Cell wall invertases from sugar cane

Invertases in sugar cane leaf sheaths are firmly bound to the cell wall. They consist of three different enzymes distinguished on the basis of optimum pH, K_m and the response to inhibitors. This invertase complex differs from the single enzyme described for immature and mature stalk tissues.     

Fructan Content and Synthesis in Leaf Tissues of Festuca arundinacea

The concentration of fructan in tall fescue (Festuca arundinacea Schreb.) changes during growth and in response to environment. The objective of this research was to compare the fructan concentration and fructosyl-transferase activity of tall fescue leaf tissues. Expanding leaves, inner and outer sheaths, and expanded blades of greenhouse-grown tall fescue plants were assayed for fructan concentration and fructosyl-transferase activity. Leaf sheaths contained significantly more nonstructural carbohydrate than did the expanded blade. Sheaths also contained a greater percentage of fructan with more than six sugar residues (long chain fructan), than either the expanded blade or expanding leaf. Expanding leaves contained a greater concentration of fructose and oligosaccharides than did sheath or blade tissues. Expanding leaves also had the greatest fructosyl-transferase activity measured either as radiolabel incorporated into fructans in tissue pieces or protein extracts. Activity of fructosyl-transferase was greater in expanding leaf tissue than in sheath tissues.     

Genotypic Variations in Non-Structural Carbohydrate and Cell-Wall Components of the Stem in Rice,Sorghum, and Sugar Vane

We evaluated genetic variations in the non-structural carbohydrate (NSC) and the cell-wall components of stem in rice, sorghum, and sugar cane to assess the potential suitability of these gramineous crops for bioethanol production. For NSC, the maximum soluble sugar concentration was highest in sugar cane, followed by sorghum with sucrose. The major NSC in rice was starch, but there were wide variations in the starch to soluble sugar ratios among the cultivars. The total concentration of cell-wall components was negatively correlated with the NSC concentration, indicating competition for carbon sources. Among the cell-wall components, lignin was relatively stable within each group. The major sugar species composing hemicellulose was xylose in all crop groups, but there were differences in composition, with a higher fraction of arabinose and glucose in rice as compared to the other crops. In rice, there was less lignin than in sorghum or sugar cane; this might be advantageous for the efficient saccharification of cellulose.     

Genotypic variations in non-structural carbohydrate and cell-wall components of the stem in rice, sorghum, and sugar vane

We evaluated genetic variations in the non-structural carbohydrate (NSC) and the cell-wall components of stem in rice, sorghum, and sugar cane to assess the potential suitability of these gramineous crops for bioethanol production. For NSC, the maximum soluble sugar concentration was highest in sugar cane, followed by sorghum with sucrose. The major NSC in rice was starch, but there were wide variations in the starch to soluble sugar ratios among the cultivars. The total concentration of cell-wall components was negatively correlated with the NSC concentration, indicating competition for carbon sources. Among the cell-wall components, lignin was relatively stable within each group. The major sugar species composing hemicellulose was xylose in all crop groups, but there were differences in composition, with a higher fraction of arabinose and glucose in rice as compared to the other crops. In rice, there was less lignin than in sorghum or sugar cane; this might be advantageous for the efficient saccharification of cellulose.     

Fructan metabolism in wheat in alternating warm and cold temperatures

The objective of this research was to develop a system in which the direction of fructan metabolism could be controlled. Three-week-old wheat seedlings (Triticum aestivum L. cv Caldwell) grown at 25°C were transferred to cold temperature (10°C) to induce fructan synthesis and then were transferred to continuous darkness at 25°C after defoliation and fructan degradation monitored. The total fructan content increased significantly 1 day after transferring from 25°C to 10°C in both leaf blades and the remainder of the shoot tissue, 90% of which was leaf sheath tissue. Leaf sheaths contained higher concentrations of fructan and greater portions of high molecular weight fructan than did leaf blades. Fructan content in leaf sheaths declined rapidly and was gone completely within 48 hours following transfer to 25°C in darkness. In leaf blades the invertase activity fluctuated during cold treatment. The activity of sucrose:sucrose fructosyl transferase increased markedly during cold treatment, while fructan hydrolase activity decreased slightly. In leaf sheaths, however, the activity of invertase decreased rapidly upon transfer to cold temperature and remained low. Trends in sucrose:sucrose fructosyl transferase and hydrolase activity in sheaths were the same as those of leaf blades. Sheath invertase and hydrolase activity increased when plants were transferred back to darkness at 25°C, while sucrose:sucrose fructosyl transferase activity decreased. These results indicate that changing leaf sheath temperature can be utilized to control the direction of fructan metabolism and thus provide a system in which the synthesis or degradation of fructan can be examined.     

