The Metabolic Fate of (4-Chloro-2-Methylphenoxy)Acetic Acid in Higher Plants: I. GENERAL RESULTS

The metabolic fate of the auxin herbicide (4-chloro-2-methylphenoxy)aceticacid (MCPA) has been determined in a number of species usinga vacuum infiltration technique. In all cases MCPA became hydroxylatedto form (4-chloro-2-hydroxymethylphenoxy)acetic acid, whichaccumulated largely as a glycosidic conjugate. The nature ofthe oxidized metabolite from oat (Avena sativa L.) was verifiedby GC/MS. In all cases at least one diethyl ether-soluble conjugateof MCPA was formed; these are suggested to be amino acid conjugates.Several minor aglycones were also formed. Important speciesvariations in both the rate and quantitative nature of metabolismwere observed. Pretreatment of potato (Solarium tuberosum L.)tuber slices with unlabelled MCPA and other auxins increasedthe capacity for hydroxylation, but particularly induced theformation of an MCPA-glycoside. This was never a major metaboliteunder normal circumstances. The rate of hydroxylation was alsoenhanced by ageing in MnCl₂. Although the ether-soluble conjugatesof MCPA were stable metabolites, exogenously applied conjugateisolated from carrot (Daucus carota L.) was readily cleavedin four species. Free MCPA and the products normally derivedfrom it were identified. MCPA Metabolism Hydroxylation Conjugation     

不同诱变因素对小麦性状的影响

以粉质、中杆、无芒小麦辐３６为材料，分别用Ｎ２激光、氮离子注入和＾６０Ｃｏγ射线三种诱变因素处理，对第二代植株高度有影响，经前二者处理的对株高有提高趋势，氮离子注入的，二代出现高杆植株占７２．６％，１焦耳Ｎ２激光处理的在二代中有４５．５％是高杆。＾６０Ｃｏγ射线处理的Ｍ２株高明显变矮，７９ｃｍ以下的单株占总株数中４６．３％；在芒性变异上出现顶芒和长芒类型，处理间诱变效果顺序为γ射线〉１焦耳Ｎ２激光     

The Mechanics of Anchorage in Wheat Triticum aestivum L.: II. ANCHORAGE OF MATURE WHEAT AGAINST LODGING

The root system of mature wheat Triticum aestivum Marts Doveis dominated by the 7 to 15 adventitious roots which emergefrom the perimeter of the stem base, pointing radially outwardsand downwards. The basal, coronal region of these roots is thickand unbranched, attached to a rhizosheath of earth by a densecovering of root hairs and stiffened in bending by lignificationof outer layers of the cortex. Root lodging of plants involves bending of the coronal rootsat their base and axial movement of leeward and windward rootsthrough the soil; their resistance to these motions providemoments resisting lodging. A model of anchorage was producedby summing the resistance of each root to both forms of motionto give two anchorage components. The model was tested in aseries of mechanical experiments in which simulated lodgingwas followed by loading of individual roots; results supportedthe anchorage model and suggested that in the experimental conditionsthe two components of anchorage were approximately equal inmagnitude. The stem was about 30% stronger than the anchoragesystem. The coronal anchorage roots made up 4.4% of total dry mass;it is suggested that anchorage could be improved either by increasinginvestment in this region or by altering root orientation. Sequentialdevelopment of seminal and adventitious root systems is relatedto the changes in anchorage requirement with age.     

The Mechanics of Anchorage in Wheat Triticum aestivum L.: I. THE ANCHORAGE OF WHEAT SEEDLINGS

Model of the mechanics of uprooting lead to the identificationof ‘optimal’ anchorage systems which can withstanda given upward force at a minimum construction cost. Such systemshave many downward-pointing fibrous roots which are strengthenedprogressively towards the base. A study of the anchorage systemof 7- and 21-d-old wheat (Triticum aestivum L.) plants showedthat the plants possessed five seminal roots, of which onlythree pointed vertically. Each root was well suited for anchorage,being convered in root hairs and strengthened progressivelytowards the base by lignification of the stele. Strength andstiffiness of roots but not their mass per unit length increasedwith age. There was little interaction between roots when plantswere uprooted; the three vertical roots broke while the twohorizontal ones pulled out, as occurred when roots were pulledout singly, Uprooting forces increased with age and the rootsystem could withstand uprooting forces greater than those requiredto pull out upper leaves, so reducing the chances of the plantbeing uprooted by a herbivore, By 3 weeks a stiff adventitiousroot system, which would later help prevent the wheat lodging,was developing.     

