莲藕干物质和氮磷钾养分的累积与分配研究

连续2年采用盆栽试验研究了莲藕（Nelumbo nucifera Gaertn）干物质和氮磷钾养分的累积与分配规律。结果表明：莲藕苗期以叶片生长并积累光合产物为主,膨大根状茎成型后,叶片、叶柄和根状茎中的干物质不断运输并贮存到膨大根状茎中,以产量形成为主,干物质累积总量增长呈＂慢-快-稳定＂的变化趋势;氮磷钾累积量与干物质累积量变化趋势一致,并与之呈极显著正相关,莲藕氮磷钾养分累积总量之比为1∶0.12∶1.31。移栽后97-160 d是莲藕产量形成的关键时期,不仅叶片、叶柄和根状茎中的氮磷钾随同干物质运输并贮存到膨大根状茎中,根系还从土壤中吸收更多的氮磷钾直接运输并贮存到膨大根状茎中,后者分别占同期氮磷钾累积量的69.8%、79.2%和75.0%。160 d膨大根状茎中干物质、氮、磷和钾累积量分别平均占植株总累积量的81.1%、85.2%、88.8%和80.2%。     

Translocation and Metabolism of Endosperm-Applied [2-C] Indoleacetic Acid in Etiolated Avena sativa L. Seedlings

The role of free indole-3-acetic acid (IAA) in the endosperm of Avena sativa L. seedlings was investigated to determine its contribution to free IAA in the shoot. [2-¹⁴C]IAA was injected into the endosperm of darkgrown seedlings and the transport and metabolism of the [¹⁴C]-labeled compounds determined. It was concluded that translocation of free IAA directly from the endosperm is probably not a significant source of free IAA in the shoot, mainly because even small amounts of [¹⁴C]IAA introduced into the endosperm were rapidly metabolized. This suggested that, in Avena, free IAA does not normally exist in the liquid endosperm.     

Changes in lipoxygenase properties and activity related to postgerminative growth and senescence in oat (Avena sativa L cv. Victory 1 )

Lipoxygenase (LOX), one of the main oxidative catalysts in plants, is involved in the regulation of growth and senescence. We investigated changes in LOX activity or its properties as they related to the development of oat plants at four stages (germination, growth, natural senescence, and dark-incubated senescence). LOX activity was high during early growth and at senescence. At pH 4.5, activity showed an abrupt surge compared with a normal enzyme reaction pattern at pH 6.5. The optimum reaction temperature was 25°C; LOX and peroxidase exhibited similar activity patterns. Polyacrylamide gel electrophoresis revealed that the purified LOX consisted of three isoenzymes in germinating seeds, two in growing seedlings, and three during both natural and dark-induced senescence. As determined by isoelectric focusing, the isoelectric points (pl) of LOX ranged from 3.6 to 6.5 throughout the four developmental stages; for natural or dark-induced senescence, the pl was 9.0.     

黄芩干物质累积和氮磷钾吸收、分配规律研究

为了探讨黄芩干物质累积和氮、磷、钾吸收与分配的特点及两者间的相互关系,通过田间试验和采样分析,研究了黄芩不同生育期植株的干物质和氮、磷、钾累积量.结果表明,黄芩干物质的累积量随生育进程不断地增加,出苗后52～85 d干物质累积量占总累积量的61.62％.在整个生育期,黄芩对K2O的吸收累积量最大,N次之,P2O5最小,N、P2O5、K2O吸收比例约为2.8∶1.0∶2.9,并且黄芩地上部氮磷钾的累积量大于根部,不同生育期,根部N、P2O5、K2O的累积比例呈现增加—降低—增加的趋势.黄芩对氮磷钾的积累量与干物质积累量呈极显著正相关关系.在供试的土壤和施肥条件下,每生产100 kg的黄芩根需要从土壤和肥料中吸收6.34 kg的N,2.60 kg的P2O5,7.02 kg的K2O.     

Two new secondary metabolites isolated from Avena sativa L. (Oat) seedlings and their effects on osteoblast differentiation

Seedlings of natural crops are valuable sources of pharmacologically active phytochemicals. In this study, we aimed to identify new active secondary metabolites in Avena sativa L. (oat) seedlings. Two new compounds, avenafuranol (1) and diosgenoside (2), along with eight known compounds (3–10) were isolated from the A. sativa L. seedlings. Their chemical structures were elucidated via 1D and 2D NMR spectroscopy, high-resolution ESIMS, IR spectroscopy, optical rotation analysis, and comparisons with the reported literature. The effect of each isolated compound on alkaline phosphatase (ALP) activity for osteoblast differentiation induced by bone morphogenetic protein-2 (BMP-2) was investigated using the C2C12 immortal mouse myoblast cell line. Compounds 1, 4, 6, 8, and 9 induced dose-dependent increases in ALP expression relative to ALP expression in cells treated with only BMP-2, and no cytotoxicity was observed. These results suggest that A. sativa L. seedlings are a natural source of compounds that may be useful for preventing bone disorders.     

