 days and 8 days, respectively. For both A23187- and EGTA-treated plants, their leaf Ca2+ at stage II was more allocated in cytoplasm. The leaf sucrose and soluble sugar contents of A23187-treated plants reached a peak on the 2nd day after treatment, and the time to reach the peak was shortened by 2 days, compared with the control, which was consistent with the peak time of Ca2+. The leaf sucrose and soluble sugar contents of EGTA-treated plants had no significant changes on the 2nd day of treatment, but increased rapidly and reached the peak on the 8th day of treatment (stage II), and then decreased. However, the leaf sucrose and soluble sugar contents during the whole period of bud differentiation were higher than those before photoperiodic induction. The leaf starch content of A23187-treated plants and the control decreased 2 days after treatment, while that of EGTA-treated plants began to decrease 8 days after treatment, and maintained at a lower level by the end of bud differentiation. The results indicated that Ca2+ and carbohydrates participated in the flower formation of chrysanthemum under photoperiodic induction.

In this study, cucumber seedlings were cultivated in nutrient solution added with different concentration (0.05, 0.1, 0.2, and 0.3 mmol x L(-1)) sodium nitroprusside (SNP) as nitric oxide (NO) donor to study the effects of exogenous NO on the growth of cucumber seedlings and the activities of antioxidant enzymes in cucumber leaves under NO3- stress. Under the stress of 140 mmol x L(-1) NO3-, treating with 0.1 mmol x L(-1) of SNP for 1 d or 7 d increased the leaf soluble protein content and superoxidase (SOD), catalase (CAT), and ascorbic acid peroxidase (APX) activities, and decreased the leaf malondialdehyde (MDA) content significantly, suggesting that exogenous NO could enhance the capacity of cucumber seedlings in scavenging active oxygen species, protect the seedlings from the peroxidation of membrane lipids, and promote the seedlings growth and increase their resistance to high concentration NO3- stress. After the cucumber seedlings grew in 0.3 mmol x L(-1) of SNP for 7 d, the activities of leaf SOD, POD, and CAT decreased, and the MDA content increased, resulting in the injury of cucumber seedlings. It was indicated that certain concentration (0.1-0.2 mmol x L(-1)) exogenous NO could alleviate the NO3- stress to cucumber seedlings.

A pot experiment was conducted to study the effects of rotation and fallowing on the microbial communities and enzyme activities in a greenhouse soil continuously cropped with cucumber and on the growth and yield of followed cucumber. Comparing with continuous cropping, rotation improved the components of soil microbial communities, which was manifested in the increase of bacteria and actinomycetes and the decrease of fungi. Rotation and fallowing enhanced the activities of soil invertase, urease, catalase, and polyphenol oxidase significantly. The quantities of soil bacteria and actinomycetes and the activity of soil invertase increased at the fruiting stage of cucumber plants, being the maximum at harvest stage, but decreased thereafter. In contrast, the quantity of soil fungi had a linear increase, and the activities of soil urease, catalase, and polyphenol oxidase decreased gradually during fruit development. Welsh onion and waxy maize promoted the growth and fruiting of the followed cucumber plants significantly, being the optimal rotation crops for cucumber.

By the method of hydroponic culture, this paper studied the alleviation effects of LaCl3 on the photosynthetic characteristics of cucumber seedlings under nitrate (140 mmol NO3(-) x L(-1)) stress, with the related mechanisms discussed. Under nitrate stress, the seedlings leaf chlorophyll and carotenoids contents decreased significantly, and the leaf Mg2+-ATPase, Ca2+-ATPase activities also decreased. On the 7th day of nitrate stress, the decrease of seedlings photosynthetic rate was mainly due to stomatal limitation; but on the 12th day of nitrate stress, the decrease was mainly due to no-stomatal limitation. Supplement with LaCl3 could make the cucumber seedlings keep relatively higher leaf Mg2+-ATPase and Ca2+-ATPase activities and chlorophyll and carotenoids contents, and applying 20 micromol x L(-1) of LaCl3 could increase the carotenoids content significantly. LaCl3 could also improve the leaf gas exchange, and alleviate the decrease of leaf Fv/Fm, PhiPSII, AQY, CE, and qp under nitrate stress, which helped the leaves making good use of light energy and maintaining higher CO2 assimilation capacity. An additional 20 micromol x L(-1) of LaCl3 could alleviate the nitrate stress on the photosynthesis of cucumber seedlings efficiently, but an additional 200 micromol x L(-1) of LaCl3 only had the alleviation effect at the initial period of nitrate stress. Our results could benefit to the improvement of greenhouse soil.