Aluminum Tolerance in Wheat (Triticum aestivum L.) (II. Aluminum-Stimulated Excretion of Malic Acid from Root Apices)

We investigated the role of organic acids in conferring Al tolerance in near-isogenic wheat (Triticum aestivum L.) lines differing in Al tolerance at the Al tolerance locus (Alt1). Addition of Al to nutrient solutions stimulated excretion of malic and succinic acids from roots of wheat seedlings, and Al-tolerant genotypes excreted 5- to 10-fold more malic acid than Al-sensitive genotypes. Malic acid excretion was detectable after 15 min of exposure to 200 [mu]M Al, and the amount excreted increased linearly over 24 h. The amount of malic acid excreted was dependent on the external Al concentration, and excretion was stimulated by as little as 10 [mu]M Al. Malic acid added to nutrient solutions was able to protect Al-sensitive seedlings from normally phytotoxic Al concentrations. Root apices (terminal 3-5 mm of root) were the primary source of the malic acid excreted. Root apices of Al-tolerant and Al-sensitive seedlings contained similar amounts of malic acid before and after a 2-h exposure to 200 [mu]M Al. During this treatment, Al-tolerant seedlings excreted about four times the total amount of malic acid initially present within root apices, indicating that continual synthesis of malic acid was occurring. Malic acid excretion was specifically stimulated by Al, and neither La, Fe, nor the absence of Pi was able to elicit this response. There was a consistent correlation of Al tolerance with high rates of malic acid excretion stimulated by Al in a population of seedlings segregating for Al tolerance. These data are consistent with the hypothesis that the Alt1 locus in wheat encodes an Al tolerance mechanism based on Al-stimulated excretion of malic acid.     

小麦辐射二代性状的数量遗传分析

本文采用生物统计和数量遗传学方法、分析了辐照剂量为0（对照）、15、25、35KR的铯─137γ射线对二个小麦品种的诱变效应及其选择效果;估算了七个数量性状的分布特征数和遗传方差、遗传变异系数、遗传力、遗传进度、相对遗传进度等遗传参数。辐射二代的变异较大,有大粒、大穗、早熟突变体出现;株粒重、穗粒重、穗长、穗粒数、抽穗期的遗传变异系数和相对遗传进度都较大,选择效果较好;铯-137γ射线能有效地应用于小麦辐射育种,且适宜辐照剂量为35KR。     

SOMATIC EMBRYOGENESIS IN LONG-TERM CALLUS CULTURES OF ZEA MAYS L. (GRAMINEAE)

Long-term (1 yr), soft, embryogenic callus tissue cultures were established from excised immature embryos of a commercial cultivar of hybrid maize (Zea mays L.). Plant regeneration occurred by the formation of somatic embryos, and the regenerated plants were morphologically normal with 2n = 20 chromosomes. Such cultures may be useful for the isolation of mutants and the establishment of embryogenic cell suspension cultures.     

The Purification and Characterization of Soluble Acid Invertase from Coleoptiles of Wheat (Triticum aestivum L. cv. Avalon)

Soluble acid invertase from wheat coleoptiles was purified toelectrophoretic homogeneity. A comparison of molecular weightby SDS-PAGE and gel filtration suggested that the enzyme wasa monomer of M_r50 000. The enzyme was a glycoprotein and, afterchemical deglycosylation, possessed a M_rof 48000. A polyclonalantiserum was raised against the deglycosylated protein. Thiscross-reacted specifically with acid invertase. A putative precursorof invertase synthesized in a cell-free translation system wasdetected by SDS-PAGE and fluorography of the immunoprecipitatedpolypeptides. The distribution of acid invertase in wheat seedlingshoots was investigated both by visualizing invertase activityafter starch gel electrophoresis and by immunoblotting. Bothtechniques identified two forms of invertase in extracts ofthe primary leaf and only one form in extracts of coleoptiles.The low pH optimum and the glycoprotein nature of wheat coleoptileinvertase are consistent with a vacuolar location. Fructoseinhibited its activity, suggesting that enzyme activity couldbe modulated by end-product inhibition. Key words: Acid invertase, purification, antiserum, glycoprotein, Triticum aestivum, wheat, coleoptiles     

