Localization of Galactolipid Biosynthesis in Etioplasts Isolated from Dark-Grown Wheat (Triticum aestivum L.)

Etioplasts were isolated from leaves of dark-grown wheat (Triticum aestivum L. var Starke II). Galactolipid biosynthesis was assayed in an envelope-rich fraction and in the fraction containing the rest of the etioplast membranes by measuring incorporation of ¹⁴C from uridine-diphospho[¹⁴C]galactose into monogalactosyl diacylglycerol and digalactosyl diacylglycerol. More than half of the galactolipid biosynthetic capability was found in the fraction of inner etioplast membranes. This fraction was subfractioned into fractions enriched in prolamellar bodies and membrane vesicles (prothylakoids), respectively. All membrane fractions obtained from etioplasts were able to carry out galactolipid biosynthesis, although the activity was very low in prolamellar body-enriched fractions. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed markedly different polypeptide patterns between the different fractions. It is concluded that the capability of galactolipid biosynthesis of etioplasts probably is not restricted to the envelope, but is also present in the inner membranes of this plastid.     

Influence of ozone on ribonuclease activity in wheat (Triticum aestivum) leaves

Ribonucleases (RNases) degrade RNA and exert a major influence on gene expression during development and in response to biotic and abiotic stresses. RNase activity typically increases in response to pathogen attack, wounding and phosphate (P(i)) deficiency. Activity also increases during senescence and other programmed cell death processes. The air pollutant ozone (O(3)) often induces injury and accelerated senescence in many plants, but the biochemical mechanisms involved in these responses remain unclear. The objective of this study was to determine whether RNase activity and isozyme expression was stimulated in wheat (Triticum aestivum L.) flag leaves following treatment with O(3). Plants were treated in open-top chambers with charcoal-filtered air (27 nmol O(3) mol(-1)) (control) or non-filtered air plus O(3) (90 nmol O(3) mol(-1)) (O(3)) from seedling to reproductive stage. After exposure for 56 days, RNase activity was 2.1 times higher in flag leaf tissues from an O(3)-sensitive cultivar in the O(3) treatment compared with the control, which generally coincided with foliar injury and lower soluble protein concentration, but not soluble leaf [P(i)]. Soluble [P(i)] in leaf tissue extracts from the O(3) and control treatments was not significantly different. RNase activity gels indicated the presence of three major RNases and two nucleases, and their expression was enhanced by the O(3) treatment. Isozymes stimulated in the O(3) treatment were also stimulated in naturally senescent flag leaf tissues from plants in the control. However, soluble [P(i)] in extracts from naturally senescent flag leaves was 50% lower than that found in green flag leaves in the control treatment. Thus, senescence-like pathological responses induced by O(3) were accompanied by increased RNase and nuclease activities that also were observed in naturally senescent leaves. However, [P(i)] in the leaf tissue samples suggested that O(3)-induced injury and accelerated senescence was atypical of normal senescence processes in that P(i) export was not observed in O(3)-treated plants.     

Developmental Base Temperature in Different Phenological Phases of Wheat (Triticum aestivum)

The linear relationship between temperature and developmentrate has been widely recognized and it has been suggested thatthermal units (the summation of daily mean temperature abovea base temperature) can predict the phenological developmentof a crop. The aim of this paper was to determine the base temperaturefor different phenological phases of wheat. Two mediterraneanwheat cultivars and five sowing dates were used to obtain differentmean temperatures during development and different developmentalrates. The linear regression of development rate against meantemperatures for each period indicated that there were no uniquebase temperatures for all stages of the life span and valuesclose to 4°C and to 9·5°C were found to be bestfits for base temperatures before and after the terminal spikeletstage of both cultivars. A model to predict wheat developmentwas validated with another data set, which included differentwheat cultivars and sowing dates. Estimates of the error indevelopmental prediction by using a single base temperatureof 0°C is discussed as a function of separate developmentstages. Key words: Wheat development, base temperature, thermal time, Triticum aestivum     

Influence of Rhizobial inoculation on yield of wheat (Triticum aestivum L.)

Summary Soil + charcoal (1∶3) carrier based and liquid cultures of Rhizobia were used to inoculate wheat seed cv. HD2329. The plants received 100 kg N in two equal splits and 60 kg P₂O₅ and 40 kg K₂₀ ha⁻¹. Inoculation with rhizobia had little effect on grain yield of wheat. Significant increase in straw yield and N-uptake occurred due to inoculation. A comparison of results of a similar experiment conducted during 1983–84, showed that inoculation with the same strains of rhizobia and application 50 kg N ha⁻¹ as basal dressing, was more effective in increasing yield and N-uptake in wheat cv. HD2329. It appears reasonable to assume occurrence of nitrogen fixation by root nodule bacteria in rhizosphere of wheat.     

