Influence of ferredoxin levels on nitrate reductase activity in iron deficient lemon leaves

The relationship between nitrate reductase activity and ferredoxin levels in lemon tree leaves was studied. The experiments were carried out on leaves from full‐nutrient sufficient trees as the reference, and on leaves from trees with several nutritional stresses, mainly iron chlorosis from trees growing under Fe‐stressed conditions.

Iron deficiency reduced leaf ferredoxin concentration and consequently decreased nitrate reductase activity. Fe(II) infiltration treatments of intact leaves, as well as several incubation assays, permit to deduce the dependence of the enzymatic nitrate reduction of the leaf ferredoxin levels.     

Lime,molybdenum, and cultivar effects on molybdenum deficiency of poinsettia

Poinsettia (Euphorbia pulcherrima Willd. ex Klotz) cultivars ‘Annette Hegg Brilliant Diamond’ (AH), ‘Gutbier V‐14 Glory’ (GG), and ‘Eckespoint C‐1 Red’ (ER) were grown in a peat‐perlite potting medium to study lime and Mo effects on the occurrence of Mo deficiency. Two rates of dolomitic limestone, 0 and 3 kg/m³of growing medium, and weekly applications of micronutrient solutions containing 0.0 or 1.0 ppm Mo were made in factorial combination. Lime, Mo, or both prevented Mo deficiency symptoms in all cultivars. Without both lime and Mo, Mo deficiency symptoms appeared on AH and GG, but not on ER. Lime and/or Mo reduced NO₃‐N content, increased Mo content and increased nitrate reductase enzyme activity (NRA) in the upper recently matured leaves of all cultivars. Lime and Mo interacted to affect these parameters in all cultivars. Comparing the three cultivars without both lime and Mo, NO‐‐N content was lowest and NRA highest in ER. However, the Mo content of ER leaves was equal to or less than that of AG and GG which showed Mo deficiency symptoms.     

Physiological responses of tomato roots grown in organ culture to iron-deficiency stress

Roots of the Fe-efficient tomato (Lycopersicon esculentum Mill., cultivar Floradel) were cultured in an inorganic medium supplemented with glycine, thiamine, pyridoxine, and nicotinic acid, with sucrose as an energy and carbon source. Iron was supplied as ferric hydroxyethylethylenediaminetriacetic acid (FeHEDTA) and the initial PH was 5.5. Root growth was limited when less than 40 μm FeHEDTA was supplied. Roots grown at lower Fe concentrations decreased the pH of the FCR assay medium to a greater extent than did roots grown at higher Fe concentrations. Cultured roots grown with 10 μm FeHEDTA had increased levels of ferric chelate reductase (FCR) activity compared to roots grown with either lower or higher concentrations of FeHEDTA. Low FCR activity of roots grown at 2.5 or 5 μm FeHEDTA was attributed either to impaired metabolism due to Fe-deficiency or the lack of sufficient Fe for enhanced FCR formation. Roots of hydroponically grown tomato plants exhibited typical increases in FCR activity with Fe-deficiency. Based on these preliminary results, cultured roots were found to exhibit similar Physiological responses to Fe-deficiency stress as intact root systems. Cultured roots should provide a useful system for the investigation of the role of the root in plant Fe-deficiency stress responses as previously suggested by Bienfait et al.(Plant Physiol., 83, 244–247, 1987).     

苯甲酸钠对土壤亚硝酸还原酶动力学参数的影响

采用改进的α-荼胺-对氨基苯磺酸比色法研究了苯甲酸钠对紫色土亚硝酸还原酶动力学参数的影响。结果表明,苯甲酸钠对灰棕紫泥土亚硝酸还原酶酶促反应的抑制能力随苯甲酸钠浓度的增大而增强,苯甲酸钠的加入,降低了V0、Km和Vmax值,表明苯甲酸钠对土壤亚硝酸还原酶的作用类型表现为反竞争性抑制作用;苯甲酸钠是一种优良的反硝化抑制剂,有良好的应用前景。     

Hypolipidemic effect of coriander seeds (Coriandrum sativum): mechanism of action

The effect of the administration of coriander seeds (Coriandrum sativum) on the metabolism of lipids was studied in rats fed a high fat diet with added cholesterol. The spice had a significant hypolipidemic action. The levels of total cholesterol and triglycerides decreased significantly in the tissues of the animals of the experimental group which received coriander seeds. Significant increases in -hydroxy, -methyl glutaryl CoA reductase and plasma lecithin cholesterol acyl transferase activity were noted in the experimental group. The level of LDL + VLDL cholesterol decreased while that of HDL cholesterol increased in the experimental group compared to the control group. The increased activity of plasma LCAT, enhanced hepatic bile acid synthesis and the increased degradation of cholesterol to fecal bile acids and neutral sterols appeared to account for its hypocholesterolemic effect.     

