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1.
Following the prevalent agronomic practice of applying N fertilizer in two splits at optimum levels recommended for maximum yield viz. 120 kg N ha, to two wheat (Triticum aestlvum L.) cultivars, which differ in in vivo nitrate reductase (NR) activity, it was observed that the activity is high in the first formed leaf blades and declines in the successively formed ones. Enhancement in the activity subsequent to incubation of excised leaf blades in NO3 ‐ suggests that the substrate (NO‐ 3) is limiting and that the leaf blades, particularly the upper ones, have the potential to reduce additional amounts of NO3 ‐. High NR cultivar has greater potential than the low NR cultivar. The studies suggest that it may be possible to increase the NO3 ‐ moles reduced and thus enhance the reduced N content in case the nitrogen is available at later stages of growth.  相似文献   

2.
Bean plants (Phaseolus vulgaris L.) were cultured for 10 or 18 days on phosphate sufficient (+P) or phosphate deficient (‐P) nutrient medium. Nitrate and phosphate distribution between shoot and root, nitrate uptake, and nitrate reductase activity (NR activity, in vivo and in vitro) in root and leaves was estimated. The decrease in Pi concentration in leaves and roots led to decreased rate of NO3 uptake and increased NO3 accumulation in roots, accompanied by alterations in NO3 distribution between shoot and roots. Nitrate reductase activity estimated in vitro was twice higher than estimated in vivo and both in +P and ‐P plants was lower in the roots than in the shoots. The decrease of NR activity in ‐P plants was more pronounced in the roots and after 2 weeks of phosphate starvation it was about 40% lower as compared with the control. The depression in nitrate uptake may be the result of feedback inhibition due to accumulation of nitrate in the roots. The increased NO3 concentration in root tissue may be explained by decreased NR activity and lower transport of nitrate from roots to shoot.  相似文献   

3.
探明桑轮纹病发生区冠层内叶表面微生物多样性、结构组成和功能的变化情况,有助于快速筛选控制桑轮纹病病原菌(Gonatophragmium mori)潜在的拮抗微生物。本研究基于高通量测序技术,分析冠层上部和下部叶片上表面和下表面细菌相对丰度的差异。结果发现:1)在多样性指数(Shannon)上,冠层上部叶片是冠层下部叶片的1.26倍,冠层内叶片上表面是下表面的1.49倍。2)在结构上,冠层下部叶片的下表面(LB)和冠层上部叶片的下表面(UB)的优势属均为泛菌属(Pantoea),其相对丰度分别为38.04%和25.31%,而冠层下部叶片的上表面(LS)为沙雷氏菌属(Serratia)、冠层上部叶片的上表面(US)为寡养单胞菌属(Stenotrophomonas),其相对丰度分别为18.0%、23.73%。3)在功能上,冠层下部叶片细菌的碳水化合物和氨基酸的运输和代谢功能比冠层上部叶片强,然而脂质的运输和代谢功能比冠层上部叶片弱;冠层上部叶片上表面细菌的细胞壁生物发生功能比下表面强,而氨基酸的运输和代谢功能弱于下表面;冠层下部叶片上表面细菌的次生代谢物的生物合成、运输和分解代谢和脂质运输和代谢功能强于下表面,而细胞运动比下表面弱。4)冠层内叶片表面芽孢杆菌属(Bacillus)、不粘柄菌属(Asticcacaulis)和苯基杆菌属(Phenylobacterium)的相对丰度与病原菌的相对丰度负相关性显著(P0.05),相关性最大的为芽孢杆菌属,系数为-0.87。上述结果表明桑轮纹病发生区冠层内桑叶上下表面细菌群落的多样性、结构组成和功能存在显著差异,对进一步研究桑轮纹病的生物防控具有一定的科学意义。  相似文献   