Changes in the Distribution of Magnesium, Potassium, Calcium and Phosphorus during Growth of Cucurbita Seedlings

Ockenden, I. and Lott, J. N. A. 1988. Changes in the distributionof magnesium, potassium, calcium and phosphorus during growthof Cucurbita seedlings—J. exp. Bot. 39: 973–980. Etiolated seedlings of Cucurbita maxima cv. Warted Hubbard andCucurbita andreana, grown in distilled water, showed considerablegrowth. However, only a small percentage of the minerals storedin the large cotyledons was mobilized to the root-shoot axisof the etiolated seedlings. The proportion of minerals removedfrom the cotyledons to the root-shoot axis was about two-timeshigher in C. andreana than in C. maxima. When the seedlingswere grown in distilled water in the presence of light, thepercentage of cotyledon mineral content that was mobilized waslower than the amount mobilized during growth in the dark. Cotyledonsof light-grown seedlings that were given adequate nutrients,took up minerals from the medium. These fully-expanded and photosyntheticcotyledons had slightly more P and Mg than did the cotyledonsof the dry embryos but had increased their K content 5-foldand their Ca content 50-fold. Key words: Cucurbita, minerals, seeds, seedings, NAA     

Uridine and the Control of Phototropism in Oat (Avena sativa L.) Coleoptiles

The short-term growth response of oat (Avena sativa L.) coleoptiles to exogenously applied uridine was studied both in excised apical segments and in the intact seedlings. In both cases growth of coleoptile tissue was inhibited by uridine. The inhibition of coleoptile growth consistently occurred 20–30 min after uridine treatment, which is within the lag period of their phototropic response. Asymmetric application of uridine to coleoptiles in the intact seedlings resulted in their bending toward the direction to which uridine was applied in the absence of light stimulus. These findings suggest that uridine or its metabolites, plays an important role in the phototropism of oat coleoptiles and provide support to the Bruinsma–Hasegawa theory as an alternative to the Cholodny–Went theory for explaining phototropism.     

Induction of Flavonoid Synthesizing Enzymes by Light in Etiolated Pea (Pisum sativum cv. Midfreezer) Seedlings

Etiolated pea (Pisum sativum cv. Midfreezer) seedlings respond to illumination with white light by changes in the activity of phenylpropanoid and flavonoid synthesizing enzymes. Unlike in cell cultures, changes in enzyme activity in pea seedlings are not concerted. Phenylalanine ammonia-lyase (EC 4.3.1.5) activity peaked approximately 18 hours after onset of illumination. The phenylacetate path did not interfere with the measurement of phenylalanine ammonia-lyase activity. Activity of cinnamic acid 4-hydroxylase (EC 1.14.13.11) showed an early peak after 8 hours illumination, declined thereafter sharply, then gradually increased during the remainder of the experiment. Activities of chalcone synthase and UDP glucose:flavonol 3-O-glucosyltransferase (EC 2.4.1.91) increased steadily and reached a plateau after approximately 70 hours illumination time. Activity of 4-hydroxycinnamate:coenzyme A ligase (EC 6.2.1.12) remained relatively unchanged, whereas that of chalcone isomerase (EC 5.5.1.6) declined steadily during the course of the experiment. The relative in vitro enzyme activities suggest that the rate-limiting step for the phenylpropanoid path is the cinnamic acid 4-hydroxylase, that of the flavonoid pathway is the chalcone synthase. Integration of enzyme activity curves, however, show that only the curve deriving from phenylanine ammonia-lyase activity matches closely the production of the flavonol glycosides.     