sh-2甜玉米F2籽粒营养品质遗传特点、杂种优势及其亲子回归关系分析

研究了25个sh-2甜玉米自交系及其组配的15个sh-2型F_2籽粒的5个品质性状的遗传特点、杂种优势、亲子回归关系．结果表明,亲本间,除籽粒还原糖含量外,可溶性总糖、蔗糖、淀粉、可溶性蛋白含量是否存在显著差异,对F_2籽粒品质有明显影响．F_2籽粒可溶性总糖、还原糖、淀粉、可溶性蛋白含量近低亲遗传,而蔗糖含量近高亲遗传．杂种F_2籽粒可溶性总糖、淀粉、可溶性蛋白含量普遍介于双亲之间,杂种优势不强;还原糖含量普遍表现为低亲,没有超亲优势;蔗糖含量以超亲为主,有明显杂种优势．亲本对F_2杂交籽粒可溶性总糖、还原糖、蔗糖、淀粉、可溶性蛋白含量均表现为正效应;除还原糖品质外,其他品质性状受父本的影响较大．研究表明,了解sh-2甜玉米亲本营养品质性状,能很好的预测其F_2籽粒营养品质性状,使育种更有目的性．     

Detection of Biogenic Silica in Leaf Blade, Leaf Sheath, and Stem of Bermuda Grass (Cynodon dactylon) Using LIBS and Phytolith Analysis

Laser induced breakdown spectroscopy (LIBS) has been used to perform in situ analysis of major and minor elements present in the different parts of the Bermuda grass (Cynodon dactylon). In situ, point detection/analysis of the elements in plants without any sample preparation has been demonstrated. LIBS spectra of the different parts (leaf blade, leaf sheath and stem) of fresh C. dactylon plant have been recorded to study the pattern of silica deposition in its different parts. Atomic lines of Si, Mg, Ca, C, Al, Zn, N, Sr, etc. have been observed in the LIBS spectra of the C. dactylon. A close observation of LIBS spectra of the different parts of the plants shows that silica concentration is greater in leaf blades than leaf sheaths and stems. The results obtained with LIBS analysis are also compared with the number density of phytoliths deposited in different parts of C. dactylon. It is observed that the highest silicified cell frequency is present in leaf blades followed by leaf sheaths and stems which is in close agreement with LIBS analysis.     

Variation in the Soluble Carbohydrate Content of Climatic Races of Dactylis Glomerata (Cocksfoot) at Different Temperatures

The soluble carbohydrate content of a Mediterranean and a NorthEuropean population of cocksfoot was studied at four temperaturesduring a 16-h light and an 8-h dark period. Ethyl alcohol andwater extractions were made of leaf blades and leaf sheaths.The extracts showed significant effects of temperature, population,and time of harvest. Fructosans in the leaf sheaths showed themost marked effect of temperature and population in that risingtemperature rapidly reduced the fructosan content which in theNorth European population was significantly higher at low temperatures.The greatest diurnal fluctuations of carbohydrates occurredin alcohol extracts from the leaf blades, with a rise in theirconcentration during the light period and a rapid fall in thedark.     

