Studies on Glutamine Synthetase Activity in Sugar Beet（Beta vulgaris L.） under Different Levels of Nitrogen

It was shown from the experiment that glutamine synthetase activity (GSA) in both leaf blades and roots under different nitrogen levels rose rapidly to reach its peak from seeding stage to foliage rapid growth stage and declined to its lowest level at the latter stage of root rapid growth,and then increased slightly,GSA in leaf blades had positive correlation with nitrogen level during the whole period of growth,GSA in roots showed the same tendency as it in leaf blades at the early middle stage of growth,but at the latter stage of growth,no positive correlation was established.GSA in leaf blades was the strongest compared with crowns,petioles and roots,and could represent the highest enzyme activity of the whole pant,GSA had quadratic curvilinear correlation with root yield and sugar production.GSA in leaf blades had significant positive correlation with α-NH2-N at the foliage rapid growth stage.     

Influence of the Different Level Ammonium on NRA and GSA in Sugar Beet（Vulgaris L. ）

Ammonium nitrogen inhibited NR activity in sugar beet, NR activity was lower in endogenous substrate after ammonium nitrogen was used,and the correlation between NR activity and ammonium nitrogen levels was negative. But NR activity raised with the ammonium nitrogen levels raising in exogenous. Ammonium nitrogen prompted GS activity: the correlation between GS activity and ammonium nitrogen was positive, GS activity raised with ammonium nitrogen levels raising,GS activity of roots and leaves had same change trend in sugar beet in the whole growth duration after ammonium nitrogen was used,but GS activity in roots was hiffher than that in leaves.     

Effect of Flower Removal on Senescence and Metabolism of Faba Bean （Vicia Faba L.）

In pot experiments of Xichang,China,during 1989-1994,visual scnescence symptoms and associated changes in constituent contents and activities of leaves of faba bean(Vicia faba L.)were compared in respones to flower removal.the leaves from upper, middle and lower positions were sampled six times during reproductive development phase.At 70 DAP flower removal had caused 37%-189% and 82%-197% increase of green leaf area and green leaf dry weight per plant respectively.Flower removal led to a significant increase in the chlorophyll,soluble surar and protein contents and the catalase activity.The leaf cell relative electroconductivity of those plants was maintained at a lower level,relative to the control,during the late growing stage.These results certainly implied that the leaves of flower removal plants were still fully functional at a very late growing stage,consequently the plants increased many new branches per plant.     

Research on Glutamate Dehydrogenase Activity in Sugar Beet（Beta vulgais L）under Different Nitrogen Levels

The experiment of Glutamate Dehydrogenase(GDH) activity in various plant parts under dif-ferent nitrogen levels in frame culture during the whole period of growth was carried out on campus of Northeast Agricltural University in 1993.The result showed that GDH activity in leafblades un-der four nitrogen applied levels rose rapidly to the acme from the seedling to foliage rapid growth stage,then diminished rapidly to the lower level at the latter stage of foliage rapid growth.This level was kept to harvest.GDH activity in roots at each growth stage under all nitrogen levels exhibited little disparity and did not show ostensible regularity of changes.GDH activity in leat blades was stimulated with nitrogen,however,it reduced with nitrogen fertilizer applying further.GDH activity in leaf blades was the biggest compared with crowns,petioles and roots ,which suggested that it could represent the highest enzyme activityof the whole plant.     

The Effect of Chitosan and Sodium Alginate on the Root Growth and Enzyme Activity of Soybean

The resaerch examined the effect of the two oceanic materials as coating materials on the soybean growth.The results showed chitosan and sodium alginate seed coating can enhance the growth of seedling root increase the nodule mumber,root activity and the growth of underground,The suggested coating ratios were 0.5-1.0g/kgseed,the same as chitosan,The two materials could increase the contents of CAT and NR in soybean leaves,decrease the contents of POD in soybean leaves.     