Glycosyltransferases from Oat (Avena) Implicated in the Acylation of Avenacins

Plants produce a huge array of specialized metabolites that have important functions in defense against biotic and abiotic stresses. Many of these compounds are glycosylated by family 1 glycosyltransferases (GTs). Oats (Avena spp.) make root-derived antimicrobial triterpenes (avenacins) that provide protection against soil-borne diseases. The ability to synthesize avenacins has evolved since the divergence of oats from other cereals and grasses. The major avenacin, A-1, is acylated with N-methylanthranilic acid. Previously, we have cloned and characterized three genes for avenacin synthesis (for the triterpene synthase SAD1, a triterpene-modifying cytochrome P450 SAD2, and the serine carboxypeptidase-like acyl transferase SAD7), which form part of a biosynthetic gene cluster. Here, we identify a fourth member of this gene cluster encoding a GT belonging to clade L of family 1 (UGT74H5), and show that this enzyme is an N-methylanthranilic acid O-glucosyltransferase implicated in the synthesis of avenacin A-1. Two other closely related family 1 GTs (UGT74H6 and UGT74H7) are also expressed in oat roots. One of these (UGT74H6) is able to glucosylate both N-methylanthranilic acid and benzoic acid, whereas the function of the other (UGT74H7) remains unknown. Our investigations indicate that UGT74H5 is likely to be key for the generation of the activated acyl donor used by SAD7 in the synthesis of the major avenacin, A-1, whereas UGT74H6 may contribute to the synthesis of other forms of avenacin that are acylated with benzoic acid.     

Regulation of Growth in Avena (Oat) Stem Segments by Gibberellic Acid and Abscisic Acid

The purpose of this study was to analyze the nature of the interaction between gibberellic acid (GA₃) and abscisic acid (ABA) in the regulation of growth in excised Avena (oat) stem segments. Growth, compared to sucrose controls, was inhibited by ABA in the range of 10^?4 to 10^?6M. GA₃-promoted growth was also inhibited by ABA in the same concentration range. A Lineweaver-Burk analysis of the interaction between GA₃ and ABA indicated that ABA acts in a non-competitive fashion with GA₃. This same result was obtained previously with GA₃-indoleacetic acid (IAA) and GA₃-kinetin interactions with Avena stem sections. Our results indicate that ABA can inhibit GA₃-promoted growth within physiological concentrations, and that it is probably acting at a different physiological site from that for GA₃.     

A possible mechanism of high temperature dormancy regulation in seeds of Avena sativa L. (cv. Moyencourt)

Embryos of Avena sativa L. (cv. Moyencourt) show no high temperature dormancy. The dormancy is induced by the presence of endosperm-aleurone part of the seed. Germination of isolated embryos at 30°C can be prevented by ABA and the inhibition is reversed by GA. Inhibitors of GA synthesis also inhibit embryo germination. The embryos of dormant and non-dormant seeds vary greatly in their sensitivity to exogenous ABA. High temperature dormancy of the entire seeds can be relieved by low concentrations of ethanol. On the basis of these facts a hypothetic model is proposed showing how interaction between endogenous GA and ABA-like inhibitory substance, may regulate the high temperature dormancy of the seeds.     

不同滴灌定额对春播裸燕麦氮磷钾质量分数及产量性状的影响

在大田条件下,采用随机区组设计,研究不同灌溉定额对春播裸燕麦不同生育时期氮磷钾质量分数以及产量性状的影响。结果表明, 裸燕麦高灌溉定额处理不同生育时期茎、叶和穗中氮磷钾的质量分数显著高于低灌溉定额(P<0.05)。滴灌灌溉定额为180 mm（W4处理）时不同生育时期各器官氮磷钾质量分数最高,其他处理由高到低依次为：W5、CK、W3、W2、W1;滴灌灌溉定额为60 mm（W1处理）不同生育时期各器官氮磷钾质量分数最低。滴灌灌溉定额为180 mm（W4处理）时籽粒产量最高（3 249.7 kg/hm）,比传统灌溉（CK处理）籽粒产量提高5.98%,比最低灌溉定额（W1处理）提高31.83%。说明适宜的滴灌灌溉定额一定程度上可以促进裸燕麦不同生育时期茎、叶和穗对氮、磷、钾的吸收,使得各器官养分的积累量增加,促使后期有更多养分向穗部转移,从而有利于燕麦籽粒产量的提高。     

Gene Cloning,Expression, and Antifungal Activities of Permatin from Naked Oat (Avena nuda)

Probiotics and Antimicrobial Proteins - Thaumatin-like proteins (TLPs) are the products of a large, highly complex gene family involved in host defense. TLPs also belong to the pathogenesis-related...     

Combined effect of Nitrogen,Phosphorus and Potassium fertilizers on the contents of glucosinolates in rocket salad (Eruca sativa Mill.)

