氮素对不同开花期棉铃纤维比强度形成的生理基础的影响

于2005年在江苏南京(长江流域下游棉区)和徐州(黄河流域黄淮棉区)棉田设置不同氮素水平(零氮：0 kg N·hm^-2,适氮：240 kg N·hm^-2,高氮：480 kg N·hm^-2)试验,研究氮素对不同开花期棉铃(伏前桃、伏桃和秋桃)纤维比强度形成生理基础的影响.结果表明：与适氮处理相比,零氮处理显著降低了棉铃对位叶氮浓度,增加了C/N,影响程度随开花期的推迟而加大,导致伏桃、秋桃对位叶制造和运输光合产物的能力在棉铃发育中后期大幅度下降,棉纤维的相对生长速率以及纤维发育关键酶蔗糖合成酶和β-1,3-葡聚糖酶活性降低,纤维素快速累积持续期缩短,纤维比强度显著降低;高氮处理显著增加了棉铃对位叶氮浓度,降低了C/N,影响程度随开花期的推迟而降低,其降低了伏前桃、伏桃发育过程中光合产物向纤维分配的比例、棉铃发育前中期的纤维发育关键酶活性及纤维素累积速率,导致其纤维比强度亦显著降低.综合分析认为,适宜的施氮量可以协调棉花的“源库”关系,有利于促进不同开花期棉铃高纤维比强度的形成.与适氮处理相比,零氮处理的伏前桃、伏桃和秋桃纤维比强度分别降低了1.8%、5.8%和13.0%,高氮处理则分别降低了8.2%、7.4%和-2.4%.     

低温对棉纤维比强度形成的生理机制影响

通过设置播期试验使棉纤维加厚发育过程(铃龄25~50 d)处于不同的温度条件下,研究低温对棉花纤维比强度形成的内在生理机制影响,为采取调控措施解决目前棉花(Gossypium)生产中存在的晚熟劣质问题提供理论依据。两年试验结果表明:棉纤维加厚发育期24.0 ℃左右的日均温是高强纤维形成的最佳温度,其内在生理机制表现为棉纤维蔗糖合成酶活性最高,β_1,3_葡聚糖酶活性最低,纤维素的累积量和累积速率均明显高于其它低温条件,纤维超分子结构取向参数角较小,处于优化状态,最终表现为纤维比强度亦最大;低于21.0 ℃时即对棉纤维加厚发育相关酶活性产生明显影响,纤维比强度降低。当温度降到15.0 ℃左右时,棉纤维蔗糖合成酶活性显著降低,而β-1,3_葡聚糖酶活性显著升高,同时纤维素累积量和累积速率均显著降低,纤维超分子结构取向参数角明显宽化,棉纤维不能正常发育,不利于高强纤维的形成(铃重仅为3.22 g,纤维比强度仅为15.73 cN·tex^-1)。     

不同温度敏感性棉花纤维发育相关酶活性变化对低温的响应

选用纤维比强度形成存在温度敏感性差异的两个棉花品种（科棉1号：温度弱敏感型品种,苏棉15：温度敏感型品种）为材料,于2006—2007年在江苏南京设置大田分期播种试验,使棉纤维发育处于不同的温度条件,研究低温对棉纤维发育相关酶（蔗糖酶、蔗糖合成酶、磷酸蔗糖合成酶、β-1,3-葡聚糖酶）活性及相应基因表达的影响.结果表明：由晚播造成的低温（棉纤维发育期日均最低温分别为21.1、20.5和18.1 ℃）影响了纤维发育相关酶的活性变化,从而影响了棉纤维素累积和纤维比强度的形成.低温提高了纤维中蔗糖酶和β-1,3-葡聚糖酶的活性,降低了蔗糖合成酶和磷酸蔗糖合成酶的活性.低温使Expansin、蔗糖合成酶基因的高表达时间延长,β-1,3-葡聚糖酶基因的表达峰值出现时间延迟,且表达量降低.两个棉花品种的纤维素合成相关酶对低温的响应存在差异,温度敏感型品种（苏棉15）的酶活性的变化幅度明显高于温度弱敏感型品种（科棉1号）, 可能是导致不同棉花品种纤维比强度形成存在温度敏感性差异的主要原因.     