4.
The effects of three N levels on etiolated and green leaves of Zea mays were studied. It was found that the activity of both nitrate reductase (NR) and nitrite reductase (NiR) was affected, although differently, and the former showed higher sensitivity. NR activity rose with N increase, but different values in the three groups of seedlings appeared only after the second day in light/darkness; both nitrate and light were necessary to obtain a high level of activity. The interference of the N supply on NiR was observed only in seedlings grown in light. Seedling growth was also affected and the leaf weight appeared to correspond with the level of N supplied. In seedlings grown in darkness, the nitrate accumulated in the leaf increased with the decrease of the supplied N, whereas in light/darkness the opposite occurred. Different values of the leaf protein in the three seedling groups appeared only under light/dark and after the second day and by SDS‐PAGE they were found to be quantitative.  相似文献   

5.
Endogenous inhibitors of nitrate reductase (NR) of peach [Prunus persica (L.) Batsch] seedlings were identified as mandelonitrile and cyanide. The compounds gave greater than 90% inhibition at 0.019 μM and were noncompetitive with respect to nitrate when preincubated with the enzyme in the absence of nitrate. Competitive inhibition in respect to nitrate occurred when nitrate was present prior to the addition of enzyme. Concentration and distribution of NR inhibitors were: leaf > stem > roots as determined by two independent methods. Nitrate reductase inhibitor was detected in 12 diverse species of Prunus and was tentatively identified as cyanide by high‐performance liquid chromatography (HPLC) and biological activity. The degradation products of the cyanogenic‐glucoside amygalin were tested to determine NR inhibition. Amygdalin, prunasin and benzaldehyde were not inhibitors of NR, whereas mandelonitrile and cyanide were. Prunasin was determined to be the precursor of the NR inhibitors in peach leaf, stem, and root tissue.  相似文献   

6.
The aim of the current study was to identify major soil and leaf factors accounting for low natural rubber (NR, Hevea brasiliensis) productivity on tropical acid Acrisols in Vietnam. Twenty NR plots were measured with NR productivity, leaf factors (N, P, K, Ca, Mg, Mn, Cu, Fe, and Zn), soil factors (pH, particle size distribution, total C, N, P, K, exchangeable K, Ca, Mg, Al, Mn, Fe, Zn, available P). Cluster analysis showed that NR productivity could be separated into three clusters with low (23.2), medium (38.2), and high (61.3 g tree?1 harvest?1) yield. High-yield cluster had higher leaf P concentration and soil pH, while low-yield cluster had higher leaf Mn, soil exchangeable Al, and Mn concentration. Simple and multiple linear regression analysis applied with backward elimination procedure suggested that leaf and soil toxic concentration may be responsible for low NR productivity in the study soil.  相似文献   

7.
Nitrate reductase (NR) was extracted from leaf, root, and stem tissue of ‘Lovell’ peach seedlings [Prunus persica (L.) Batsch] grown for 8 weeks in nutrient solution containing 15 mM nitrate. Enzyme activity of NR in leaf, stem, and root tissue was 10.20: 0.07: 0.04 nM N02/min/g tissue extracted, respectively. When seedlings wee transferred to nutrient solution containing 15 mM NH4, NR activity was not detected after 72 hours. The enzyme was specific for NADH and had a pH optimum of 7.5. The Km for NO3 was 1.3 x 10–3 M and the rate of reaction remained linear for 45 min. Enzyme activity of leaf tissue was dependent on NO3 concentration in the nutrient solution. At NO3 concentrations of 15, 7.5, 1.5, and 0.15 mM, the NR activity was 22.8, 16.2, 13.8, and 2.2 nM NO2/mg protein/hr.  相似文献   

8.
Abstract

Factors affecting the in vivo nitrate reductase (NR) assay were investigated in order to optimize the assay conditions for various tissues of MM 106 apple trees. The addition of nitrate and phosphate to the assay medium significantly increased nitrate reductase activity (NRA), but high concentrations of nitrate and phosphate inhibited the NRA. The optimum concentrations of nitrate and phosphate for in vivo NRA ranged from SO to 100 mM and were tissue‐specific. The optimum pH of the assay medium was 7.5. The addition of 2% (v/v) n‐propanol to the assay medium stimulated NRA, but concentrations of n‐propanol greater than 2% significantly decreased the NRA. Vacuum infiltration was effective in stimulating NRA. The in vivo NR assays for leaves and stems were linear for at least 60 minutes following an initial 30 minute lag, whereas there was no lag phase in root tissues.  相似文献   