烯效唑浸种对玉米幼苗生长和内源激素含量的影响

烯效唑浸种对玉米苗期叶片和叶鞘伸长生长有抑制作用,且抑制效应随烯效唑浓度的增大而增强,但植株粗壮,叶宽和茎基宽增加,根系增多,根长增加.烯效唑浸种的玉米幼苗中LAA和GA3含量下降,叶鞘中尤为明显;ZT含量则是地上部提高,根中下降,ABA含量提高,植株各器官中(IAA GA3)/ABA比值均下降,IAA/GA3比值均升高,IAA/ZT和GA3/ZT比值则是地上部降低,根中升高.     

Distribution of deoxynivalenol inFusarium-infected forage maize

A time course study was carried out to assess the appearance and distribution of DON in different organs of forage maize cultivated in the field. DON was produced after the flowering period and increased until harvest to high amounts in the rudimentary ears and leaf sheaths/leaf blades deriving from nodes located below the ear node, whereas nodes and internodes were either not or only slightly contaminated with DON. Genrally, DON was not detected in the ears, including husks, during the whole cultivation time.Fusarium biomass determined in the infected organs confirmed these findings. It seems that the contribution of DON containing rudimentary ears, leaf sheaths and leaf blades to the total DON contamination of forage maize is so far widely underestimated. Therefore advanced evaluation procedures are recommended to get a better understanding of the infection and contamination process and to prove genotypic differences in the resistance of forage maize genotypes againstFusarium infection.     

Relationships between Carbon Dioxide, Malate, and Nitrate Accumulation and Reduction in Corn (Zea mays L.) Seedlings

The observation that exposure of the leaf canopy to increasing concentrations of CO₂ (100-400 μl/l) decreases the influx of nitrate to the leaf blades, but not to the roots or stalks (largely leaf sheaths), was reconfirmed using ¹⁵NO₃⁻. Decreases in leaf nitrate supply were associated with decreases in induction of nitrate reductase, thus supporting the view that the influx of nitrate to a tissue is a major factor in regulation of the level of nitrate reductase. The whole plant ¹⁵N distribution data show that the CO₂ effects were due to decreased influx of nitrate into the leaf blade rather than CO₂-enhanced nitrate reduction. The decreases in nitrate accumulation by the leaf blade with increases in CO₂ concentration were only partially accounted for by differences in transpiration. Because the initial malate concentration of root tissue (detopped plants) had no subsequent effect on nitrate uptake, it seems unlikely that high levels of malate induced by CO₂ were responsible for the exclusion of nitrate from the leaf blades.     

Assimilation and transport of nitrogen in rice II. 15N-labelled nitrate nitrogen

An investigation was made to study the assimilation and transportof ¹⁵N-labelled nitrate nitrogen in rice plant (Oryza sativaL.). Nitrogen from labelled nitrate at the end of plant feedingwas found mainly in nitrate form, and was more prevalent inroots, stem and leaf sheaths. The nitrite fraction had the nextlargest ¹⁵N enrichment. The ¹⁵NO₃ assimilation in the newlyemerged panicle was mainly in amide and amino acid. The ¹⁵N-incorporation at day 0 was greatest in amino acid andnitrate of roots and decreased towards the stem and leaves.Incorporation in these fractions considerably decreased fromday 0 to day 10. Probably most of the nitrogen from the nitratesource was transported from the roots to the shoot in nitrateand amino acid forms. A decrease of ¹⁵N-incorporation in the soluble N fraction andincrease in the insoluble N fraction from day 0 to day 10 inplant parts, particularly the blades, suggested that proteinsynthesis occurred mostly in young parts of the shoot duringthis period. The marked variation in ¹⁵N distribution in differentparts of the plant during the 10 days indicated that the nitrogenin roots and tillers was probably remobilized and transportedto other parts, particularly the upper leaf blades. Ammonium and nitrate nitrogen transport in rice plant are compared. (Received May 11, 1974; )     