棉纤维发育响应高温胁迫的关键时间窗口

以温度弱敏感性棉花品种(科棉1号)和温度敏感性棉花品种(苏棉15)为材料,在人工气候室模拟自然温周期设置高温(34 ℃\[38/30 ℃\],HT)和对照(26 ℃\[30/22 ℃\],CK)2个温度处理,研究了花铃期不同时段进行高温胁迫后纤维发育重要相关物质的变化及其与纤维品质的关系.结果表明： 在花后不同时间开始高温胁迫持续处理5 d,苏棉15纤维长度、纤维比强度、马克隆值响应高温胁迫的关键时间窗口分别为花后0～18.3 d,花后10.9～26.1 d和花后10.5～34.0 d.因此,花后11～18 d左右是棉花综合纤维品质形成响应高温胁迫的关键时间窗口.在关键时间窗口对棉花进行高温处理5 d后,苏棉15纤维中的蔗糖含量相对常温条件下呈先降低后增加的变化趋势,胼胝质含量上升,纤维素含量下降4.2%,纤维长度变短(最大变幅为23.3%),纤维比强度上升(最大变幅为4.3%),马克隆值下降(最大变幅为10.5%)并偏离最适范围,纤维品质变差.科棉1号的上述纤维发育主要相关物质含量及纤维品质与苏棉15变化趋势一致、最敏感时间相近,仅变化幅度相对较小.     

棉铃发育期棉花源库活性对棉铃对位叶氮浓度的响应

采用大田试验,以3个铃期差异明显的棉花品种为材料,研究了不同施氮量形成的棉铃对位叶氮浓度对棉花花铃期纤维发育源库活性指标的影响。结果表明:在花后同一时期,棉铃对位叶可溶性糖、蔗糖含量和磷酸蔗糖合成酶活性以及棉纤维蔗糖含量和蔗糖合成酶活性等均随对位叶氮浓度的升高呈先升高后降低的变化趋势(45、52 DPA(花后天数Days post anthesis)的纤维蔗糖含量趋势相反),可用抛物线方程Y=ax2+bx+c拟合(P<0.01),通过拟合方程得到各指标所对应的最佳对位叶氮浓度。45 DPA(德夏棉1号38 DPA)前,花后同一时期各指标对应的最佳对位叶氮浓度差异较小,通过幂函数方程建立最佳叶氮浓度随花后天数的拟合方程,得到纤维发育期内源库活性各指标达到或接近最优状态时的适宜对位叶氮浓度的动态方程。本试验条件下,德夏棉1号、科棉1号和美棉33B的适宜对位叶氮浓度的拟合方程分别为N德1=7.2263DPA-0.276(R2=0.9805**)、N科1=7.23DPA-0.3026(R2=0.9861**)、N美33B=7.0997DPA-0.2814(R2=0.9807**)。     

温度对棉纤维糖代谢相关酶活性的影响

以棉纤维比强度高的科棉1号和中等强度的美棉33B 2个基因型棉花品种为材料,于2005年在江苏南京(长江流域下游棉区)和徐州(黄河流域黄淮棉区)设置不同播期(4月25日和5月25日)试验,研究了不同温度下棉纤维发育过程中蔗糖酶、蔗糖合成酶、磷酸蔗糖合成酶和β-1,3-葡聚糖酶等糖代谢相关酶活性的动态变化特征及其与纤维长度和比强度形成的关系.结果表明：棉纤维伸长发育期,蔗糖酶、β-1,3-葡聚糖酶活性较高;纤维加厚发育期,蔗糖合成酶和磷酸蔗糖合成酶活性上升速度快、活性高,蔗糖酶和β-1,3-葡聚糖酶活性下降速度快.纤维伸长期,蔗糖酶活性升高对纤维的伸长具有明显促进作用;纤维加厚发育期,提高蔗糖合成酶、磷酸蔗糖合成酶活性及加快蔗糖酶和β-1,3-葡聚糖酶活性下降速度有利于提高纤维比强度.科棉1号前期蔗糖酶、β-1,3-葡聚糖酶活性及中后期蔗糖合成酶、磷酸蔗糖合成酶活性均较美棉33B高.在本试验条件下,23.3 ℃是高强纤维形成的适宜温度,23.3 ℃～25.5 ℃是纤维长度形成的适宜温度.     

