A simple and efficient system for green note compound biogenesis by use of certain lipoxygenase and hydroperoxide lyase sources

Six-carbon (C(6)) aldehydes and alcohols are important components of the aroma and flavor of fruits and vegetables. Soybean lipoxygenase (LOX) isozyme LOX 3 was reported not only to produce less 13-hydroperoxides, precursors of C(6) aldehydes, but also to convert them to ketodiene products. Here, we examined the effects of LOX 3 on hexenal formation from linolenic acid homogenized with watermelon 13-hydroperoxide lyase (HL)-overexpressing Nicotiana tabacum leaves and soybean acetone powder. Compared to the wild type, which contains LOXs 1, 2, and 3, the elimination of LOX 3 in LOX 1 + 2 facilitates greater production of hexenals. The use of LOX 2 alone yielded the highest hexenal production, while a two-step conversion was required for LOX 1 to produce hexenals at high levels due to different pH optima of the enzymes involved. These results clearly demonstrate that the soybeans lacking LOX 3 in combination with watermelon HL-overexpressing leaf tissues greatly enhance hexenal formation.     

生物炭对盐胁迫下黄瓜叶片抗氧化酶活性和矿质元素累积的影响

  目的  研究生物炭对盐胁迫下设施黄瓜生长和生理特性的影响。  方法  以设施黄瓜（Cucumis sativus L.）专用品种‘翠龙’为试验材料,开展温室盆栽试验,设非盐胁迫和盐胁迫下栽培基质（草炭∶蛭石 = 2∶1）中添加0%（B0,w/w）、3%（B3）和5%（B5）的花生壳炭共6个处理,调查黄瓜的生长、产量、品质、叶片抗氧化酶活性以及矿质元素含量等指标。  结果  生物炭施用可明显提高黄瓜的耐盐性,在NaCl胁迫下,B5处理黄瓜的株高、最大单叶叶面积、产量和抗坏血酸含量均显著高于不施生物炭处理,且B3和B5处理的黄瓜果实硝酸盐含量在非盐胁迫和盐胁迫下均显著低于对照。盐胁迫下,春、秋两季栽培试验中B5处理黄瓜产量分别为对照处理的2.97倍和2.57倍。生物炭处理使黄瓜叶片抗氧化酶活性在盐胁迫下维持较高水平,特别是B5处理黄瓜植株叶片超氧化物歧化酶（SOD）、过氧化物酶（POD）活性与对照相比显著增加而丙二醛（MDA）含量与对照相比显著降低。盐胁迫下,生物炭处理黄瓜顶部叶片中氮和钾的含量与对照相比显著升高,磷、钠、钙和镁的含量与对照相比显著降低;而在底部叶片中除钠含量显著高于对照外,其他元素的含量在不同生物炭施用量间存在差异。  结论  基质中添加适量的生物炭促进盐胁迫下黄瓜生长,增强抗氧化酶活性,促进氮和钾在顶部叶片的累积,减少钠的累积,缓解盐胁迫对黄瓜的伤害,且以添加5%生物炭处理效果较好。     

Analysis of CoQ10 in cultivated tobacco by a high-performance liquid chromatography-ultraviolet method

Coenzyme Q (CoQ) is a naturally occurring lipid-soluble quinone that performs multiple functions in all living cells and has become a popular antioxidant supplement, a coadjuvant in the treatment of heart disease, and the object of study for treating neurodegenerative disorders. Although there are many tools for CoQ analysis of microbial and animal samples, there have been relatively few reports of methods for CoQ analysis of green plants. This work describes a method for the routine analysis of coenzyme Q(10) in green leaf tissue of cultivated Nicotiana tabacum (tobacco) using high-performance liquid chromatography (HPLC) with UV detection. The method was applied to the analysis of CoQ(10) in N. tabacum 'KY14' leaves at different stalk positions representing young lanceolate to senescing leaves, and it was found that CoQ(10) increased as leaf position changed down the stalk from 18.69 to 82.68 μg/g fw. The method was also used to observe CoQ(10) in N. tabacum 'NC55' and N. tabacum 'TN90LC' leaves over time, finding that CoQ(10) leaf content remained relatively stable from 3 to 6 weeks but increased in both cultivars at 8 weeks. This method will likely be useful in the analysis of CoQ(10) in the green leaves of other plant species.     