Nucleic Acid Metabolism,Proline Concentration and Antioxidants Enzyme Activity in Canola （Brassica nupus L.） Under Salinity Stress

Seedling of five canola genotypes, Hyola 308, Hyola 401, Hyola 60, Option 50 and RGS003, were grown in Hoagland nutrient solution containing S1 = 0, S2 = 100, S3 = 200 and S4 = 300 mmol L-1 NaCl in controlled environment. Proline, antioxidant activities like catalase （CAT）, ascobrate peroxidase （APX） and guaiacol peroxidase （GPX） and some enzyme activities of nucleic acid metabolism were determined in shoot and root 20 days after induction of salinity stress. Results showed application of stress significantly affected plant growth components such as fresh （FW） and dry weight （DW） of canola genotypes. Among the genotypes, RGS003 had the highest reduction of FW and DW in S3 treatment. By increasing NaCl levels from 0 to 300 mmol L-1, the activity of two antioxidant enzymes （APX and CAT） in shoot and root increased but GPX in all of genotypes decreased. The increase in salinity stress, increased proline concentration in both root and shoot tissues of canola genotypes. Hyola 401 genotype had the maximum concentration of proline in root and shoot in S3 treatment. Along with increased salinity stress in all of the studied plants, salinity significantly increased the level of the total nucleic acid and the activity of DNase I in all of salinity treatments and at the S3 level, RGS003 had the maximum concentration of nucleolytic enzyme.     

Effect of Host Plants on Development,Fecundity and Enzyme Activity of Spodoptera exigua （Hübner）（Lepidoptera：Noctuidae）

The beet armyworm,Spodoptera exigua (Lepidoptera:Noctuidae),is an economically important pest of crops worldwide,attacking plants from over 20 families including trans-continental agricultural cotton,corn and citrus crops.In this study,performance and subsequent enzyme activity of beet armyworm reared on host plants from five families were investigated.Significant differences were found in development,fecundity and enzyme activity on different host plants.Survival rate was the highest (42.8％) on asparagus lettuce (Lactuca sativar var.asparagina) and the lowest (17.0％) on sweet pepper (Capsicum annuum).Larval duration was the shortest on asparagus lettuce (12.0 d),and was 43.4％ longer on sweet peppers (21.2 d).The activity of acetylcholine esterase (AChE) and carboxylesterase (CarE) in 3rd instar larvae,and soluble carbohydrate and crude protein contents in different host plants were determined.AChE activity was the highest in the larvae feeding on Chinese cabbage (Brassica rapa),but declined by nearly 60％ on maize (Zea mays) seedlings.The ratio of soluble carbohydrate content to crude protein content in host plants was found to have a positive effect on oviposition and a negative correlation with larval duration and life time (from larval to adult stages) of the insect.     

Effects of Zinc Deficiency and Drought on Plant Growth and Metabolism of Reactive Oxygen Species in Maize （Zea mays L.）

The combinative effects of applied zinc (Zn) and soil moisture on the plant growth, Zn uptake, and the metabolism of reactive oxygen species (ROS) in maize (Zea mays L.) plants were examined through two pot experiments under greenhouse conditions. Maize variety Zhongdan 9409 was used. In experiment 1, maize plants were grown in cumulic cinnamon soil with five Zn treatments (0, 3.0, 9.0, 27.0, and 81.0 mg Zn kg-1 soil). Three treatments of soil moisture including serious drought, mild drought, and adequate water supply were set at 30-35 %, 40-45 %, and 70-75 % (w/w) of soil saturated water content, respectively. Soil saturated water content was 36% (w/w). The dry matter weights of shoots were enhanced by Zn application and adequate water supply. There was no apparent difference in plant growth among Zn application rates from 3.0 to 81.0 mg Zn kg-1 soil. The increases of plant growth and Zn uptake due to Zn application were found more significant under well-watered condition than under drying condition. In experiment 2, two levels of Zn (0 and 5.0 mg Zn kg-1 soil) and soil moisture regimen (40-45 % and 70-75 % of soil saturated water content, respectively) were set. Zn deficiency or water stress resulted in higher concentrations of O2-· and malondiadehyde in the first fully expanded leaves.Zn deficiency lowered the activity of superoxide dismutase (SOD, EC 1.15.1.1) in leaves. Drought stress increased SOD activity in leaves regardless of Zn supply. The activity of guaiacol peroxidase (POD, EC1.11.1.11) was found to be enhanced by Zn supply only in well-watered leaves. Zinc deficiency or water stress had little effect on the activity of catalase (CAT, EC 1.11.1.6). The higher ROS level in early maize leaves due to water stress seemed not to be alleviated or lowered partially by Zn application. However, Zn fertilizer was recommended to apply to maize plants irrigated or supplied with adequate water, otherwise Zn deficiency would reduce the water use for plant biomass production.     