Regulation of Sterol Biosynthesis in Solanum Species

Regulation of sterol synthesis was studied in Solanum species.A significant negative correlation was found between sterolcontent and rate of sterol synthesis from (1-¹⁴C) acetate inplant organs of Solanum nigrum and cell cultures of S. dulcamara.Exogenous cholesterol significantly inhibited the rate of sterolsynthesis from (¹⁴C) acetate in cell cultures of S. dulcamarawithout affecting synthesis from (³H) mevalonate. Exogenouscholesterol stimulated the rate of total lipid synthesis fromboth (¹⁴C) acetate and (³H) mevalonate. Thus, cholesterol inhibitedconversion of acetate to mevalonate; this is taken as evidenceof a negative feedback control on sterol synthesis. Key words: Feedback control, Phytosterol biosynthesis, Plant cell culture, Solanum species     

Leaf wax of Triticum aestivum

Leaf waxes from spring wheat varieties Selkirk and Manitou contain hydrocarbons (6%, 10%), long chain esters (14%, 13%), free acids (5%, 8%), free alcohols (19%, 21%), β-diketone (16%, 20%), hydroxy β-diketones (8%, 10%), unidentified gum (29%, 16.5%) and minor amounts of diol diesters, glycerides and aldehydes. The major hydrocarbon is nonacosane and major esters are octacosyl esters of C₁₄–C₃₂ acids but C₂₀ and C₂₂ alcohol esters of trans 2-docosenoic and tetracosenoic acids are also present (Selkirk 20%, Manitou 10% of total esters). Previously unknown trans 2-docosen-1-ol is present as an ester (Selkirk 5%, Manitou 2.5% of total esters). Free acids are C₁₄–C₃₂ acids and trans 2-docosenoic and tetracosenoic acids (Selkirk 30%, Manitou 9% of free acids). Octacosanol is the principal free alcohol. Hentriacontane-14,16-dione is the β-diketone and the hydroxy β-diketones are a 1:1 mixture of 8- and 9- hydroxyhentriacontane-14,16-diones.     

Pollen callus culture in Triticum aestivum

Summary Pollen shed between 4–8 d from anthers of Triticum aestivum cultured in liquid medium gave rise to calluses. Tillers were harvested at the mid-to late-unicellular pollen stages and chilled for 8 d at 4–5 °C before the anthers were dissected out. Pollen cultures gave about 6 times as many calluses on a per anther basis as anthers cultured on solid medium. With the most productive of 5 cultivars tested, pollen culture results in roughly one callus for each anther used, though the calluses formed by pollen culture were less productive for the regeneration of shoots than calluses derived from anthers cultured on solid medium. The ratio of green to albino shoots is roughly 1 1 for anther cultures but considerably less for pollen cultures.     

Triparanol Inhibition of Sterol Biosynthesis in Chlorella ellipsoidea

The sterol composition of C. ellipsoidea was markedly changed when this alga was grown in the presence of 1 μg/g triparanol. Triparanol appears to inhibit the removal of 14α-methyl group, the second alkylation at C-24, Δ⁷-reductase, and Δ⁸ → Δ⁷-isomerase. The effect of triparanol in Chlorella is much more diversified than the specific effect originally assigned to it in animals.     

N-banding in Triticum aestivum following feulgen hydrolysis

Summary Terminal and/or interstitial N-bands were produced on the seven B-genome chromosomes and chromosomes 4 and 7 of the A-genome of Triticum aestivum cv. Chinese Spring by a modified BSG technique following a standard Feulgen preparation. The banding was accomplished by modifying the barium hydroxide treatment.     

Allelopathy in wheat (Triticum aestivum)

Wheat (Triticum aestivum) allelopathy has potential for the management of weeds, pests and diseases. Both wheat residue allelopathy and wheat seedling allelopathy can be exploited for managing weeds, including resistant biotypes. Wheat varieties differ in allelopathic potential against weeds, indicating that selection of allelopathic varieties might be a useful strategy in integrated weed management. Several categories of allelochemicals for wheat allelopathy have been identified, namely, phenolic acids, hydroxamic acids and short‐chain fatty acids. Wheat allelopathic activity is genetically controlled and a multigenic model has been proposed. Research is underway to identify genetic markers associated with wheat allelopathy. Once allelopathic genes have been located, a breeding programme could be initiated to transfer the genes into modern varieties for weed suppression. The negative impacts of wheat autotoxicity on agricultural production systems have also been identified when wheat straws are retained on the soil surface for conservation farming purposes. A management package to avoid such deleterious effects is discussed. Wheat allelopathy requires further study in order to maximise its allelopathic potential for the control of weeds, pests and diseases, and to minimise its detrimental effects on the growth of wheat and other crops.     