滴灌施肥对大棚西瓜生长、产量及品质的影响

该文从优质高产、高效和节水节肥的三重目标出发,通过大田试验,研究在西北旱区对大棚膜下滴灌施肥条件下不同生育时期水肥组合对西瓜生长、产量、灌溉水分利用效率和果实品质的影响,从而确定西瓜适宜滴灌施肥的水肥用量。试验设置3个灌溉量水平:450 m3/hm2(W1)、900 m3/hm2(W2)、1350 m3/hm2(W3),3个施肥水平:N 81.53 kg/hm2+P2O5 33.43 kg/hm2+K2O 101.09 kg/hm2(F1),N 163.05 kg/hm2+P2O5 66.85 kg/hm2+K2O202.18 kg/hm2(F2),N 244.58 kg/hm2+P2O5 100.28 kg/hm2+K2O 303.27 kg/hm2(F3),共9个处理。结果表明:在相同肥料处理条件下,提高灌水量有利于西瓜株高生长,但茎粗减小,发生徒长。F2W2处理能使西瓜叶片叶绿素含量在各个生育期保持较高水平。在西瓜苗期,增加水肥用量的F3W3处理提高了西瓜叶片净光合速率和蒸腾速率,但与F2W2处理差异不显著。坐果期后,F2W2处理的西瓜光合能力较强,获得了较高的产量和水分利用效率,较提高灌水量和施肥量的F3W3处理增产3.6%,灌溉水分利用效率(irrigation water use efficency,iWUE)提高35.73%。在果实品质方面,F2W2处理的西瓜中、边可溶性固形物、可溶性蛋白质和番茄红素等质量分数表现最好,F2W1处理的西瓜可溶性总糖质量分数最高,F3W2处理的西瓜总维生素C质量分数最高,但与F2W2处理差异不显著,且F2W2处理西瓜产生最佳的糖酸比,口感极佳。综合分析表明,F2W2处理的西瓜生长健壮,光合作用强,优质高产,且水分利用效率较高,是利于西北旱作膜下滴灌条件下西瓜生产中适宜的水肥组合。     

玉米/大豆套作下作物叶片氮、磷动态特征及其相关性分析

在田间小区试验条件下,以登海605（紧凑型）、 川单418（半紧凑型）、 雅玉13（松散型）3个玉米品种,贡选1和桂夏3两个大豆品种为试验材料,采用玉米/大豆套作种植模式,在仁寿和雅安试验点研究玉米拔节期、 大喇叭口期、 子粒建成期和成熟期以及大豆苗期、 始花期和鼓粒期叶片氮、 磷养分动态规律,分析玉米和大豆叶片氮磷含量之间的相关性。结果表明,两大豆品种无论是净作还是套种,叶片氮含量在苗期最低,磷含量在苗期最高;大豆与雅玉13套作比净作其叶片氮和磷含量分别高出5.81% 和 38.56%以上,而套作大豆叶片氮磷比值却低于净作,仁寿试验点高于雅安试验点,始花期之后净、 套作大豆叶片氮磷含量及其比值变化规律不明显。三种株型玉米叶片磷含量随生育期呈现低高低的规律,其中松散型玉米品种雅玉13叶片磷含量最高;而叶片氮含量在子粒建成期之前变化幅度较小,成熟期达到最低。同样,玉米氮磷比值仁寿试验点高于雅安试验点。通过叶片氮和磷含量及其比值间的相关性分析,玉米和大豆叶片氮、 磷含量与其之间的比例相关性达到显著水平（r0.46, P0.05）,特别是叶片磷含量与氮、 磷比之间的相关性极显著（P0.01）     