小麦等离子束处理的生物学效应研究

本文以早熟品种冀麦31号和晚熟品系88—4284萌动种子为材料,报道了等离子束处理对小麦种子萌发的影响和细胞学效应。观察表明,等离子束长时间处理抑制种子发芽。在根尖细胞有丝分裂中期观察到染色体断裂和断片,冀麦31号染色体断裂的频率为0.49—1.34％,88—4284为0.21—2.14％。随着处理时间延长,染色体断裂频率逐渐提高。有丝分裂后期和末期出现大量的落后染色单体和染色体桥。在花粉母细胞减数分裂中期Ⅰ,经过等离子束处理的材料出现环状单价体。后期Ⅰ观察到染色体倒位造成的染色体桥和断片。在四分体期还有微核出现。     

水稻游离花粉培养的高频率再生植株

用二个水稻栽培品种(Oryza sativa L Sub.japonica.)中花11号和盐粳的花粉处于单核靠边期的花药,经低温处理10—20天,在无糖培养基中预培养2—4天后游离花粉进行培养。培养基为KM8P,附加1mg/L 2,4-D,100mg/L脯氨酸,500mg/L水解酪蛋白,9%蔗糖。培养5天,花粉进行一次分裂,10天后分裂频率为21.3%,21天可见小愈伤组织形成。随即将直径为0.5—1.0mm的愈伤组织移至分化培养基上,2—4星期后得到绿苗,频率为70%。并从许多花粉诱导的愈伤组织克隆中筛选出高频率再生绿苗的花粉细胞悬浮系。     

Combining ability in the F1 and F2 generations of diallel cross in hexaploid wheat (Triticum aestivum L. em. Thell)

The F(1) and F(2) progenies of a ten-parent diallel cross (excluding reciprocals) of hexaploid wheat (Triticum aestivum L. em. Thell) were analyzed for combining ability for quantitative and quality traits. The results indicated significant differences among the parents for general combining ability (gca) and crosses for specific combining ability (sca) for all the characters studied. The gca and sca components of variance were significant for all the traits. However, the gca component of variance was predominant indicating the predominance of additive gene effects for the traits studied. Among the parents Durgapura 65, HD 2285, Lok-1, Raj 1972 and HD 2329 were the best general combiners for grain yield and average to high combiners for tillers per plant, grain yield per spike, grains per spike and 1000-grain weight. The best specific crosses for grain yield were Sonalika x WH 157, HD 2428 x Durgapura 65, Durgapura 65 x Sonalika, HD 2428 x Lok-1 and CPAN 3004 x Raj 1972. The parent Raj 1972, Lok-1 and HD 2285 were the best general combiners for grain yield and protein content, however, Raj 3077 was the best general combiner for protein content. The most suitable specific crosses for protein content were HD 2329 x HD 2285, HD 2428 x Raj 1972 and CPAN 3004 x WH 157. Most of the specific crosses for grain yield as well as protein content involved high x average, average x average and average x poor general combiners. To ensure further increase in grain yield along with high protein, combinations of desirable yield components is advocated. Inclusion of F(1) hybrids showing high sca and having parents with good gca, into multiple crosses and/or bi-parental mating, or diallel selective mating could prove a worthwhile approach for further improvement of grain yield in bread wheat.     