Nitrogen (N), phosphorous (P) and potassium (K) are the most limiting factors in crop production. N often affects the amino acid composition of protein and in turn its nutritional quality. In Brassica plants, abundant supply of N fertilizer decreases the relative proportion of glucosinolates (GSLs), thus reducing the biological and medical values of the vegetables. Hence effort was made to evaluate the influence of different proportions of nutrient solutions containing N–P–K on the GSL profiles of rocket salad (Eruca sativa Mill.). Fifteen desulpho-(DS) GSLs were isolated and identified using liquid chromatography–mass spectrometry (LC/MS) analysis. Rocket salad plants supplied with lesser amount of N, P or higher concentrations of K showed a typical improvement in total GSL contents. In contrast, total GSL levels were less at higher N supply. Furthermore, with N concentrations above 5 mM and K concentrations less than 2.5 mM, the GSL amounts were on average 13.51 and 13.75 μmol/g dry weight (DW), respectively. Aliphatic GSLs predominated in all concentrations of NPK while indolyl GSLs made up marginally less amount of the total compositions. Five and 2 mM N and P possessed much higher levels of several types of aliphatic GSLs than other concentrations, including glucoerucin, glucoraphanin and dimeric 4-mercaptobutyl GSL. From this perspective, it is contended that supply of less N results in enhancing the metabolic pathway for the synthesis of GSLs in rocket salad.     

Absorption of Nitrogen, Phosphorus, and Potassium from Nutrient Sprays by Leaves

Barley, Brussels sprout, French bean, tomato, and sugar-beetplants grown in soil in pots and sprayed, usually daily, forseveral weeks, with nutrient solutions containing nitrogen,phosphorus, potassium, and a spreader, with precautions to preventthe spray solution falling on the soil, had higher nutrientcontents and dry weights than control plants sprayed with waterand spreader only. Increase in nutrient content occurred withhigh or low levels of nutrient supply to the roots and was approximatelyproportional to the concentration of spray and to the frequencyof spraying. The nitrogen content of sugar-beet plants was increased equallyby spraying with solutions supplying ammonium sulphate, calciumnitrate, or urea in equivalent concentrations. Nutrient uptake from solutions sprayed on leaves influenceduptake by the roots so that the additional amounts of nutrientcontained in sprayed plants may be greater or smaller than theamount absorbed from the spray by the leaves.     

Chitinases and beta-1,3-Glucanases in the Apoplastic Compartment of Oat Leaves (Avena sativa L.)

To isolate chitinases and β-1,3-glucanases from the intercellular space of oats (Avena sativa L.), primary leaves were infiltrated with buffer and subjected to gentle centrifugation to obtain intercellular washing fluid (IWF). Approximately 5% of the chitinase and 10% of the β-1,3-glucanase activity of the whole leaf were released. Only small amounts (0.01-0.03%) of the intracellular marker malate-dehydrogenase were released into the IWF during infiltration. Activities of chitinase and β-1,3-glucanase in the IWF and in the leaf extract were compared by different chromatographic methods. On Sephadex G-75, chitinase appeared as a single peak (M_r 29.8 kD) both in IWF and homogenate. β-1,3-Glucanase, however, showed two peaks in the IWF (M_r 52 and 31.3 kD), whereas the elution pattern of the homogenate showed only one major peak at 22 kD. Chromatofocusing indicated that the IWF contained four chitinases and five β-1,3-glucanases. The elution pattern of the homogenate and IWF were similar with regard to the elution pH, but the peak intensities were distinctly different. Our results demonstrate that extracellular β-1,3-glucanases are different from those located intracellularly. Extracellular and intracellular chitinases do not differ in molecular properties, except for one isozyme which seems to be confined to the extracellular space. We suggest that both enzymes might play a special role in pathogenesis during fungal infection.     

Isolation and structure of peptides from oat (Avena sativa) seedlings

The level of proteolytic activity in tissues of oat seedlings was characterized under acidic conditions, and the number and content of the main components in low-molecular-mass fractions of the extract were determined. The structures of the majority of predominant peptide components isolated from the extract were studied. The use of a database of protein structures helped suggest possible structures of protein precursors of the peptides isolated. Detailed information on a plant peptidome was obtained for the first time.     

Isolation, purification, and characterization of glutathione S-transferase from oat (Avena sativa) seedlings

Glutathione S-transferase (GST) from oat seedlings was purified by ammonium sulfate precipitation and glutathione (GSH) affinity chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed the presence of two major protein subunits with molecular masses of 29 and 31 kDa, respectively. Isoelectric focusing revealed a major band with pI of 3.43 and a minor band with pI of 7.42. Kinetic analysis with respect to 1-chloro-2,4-dinitrobenzene (CDNB) as substrate revealed a K _m of 1.18 mM and V _max of 0.94 mol/min and a specific activity of 17.96 mol/min/mg. Inhibition studies indicated that oat GST is strongly inhibited by chlorophyllin, hemin, and anthocyanin and only weakly by bilirubin and biliverdin.