Silicon Compounds in Xylem Exudates of Plants

An account is given of a study of silicon compounds in the xylemexudates of Equisetum hyemale and Zea mays. When fractionatedby gel filtration the compounds behaved as silicic acid andnot as an organo-silicon complex.     

细枝木麻黄导管分子及穿孔板解剖学研究

运用细胞图象分析系统和显微照相的方法对细枝木麻黄(CasuarinacunninghamianaMiq.)次生木质部导管分子进行了观察研究。细枝木麻黄次生木质部导管分子有3种类型,即两端具尾导管、一端具尾导管和无尾导管。导管分子穿孔板有4种类型:两端均为梯状穿孔板、一端为单穿孔板,另一端为梯状穿孔板、两端均为单穿孔板、一梯状穿孔板与一单穿孔板位于同一端壁两侧相互对应以及一些过渡类型穿孔板。根据观察结果,分析了各类型穿孔板之间的演化关系。     

Amino Acid Composition of the Protein from a Mushroom (Pleurotus sp.)

Approximate analyses of mushroom protein (Pleurotus sp.) revealed that it contains 2.78% protein and 0.14% nonprotein nitrogen on a fresh-weight basis. A total of 17 amino acids, including all the essential amino acids, were qualitatively identified. Quantitative estimation of essential amino acids showed that, except for methionine and phenylalanine, all are in fairly high concentration. From these studies, it was concluded that the supplementation of this mushroom with cereal diet would help to overcome lysine deficiency.     

刺柳珊瑚Echinogorgia sp.中几个含氮化合物

从南海硇洲岛海域采集的刺柳珊瑚(Echinogorgia sp.)中分离到6个含氮化合物,经MS、NMR等光谱技术和比较文献,确定其结构分别鉴定为N-2-(1,3-二羟基-4,8-十八二烯基)-十六酰胺(1)、(E)-N-2-(1,3-二羟基-4-十八烯基)-十六酰胺(2)、尿嘧啶(3)、胸腺嘧啶脱氧核苷(4)、尿嘧啶脱氧核苷(5)、胸腺嘧啶(6)。这些化合物均为首次从该属柳珊瑚中的分离得到。     

Chemical Composition of Bleeding Xylem Sap from Kiwifruit Vines

A study of the chemical composition and charge balance was madeof bleeding xylem sap collected from excised one-year-old extensionshoots of healthy, Mn-deficient, Mn-toxic and Zn-deficient kiwifruitvines (Actinidia deliciosa (A. Chev.) C. F. Liang et A. R. Ferguson)immediately prior to leafburst. The exudates were analysed formacronutrient cations and anions, trace elements, amino acids,organic acids and sugars. Major charged species measured wereCa (13.3 mM), K (8.9 mM), Mg (5.6 mM), malate (12.5 mM) andphosphate (5.8 mM). Glutamine (12 mM) was the predominant Ncarrier identified, accounting for 58 per cent of the totalN followed by NO₂^–-N (4.5 per cent), NH₄⁺-N (3.5 per cent)and arginine-N (2.9 per cent). Approximately 22 per cent ofthe N was in a hydrolysable proteinaceous fraction comprisingmainly glutamine and glutamate. Eighteen free proteinaceousamino acids were idetified in sap, the most abundant being glutamine,glutamic acid, valine, isoleucine and phenylalanine. Computersimulation of the chemical composition predicted that in additionto hydrated cations, ion pairs formed between inorganic components(SO₄^2–, HPO₄^2–, H₂PO₄^–) and cations (Ca²⁺,Mg²⁺, Mn²⁺), plus metal-organic ligand complexes (Ca Malate,Zn Malate, FeCit, CuHis, CuGln) are important species involvedin translocation. The solubility product of hydroxyapatite wasexceeded in all exudates although in vitro precipitation wasnot observed. To achieve electroneutrality with the componentsmeasured, however, formation of precipitate precursors (hydroxyapatitenuclei) had to be assumed. Irregularities in Mn nutrition (butnot Zn) were clearly indicated by the elemental compositionof exudate suggesting the use of sap analysis as a possiblepre-season indicator of nutritional status for this species. Actinidia deliciosa (A. Chev.) C. F. Liang et A. R. Ferguson, kiwifruit, xylem sap composition, trace metals, amino acids, organic acids     