The Influence of Potassium on the Transpiration Rate and Stomatal Opening in Triticum aestivum andPisum sativum

The investigation concerns the influence of potassium on the transpiration rate of Triticum aestivum and Pisum sativum grown in nutrient solutions. Plants with high amounts of potassium were found to have the lowest transpiration rates. Shoot/root ratio, stomatal frequency, and stomatal aperture were correlated with the potassium concentration in the leaves. In Triticum no correlations with leaf concentration of Na were evident. Short term experiments were carried out in order to investigate the effects on the transpiration rate of a sudden increase in potassium concentration in the nutrient solution. An addition of potassium chloride to potassium deficient wheat plants resulted in a decrease in the transpiration rate of up to 50% within two hours. Comparative tests with sodium chloride resulted in a decrease in transpiration rate of the same magnitude, indicating that the short-time reaction is not specific to potassium. The experiments show that the transpiration rate can be regulated by varied potassium and sodium concentrations. The observed effect is supposed to be due to changes in the stomatal aperture.     

小麦种子基因的表达序列标签分析(英文)

以授粉后12d的小麦(TriticumaestivumL.)种子为材料,构建起cDNA文库。从中随机挑选10000个克隆,利用Biomek2000核酸工作站制成高密度cDNA阵列。然后分别以未受精子房、胚和胚乳中提取的RNA为模板,反转录合成探针与膜杂交,进行差示筛选。根据筛选结果,选取800个在胚、胚乳或胚和胚乳中表达的克隆进行表达序列标签(EST)分析,鉴定出216个不同的基因序列。其中24个ESTs属于已知的小麦基因;122个ESTs为推测的小麦新基因,它们编码的产物与种子贮藏蛋白或与生化代谢、发育等其他的生物学过程有关;70个ESTs的序列特征尚未确定。本研究为研究种子发育和小麦品质改良等提供了基础资料。     

Some Aspects of Germination of Triticum aestivum

An examination of the germinating wheat seed has been made withthe light microscope. Although the resting seed possesses onlypro vascular strands, these mature within about 24 h. By thistime the endosperm cheeks have swollen and forced the creaseoutwards, producing a cavity adjacent to the scutellum, exposingthe epithelium to the solution of endosperm hydrolysis products.Application of a direct silver method for staining the golgiapparatus has revealed the presence of particles in the aleurone,endosperm, scutellum, and coleorhiza which appear to move towardsthe developing embryo. It is unlikely that these particles areconcerned with the transport of hydrolysed food reserves butpossible alternative roles are discussed.     

小麦种子基因的表达序列标签分析

以授粉后12 d的小麦(Triticum aestivum L.)种子为材料,构建起cDNA文库.从中随机挑选10 000个克隆,利用Biomek 2000核酸工作站制成高密度cDNA阵列.然后分别以未受精子房、胚和胚乳中提取的RNA为模板,反转录合成探针与膜杂交,进行差示筛选.根据筛选结果,选取800个在胚、胚乳或胚和胚乳中表达的克隆进行表达序列标签(EST)分析,鉴定出216个不同的基因序列.其中24个ESTs属于已知的小麦基因;122个ESTs为推测的小麦新基因,它们编码的产物与种子贮藏蛋白或与生化代谢、发育等其他的生物学过程有关;70个ESTs的序列特征尚未确定.本研究为研究种子发育和小麦品质改良等提供了基础资料.     

Somatic association of homoeologous chromosomes in Triticum aestivum

The distributions of distances between members of homoeologous pairs was studied in common wheat in root-tip cells and meiocytes. In the majority of the pairs the mean distances were found to be significantly shorter than that calculated for two randomly distributed chromosomes. It could be concluded that homoeologues are loosely associated in somatic cells and more markedly so in meiocytes. However, this association is less intimate than that established previously for homologues. The tests were made in material which carries the association suppressor gene in two doses and the present findings support the assumption that in this dosage the suppressor gene has a smaller effect on homologues than on homoeologues.     

