盐生境下硅对坪用高羊茅生物学特性的影响

干旱半干旱区草坪绿地的长期灌溉容易引发土壤次生盐渍化,提高草坪草在盐生境下的生长发育能力是应对土壤次生盐渍化的主要途径之一.采用盆栽试验研究了盐生境下硅对坪用高羊茅(Festuca arundinaea)生物学特性的影响.结果表明,向盐生境土壤中添加不同浓度硅均提前高羊茅出苗时间2d,加快出苗速率,增加出苗总数,提高保苗率,且总出苗率和保苗率随着硅浓度增加而显著增大(P＜0.05),这说明盐生境下向土壤添加硅改善了幼苗完全死亡的现象.盐生境下硅显著增加了高羊茅叶长,株高和分蘖数,但对叶宽影响不显著,说明硅能够促进高羊茅生长,但对草坪绿地的质地影响不大.虽然硅能显著增加高羊茅总生物量(P＜0.05),但较低浓度时促进其茎叶生长,高浓度促进其根系生长.硅在高羊茅体内的沉积量随施入硅增加而增大,但其茎叶和根系内硅含量不超过3.0％,且根系内硅含量约为茎叶内硅含量的2倍.结果显示,硅提高了坪用高羊茅在盐生境下的适应能力,这为以后草坪绿地管理中应对土壤潜在盐渍化的问题提供了一定的科学依据.     

Seasonal changes in neutral sugars and amino acids of particulate matter in Lake Nakanuma,Japan

Amino acids and neutral sugars in particulate matter were measured weekly from April in 1987 to March in 1988 in Lake Nakanuma, Japan. Changes in concentrations of total amino acids and total neutral sugars corresponded to those of chlorophylla. The composition of amino acids varied little seasonally and vertically. On the contrary, the composition of neutral sugars changed seasonally and vertically. We discuss the relationship between the changes in the biochemical components and environmental factors.     

Amino acids in Hordeum distichon and Panicum miliaceum grown in sand culture

In comparison with barley, Proso millet was characterized by high levels of alanine and glutamic acid in the leaf free amino acid fraction. In both species, analyses of root amino acids and xylem exudates suggest the existence of specific mechanisms for the transfer of certain amino acids into the xylem vessels.     

Free amino acids of maize seedlings

The free amino acids were determined in different parts of maize seedlings (seeds, roots and shoots), 0, 2, 4 and 6 days after sowing.     

The role of free sugars and amino acids in the regulation of biomass partitioning and plant growth

Theoretical plant growth models postulate an important role for growth substrates such as sugars and amino acids. To test this experimentally, spinach plants were grown under controlled conditions and with nitrogen added daily, following different exponential addition schemes. Plants were harvested during exponential growth. Free amino acid levels or free sugar levels were only weakly correlated with growth and biomass partitioning. Factor analysis showed however that the product of free sugar concentration and amino acid concentration yielded a parameter adequately reflecting the plant's nutritional state.It is concluded that growth and biomass partitioning under limiting N conditions cannot be modelled solely based on N substrate levels.     

Gustatory discrimination of sugars, amino acids, and selected allelochemicals by the tarnished plant bug, Lygus lineolaris

ABSTRACT. Selected sugars, amino acids and allelochemicals were tested over a range of concentrations to determine their effect on the ingestion rates of adult tarnished plant bugs. Experiments were performed with a two-choice bioassay technique utilizing artificial membranes. Sucrose was the most effective feeding stimulant of all the compounds tested. Glucose was an effective stimulant but was 8 times less potent than sucrose. Fructose was 50 times less potent than sucrose. Methionine and phenylalanine were the only amino acids of seven tested which stimulated feeding. Leucine produced a deterrent effect. Cotton tannin was the most effective deterrent of all allelochemicals tested and was 10 times more potent than gossypol. The quinone, 1, 4-napthoquinone, and the alkaloid, tomatine, were also effective feeding deterrents. Sinigrin and its aglycone, ethyl isothiocyanate, were among the weakest deterrents of all the allelochemicals tested. Hydroquinone was the least potent deterrent of all compounds tested. The results indicate a strong chemosensory component regulating the feeding response of the tarnished plant bug. It is suggested that this response is mediated by epipharyngeal chemosensitive sensilla.     