Proteomic analysis of rice seedlings during cold stress

Low temperature is one of the important environmental changes that affect plant growth and agricultural production. To investigate the responses of rice to cold stress, changes in protein expression were analyzed using a proteomic approach. Two-week-old rice seedlings were exposed to 5 degrees C for 48 h, then total crude proteins were extracted from leaf blades, leaf sheaths and roots, separated by 2-DE and stained with CBB. Of the 250-400 protein spots from each organ, 39 proteins changed in abundance after cold stress, with 19 proteins increasing, and 20 proteins decreasing. In leaf blades, it was difficult to detect the changes in stress-responsive proteins due to the presence of an abundant protein, ribulose bisphosphate carboxylase/oxygenase large subunit (RuBisCO LSU), which accounted for about 50% of the total proteins. To overcome this problem, an antibody-affinity column was prepared to trap RuBisCO LSU, and the remaining proteins in the flow through from the column were subsequently separated using 2-DE. As a result, slight changes in stress responsive proteins were clearly displayed, and four proteins were newly detected after cold stress. From identified proteins, it was concluded that proteins related to energy metabolism were up-regulated, and defense-related proteins were down-regulated in leaf blades, by cold stress. These results suggest that energy production is activated in the chilling environment; furthermore, stress-related proteins are rapidly up-regulated, while defense-related proteins disappear, under long-term cold stress.     

Effects of the Fungal Endophyte Acremonium coenophialum on Nitrogen Accumulation and Metabolism in Tall Fescue

Infection by the fungal endophyte Acremonium coenophialum affected the accumulation of inorganic and organic N in leaf blades and leaf sheaths of KY 31 tall fescue (Festuca arundinacea Schreb.) grown under greenhouse conditions. Total soluble amino acid concentrations were increased in either the blade or sheath of the leaf from infected plants. A number of amino acids were significantly increased in the sheath, but only asparagine increased in the blade. Infection resulted in higher sheath NH₄⁺ concentrations, whereas NO₃⁻ concentrations decreased in both leaf parts. The effects on amino acid, NO₃⁻, and NH₄⁺ concentrations were dependent upon the level of N fertilization and were usually apparent only at the high rate (10 millimolar) of application. Administration of ¹⁴CO₂ to the leaf blades increased the accumulation of ¹⁴C in their amino acid fraction but not in the sheaths of infected plants. This may indicate that infection increased amino acid synthesis in the blade but that translocation to the sheath, which is the site of fungal colonization, was not affected. Glutamine synthetase activity was greater in leaf blades of infected plants at high and low N rates of fertilization, but nitrate reductase activity was not affected in either part of the leaf. Increased activities of glutamine synthetase together with the other observed changes in N accumulation and metabolism in endophyte-infected tall fescue suggest that NH₄⁺ reassimilation could also be affected in the leaf blade.     

Abscisic acid in immature apical tissue of sugar cane and in leaves of plants subjected to drought

Summary Abscisic acid was extracted from immature leaf and stem tissue of sugar cane. Mature leaves of well watered plants contained trace quantities of this hormone but plants subjected to drought accumulated relatively large amounts in their mature leaves. Extracts from wilting leaves contained a substance similar to or identical with (+)-phaseic acid.     

Identification of maize silicon influx transporters

Maize (Zea mays L.) shows a high accumulation of silicon (Si),but transporters involved in the uptake and distribution havenot been identified. In the present study, we isolated two genes(ZmLsi1 and ZmLsi6), which are homologous to rice influx Sitransporter OsLsi1. Heterologous expression in Xenopus laevisoocytes showed that both ZmLsi1 and ZmLsi6 are permeable tosilicic acid. ZmLsi1 was mainly expressed in the roots. By contrast,ZmLsi6 was expressed more in the leaf sheaths and blades. Differentfrom OsLsi1, the expression level of both ZmLsi1 and ZmLsi6was unaffected by Si supply. Immunostaining showed that ZmLsi1was localized on the plasma membrane of the distal side of rootepidermal and hypodermal cells in the seminal and crown roots,and also in cortex cells in lateral roots. In the shoots, ZmLsi6was found in the xylem parenchyma cells that are adjacent tothe vessels in both leaf sheaths and leaf blades. ZmLsi6 inthe leaf sheaths and blades also exhibited polar localizationon the side facing towards the vessel. Taken together, it canbe concluded that ZmLsi1 is an influx transporter of Si, whichis responsible for the transport of Si from the external solutionto the root cells and that ZmLsi6 mainly functions as a Si transporterfor xylem unloading.     