Performance and Enzyme Activity of Beet Armyworm Spodoptera exigua （Hübner） （Lepidoptera：Noctuidae） Under Various Nutritional Conditions

We explored the influence of the artificial diets with different protein and glucose contents on larval development, development, fecundity and population growth index of beet armyworm increased with increased nutritional content in the artificial diets; however, when the yeast to cellulose content ratio reached 46.8:53.2, the fecundity and population growth had reached a maximum and additional protein did not yield additional growth. Additionally, 3rd instar beet armyworm larvae fed on different artificial diets had increased enzymatic activities of acetylcholinesterase (ACHE) with the increased nutritional content, but carboxylesterase (CarE) activities did not significantly change under variation in the nutritional content.     

Studies on some characteristics of nitrate reductase from sugar beet （Beta vulgaris L.）leaves

Some characteristics of nitrate reductase from sugar beet leaves shown in this paper were as follows:The nitrate reductase from sugar beet leaves required NADH as an electron donor.Accordingly,the nitrate reductase was classified as NADH-dependent(E.C.1.6.61).The Km value of the nitrate reductase for NADH and NO3^- were 0.86m mol and 0.18μ mol respectively.The optimum pH in reaction mixture solution for nitrate reduction activity was 7.5.The effect of variable concentrations of inorganic phosphorus in the reaction buffer on nitrate reductase activity was investigated.When the inorganic phosphorus concentration was below 35m mol,the nitrate reductase activity was increased with increase of inorganic phosphorus concentration.Conversely,when the inorganic phosphorus concentration was over 35m mol,the nitrate reductase activity was inhibited.The nitrate reductase activity assayed in vitro was 3.2 and 5.6times of that assayed in vivo under the condition of exogenous and endogenous ground substance respectively.     

氮素用量对寒地水稻氮代谢关键酶活性的影响

本试验以寒地水稻松粳6号和松粳9号为材料,研究了氮素用量对寒地水稻功能叶片氮代谢关键酶活性的影响。研究结果表明:寒地水稻功能叶片NR、GS活性在整个生育期均呈单峰曲线变化,峰值均出现在抽穗期,氮素用量对功能叶片NR、GS活性的影响因品种和时期而异;寒地水稻功能叶片RuBP羧化酶活性从齐穗后呈下降趋势,并且随施氮量的增加而提高;不同生育时期NR、GS、RuBP羧化酶活性与产量及产量构成因子相关关系和相关程度不一致;在一定范围内,水稻产量随着氮量增加而增加,氮素用量与产量间呈一元二次曲线关系。     