Activated antioxidant enzymes-reduced malondialdehyde concentration,and improved mineral uptake-promoted watermelon seedlings growth under boron deficiency

Although boron deficiency (BD) is a drastic disorder to the agriculture crops, its effects on watermelon still unknown. Therefore, the present study investigates the effect of BD (0 and 0.5 mg L^?1) on different morphological, physiological and biochemical traits, and mineral uptake during early seedlings stage of watermelon. B-deficiency induced leaf chlorosis in watermelon initiated from the leaf margins and tips. Despite that, BD increased shoot length, and root and shoot dry weight of BD-watermelon seedlings. BD decreased leaf chlorophyll and carotenoid contents, and photosynthetic parameters without affecting quantum yield of PSII. BD significantly inhibited total soluble protein accumulation, while leaf proline content was unaffected. A significant increase in antioxidant enzyme activities in response to higher hydrogen peroxide (H₂O₂) generation could possibly reduced lipid peroxidation and promoted BD-watermelon plant growth. BD influenced mineral uptake variously: the induction of phosphorus (P) and zinc (Zn), and the preservation of potassium (K), calcium (Ca) and molybdenum (Mo) levels in the leaves could maintain watermelon growth; while, the inhibition of magnesium (Mg) uptake seemed to be responsible for suppressed leaf chlorophyll and photosynthesis. These results would further help in understanding the physiological pathways and mechanisms associated with BD especially in watermelon, and provide database for fertilizer recommendations in B-deficient areas.     

Field estimation of leaf nitrogen by light transmittance

A highly significant negative correlation was found between percentage transmittance of photosynthetically active radiation (%TPAR) through a varied sample of walnut leaves and their extractable chlorophyll content (expressed on a leaf‐area basis). The %TPAR was negatively correlated with leaf nitrogen (N) expressed on a leaf‐area basis. When leaves were sampled from throughout the canopy of a walnut tree, no correlation was obtained between either chlorophyll content or %TPAR and leaf N based on leaf dry wt.; this was due to variation between exposed and shaded leaves in leaf thickness and specific leaf weight (SLW). Regression analysis indicated better correlation between transmittance of photosynthetically active radiation (%TPAR) and leaf N when data were fitted to quadratic or exponential functions rather than to a linear formula. Thus, estimation of leaf N level by %TPAR is more sensitive at lower levels of leaf N. When exposed leaves from trees differing in N status were analyzed, %TPAR was negatively correlated with almond and nectarine leaf N levels. Although variation among %TPAR determinations is greater than variation among analytical N determinations, the ease and rapidity of the proposed method could provide a rapid, inexpensive estimate of leaf N in the field.     

白菜NAC转录因子BrcCUC3基因克隆及其对叶缘和主枝发育的影响

植物NAC (矮牵牛NAM基因、拟南芥ATAF1/2和CUC2基因)转录因子CUP-SHAPED COTYLEDON(CUC)亚家族成员在植物茎尖分生组织形态建成、器官边界分离、叶发育方面发挥着重要作用.采用基因同源克隆的方法获得了白菜(Brassica rapa ssp.chinensis)基因BrcCUC3,并转化拟南芥(Arabidopsis thaliana)做了初步的功能鉴定.研究结果表明,白菜Brc CUC3的编码区长1 008 bp,编码335个氨基酸,基因结构分析显示BrcCUC3包含3个外显子、2个内含子,内含子剪接位点符合GT-AG规则.氨基酸序列分析表明,BrcCUC3蛋白具有典型的植物NAC domain结构域.BrcCUC3编码区氨基酸序列与其它植物的CUC3蛋白有很高的一致性,尤其与甘蓝(Brasica oleracea)、萝卜(Raphanus sativus)和拟南芥CUC3蛋白高度一致,一致性分别达到98％,97％和83％.在不同物种CUC3的系统进化树上,BrcCUC3归属于双子叶植物分支的十字花科亚组,由不同植物20条CUC3编码区氨基酸序列所建立的系统进化树与真实的植物进化基本一致.荧光定量PCR分析结果表明,BrcCUC3在白菜叶深裂株系叶片中的表达量比叶全缘叶片中的高.利用根癌农杆菌(A grobacterium tumefaciens)浸花法转化拟南芥,获得了转BrcCUC3基因的拟南芥植株.过表达BrcCUC3的转基因拟南芥呈现叶缘出现裂刻、主枝增加的新表型.初步说明该基因参与叶形和主枝的发育调控,为揭示白菜叶形发育分子调控机制和通过基因工程创制植物叶形新种质提供分子依据.     