Genotypic differences in some physiological characteristics during cotton fiber thickening and its influence on fiber strength

Cotton (Gossypium L.) fiber strength is linked with many complex physiological and biochemical processes in the stage of secondary fiber cell wall thickening. With the aim of further exploiting of the relationship between fiber strength and genotypic differences in physiological characteristics, the experiment was implemented in Nanjing, China (in the lower reach of Yangtze River Valley in China) at the stage of cotton fiber thickening stage in 2004–2005. The result showed that the higher strength fiber (genotype Kemian 1) always had higher activities of sucrose synthetase (SuSy) and β-1,3-glucan synthase, and more sucrose and callose existed and transformed for cellulose synthesis than these of the other genotypes during the fiber secondary wall thickening period These resulted in a longer and more gently cellulose accumulation and wider range and longer period of fiber strength enhancing. Interestingly, the opposite effects were observed in lower strength fiber of Dexiamian 1 and intermediary indices were found in NuCOTN 33B with middle strength fiber. Taken together, above results suggested the variations in the transformation of sucrose and callose contents, and the dynamics of sucrose synthase and β-1,3-glucan synthase activities, might be one of the physiological reasons causing the differences in the speed of cellulose accumulation and fiber strength formation. Additionally, other results showed: (1) the occurrence of callose content peak might be an important sign of the onset of the secondary wall thickening in the fiber cell; (2) the duration and the maximum growth rate of cellulose rapid accumulation contribute more to fiber strength development than other indices of cellulose rapid accumulation.     

Plant density influences fiber sucrose metabolism in relation to cotton fiber quality

Planting density plays an important role in improving cotton yield and regulating fiber quality. A 2-year experiment was conducted to investigate the effects of plant density on sucrose metabolism in relation to fiber quality of field-grown cotton. The results showed that lint yield increased with increasing plant density, fiber micronaire, fiber maturity ratio, and fiber fineness decreased with the increasing of plant density, whereas fiber length, fiber uniformity index, fiber strength, and fiber elongation were little affected by plant density. Increased plant density decreased sucrose synthase (SuSy) activity, sucrose content, and cellulose content in cotton fiber, but increased invertase activity. Increased invertase activity would restrain SuSy activity in cotton fiber: therefore, SuSy activity was the most severely affected enzyme in fiber sucrose metabolism by cotton plant density during fiber development. Abundant sucrose content in fiber after 24 days post anthesis (DPA) and high activities of SuSy and sucrose phosphate synthase (SPS) at 38 DPA were beneficial for cellulose synthesis, and were propitious to optimize the fiber maturity properties. The results also showed that fiber micronaire, maturity ratio, and fineness decreased 0.11, 0.02, and 5.89 mtex, respectively, with each increase of 10,000 plants per hectare. It was concluded that high plant density decreased SuSy activity, sucrose content, and cellulose content, but increased invertase activity in sucrose metabolism, resulting in low fiber micronaire, fiber maturity ratio, and fiber fineness.     

Molecular characterization and expression in Escherichia coli of three beta-1,3-glucanase genes from Lysobacter enzymogenes strain N4-7