The Influence of NO-3 and NH+4 Nutrition on the Gas Exchange Characteristics of the Roots of Wheat (Triticum aestivum) and Maize (Zea mays) Plants

Respiratory oxygen consumption by roots was 1·4- and1·6-fold larger in NH⁺₄-fed than in NO^-₃-fed wheat (Triticumaestivum L.) and maize (Zea mays L.) plants respectively. Higherroot oxygen consumption in NH⁺₄-fed plants than in NO^-₃-fedplants was associated with higher total nitrogen contents inNH⁺4-fed plants. Root oxygen consumption was, however, not correlatedwith growth rates or shoot:root ratios. Carbon dioxide releasewas 1·4- and 1·2-fold larger in NO⁺3-fed thanin NH⁺₄-fed wheat and maize plants respectively. Differencesin oxygen and carbon dioxide gas exchange rates resulted inthe gas exchange quotients of NH^-₄-fed plants (wheat, 0·5;maize, 0·6) being greatly reduced compared with thoseof NO^-₃-fed plants (wheat, 1·0; maize, 1·1). Measuredrates of HCO^-₃ assimilation by PEPc in roots were considerablylarger in 4 mM NH⁺₄-fed than in 4 NO^-₃ plants (wheat, 2·6-fold;maize, 8·3-fold). These differences were, however, insufficientto account for the observed differences in root carbon dioxideflux and it is probable that HCO^-₃ uptake is also importantin determining carbon dioxide fluxes. Thus reduced root extension in NH⁺₄-fed compared with NO^-₃-fedwheat plants could not be ascribed to differences in carbondioxide losses from roots.Copyright 1993, 1999 Academic Press Triticum aestivum, wheat, Zea mays, maize assimilation, ammonium assimilation, root respiration     

Role of rye chromosome 2R from wheat-rye substitution line 2R(2D)1 (Triticum aestivum L. cv. Saratovskaya 29-Secale cereale L. cv. Onokhoiskaya) in genetic regulation of meiotic restitution in wheat-rye polyhaploids

A study was made of the role of rye chromosome 2R from the wheat-rye substitution line 2R(2D)1 (Triticum aestivum L. cv. Saratovskaya 29-Secale cereale L. cv. Onokhoiskaya) in genetic regulation of meiotic restitution in wheat-rye polyhaploids 2R(2D)1 x S. cereale L. cv. Onokhoiskaya. Rye chromosome 2R proved to affect the completeness of the meiotic program, suppressing the formation of restitution gametes. This was evident from the reductional division of univalent chromosomes in AI and the occurrence of the second meiotic division. The interrelationships between the type of chromosome division in AI and the two-step character of meiosis are discussed. The structural and functional organization of the centromeric regions of chromosomes undergoing reductional division is assumed to determine the two-step character of division.     

Features of recombination of nuclear genome in back crossed offspring of barley-wheat hybrids Hordeum vulgare L. (2n=14) x Triticum aestivum L. (2n+42) with the use of SSR-analysis

The backcross progenies of the barley-wheat hybrids Hordeum vulgare L. (2n = 14) x Triticum aestivum L. (2n = 42) and two alloplasmic lines derived from them were studied using microsatellite markers of barley and wheat. The F1 hybrids and first backcross plants BC1 contained the genetic material of both cultivated barley and the cultivars of common wheat involved in developing of these hybrid genotypes. The genomes of BC3, BC4, and alloplasmic lines contained no microsatellite markers of the cultivated barley, whereas chromosomes of each homeologous group of common wheat were identified. In chromosomes of backcross progenies BC3, BC4, and alloplasmic lines yielded by backcrosses of hybrids and various common wheat cultivars, microsatellite markers of the parental wheat cultivars were shown to undergo recombination.     

The Metabolism of Proline in Higher Plants: II. L-PROLINE DEHYDROGENASE FROM COTYLEDONS OF GERMINATING PEANUT (ARACHIS HYPOGAEA L.) SEEDLINGS