Inhibition of Sterol Biosynthesis in Chlorella sorokiniana by Triparanol

When Chlorella sorokiniana was cultured in the presence of 1 mg/1 triparanol succinate, there was a 42% reduction in total sterol concentration. Algal biomass was reduced by approximately the same amount. In addition to the cycloartenol, cyclolaudenol, 24-methyl-pollinastanol, ergosta-5, 7-dien-3β-ol, and ergosterol that occur in control culture, pollinastanol, 14α-methyl-5α-ergost-8-en-3β-ol, 5α-ergosta-8, 14, 22-trien-3β-ol, 5α-ergosta-8(14), 22-dien-3β-ol, 5α-ergosta-8(9), 22-dien-3β-ol, 5α-ergosta-8, 14-dien-3β-ol, 5α-ergost-8(9)-3n-3β-ol, 5α-ergost-8(14)-en-3β-ol, 5α-ergosta-7, 22-dien-3β-ol, and 5α-ergost-7-en-3β-ol were isolated and identified from triparanol succinate-treated cells. A biosynthetic pathway for sterol biosynthesis in this organism is postulated based on all the sterols that were isolated and identified in triparanol-treated cultures of C. sorokiniana. Cyclolaudenol appears to be the product of the first alkylation at C-24 in this organism rather than the more common 24-methylene cycloartanol. Since 24-methylene sterols are needed for the second alkylation reaction, this would explain the absence of C-29 sterols in C. sorokiniana. Four of the sterols identified in C. sorokiniana are reported for the first time in a living organism. They are: 24-methyl pollinastanol, 5α-ergosta-8, 14, 22-trien-3β-ol, 5α-ergosta-8(14), 22-dien-3β-ol and 5α-ergost-8(14)-en-3β-ol.     

Abnormal Sporogenesis in Wheat (Triticum aestivum L.) Induced by Short Periods of High Temperature

Plants of Triticum aestivum L. cv. Gabo, grown at 20 °C,were exposed to 30 °C for short periods during the timebetween the beginning of meiosis in the pollen mother cellsand anthesis. Plant water deficit at this temperature was avoidedby maintaining a high atmospheric relative humidity and tissuewater potential did not change. This temperature treatment appliedfor 3 days, at the time of reduction division and tetrad breakup in the male tissue, lowered grain yield through a drasticreduction in grain set, but was without effect at other stagesof development. Grain set was also reduced by exposing plantsto 30 °C for 1 day only or to a 30 °C day, 20 °Cnight (16 h photoperiod) regime for 3 days during the sensitiveperiod. A reduction in grain set did not result in a compensatoryincrease in the weight of remaining grains. The female fertility of previously heat-stressed plants wasassessed by pollinating with pollen from plants grown at a lowertemperature (20 °C). Grain set in such plants was less thanthat in plants grown at the lower temperature and hand pollinatedwith similar pollen, indicating that female fertility was reducedby high temperature. This was not the sole reason for reducedgrain set, however, as some anthers on heat-stressed plantswere small and neither extruded nor dehisced normally. Suchanthers contained pollen grains that were mostly shrivelled,had abnormal cytoplasm and showed no reaction to 2, 3, 5-triphenyltetrazolium chloride. Similar effects were also noted in pollenfrom apparently normal anthers on heat-stressed plants. Triticum aestivum, wheat, heat stress, pollen, sporogenesis, grain set, male sterility, female sterility     

Some Effects of Temperature and Irradiance on Growth of the First Four Leaves of Wheat, Triticum aestivum

Plants of Heron wheat were grown at 20 and 15 °C and inquantum flux densities of 400 and 200 µmol m^–2 s^–1.At completion of expansion of the first or second leaf, plantswere transferred between temperatures and quantum flux densities.Final size and cell number were measured for each of the firstfour main-stem leaves. Leaf area was affected only slightlyby treatment and effects on leaf length and width were alsosmall. It was concluded that leaf extension rate, which waslower at the lower temperature and in the lower light regime,is inversely related to the duration of leaf expansion. Leafdry wt was higher for plants grown in high light and for plantsgrown at 15 °C; transfer treatments led to readjustmentswhereby dry wts of leaves expanded after transfer resembledthose of leaves on plants kept throughout in the post-transferconditions. Leaf cell number was not affected by treatment but mean drywt per cell was significantly greater in high light, and forthe first two leaves, at 15 °C. There was a major and highlysignificant effect of treatment on the ratio of dry: fresh wtper cell, this being larger for leaves in high light. Transfertreatments between light regimes led to rapid changes in expandingleaves as was found for leaf dry wt. It was concluded that theexpanding grass leaf is much less dependent on older leavesto provide the necessary materials for cell division and expansionthan is the dicotyledon leaf. It is suggested that the increasein cell dry wt in high light is associated with an increasein cell wall material which is under photomorphogenic control. Triticum aestivum, wheat, leaf growth, cell division, cell expansion, cell size