HPLC-MSn法检测毛白杨CCR酶活及反应产物4-羟基肉桂醛类的制备

为更直观、便捷地研究木质素合成途径中CCR的酶学特性,从产物生成的方向来监测CCR的酶学特性。试题采取化学合成方法制备CCR的产物——4-羟基肉桂醛物质(香豆醛、松柏醛、咖啡醛)并利用HPLC进行纯化,液相色谱质谱联用仪(HPLC-MSn)进行鉴定,合成的4-羟基肉桂醛可作为HPLC-MSn技术研究CCR酶学特性时的标样。建立了一套HPLC-MSn技术检测CCR酶活的新方法,将毛白杨重组CCR蛋白在大肠杆菌中高效表达并利用亲和层析法获得电泳纯CCR蛋白,利用HPLC-MSn技术监测CCR酶对4种底物的酶学特性。结果显示,通过该方法能够监测到CCR底物的减少和产物的增加过程,为木质素合成途径中关键酶的酶学活性研究提供新方法。     

两个品种水稻中硝酸盐吸收和利用率对氮素饥饿的响应特征

Ammonium（NH＋4） is the main nitrogen（N） form for rice crops, while NH＋4near the root surface can be oxidized to nitrate（NO-3）by NH＋4-oxidizing bacteria. Nitrate can be accumulated within rice tissues and reused when N supply is insufficient. We compared the remobilization of NO-3stored in the tissue and vacuolar between two rice（Oryza sativa L.） cultivars, Yangdao 6（YD6, indica）with a high N use efficiency（NUE） and Wuyujing 3（WYJ3, japonica） with a low NUE and measured the uptake of NO-3, expression of nitrate reductase（NR）, NO-3transporter genes（NRTs）, and NR activity after 4 d of N starvation following 7-d cultivation in a solution containing 2.86 mmol L-1NO-3. The results showed that both tissue NO-3concentration and vacuolar NO-3activity were higher in YD6 than WYJ3 under N starvation. YD6 showed a 2- to 3-fold higher expression of OsNRT2.1 in roots on the 1st and 4th day of N starvation and had significantly higher values of NO-3uptake（maximum uptake velocity, Vmax） than the cultivar WYJ3.Furthermore, YD6 had significantly higher leaf and root maximum NR activity（NRAmax） and actual NR activity（NRAact） as well as stronger root expression of the two NR genes after the 1st day of N starvation. There were no significant differences in NRAmax and NRAact between the two rice cultivars on the 4th day of N starvation. The results suggested that YD6 had stronger NRA under N starvation, which might result in better NO-3re-utilization from the vacuole, and higher capacity for NO-3uptake and use, potentially explaining the higher NUE of YD6 compared with WYJ3.     

Oxidative Stress and Antioxidants in Wheat Genotypes: Possible Mechanism of Water Stress Tolerance

The role of plant antioxidant systems in water stress tolerance was studied in three contrasting wheat genotypes. Water stress imposed at different stages after anthesis resulted in an increase in lipid peroxidation and a decrease in membrane stability and chlorophyll and carotenoid contents. The antioxidant enzymes ascorbate peroxidase, glutathione reductase and non-specific peroxidase also increased significantly under water stress. Genotype PBW 175, which had highest ascorbate peroxidase, glutathione reductase and peroxidase activity, had the lowest lipid peroxidation (malondialdehyde content) and highest membrane stability and contents of chlorophyll and carotenoids under water stress, while the susceptible genotype WH 542 exhibited the lowest antioxidant enzyme activity, membrane stability and contents of chlorophyll and carotenoids and the highest lipid peroxidation. Genotype HD 2402 showed intermediate behaviour. It seems that drought tolerance of PBW 175, as represented by higher membrane stability and chlorophyll and carotenoid contents and lower lipid peroxidation, is related to its higher antioxidant enzyme activity.     

桤木叶片中NO与硝酸盐还原系统关系的研究

在桤木生长期间,叶片中的一氧化氧（ＮＯ）含量和一氧化氮合成酶（ＮＯＳ）活力随生长而变化,即生长初期水平较低,以后逐渐升高,生长高峰期达到最高值,随后在叶片开始衰老时下降,硝酸还原酶（ＮＲ）和谷氨酰胺合成酶（ＧＳ）的活力变化与ＮＯＳ活力的变化类似,但ＮＲ活力高峰出现比ＮＯＳ早,而ＧＳ活力高峰期在ＮＯＳ之后。用ＮＯ处理,叶片中ＮＯ含量和ＮＯＳ活力都有所增加,但ＮＲ活力只在幼苗中表现增加,而在离体枝条的