9.
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10.
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.  相似文献   

11.
Abstract

A field study was conducted to study effects of four nitrogen (N) supplemental levels on biomass, protein‐N, non‐protein‐N, and starch of an upper and a lower leaf in rice (Oryza sativa L.). The ranges of leaf protein‐N, non‐protein‐N, total N, and starch concentrations were from 1.18% to 3.66%, from 0.13% to 0.67%, from 1.32% to 4.14%, and from 38.4 mg g?1 to 108.6 mg g?1, respectively. The upper leaf appeared to be more sensitive than the lower leaf in response to N levels on biomass, but larger differences of protein‐N, total N, and starch contents were observed among nitrogen level treatments in the lower leaf than in the upper leaf. Protein‐N may be the best indicative of N status in rice. The lower leaf had a considerably higher ratio of protein‐N to non‐protein‐N at panicle formation and heading growth stage. The lower leaf had higher starch contents, which decreased with increasing N level. The response differences between the upper leaf and the lower leaf with relation to light conditions, developmental extent and leaf function were discussed. The results suggested that the lower leaf could be more suitable as a test sample for N status diagnosis by leaf chemical analysis, especially during the reproductive growth stage.  相似文献   

12.
Effect of plant growth regulators (PGR) viz. gibberellic acid (GA), kinetin (KN), and abscissic acid (ABA) were investigated on growth and activities of nitrate reductase (NR) and glutamine synthetase (GS) in mustard (Brassica juncea) seedlings. All the PGRs tested promoted in vivo NR activity in cotyledons, but the magnitude differed with different treatments. Cytosolic GS in root and hypocotyl was promoted by GA treatment and inhibited by ABA and KN treatments although the latter showed slight promotion initially in hypocotyl; the trend was not clear in cotyledons. Determination of Km value of GS extracted from 96‐h‐old cotyledons recorded lower Km value in GA treatment (2.5 mM), while it increased in ABA treatment (4.35 mM), There was little change in Km value in KN (3.03 mM) treatment. The kinetics of GS enzyme in cotyledons of different treatments showed marked variation in Vmax . Both GA and ABA treatments inhibited GS activity while no significant effect by KN treatment was observed. It is argued that GA treatment inhibits chloroplastic GS (an enzyme which has higher Km value), while ABA‐induced inhibition may not be specific to cytosolic or chloroplastic isoforms. Kinetin treatment was ineffective in promoting or inhibiting GS activity in cotyledons. The above conclusion is further supported by chloroplastic pigment data where inhibition is recorded in all the PGRs tested.  相似文献   

13.
Several hypotheses have been put forward to explain the causes of damage to plants by atmospheric pollution. None however, fully explain why some species are more prone to damage than others. In the literature, certain higher plants are more commonly reported as suffering damage from atmospheric pollution. These include climax species such as conifers, some broadleaf species such as oak and beech, and ericaceous species. Pioneer species such as highly nitrophillous woody species and ruderal herbaceous species are seldom reported in connection with damage from atmospheric pollutants. A screening of 18 species (woody and herbaceous) for 5 physiological and metabolic parameters and subsequent regression analysis of the data, showed that plants could be grouped according to their tolerance to acidity. There was a marked positive correlation between leaf nitrate reductase (NR) activity and the buffering capacity index (BCI) of the leaf. Foliar mistings and soil applications of 3 mol m?3 KNO3 to 6 assorted plant species also revealed that pioneer species, can induce NR activity when NO3 ? is applied directly to the foliage or soil. However, climax species have a much lower ability to increase NR activity in response to foliar and soil NO3 ? inputs. Leaf NO3 ? assimilation carries with it the direct generation of OH?, involves greater uptake of base cations and confers greater physiological buffering capability through the close interaction of carbon and nitrogen acquisition in the leaf. The hypothesis states that leaf nitrate assimilators are physiologically more competent at buffering acidic inputs whether directly as H+, or indirectly through uptake of acidic pollutants.  相似文献   