铵态氮和硝态氮对谷子形态和生物量的影响研究

为了明确铵态氮和硝态氮营养对谷子形态和生物量的影响,合理选择谷子施氮形式,采用蛭石浇灌不同氮形态营养液的方法培养谷子植株。结果表明:两种氮形态显著影响了谷子形态和生物量累积,氮形态对根形态、穗长的促进作用无显著差异。氮形态在生物量、株高、叶面积、叶绿素含量方面的影响存在显著差异:相比铵态氮,硝态氮分别提高了17%的根重、32%的茎重、39%的叶重和40%的总生物量,硝态氮还提高了38%的株高和40%的叶面积;相比硝态氮,铵态氮提高了173%的叶绿素含量和12%的穗重。氮形态在根冠比和穗比重也存在极显著差异,相比硝态氮,铵态氮显著提高了8%的根冠比和44%的穗比重。以上结果表明,硝态氮显著促进谷子株高、叶面积、生物量的提高,在株体扩建方面发挥重要的作用,铵态氮显著促进谷子叶绿素合成和生殖器官建成,在功能建成方面发挥重要作用。     

甜菜氮糖代谢酶活力与蔗糖代谢的关系

初步探讨了甜菜生育期间叶片和根体中氮糖代谢关键酶 NR、GS、Ru SPase、SS活力的协调关系以及蔗糖的积累转化。结果表明 (1)氮糖代谢酶活力及其相关性主要在叶丛形成期和块根增长期达到显著 ,这两个时期是通过氮素协调氮代谢酶活力 ,实现以正常氮代谢促进蔗糖积累和转化的关键时期。 (2 )在叶丛形成期 ,随施氮量增加 ,NR、 GS、 Ru BPase和 SS分解方向活力提高 ,蔗糖和单糖含量下降 ;生育中后期 ,随施氮量增加 ,NR和 SS分解方向活力增强 ,GS和 SS合成方向活力减弱 ,蔗糖含量下降 ,单糖含量上升 ,总糖量降低。 (3)氮素对糖分含量的影响是通过氮素对氮糖代谢谢酶之间的协调作用的结果。根体中 GS与 SS活力的矛盾贯穿整个生育期 ,GS对 SS催化方向的改变可能起很关键的作用。     

不同形态氮素对甜菜谷氨酰胺合成酶活性的影响

不同施肥水平下利用桶栽研究了硝态氮和铵态氮对甜菜体内氮素同化关键酶－谷氨酰胺合成酶（GS）活性的影响，并分析了不同处理甜菜块根产量与含糖率的变化，初步探讨了氮素营养与甜菜GS活性以及与丰产高糖的关系。结果表明，不同形态氮氮及其不同施肥水平对甜菜体内的GS活性的影响不同，在同一施氮水平上，铵态氮处理的GS活性高于硝态氮处理的甜菜GS活性，而施用同一形态氮素时，GS活性随两种氮素施量的增加而增加，根产量也表现相似变化，但含糖率的变化不尽相同。     

Research on Glutamate Synthase Activity in Sugar Beet (Beta Vulgaris L.) under Different Levels of Nitrogen

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不同形态氮素吸收利用及其对植物生理代谢影响的综述

对不同形态氮素的吸收利用过程及其对植株生长、抗逆性、品质和安全性的影响,以及外界环境条件对其作用效果的影响进行了综述,发现硝态氮(NO₃^--N)可促进植株根系伸长及植株对阳离子的吸收;铵态氮(NH₄⁺-N)可缓解盐胁迫及活性氧对植株的伤害,还能提高植株对病害的抵抗能力,但单一施NH+4-N易造成NH+4毒害,如细胞酸度增加、活性氧伤害、细胞壁木质化等。此外,对今后的研究方向进行了展望,以期为农业氮肥的合理施用提供理论依据。     

采收时间对雪茄碳氮代谢关键酶活性和化学成分的影响

为探索优质雪茄的生产条件,了解不同采收时间雪茄烟的生理生化变化规律,进而确定雪茄烟适宜的采收时间和成熟度,采用大田试验的方法,研究雪茄烟叶片在不同采收时间的碳氮代谢关键酶活性及其化学成分的变化规律。结果发现,中部叶硝酸还原酶活性随采收时间推迟逐渐下降,上部叶先升高后降低;中部叶和上部叶淀粉酶活性随采收时间的推迟先降低后升高。中部叶和上部叶的总氮、总糖、还原糖和淀粉含量均随采收时间的推迟呈先升高后降低的趋势;上部叶的总糖、还原糖和淀粉含量虽然在打顶后45～50 d降低,但差异不显著;中部叶在打顶后35～40 d,这些化学成分均显著降低。因此,雪茄烟的中部叶宜在打顶后35 d采收,上部叶宜在打顶后45～50 d采收。这些结果为海南省五指山市雪茄适时采收提供理论依据。     