Nitrogen‐use efficiency traits of mini‐watermelon in response to grafting and nitrogen‐fertilization doses

Two experiments were conducted to study the effect of grafting on nitrogen‐use efficiency (NUE) in mini‐watermelon plants. In the first study, mini‐watermelon plants (Citrullus lanatus [Thumb.] Matsum. and Nakai cv. Minirossa) either ungrafted or grafted onto Macis, Vita (Lagenaria siceraria [Mol.] Standl.), PS1313, and RP15 (Cucurbita maxima Duchesne × Cucurbita moschata Duchesne) rootstocks grown in hydroponics were compared in terms of shoot dry biomass, leaf area, root‐to‐shoot ratio, SPAD index, shoot N uptake, and nitrate reductase (NR) activity 40 d after transplantation in response to nitrate concentration in the nutrient solution (0.5, 2.5, 5, 10, 15, or 20 mM of NO$ _3^- $ ). In the second experiment, the suitability of a selected rootstock with high NUE (Vita) to improve crop performance and NUE of grafted mini‐watermelon plants was evaluated under field conditions. In the hydroponic experiment mini‐watermelon grafted onto Vita rootstock needed the lowest nitrate concentration (1.31 mM of NO₃) in the nutrient solution to reach half maximum shoot dry weight. Total leaf area, SPAD index, and shoot N uptake increased in response to an increase of N concentration in the nutrient solution. At 2.5 mM NO$ _3^- $ , mini‐watermelon grafted on either Vita or RP15 had the highest NR activity whereas no significant difference was observed at 10 mM NO$ _3^- $ . The open‐field study indicated that increasing N‐fertilization rates from 0 to 100 kg ha^–1 improved total and marketable yields of mini‐watermelon plants while decreasing NUE. When averaged over N levels, the marketable yield, NUE, N‐uptake efficiency, and N‐utilization efficiency were significantly higher by 39%, 38%, 21%, and 17%, respectively, in Minirossa grafted onto Vita compared to ungrafted Minirossa plants. Therefore, grafting mini‐watermelon plants onto selected rootstocks can be used as a quick and effective method for improving productivity and NUE.     

Thermally generated 3-aminopropionamide as a transient intermediate in the formation of acrylamide

On the basis of the recent findings that "biogenic amines" can also be formed during thermal food processing from their parent amino acids in a Strecker-type reaction, the formation of 3-aminopropionamide, the biogenic amine of asparagine, was investigated in model systems as well as in thermally processed Gouda cheese. The results of model studies revealed that, besides acrylamide, 3-aminopropionamide was also formed in amounts of 0.1-0.4 mol % when asparagine was reacted in the presence of either glucose or 2-oxopropionic acid. Results of a second series of model experiments in which [(13)C(4)(15)N(2)]-asparagine ([(13)C(4)(15)N(2)]-Asn) and unlabeled 3-aminopropionamide were reacted together in the presence of glucose revealed a >12-fold higher efficacy of 3-aminopropionamide in acrylamide generation as compared to asparagine. Both [(13)C(3)(15)N(2)]-3-aminopropionamide and [(13)C(3)(15)N(1)]-acrylamide were formed during [(13)C(4)(15)N(2)]-Asn degradation in a ratio of about 1:4, supporting the idea that 3-aminopropionamide is a transient intermediate in acrylamide formation. In this study, 3-aminopropionamide was identified and quantified for the first time in foods, namely, in Gouda cheese. Although the fresh cheese contained low amounts of 3-aminopropionamide, its concentrations were much increased to approximately 1300 mug/kg after thermal processing. In isotope labeling studies, performed by administering to the cheese [(13)C(4)(15)N(2)]-Asn in a ratio of 1:2 as compared to the "natural" concentrations of asparagine, similar ratios of unlabeled/labeled 3-aminopropionamide and unlabeled/labeled acrylamide were determined. Thus, 3-aminopropionamide could be verified as a transient intermediate of acrylamide formation during food processing.     