Lipids and lipid metabolism in the brown alga, Fucus serratus

The lipids of the brown alga Fucus serratus were isolated, identified and quantified. The major acyl lipids were the three glycosylglycerides, diacylgalactosylglycerol, diacyldigalactosylglycerol and diacylsulphoquinovosylglycerol. These represent over 70% of the total acyl lipids. The fatty acid compositions of the major lipids were examined and most showed rather distinctive fatty acid contents. For example, diacylgalactosylglycerol was enriched in n-3 polyunsaturated fatty acids while phosphatidylcholine and phosphatidylethanolamine had very high levels of arachidonate. Phosphatidylglycerol contained the unusual trans-Δ3-hexadecenoic acid. The labelling of lipids and fatty acids from [¹⁴C]acetate was examined and the distribution of label between individual components as a function of the incubation period and in algae collected at different times of the year is reported. Algae collected in the winter incorporated much more radioactivity into non-esterified fatty acids when compared to algae collected in the summer. All algae could label myristate, palmitate, stearate and oleate at high rates. Longer incubation times allowed the labelling of polyunsaturated fatty acids such as linoleic acid.     

Biosynthesis of lysine and other amino acids in the developing maize endosperm

Tracer studies with aspartic acid-[4-¹⁴C], alanine-[1-¹⁴C] acetate-[2-¹⁴C] and diaminopimelic acid-[1,(7)-¹⁴C] injected into the developing endosperm of maize revealed that the biosynthesis of lysine and other amino acids occurs in this organ. The data suggest that lysine is synthesized via the diaminopimelic acid pathway.     

Free amino acids in Crotalaria seeds

The free amino acids of seeds of 163 species of Crotalaria have been identified. Their pattern of distribution is compared with recent classifications of the genus and the possible ecological significance of their presence is discussed. Attention is drawn to the occurrence of toxic amino acids.     

Co-occurrence of nicotianamine and avenic acids in Avena sativa and Oryza sativa

An amino acid derivative isolated from seedlings of Avena sativa and Oryza sativa, along with avenic acid A and its derivatives which possess a chelating ability with iron ions, has been shown to be nicotianamine. The co-occurrence of nicotianamine and avenic acids in the same plant, as well as their structural similarity, reveals their close biosynthetic relationship.     

Sterols, fatty acids and free amino acids from two Helvella species

Sterols, fatty acids and free amino acids of Helvella crispa and H. monachella were investigated. They contained traces of ergosterol and a high amount of ergosta 5.22-dien-3β-ol. Linoleic acid and l-Dopa are the most abundant fatty acid and free amino acid, respectively. The aqueous extract of H. monachella inhibits prostaglandin release by rat peritoneal leucocyres in vitro.     

Lipids of Fontinalis antipyretica

Fatty acid compositions of the lipids of Fontinalis antipyretica shows the presence of octadeca-9, 12-dien-6-ynoic, octadeca-9,12,15-trien- 6-ynoic and eicosa-11,14-dien-8-ynoic acids as the major components of the triglycerides. These acetylenic acids were not present in the galactosyl diglycerides. The moss lipids also contained relatively large amounts of two novel acetylenic methyl ketones with an unsaturation pattern analogous to that of the C₁₈ acetylenic acids.     

Plant growth regulators and amino acids released by Azospirillum sp in chemically defined media

AIMS: To investigate the ability of Azospirillum sp., a facultative endophitic diazotrophic bacterium, to release plant growth regulators (PGR) such as polyamines, ethylene, indoleacetic acid and amino acids in both combined-N and N-free cultures. METHODS AND RESULTS: The presence of those substances was analysed by HPLC. Azospirillum sp. is capable of releasing PGR and amino acids into the culture medium. CONCLUSIONS: The type and quantity of the released substances varied, depending on the presence of combined-N in the medium. SIGNIFICANCE AND IMPACT OF THE STUDY: A better knowledge of PGR produced by Azospirillum sp. has been gained.     

