Search

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

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

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

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.

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.

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.

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.

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.