氮钾肥施用方法对烤烟品质及经济效益的影响

针对河南烟区烤烟生产中施肥时所提供的氮、钾量与烟株生长的需氮、钾规律不吻合现状,采用大田小区试验,设置不同烟草专用氮钾肥基追肥比例10∶0、7∶3、5∶5,并配合钾肥在烟株生长旺长期—圆顶期不同兑水淋施处理,研究不同氮钾肥施用方法对烤烟化学成分、中性致香成分质量分数及经济效益的影响。结果表明：1）采用前期施足基肥（70%烟草专用肥）,适量追肥（30%烟草专用肥）,硝酸钾在旺长期—圆顶期分3次兑水追施的施肥方式能够显著提高中、上部烟叶的钾质量分数,使烟叶糖/碱比、钾/氯比趋于协调,提高了上部烟叶的可用性;该处理与对照相比,中、上部烟叶钾质量分数分别提高了49.70%和95.2%。2）从香气物质上来看,该处理中部烟叶中性致香成分中的棕色化产物、类胡萝卜素类、新植二烯香气物质和香气总量分别比对照提高6.59、45.45、249.13和326.89μg/g,增幅分别达36.96%、36.29%、51.70%和49.52%。3）从经济效益上来看,该处理与对照相比增产125.05 kg/hm2,增加产值3 737.81元/hm2。因此,烟草专用肥以7∶3的比例分别在移栽时和大培土时施用、全部的硝酸钾肥在旺长期—圆顶期分3次兑水淋施的施肥措施下烟叶化学成分更协调。该处理增加了烟草香气物质的质量分数,从而显著提高了烟叶产值。     

Diurnal patterns of nitrate assimilation in Kentucky bluegrass

Kentucky bluegrass (Poapratensis L.) is a major C₃‐type forage and turfgrass, but it is less efficient than many grasses in utilizing nitrogen(N). To determine how this grass can accommodate its greater N need, diurnal patterns of nitrate reductase activity (NRA) and nitrite reductase activity (NiRA) in its leaves and roots were examined and compared with those in barley (Hordeum vulgare L.). Plants were grown under greenhouse or growth room conditions and assayed for NRA and NiRA by optimized in vivo methods. The diurnal patterns of NRA and NiRA indicated that Kentucky bluegrass could assimilate nitrate during the night at rates greater than or similar to those during the day. Leaf NRA of Kentucky bluegrass was minimal approximately 4 and 10 h after illumination commenced and increased at night. The diurnal pattern of leaf NRA among Kentucky bluegrass cultivars did not differ significantly. In roots, NRA of Kentucky bluegrass was high in the morning and decreased sharply during the afternoon and evening, but increased again late at night. Unlike Kentucky bluegrass, barley exhibited greater leaf NRA during the day than during the night and exhibited the greatest activity 6 or 10 h after illumination commenced. In both species, the equilibrium leaf nitrate pool was 20 to 30 times larger than the ammonium pool and 3, 000 to 13, 000 times larger than the nitrite pool. Leaf nitrate pool size showed a diurnal pattern complementary to that of leaf NRA. Our results suggest that a nighttime N use strategy might exist in Kentucky bluegrass.     