14.
A nutrient solution experiment was done to evaluate effects of different concentrations of nitrogen (N), phosphorus (P) and potassium (K) on leaf mineral concentrations and some enzymes activity of melon seedlings (Cucumismelo var. inodorus subvar. Khatouni). Different levels of these nutrients including 0, 53, 105, 158 and 210?mg L?1 N; 0, 8, 16, 23 and 31?mg L?1 P; 0, 59, 118, 176 and 235?mg L?1 K, all corresponding to 0, 25, 50, 75 and 100% of their concentrations in Hoagland nutrient solution, were applied to plants. The results showed that the highest leaf nitrate reductase (NR) activity was observed at highest N and P levels, whereas the three highest K levels showed the highest NR activity. The highest leaf peroxidase activity was observed at 8?mg L?1 P, 59?mg L?1 K and 158?mg L?1 N. The leaf catalase activity was highest at zero concentration of P, 158?mg L?1 N and 176?mg L?1 K; however, catalase activity was decreased by increasing P levels. Leaf protein content showed an increasing trend with increasing N, P and K levels of nutrient solution, while there was no significant difference between 158 and 210?mg L?1 N. The highest leaf concentrations of N, P, K and Mg were observed at highest nitrogen, potassium and phosphorus levels of nutrient solution, whereas the highest leaf concentration of Ca were obtained at 53 or 105?mg L?1 N, 176?mg L?1 K and 23–31?mg L?1 P. The highest iron concentration of leaves was obtained from 23 to 31?mg L?1 P, 176?mg L?1 K and 210?mg L?1 N.  相似文献   

15.
Studies were conducted to determine relationships among nitrate reductase activity (NRA), dry weight (DW), nitrogen (N) uptake, and N concentration in soft red winter wheat (Triticum aestivwn L.). Data were collected for three growing seasons from field plots grown on a silt loam and one growing season on a sandy loam. Ten cultivars were measured under field conditions with plant samples taken at Feekes Growth Stages 6, 10, 10.5, and 11.1. NRA was measured using an in vivo assay method on fully expanded leaves representing the upper most part of the canopy. Results indicated that N uptake was highest during Stages 10.5 to 11.1, although not significantly different for all cultivars. Few differences were found among cultivars for N concentration. The NRA measured under field conditions was more stable at Growth Stage 6. Path coefficients between NRA and DW, N uptake, and N concentration varied considerably depending on the growth stage, indicating that selection for N utilization using one or more of the measurements evaluated in this study should consider the stage of growth.  相似文献   

16.
Nitrate reductase activity (NRA) was determined to investigate the effect of salinity and nitrogen (N) interactions on alfalfa [Medicago sativa (L) cv. Gilboa] during its vegetative growth. Increasing levels of sodium chloride (NaCl) (0, 30, 65, and 100 mM) decreased NRA in both plant parts, i.e., root and leaf, however to a lesser extent in leaves. The inclusion of Neither as nitrate (NO3) or ammonium (NH4) (0, 3, and 6 mM) to the nutrient medium resulted in a substantial enhancement of NR activity in salinized and non‐salinized plants as well.  相似文献   

17.
The effectiveness of reforestation programs on degraded soils in the Mediterranean region is frequently limited by a low soil availability and a poor plant uptake and assimilation of nutrients. While organic amendments can improve the nutrient supply, inoculation with mycorrhizal fungi can enhance plant nutrient uptake. A pot experiment was conducted in 2004 to study the influence of inoculation with an arbuscular mycorrhizal (AM) fungus (Glomus intraradices Schenck & Smith) or with a mixture of three AM fungi (G. intraradices, G. deserticola Trappe, Bloss. & Menge, and G. mosseae (Nicol & Gerd.) Gerd. & Trappe) and of an addition of composted sewage sludge or Aspergillus niger–treated dry‐olive‐cake residue on plant growth, nutrient uptake, mycorrhizal colonization, and nitrate reductase (NR) activity in shoot and roots of Juniperus oxycedrus L. Six months after planting, the inoculation of the seedlings with G. intraradices or a mixture of three AM fungi was the most effective treatment for stimulating growth of J. oxycedrus. There were no differences between the two mycorrhizal treatments. All treatments increased plant growth and foliar N and P contents compared to the control plants. Mycorrhizal inoculation and organic amendments, particularly fermented dry olive cake, increased significantly the NR activity in roots.  相似文献   