The L-proline-dependent reduction of NAD⁺ has been obtainedwith a soluble enzyme extracted from acetone powders of thecotyledons of 3- to 5-day-old germinating peanut seedlings.The enzyme has been purified approximately 20-fold. NAD⁺ ismuch more effective as an electron acceptor than NADP⁺, thereaction rate with the latter being only 15 per cent that withthe former. The K_m for L-proline at pH 10.3, with NAD⁺ saturating,is 0.30 mM, and that for NAD⁺, with L-proline saturating, is0.25 mM. NADP⁺ is an excellent competitive inhibitor for NAD⁺with a K₁ of 6.2 µM. L-proline, L-proline methyl ester, and 3,4-dehydro-DL-prolineare equally effective as substrates. Thiazolidine-4-carboxylatecatalyses the reduction of NAD⁺ at 63 per cent the rate withL-proline. D-proline is not a substrate nor an inhibitor. L-prolineamide has 11 per cent the activity of L-proline and N-methyl-L-prolinehas a very slight activity. Other proline derivatives or thelower and higher homologues are completely inactive. Incubation with L-proline-¹⁴C in the presence of NAD⁺ yieldsone product which has a higher Rf than proline using butanol-aceticacid-water as the solvent in paper chromatography. Elution ofthis product and treatment with hydrogen peroxide gives severalproducts of high Rf with the same solvent mixture. None of theproducts is -aminobutyrate or glutamic acid. This eliminateseither P2C or P5C as the reaction product.     

LOCALIZATION OF CA2+-STIMULATED ATPASE IN THE COCCOLITH-PRODUCING COMPARTMENT OF CELLS OF PLEUROCHRYSIS SP. (PRYMNESIOPHYCEAE)1

Cell homogenates of Pleurochrysis sp. (CCMP299) were fractionated by means of sucrose gradients. Ca²⁺-stimulated ATPase (EC 3.6.1.3., ATP phosphohydrolase) was associated primarily with the plasma membrane, Golgi, and high density (1.21 g·cm^?3) membranous structures. Ca²⁺-stimulated ATPase was highly enriched in the latter. Based on treatments with Triton X-100 and NBD ceramide, we conclude that the high-density structures were membrane-delimited organelles. These vesicle-like organelles contained complex polysaccharides, a high concentration of calcium, and, upon microscopic examination, structures resembling coccoliths. These findings are consistent with observations on the known composition of coccoliths and the presumed mineralizing function of the sub-cellular coccolith-producing compartment. The high-density vesicles were linked to the Golgi by means of colchicine-sensitive materials, presumably microtubules. These data and prior ultrastructural observations by other investigators indicating vectorial assembly and secretion suggest that the subcellular movement of the newly formed coccoliths may be directed and/or powered by colchicine-sensitive cytoskeletal elements. We interpret the data to mean that the high-density vesicles represent the coccolith-producing compartment previously observed by others in electron micrographs.     

Molecular Markers for Ion Compartmentation in Cells of Higher Plants: II. LIPID COMPOSITION OF THE TONOPLAST OF THE HALOPHYTE SUAEDA MARITIMA (L.) DUM.

Vacuoles of high purity were isolated from the leaves of thehalophyte Suaeda maritima (L.) Dum. The relative compositionsof phospholipids, phytosterols, and fatty acids in the tonoplastmembrane were determined and membrane fluidity was assessedby electron spin resonance. The characteristics of the tonoplastwere consistent with minimizing passive permeability to NaCI.The phospholipid: protein ratio (1.1: 1.0) was higher than thatrecorded in other membrane preparations, including vacuolesfrom beetroot storage material, commensurate with the low density(1.05 g cm^–3) of the S. maritima tonoplast. The tonoplastfatty acids were highly saturated and dominated by n-hexadecanoicacid and n-octadecanoic acid. Phytosterols identified by gaschromatography were cholesterol, campesterol, stigmasterol,and ß-sitosterol. Cholesterol was a trace percentagein protoplasts, but comprised 30% of the tonoplast sterols.Semi-quantitative analysis by chromatography on silica gel revealedan enrichment in the tonoplast of glycolipid which was not accountedfor as chloroplast contamination. The fluidity of the tonoplast,determined by electron spin resonance, was lower than the protoplasts,consistent with the high degree of saturation of the fatty acidchains. The relevance of the lipid composition of the tonoplastto its central role in ion compartmentation within the halophytecell is discussed. Key words: Ion compartmentation, membrane lipids, salinity, vacuole