Stimulation of nicotine demethylation by NaHCO(3) treatment using greenhouse-grown burley tobacco

Experiments were conducted in tobacco (Nicotiana tabacum L.) to investigate the effect of sodium bicarbonate (NaHCO(3)) on the conversion of nicotine to nornicotine, a secondary alkaloid that can form the tobacco-specific nitrosamine N-nitrosonornicotine (NNN). The results showed that, under optimum conditions, NaHCO(3) stimulated nicotine conversion in converter plants to the maximum level predetermined by the genetic background. The conversion level in NaHCO(3)-treated leaves was 2-3 times higher than that in control leaves. For young seedlings the optimum concentration of sodium bicarbonate was 0.8% aqueous solution, and for adult plants the optimum concentration was 1%. Lower concentrations resulted in partial stimulation, whereas higher concentration damaged leaf tissue and resulted in a lower conversion level. Studies with different temperatures (from 22 to 43 degrees C) showed that 37 degrees C was optimal. This temperature allowed the least amount of time, 2-3 days for mature leaves and 4-6 days for green leaves, for the major converters to reach >95% of nicotine conversion. An examination of leaves from different growth stages and stalk positions showed that the amount of time needed for conversion was longer for young leaves and shorter for mature leaves. Treatment of leaves with NaHCO(3) affords a rapid and convenient means of identifying and removing nornicotine converter plants during growth in the greenhouse or field.     

Nitrogen rate and source affects leaf elemental concentration and plant growth in muscadine grapes

Leaf concentrations of nitrogen (N), phosphorus (P), potassium (K), iron (Fe), and manganese (Mn) in ‘Sterling’ muscadine grapes (Vitis rotundifolia Michaux) grown for two years in sand culture were not influenced by different N‐fertilizer sources. Leaf zinc (Zn) and copper (Cu) were higher with ammonium nitrate (NH₄NO₃)than ammonium sulfate [(NH₄)₂SO₄]. Shoot growth was greatest with NH₄NO₃. Leaf Ca, Mg, Mn, and Cu content decreased and leaf N increased as N‐fertilizer rates were raised. Plant growth was positively correlated with leaf N, but was negatively correlated with leaf Ca, Mg, Fe, Cu, and Mn content. Percent Mg in the leaves was reduced when N levels, regardless of N source, were raised from the low (1.8 mM) to the middle (5.4 mM) rate. High leaf‐N levels were correlated with lower Ca and Mg in the leaves, indicating a relationship between N fertilization and the late‐season Mg deficiency often observed in muscadine grapes.     

Variation in soil nitrifiers and leaf nitrate reductase activity of selected tree species in a forest community

Nitrate reductase activity of green leaves of red oak, hemlock, basswood, sugar maple and beech were studied in relation to soil ammonifier and nitrifier populations and available mineral N of associated soils in a forest community near Ithaca, New York. Significant intersite, i.e. interspecific, differences were found for all plant and soil factors studied. Extractable NH⁺₄-N was higher than NO₃⁻-N under all species. Nitrate reductase activities (NRA) of the green leaves of the five dominant species were significantly correlated with soil NO₃⁻-N beneath the tree canopies (P < 0.001). Nitrosomonas and Nilrobacter counts were intercorrelated (P < 0.001), and Nitrobacter was found to be related to both soil NH⁺₄ (P < 0.05) and soil NO⁻₃ (P < 0.001). Nitrosomonas and Nitrobacter counts were highest under basswood, and leaf NRA was 20–50 times higher in basswood leaves than in any of the other four species. Basswood also had the highest total leaf N, 5.02 ± 0.06%. Our data suggest that in these forest stands, green-leaf nitrate reductase activity is a reliable index of soil mineral N usage by the five species. Moreover, we believe that the data support the notion that Nitrobacter populations, and thus nitrification rates, are inhibited by the dominant tree species to result in a more ammonium-based nutrition, which on the system level ultimately has a conserving effect on the N economy of these stands.     