施氮水平对不同花生品种氮代谢及相关酶活性的影响

 【目的】花生籽仁蛋白质含量较高,研究花生不同器官中氮代谢酶活性在施氮水平和品种间的差异及其与籽仁蛋白质含量间的关系,阐述花生氮素代谢的生理特性。【方法】选用生产中普栽品种花育22号和白沙 1016,设置4个氮素水平,测定两品种不同生育期各器官中主要含氮物质(可溶性蛋白质(Pro)、游离氨基酸(AA))含量及主要氮代谢酶(硝酸还原酶(NRase)、谷氨酰胺合成酶(GS)和谷氨酸脱氢酶(GDH))活性。【结果】两品种各器官Pro、AA、NRase、GS、GDH活性的变化态势大致相同,但其含量的高低因品种和施氮量不同而变化,各器官中各指标含量均以白沙1016较高;适当提高氮素水平可增加各器官中可溶性蛋白质和游离氨基酸的含量和主要氮代谢酶活性;氮素水平过高虽能提高硝酸还原酶和籽仁蛋白质含量,但谷氨酰胺合成酶(GS)和谷氨酸脱氢酶(GDH)的活性下降;各营养器官中可溶性蛋白质含量与GS和GDH活性间的相关关系不明显,但与其相应器官中的NRase活性表现显著或极显著相关,荚果中Pro与AA和NRase间、GS和GDH、NRase与游离氨基酸间均呈极显著的相关关系。【结论】施氮量和品种差异对花生各器官中游离氨基酸和可溶性蛋白质含量及氮代谢酶活性有影响,白沙1016对高量氮肥较敏感,花育22号则较适应高氮;增施氮肥通过改变氮素代谢的生理特性改善花生品质。     

氮素营养水平对黄瓜氮代谢关键酶活性变化及氮化物的影响

探讨黄瓜叶片氮代谢关键酶类活性与果实氮化物含量的相互关系,为黄瓜氮素的高效利用和品质优化提供依据。采用二因素裂区设计,研究了氮肥用量对黄瓜叶片氮代谢酶活性和结果盛期果实氮化物含量的影响。结果表明:在225~375 kg/hm~2施氮情况下,随施氮量增加功能叶片硝酸还原酶(NR)、谷氨酰胺合成酶(GS)、谷氨酸草酰乙酸转氨酶(GOT)和谷氨酸丙酮酸转氨酶(GPT)的活性逐渐升高,处理间差异显著,施氮量超过375 kg/hm~2其酶活性增加不明显且有下降的趋势。不同品种间酶活性大小依次为津优35号、园丰元6号、永昌9618,博特202,其中津优35号与园丰元6号酶活性差异不显著,与永昌9618和博特202差异显著。果实中氮化物的含量随施氮量的增加逐渐提高;施氮量为375 kg/hm~2时游离氨基酸、可溶性蛋白及粗蛋白含量达到最大值;增加到450 kg/hm~2时3种氮化物含量均下降,而硝酸盐含量持续增加;在525 kg/hm~2时含量最高,津优35号硝酸盐和游离氨基酸含量最低,可溶性蛋白和粗蛋白含量最高,博特202与之相反。相关分析表明,果实中硝酸盐含量与NR和GS活性呈显著正相关关系,与GPT和GOT无显著相关关系;可溶性蛋白和粗蛋白含量与4种酶类存在显著或极显著正相关关系。不同品种间果实氮化物的差异是氮素吸收同化综合作用的结果。选择氮素吸收同化能力强的品种,既有利于提高氮素利用,又可改善产品质量。