Characteristics of the rRNA synthesis taking place at low temperatures in wheat cultivars with varying degrees of frost hardiness

The characteristics and intensity of rRNA synthesis occurring at temperatures around freezing point were examined in connection with frost hardiness in wheat cultivars. The intensity of rRNA synthesis taking place near freezing point showed a close positive correlation with the critical temperature (LT₅₀) characteristic of the frost resistance of the varieties. The quantity of high MW precursors to rRNA appears to be heterogeneous in hardy and non hardy varieties at low temperatures and point primarily to an inhibition in the maturation processes of ribosomes in the final nuclease processing step in non-frosthardy varieties.     

Incorporation of 15N labelled urea and ammonium into proteins and amino acids of Sorghum

Protein fractionation studies in developing Sorghum kernel indicated a considerable decrease in the proportion of albumin and increase in prolamin, glutelin and residue proteins during grain development. The globulin fraction remained more or less constant. ¹⁵N analysis indicated a turnover of albumin and globulin fractions. The nitrogen present in these fractions appeared into glutelin and residue proteins. At an early maturation stage ¹⁵N from ammonium was detected in the residue fraction while that from urea was incorporated in both albumin and residue fractions. However, this difference disappeared as the grains matured. Incorporation of ¹⁵N into basic amino acids was lower when compared to that in neutral and acidic amino acids at all stages of grain development.     

Non-protein amino acids of Acacia species and their effect on the feeding of the acridids Anacridium melanorhodon and Locusta migratoria

The leaves of Acacia species have been found to contain homoarginine, pipecolic acid and 4-hydroxy-pipecolic acid. The nymphs of the tree locust Anacridium melanorhodon, which feed on the leaves of Acacia species, were not inhibited from feeding on palatable media containing concentrations of these amino acids equivalent to, or greater than, those found in the leaves. The graminivorous Locusta migratoria was more sensitive to these compounds, inhibitory effects being observed at concentrations comparable to those found in the leaves. The inhibitory effects of mixtures of homoarginine and pipecolic acid were additive in A. melanorhodon but not in L. migratoria. Three of the non-protein amino acids found in the seeds of Acacia species, 2,3-diaminopropionic acid, 2-amino-3-acetylaminopropionic acid and 2-amino-3-oxalylaminopropionic acid, were more effective inhibitors of feeding in Anacridium than were the leaf amino acids.     

Effect of various kinds of dietary protein and supplementation with limiting amino acids on growth,haemolymph components and uric acid excretion in the silkworm, Bombyx mori

Effects of various kinds of dietary protein on growth of the silkworm, Bombyx mori, were determined using semi-synthetic diets. Also, the ingestion, digestion and utilization of dry matter and of nitrogen were measured. Nutritive effects of dietary proteins and supplementation of limiting amino acids on haemolymph protein and amino acids pattern were also investigated. Larval growth was largely dependent on the dietary proteins. When the larvae were reared on a diet containing weakly nutritive proteins such as gluten and zein, haemolymph protein was decreased and uric acid excretion was markedly accelerated. The free amino acid composition of the haemolymph manifested characteristic patterns according to the kinds of dietary protein.The supplementation of gluten and zein with their limiting amino acids resulted in a rise of haemolymph protein and a drop in uric acid excretion. The amino acid patterns in the haemolymph were greatly changed according to supplementation.     

Free amino acids in the seeds of Acacia species

Free amino acids in the seeds of 80 species of Acacia have been determined. In addition to confirming the known difference in seed amino acid ‘patterns’ shown by species of the series Gummiferae on the one hand and species of the series Phyllodineae and Botryocephalae on the other, we have found that species of the series Vulgares Benth. show two additional ‘patterns’. One of these is common to some of the Afro-Asian species of the series which have been analysed and the other is common to species from America and Africa. One of the ‘marker’ amino acids of the Afro-Asian group is the neurotoxic lathyrogen α-amino-β-oxalylaminopropionic acid. The possible taxonomic and phylogenetic significance of these results is discussed, with special reference to five species A. albida, A. confusa, A. heterophylla, A. coulteri and A. kauaiensis.