Xylem Sap from Actinidia chinensis: seasonal Changes in Composition

Seasonal variation was followed in the content of total a-aminoacids, arginine, calcium, total carbohydrate, ß-galactosidaseactivity, magnesium, nitrate, phosphatase activity, phosphateand sulphate in vacuum-extracted xylem sap from Actinidia chinensisvar. hispida, the Chinese gooseberry or kiwifruit. There wasa marked increase in the concentration of most sap componentsjust prior to leaf emergence followed by a rapid decrease afterthe leaves had expanded. Experiments with excised extensionshoots showed that much of this spring-time increase in concentrationsof sap components was due to mobilization of nutrients withinthe shoot itself. Sap from the trunk and the older brancheschanged less in composition than did sap from the younger partsof the plant. The amplitude and direction of trends in concentrationof sap from the different parts of the plant varied with nutrientand with time. Analysis of vacuum-extracted xylem sap collectedduring periods of rapid transpiration from early summer onwardsgives a reliable indication of the composition of the transpirationstream. Actinidia chinensis, Chinese gooseberry, kiwifruit, storage reserves, xylem sap, amino acids, arginine, calcium, carbohydrate, ßgalactosidase, magnesium, nitrate, phosphatase, phosphate, potassium, sulphate     

Xylem Sap from Actinidia chinensis: Gradients in Sap Composition

In early spring, just prior to leaf break, there were substantialgradients in the concentration of many solutes in xylem sapcollected by vacuum extraction from shoots of different ages,from the branches, trunk and roots of mature Chinese gooseberryvines (Actinidia chinensis Planchon) For most nutrients therewas a progressive fall in concentration from youngest shootsdown to the roots and nitrate was the only nutrient to showa trend in the opposite direction These gradients in concentrationare probably sufficient to account for most of the changes observedin the composition of bleeding xylem sap during the first fewhours of bleeding after a branch is cut or wounded Actinidia chinensis, Chinese gooseberry, kiwifruit, xylem sap, nutrient gradients     

Distribution and Chemical Composition of Lignin in Secondary Xylem of Cactaceae

Cactaceae family has heterogeneity in the accumulation of lignocellulose due to the diversity of shapes and anatomy of the wood. Most studies focus on fibrous and dimorphic species; but the non-fibrous species are poorly studied. The aims of this work were to analyze the syringyl/guaiacyl ratio of lignin and its distribution in secondary xylem, especially in non-fibrous species. The syringyl/guaiacyl (S/G) ratio was quantified from 34 species of cacti by nitrobenzene oxidation of free-extractive wood. The distribution of lignocellulose in wood sections stained with safranin O/fast green was determined with epifluorescence microscopy. The S/G ratio was heterogeneous; most of the non-fibrous species had a higher percentage of syringyl, while the fibrous ones accumulate guaiacyl. Fluorescence emission showed that vessel elements and wide-band tracheids had similar tonalities. It is hypothesized that the presence of a higher percentage of syringyl in most cacti is part of the defense mechanism against pathogens, which together with the succulence of the stem represent adaptations that contribute to survival in their hostile environments.     

Rate of Movement and Composition of Rapidly Transported Proteins in Regenerating Olfactory Nerve

In a previous study, three successive groups of regenerative fibers, growing initially at 5.8, 2.1, and 0.8 mm/day, were observed in the regenerating garfish olfactory nerve. In the present study, fast axonal transport in the most rapidly regenerating axons (phase I and II) has been examined. Rapid transport in phase I fibers occurs at a velocity of 208 +/- 9 mm/day at 23 degrees, a rate identical to that measured in intact nerves. This first phase of regenerating fibers represents only 3 to 5% of the original axonal population, but each fiber appears to contain 6 to 16 times more transported radioactivity than an axon in an intact nerve. Subcellular distribution of rapidly moving material in phase I and II fibers was closely related to the distribution obtained in intact nerves. Small but significant differences indicate a shift of the transported radioactivity from a heavier to a light axonal membranous fraction. This shift might be characteristic of the immature membrane of a growing axon. The polypeptide distribution of transported radioactivity was also very similar to that of a normal nerve, with most of the radioactivity associated with high-molecular-weight polypeptides.     

The Amino Acid Requirements of Acanthamoeba sp. Neff

SYNOPSIS. Acanthamoeba sp. Neff can synthesize 4 of the 10 essential amino acids, namely, histidine, lysine, threonine and tryptophan. However, in this minimal medium, the non-essential amino acid glycine was also required for growth. Serine or threonine could replace glycine, but the growth rate was reduced.     

615小鼠血红蛋白α链的氨基酸组成及个别肽段的氨基酸序列

用CM-Cellulose-23柱层析分离纯化了615小鼠珠蛋白α链,测定其N端氨基酸残基为缬氨酸.615小鼠珠蛋白α链含有141个氨基酸残基,其中19个亮氨酸残基,10个组氨酸残基,9个缬氨酸残基,上述氨基酸残基的数目与文献中其亲本C₅₇BL不同.用胰蛋白酶水解615小鼠珠蛋白α链,发现有不溶性的‘核心’和可溶性的酶解片段.其中一个酶解肽段从N端数第8位氨基酸残基发生了突变,由亲本的缬氨酸变为亮氨酸.     