蓖麻叶片粗提物对黄瓜瓜绢螟的作用

为了测定蓖麻对瓜绢螟的作用,也为黄瓜害虫无公害控制提供新的手段,用不同浓度的蓖麻叶片粗提物处理黄瓜叶片,测定瓜绢螟取食量、存活率及体内解毒酶活性的变化。结果显示,蓖麻叶片粗提物对瓜绢螟的取食和存活有明显的抑制作用,处理浓度越大,取食量和存活率越小。如用稀释200倍的蓖麻叶片粗提液处理黄瓜叶片,瓜绢螟的取食面积(1.89 cm2)仅为对照(3.51 cm2)的53.7%,存活率为对照的2.3%;600倍浸提液处理的瓜绢螟取食面积(3.43 cm2)为对照的97.7%,存活率为对照的51.4%。瓜绢螟幼虫虫龄对粗提物的作用有明显影响,粗提物对低龄幼虫的作用明显强于高龄幼虫,200倍液处理24 h后,1龄幼虫的存活率(22.22%)仅为5龄幼虫(66.67%)的33.33%。不同剂量蓖麻叶片粗提物处理后,瓜绢螟体内的谷胱甘肽转移酶、羧酸脂酶、多功能氧化酶等解毒酶活性迅速上升,随着处理剂量的增加,解毒酶的活性上升幅度增大。取食用稀释200倍的蓖麻粗提液处理的黄瓜叶片24 h后,1龄幼虫和5龄幼虫体内谷胱甘肽转移酶活性分别较对照高23.79%和78.02%,羧酸脂酶活性分别较对照高72.42%和23.84%,多功能氧化酶活性分别较对照高100.58%和122.39%。结果表明,蓖麻叶片粗提物对瓜绢螟有明显的拒食和毒杀作用。     

西瓜钾营养诊断的叶片含量法分析

采用不同土壤钾水平的多点田间试验,研究了施用钾肥对西瓜植株钾含量以及产量、品质的影响,探讨了西瓜植株各叶位钾含量与西瓜产量之间的相关性,分析了叶片钾含量诊断西瓜钾营养的临界指标。结果表明:西瓜新叶钾含量与西瓜产量达极显著相关关系,相关系数为0.600 8(P_(0.01)=0.575)。90%相对产量下新叶钾含量为32.6 g/kg时,西瓜产量可达91.39 t/hm~2。在极低钾含量(50 mg/kg和70 mg/kg)的土壤上,施用钾肥显著提高西瓜产量、开花期西瓜植株新叶和老叶钾含量;显著提高开花期、坐果期和膨大期西瓜植株茎和根中的钾含量。在低钾含量(84 mg/kg和85 mg/kg)的土壤上,施用钾肥显著提高西瓜产量,提高西瓜果实中的可溶性糖和可溶性固形物的含量而降低可滴定酸含量。随着钾肥施用水平的提高,新叶钾含量有提高趋势,老叶和挂果叶中的钾含量逐渐升高;施用钾肥显著提高坐果期和膨大期西瓜植株茎中钾含量。在中钾含量(170 mg/kg)和高钾含量(260 mg/kg)的土壤上,西瓜开花期新叶钾含量的最大值和最高产量相关联。总之,推荐开花期西瓜新叶钾含量32.61 g/kg为营养诊断临界值。     

Foliar Nitrogen Uptake from Wet Deposition and the Relation with Leaf Wettability and Water Storage Capacity

This study assessed the foliar uptake of ¹⁵N-labelled nitrogen (N) originating from wet deposition along with leaf surface conditions, measured by wettability and water storage capacity. Foliar ¹⁵N uptake was measured on saplings of silver birch, European beech, pedunculate oak and Scots pine and the effect of nitrogen form (NH ₄ ⁺ or NO ₃ ^? ), NH ₄ ⁺ to NO ₃ ^? ratio and leaf phenology on this N uptake was assessed. Next to this, leaf wettability and water storage capacity were determined for each tree species and phenological stage, and the relationship with ¹⁵NH ₄ ⁺ and ¹⁵NO ₃ ^? uptake was examined. Uptake rates were on average five times higher (p?<?0.05) for NH ₄ ⁺ than for NO ₃ ^? and four times higher for deciduous species than for Scots pine. Developing leaves showed lower uptake than fully developed and senescent leaves, but this effect was tree species dependent. The applied NH ₄ ⁺ to NO ₃ ^? ratio did only affect the amount of N uptake by senescent leaves. The negative correlation between measured leaf contact angles and foliar N uptake demonstrates that the observed effects of tree species and phenological stage are related to differences in leaf wettability and not to water storage capacity.     