Cut flower chrysanthemum (Dendranthema grandflora 'Jinba') plants were treated with 40 degrees C/35 degrees C or 33 degrees C/28 degrees C (day/night) for 11 days and then transferred to 23 degrees C/18 degrees C for 5 days to study the changes in their photosynthesis and fluorescence parameters under high temperature stress and normal temperature recovery. The results showed that on the 5th day of 33 degrees C/28 degrees C treatment, net photosynthesis (P(n)) decreased gradually and stomatal conductance (G(s)) decreased evidently; while after recovery for 5 days, both P(n) and G(s) resumed to 80% of the control. At 40 degrees C/35 degrees C, P(n) and G(s) decreased dramatically. The increase of intercellular CO2 concentration (C(i)) at the early stage under given high temperatures showed that the photosynthesis inhibition by high temperature stress was resulted from non-stomatal limitations. However, 9 days later, stomatal limitation became the mainly cause of photosynthesis inhibition. The intrinsic photochemical efficiency (F(v)/F(m)), quantum yield of PS II (phi(PS II), and the efficiency of excitation energy capture by open PS II reaction center (F(v)'/F(m)') at 33 degrees C/28 degrees C and 40 degrees C/35 degrees C all decreased, with antenna heat dissipation increased, indicating that reaction center was protected by decreased light capture and efficiency of electron transfer through PS II. The photochemical quenching (q(p)) at 33 degrees C/28 degrees C descended first and turned to rise then, suggesting that the electron transfer was firstly restrained by the stress. Contrastively, q(p) rose continuously at 40 degrees C/35 degrees C, indicating that oxygen-evolving complex (OEC) was the location in chrysanthemum photosynthesis apparatus most sensitive to extreme high temperature.

By a solution culture experiment, cucumber seedlings were treated with different concentration (0, 25, 50 and 75 mmol x L(-1)) NaCl and NaHCO3, and their physiological responses were studied. The results showed that with increasing NaCl and NaHCO3 stress, the shoot and root growth, the leaf chlorophyll content and relative water content of the seedlings decreased dramatically, and the decrements were greater under NaHCO3 than under NaCl stress. The shoot Na content increased significantly with increasing NaCl and NaHCO, stress, while shoot K+ content was in adverse. At the same concentration of Na+ in culture solution, the addition of NaHCO3 induced a greater decrement of shoot K+ content, and thus, a lower shoot K+/Na+ ratio. Under NaHCO3 stress, the leaf electrolyte leakage rate and the leaf MDA, proline, and soluble sugar contents increased much greater, compared with those under NaCl stress. Under NaCl and NaHCO3 stress, the leaf superoxide dismutase (SOD), ascorbate peroxidase (APX) and dehydroascorbate reductase (DHAR) activities were induced significantly, while the leaf peroxidase (POD) activity was inhibited obviously.

The study with water culture showed that nitrate stress had significant inhibitory effects on the plant growth, especially the shoot growth of cucumber seedlings. On the 7th day under nitrate stress, the shoot fresh mass per plant decreased by 12.77 g, leaf SOD, POD and CAT activities increased, while leaf APX, DHAR and GR activities decreased significantly, compared with the control. The addition of low concentration (0.05 mmol L(-1)) LaCl3 increased the shoot fresh mass per plant by 35%, enhanced the leaf thermally stable protein content and SOD, POD, CAT, APX, DHAR and GR activities, and decreased the leaf MDA content and electrolytic leakage, resulting in a definite alleviation of the inhibitory effects of nitrate. However, an addition of high concentration (0.5 mmol L(-1)) LaCl3 had no obvious alleviation effect. It was concluded that the addition of certain concentration LaCl3 could alleviate the nitrate stress on cucumber via increasing anti-oxidative enzymes activities and thermally stable protein content.

This paper studied the effects of different NO3- concentration on the photosynthetic rate, photochemical efficiency, and absorbed light energy allocation in cucumber seedling leaves. The results indicated that when the available NO3- concentration in the medium was low (14-98 mmol NO3- x L(-1)), an appropriate supplement of NO3- could enhance the capability of cucumber leaves in capturing light energy, and promote the photosynthesis. However, with further increase of NO3-, the photochemical efficiency of PS II decreased, electron transfer restrained, and net photosynthetic rate as well as the absorbed light energy used in photochemical reaction of PS II decreased. At the same time, the light energy used in antenna heat dissipation increased, while the photochemical efficiency decreased. After treated with 140 and 182 mmol NO3- x L(-1) for 6 days, the photosynthetic rate (P(n)) was decreased by 35% and 78%, respectively, maximal PS II efficiency at open centers in the absence of NPQ (F(v)/F(m)), antenna efficiency at open centers in the presence of NPQ (F(v)'/F(m)'), actual PS II efficiency (phi (PSII ) and photochemical quenching (q(P)) were lower, non-photochemical quenching (NPQ) was higher, and the deviation from full balance between PS I and PS II (beta/alpha - 1) was improved significantly, compared with the control. The fluctuant ranges of these chlorophyll fluorescence parameters were increased at higher NO3- concentration, compared with those at lower NO3- concentration. The absorbed light energy allocated to the photochemical reaction of PS II (P) was reduced by high light intensity and high NO3- concentration. Meanwhile, the proportion allocated in antenna heat dissipation (D) increased significantly. Antenna heat dissipation was the main way for excessive energy dissipation.