Xylem Transport and Storage of Amino Acids by S.W. Australian Mistletoes and their Hosts

Amino acid composition of xylem (tracheal) sap and ethanolicextracts of shoots of mistletoes (Amyema spp. and Lysiana casuarinae)and their hosts were compared, using material collected in theirnative habitats. Data indicated that certain host xylem soluteswere transferred directly to the parasite xylem, while otherswere either not absorbed or were metabolized prior to transfer.Certain solutes were major constituents of parasite xylem, butundetected or only in trace amount in the host. Shoot aminoacid pools of parasites differed markedly from those of hosts.The mistletoe, Amyema preissii, exhibited differential storageand transport of arginine when parasitizing three differentspecies, but accumulated proline on only two of these hosts.Host- specific amino acids (djenkolic acid in Acacia saligna,and tyramine in Acacia acuminata) were transported and accumulatedin relatively large amounts by the parasite, but were not detectedin other associations. Proline was the major solute of Amyemalinophyllum parasitizing Casuarina obesa, but arginine predominatedin Lysiana casuarinae on the same host. However, when L. csuarinaeparasitized A. linophyllum, in turn parasitic on C. obesa, theLysiana accumulated equal amounts of proline and arginine andmore asparagine than when directly on the Casuarina. Xylem feedingof ¹⁵N-labelled aspartic acid or ¹³N-(amide labelled) asparagineto cut shoots or whole haustoria-bearing plants of the mistletoeA. preissii resulted in 68–73% of the ¹⁵N of aspartateand 24–30% of that of asparagine appearing in ethanol-solubleshoot amino compounds other than the fed solute. ¹⁵N labellingpatterns of detached shoots were not noticeably different fromthat of whole plants suggesting that the haustorium had relativelylittle effect on processing incoming solutes. Alanine, glutamine,and arginine were principal recipients of ¹⁵N from aspartate,alanine and glutamine in the case of fed asparagine. It is estimatedthat 24% of the carbon requirements for dry matter accumulationin Amyema linophyllm were met by intake of xylem sap solutesfrom its host Casuarina obesa. Key words: Amino acids, xylem transport, mistletoes, host: parasite relations, N metabolism     

Composition and accumulation of secondary carotenoids in Chlorococcum sp.

A locally isolated Chlorococcum sp. could accumulate astaxanthin and its esters as secondary carotenoids. The secondary carotenoids could reach a concentration of 5.2 mg g⁻¹ d. wt, and were located in the cytoplasm and chloroplast as globules. Cells grew best at pH 8.0 and 30 °C, at which the growth rate was about 0.066 h⁻¹. Acidic condition (pH 5.5 and 6.5) and slightly elevated temperature (35 °C) enhanced the cellular accumulation of astaxanthin. Outdoor studies indicated that Chlorococcum sp. grew well in a tubular photobioreactor. In medium containing 2 mM and 10 mM NH₄CI, the cellular contents of total secondary carotenoids and astaxanthin reached similar levels (5.0 mg g⁻¹ d. wt and 2.0 mg g⁻¹ d. wt, respectively) in the 15 days of cultivation, while the yield of total secondary carotenoids and astaxanthin in 10 mM NH₄CI were higher (45 mg L⁻¹ and 18 mg L⁻¹, respectively). The advantages of tolerance to high temperature and extreme pH values, relative fast growth rate and ease of cultivation in outdoor system suggest that Chlorococcum sp. could be a potential candidate for mass production of secondary carotenoids in particular astaxanthin. This revised version was published online in September 2006 with corrections to the Cover Date.     

Xylem Sap Composition in Apple Trees: Effect of the graft union

This paper records studies on the xylem sap from above and belowthe graft unions of apple trees with M·9, M·7and MM.104 rootstocks. The dry weight of solutes in sap fromabove the unions of the M·9 trees was between 30 and50 per cent lower than in sap from below, while the volume ofsap exuded was not reduced. The graft unions of the M·7and MM·104 trees had no significant effect on the xylemsap. These results are discussed in relation to the dwarfing effectsof rootstocks and interstocks.     