Photosynthesis of the flag leaf blade and its sheath in high-yielding hybrid rice 'Liangyoupeijiu'.

Using high-yielding hybrid rice 'Liangyoupeijiu' (LYP9) and hybrid rice 'Shanyou 63' (SY63) as the experimental materials and using (14)C radio-autography, the photosynthetic capacities and distribution of photosynthates in flag leaf blades and sheaths of LYP9 were studied. The results showed that net photosynthetic rates (Pn) of the flag leaf blades and sheaths of LYP9 were much higher than those of SY63; the light transmissivity rates (LT) measured at the medium height of the flag leaf sheaths and the penultimate leaf sheaths were also significantly higher than those of SY63. The incipient activities, total activities and activation percentages of Rubisco in the flag leaf blade and sheath of LYP9 were all higher than those of SY63. The photosynthate transport rate in the sheaths of LYP9, and the quantity of photosynthate transported to the spikes and transformed to economic yield of LYP9 were all higher than those of SY63. The photosynthates produced by the sheaths were mainly transported to spike to make a certain contribution (about 15%) to yield.     

果蔗叶片生理生化指标与品质性状的典范相关分析

选用果蔗（Saccharum officinarum L．）14个品种,用典范相关分析法研究不同生育期叶片生理生化指标对果蔗品质性状的影响。结果表明：分蘖期类胡萝卜素含量与蔗茎蔗糖含量,可溶性总糖含量与蔗茎含水率,可溶性总糖含量与蔗汁还原糖含量均呈正相关;伸长初期叶绿素含量、CAT活性与蔗茎蔗糖含量,可溶性蛋白质含量与蔗茎纤维含量均呈正相关;伸长盛期Mg^2＋ -ATP酶活性与蔗茎纤维含量,可溶性总糖含量与蔗茎蔗糖含量呈正相关,C／N与蔗茎含水率呈负相关;成熟期类胡萝卜素含量与蔗茎蔗糖含量呈正相关,可溶性总糖含量与蔗汁还原糖含量呈负相关。     

Nitrate Assimilation in Rice Grown under Lowland Conditions

Pattern and extent to which the main shoot of rice (Oryza sativa L.) cv. Pusa 33 assimilates NO₃^- when grown under lowland conditions was determined in a field study. The in vivo NR (nitrate reductase) activity is low as compared to the value in other cereals grown under aerobic soil conditions. The leaf blades had higher NR activity (g fr. wt.)^-1 than the sheaths and stem. Calculation of total NO₃^- (mol) reduced in the main shoot, obtained by integrating the in vivo NR assay values per plant part and per day over the duration for which the various plant parts on the main shoot remained metabolically active, showed that out of the total reduced N at harvest, 16.6% was assimilated via the enzyme nitrate reductase. In the leaf sheaths and stem the NO₃^- was reduced to slightly over 50% of the total NO₃^- that was reduced in the main shoot. The rest of the amount was reduced in the leaf blades.     

CO2浓度升高对沉水植物菹草叶表型及生理生化特征的影响

 对菹草 (Potamogeton crispus) 叶在高CO2 (1 000±50 μmol·mol-1)和对照浓度(约380 μmol·mol-1)下的表型及一些生理生化指标进行了比较研究。结果表明：CO2浓度升高明显地改变了菹草叶的表型特征,外形更为粗短,叶宽、单叶面积、单株总叶面积、叶面积率、叶重比明显增加,但特殊叶面积和叶长增加不明显。线性回归分析表明单株总叶面积和植株大小密切相关。异速生长分析表明叶面积的变化不是可塑性反应,而是受植株大小所制约。此外,CO2浓度升高后植物的色素含量和一些化学物质含量明显改变。叶绿素a、叶绿素b、总叶绿素及类胡萝卜素含量减少,且叶绿素a/b也降低;可溶性糖含量增加,而蛋白质、N和P浓度降低。