18.
《Journal of plant nutrition》2013,36(8):1381-1393
Abstract

Root and leaf ferric chelate reductase (FCR) activity in Annona glabra L. (pond apple), native to subtropical wetland habitats and Annona muricata L. (soursop), native to nonwetland tropical habitats, was determined under iron (Fe)-sufficient and Fe-deficient conditions. One-year-old seedlings of each species were grown with 2, 22.5, or 45 µM Fe in a nutrient solution. The degree of tolerance of Fe deficiency was evaluated by determining root and leaf FCR activity, leaf chlorophyll index, Fe concentration in recently mature leaves, and plant growth. Root FCR activity was generally lower in soursop than in pond apple. Eighty days after plants were put in nutrient solutions, leaf FCR activity of each species was lower in plants grown with low Fe concentrations (2 µM) than in plants grown with high (22.5 or 45 µM) Fe concentrations in the nutrient solution. Leaves of pond apple grown without Fe became chlorotic within 6 weeks. The Fe level in the nutrient solution had no effect on fresh and dry weights of soursop. Lack of Fe decreased the leaf chlorophyll index and Fe concentration in recently matured leaves less in soursop than in pond apple. The rapid development of leaf chlorosis in low Fe conditions and low root and leaf FCR activities of pond apple are probably related to its native origin in wetland areas, where there is sufficient soluble Fe for adequate plant growth and development. The higher leaf FCR activity and slower growth rate of soursop compared to pond apple may explain why soursop did not exhibit leaf chlorosis even under low Fe conditions.  相似文献   

19.
Although scarcity of irrigation water is one of the key limiting factors for wheat production in many regions of the world, by using partial irrigation at strategic times during the growing season, it might be possible to enhance productivity. We measured the changes in various parameters related to nitrogen (N) metabolism in flag leaf and grain of wheat (Triticum aestivum L.) plants (cv. Jinan 17 and Lumai 21), which were subjected to five irrigation regimes until physiological maturity. Severely deficient or excessive irrigation during grain filling decreased the photosynthetic rate (A), the concentrations of N, free amino acid, and soluble protein, as well as the activities of nitrate reductase (NR) and glutamine synthetase (GS) and increased malondialdehyde (MDA) accumulation and endopeptidase (EP) activity, though grain protein concentration might mainly depend on genotype. The activities of NR and GS were significantly positively correlated with A, but those of EP were significantly negatively correlated with A. The results indicate that while severe water stress aggravates the adverse effect on nitrogen metabolism, excessive soil moisture is also not useful during the grain‐filling stage, resulting in lower grain yield and quality. Our results suggest that applying an optimal irrigation regime in wheat fields still plays an important role in the improvement of grain yield and quality.  相似文献   

20.
Sulfur (S)‐diagnostic tools are essential for rational use of S fertilizers. There is little information about the suitability of leaf greenness intensity to detect S deficiency in corn (Zea mays L.). This work evaluates, under controlled S‐stressed conditions, (1) the performance of leaf greenness intensity as an indicator of the degree of S deficiency in corn, and (2) the advantage of the upper leaves in relation to the middle leaves for S‐deficiency determination. A pot experiment using sand as growth medium was conducted in greenhouse with corn at S rates of 0, 5, 10, 20, and 40 mg kg–1 and sufficiency of other nutrients. Measurements of aboveground biomass (AB), total nitrogen (N), and S concentrations, and chlorophyll‐meter readings (CMR) in upper and middle leaves, were performed at the growth stages of 6–7, 11–12, and 14–15 fully expanded leaves (V6‐V7, V11‐V12, and V14‐V15, respectively). Sulfur application significantly increased AB, leaf S concentration, and CMR. Significantly positive relationships were obtained between leaf S concentration and CMR. A sulfur‐sufficiency index (SSI) based on CMR measured in upper and middle leaves was significantly associated with AB (R2 = 0.58 and 0.62 for the middle and upper leaves, respectively). It is concluded that under sufficiency of other nutrients and high‐S‐stressed conditions, leaf greenness intensity could be a good indicator of corn S status, although little or no advantage was found for taking CMR from the upper leaves.  相似文献   

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