The Relations of Haemoglobin and Lignin-like Compounds to Acetylene Reduction in Symbiotic Casuarina

Nodules from six Casuarina symbioses (Casuarina cunninghamiana,C. equisetifolia, and C. glauca inoculated with each of twodifferent Frankia sources) were evaluated for (i) concentrationsof haemoglobin (measured as CO-reactive haem) at 124, 144 and165 d after inoculation, (ii) acetylene reduction and (iii)occurrence of lignin-like compounds in cell walls of the nodulesat 165 d after inoculation. Haemoglobin concentration and theoccurrence of lignin-like compounds were related to acetylenereduction at final harvest. Concentration of haemoglobin innodules ranged from 1.56 to 22.27 nmol haem (g FW)^-1. Therewere marked plant species-Frankia interactions. At final harvestplant growth was greatest in C. cunninghamiana inoculated withFrankia inoculum designated SI, while haemoglobin concentrationwas intermediate in this symbiosis. Acetylene reduction activitywas detected in all the symbioses except C. equisteifolia inoculatedwith SI, and was highest in C. glauca inoculated with SI. Haemoglobinconcentration per fresh weight nodule and acetylene reductionper plant were positively correlated (r= 0.84, n= 12). The highestlevels of cumulative nitrogen fixation were always associatedwith the highest haemoglobin concentrations and the highestrates of acetylene reduction activity. Nitrogen content waslowest in C. equisetifolia inoculated with SI (23.89±3.07mg) and highest in C. cunninghamiana inoculated with the sameinoculum (217.2±22.5 mg). Irrespective of symbiotic performance,lignin-like compounds were found in the cell walls of the nodulesin all symbioses in this study. The cells containing these compoundswere mainly localized in the infected areas of the nodule. Theroles of haemoglobin and occurrence of lignin-like compoundsin relation to nitrogen fixation in Casuarina symbioses arediscussed.     

Nitrogen-containing Compounds in the Shoot System of Pisum arvense L. I. Amino Compounds in the Bleeding Saps from Petioles

A technique is described for collecting bleeding saps from thepetioles of defoliated plants of the field pea. Analytical studiesand ¹⁴CO₂-feeding experiments indicate that these saps are physicallyrelated to the fluids delivered to the xylem by the nodulatedroot. There is a progressive decrease in the concentration ofamino-nitrogen in the bleeding saps recovered from the successivepetioles up a stem. This decrease is manifest at any time ofthe day or night and is evident in all ages of plants. It issuggested that it results from the accumulation of a proportionof the incoming amino-acids and amides in living tissues ofthe stem. As the stem ages, it appears to become less effectivein abstracting materials from the xylem. Stem tissues oftenshow a more intensive uptake of asparagine than of other constituentssuch as aspartic acid, glutamine, and homoserine. The abovestudies suggest that much of the nitrogen coming from the rootis immediately sequestered by the lower half of the shoot. Asimilar effect is observed if ¹⁴Clabelled bleeding sap is fedto complete, unlabelled shoots via the transpiration stream.     

Amino Acid Composition of Elm Seeds

In the biosynthetic pathway of aromatic amino acids of Brevibacterium flavum, ratios of each biosynthetic flow at the chorismate branch point were calculated from the reaction velocities of anthranilate synthetase for tryptophan and chorismate mutase for phenylalanine and tyrosine at steady state concentrations of chorismate. When these aromatic amino acids were absent, the ratio was 61, showing an extremely preferential synthesis of tryptophan. The presence of tryptophan at 0.01 mM decreased the ratio to 0.07, showing a diversion of the preferential synthesis to phenylalanine and tyrosine. Complete recovery by glutamate of the ability to synthesize the Millon-positive substance in dialyzed cell extracts confirmed that tyrosine was synthesized via pretyrosine in this organism. Partially purified prephenate aminotransferase, the first enzyme in the tyrosine-specific branch, had a pH optimum of 8.0 and Km’s of 0.45 and 22 mM for prephenate and glutamate, respectively, and its activity was increased 15-fold by pyridoxal-5-phosphate. Neither its activity nor its synthesis was affected at all by the presence of the end product tyrosine or other aromatic amino acids. The ratio of each biosynthetic flow for tyrosine and phenylalanine at the prephenate branch point was calculated from the kinetic equations of prephenate aminotransferase and prephenate dehydratase, the first enzyme in the phenylalanine-specific branch. It showed that tyrosine was synthesized in preference to phenylalanine when phenylalanine and tyrosine were absent. Furthermore, this preferential synthesis was diverted to a balanced synthesis of phenylalanine and tyrosine through activation of prephenate dehydratase by the tyrosine thus synthesized. The feedback inhibition of prephenate dehydratase by phenylalanine was proposed to play a role in maintaining a balanced synthesis when supply of prephenate was decreased by feedback inhibition of 3-deoxy-D-arabino-heptulosonate 7-phosphate (DAHP*) synthetase, the common key enzyme. Overproduction of the end products in various regulatory mutants was also explained by these results.