施氮对不同肥力土壤小麦氮营养和产量的影响

【目的】农田养分供应是由土壤基础肥力和肥料投入共同决定的,不同土壤肥力下土壤养分供应能力和特征也不同。本文研究了河南省高、低肥力田块下,不同施氮量对小麦主要生育时期植株氮素营养和土壤硝态氮及产量的影响,以期为河南省同类生产条件下氮肥的合理施用和产量的提升提供参考和依据。【方法】2015—2016年,以小麦品种矮抗58为供试材料进行大田试验,分别设置0、120、225、330 kg/hm^2 4个施氮处理(表示为N0、N1、N2、N3),在开花期到成熟期调查施氮量对土壤硝态氮及产量的影响;在开花期、花后10天和花后20天,测定施氮量对小麦旗叶到倒4叶的叶片氮含量、SPAD值和氮素积累量,以及对植株和所有叶片氮含量的影响。【结果】从开花期到成熟期土壤中硝态氮含量随着施氮量的增加而增加,高肥力田块的土壤硝态氮含量显著高于低肥力田块的土壤硝态氮含量。施氮能显著增加低肥力田块产量,但是高肥力田块的产量均高于低肥力田块,与不施氮相比,低肥力田块的产量最大增幅是高肥力田块产量最大增幅的2.63倍。N1和N2处理下,在开花期和花后10天倒2叶的SPAD值高肥力田块显著高于低肥力田块,但在花后20天低肥力田块显著高于高肥力田块。在N1、N2和N3处理下,旗叶的氮含量在花后10天高肥力田块显著高于低肥力田块,但在花后20天则显著相反。开花期到花后20天,对于低肥力田块旗叶的氮素积累量对上4叶的贡献率最大(N0除外),最高达52.6%;高肥力田块,旗叶和倒2叶对上4叶的氮素积累量贡献率处在同等重要的位置,最高分别达39.9%和39.7%。花后10天到花后20天,高肥力田块不同叶位的氮素转运量和转运率均高于低肥力田块(N0除外)。【结论】增施氮肥可以通过提高土壤硝态氮含量来提高土壤供氮能力,高肥力田块的叶片转运量和转运率比低肥力田块高,低肥力田块通过提高施氮量增加的产量低于高肥力田块下的产量,因此,需改善农田基础肥力来提高产量。通过对高、低肥力条件下产量的分析发现,达到最高产量时的施氮量分别为213kg/hm^2和287 kg/hm^2。     

不同产量水平下花生功能叶片氮素代谢特征的研究

大田栽培条件下, 研究了不同产量水平下花生功能叶片中氮代谢关键酶活性、可溶性蛋白质和游离氨基酸含量的变化, 重点阐述超高产水平下花生功能叶片氮素代谢变化规律。研究结果表明: 自花生初花期, 不同产量水平的功能叶片中, 硝酸还原酶(NR)活性均呈逐渐下降的变化趋势, 超高产与高产花生相比无明显差异, 但明显高于一般产量花生; 不同产量水平功能叶片中谷氨酰胺合成酶(GS)的活性变化呈单峰曲线, 峰值出现在结荚期, 超高产花生功能叶片谷氨酰胺合成酶活性明显高于高产花生和一般产量花生, 而且在生育中后期活性下降速度慢; 功能叶片中谷氨酸脱氢酶(GDH)活性未表现出规律性变化, 但超高产花生明显高于高产和一般产量的花生; 超高产花生功能叶片中可溶性蛋白质及游离氨基酸含量均明显高于高产花生和一般产量花生。研究认为, 超高产花生叶片氨的同化能力、蛋白质和氨基酸的合成能力均明显高于高产花生和一般产量花生, 而且衰老缓慢, 功能期维持时间长。