Lysobacter enzymogenes strain N4-7 produces multiple biochemically distinct extracellular beta-1,3-glucanase activities. The gluA, gluB, and gluC genes, encoding enzymes with beta-1,3-glucanase activity, were identified by a reverse-genetics approach following internal amino acid sequence determination of beta-1,3-glucanase-active proteins partially purified from culture filtrates of strain N4-7. Analysis of gluA and gluC gene products indicates that they are members of family 16 glycoside hydrolases that have significant sequence identity to each other throughout the catalytic domain but that differ structurally by the presence of a family 6 carbohydrate-binding domain within the gluC product. Analysis of the gluB gene product indicates that it is a member of family 64 glycoside hydrolases. Expression of each gene in Escherichia coli resulted in the production of proteins with beta-1,3-glucanase activity. Biochemical analyses of the recombinant enzymes indicate that GluA and GluC exhibit maximal activity at pH 4.5 and 45 degrees C and that GluB is most active between pH 4.5 and 5.0 at 41 degrees C. Activity of recombinant proteins against various beta-1,3 glucan substrates indicates that GluA and GluC are most active against linear beta-1,3 glucans, while GluB is most active against the insoluble beta-1,3 glucan substrate zymosan A. These data suggest that the contribution of beta-1,3-glucanases to the biocontrol activity of L. enzymogenes may be due to complementary activities of these enzymes in the hydrolysis of beta-1,3 glucans from fungal cell walls.     

Specific and direct measurement of theβ-1,3-glucan in developing cotton fiber

The reaction of N,N-diethylaziridinium chloride with raw cotton (Gossypium hirsutum L.) seed fibers to introduce N,N-diethylaminoethyl (DEAE) substituents at a low degree of substitution was used for demonstrating the presence of O(4)H, characteristic of a -1,3-glucan. The derivatized 1,3-glucan/cellulose was hydrolyzed to DEAE-glucoses that were analyzed by gas-liquid chromatography. Capillary columns proved effective for measuring the small amounts of 4-O-DEAE-glucose in the presence of major amounts of 2-O- and 6-O-DEAE-glucoses. Analyses of raw cotton fibers were carried out through fiber development (20, 27, 34, 41 and 48 d post anthesis, DPA) and field exposure (62, 83 and 104 DPA) periods. The yields of 4-O- and other individual DEAE-glucoses and the yield of 4-O-DEAE-glucose in relation to 2-O-DEAE-glucose were particularly informative concenring the role of the -1,3-glucan in cellulose. The results confirmed the early production and almost immediate decrease of the -1,3-glucan and demonstrated continued production of accessible cellulose followed by a sharp decrease in accessibility after boll opening. The -1,3-glucan content of the raw cotton fiber, estimated from the yield of 4-O-DEAE-glucose (representing 1,3-glucan) and the yield of 2-O-DEAE-glucose (approximating 1,3-glucan plus cellulose) was 10%, 4%, 1% and 0.6% at, in the order given, 20, 27, 48, and 104 DPA. These results are in general agreement with other conventional analyses.Abbreviations DPA days post-anthesis - DEAE diethylaminoethyl     

水氮运筹对棉花花后生物量和氮素利用率的影响

在池栽和大田条件下,以‘美棉33B’为材料,研究不同水分(自然降水、自然降水 灌水)和氮素(0、240、480kgN/hm2)运筹下棉花花后生物量和养分累积及氮素利用率动态变化特征。结果表明:施氮使棉花(整株、营养器官、生殖器官)生物量和养分快速累积期持续时间缩短、最大累积速率增大且出现时间提前、累积量及皮棉产量增加。灌水使240 kgN/hm2处理棉花(整株、营养器官、生殖器官)生物量和养分快速累积期持续时间缩短、最大累积速率出现时间提前、最大累积速率和累积量增大、氮素累积利用率和产量提高;而使480 kgN/hm2处理棉花营养器官生物量和养分快速累积期持续时间延长、最大累积速率出现时间推迟、生物量和养分最大累积速率及累积量增大、氮素累积利用率提高,而生殖器官相应指标呈降低趋势;灌水对不施氮处理棉花生物量和养分累积各项特征参数影响较小。营养器官生物量和氮磷钾最大累积速率出现时间较生殖器官早23 d左右,而快速累积期持续时间长于生殖器官11 d左右。研究发现,水分和氮素运筹可通过影响棉花生物量和养分累积的动态特征参数来影响棉花生长,进而影响最终产量品质形成;在本实验条件下,以灌水的240 kgN/hm2处理棉花的生长特征参数最为协调,皮棉产量和氮素利用率最高,品质较优。     

Carbon partitioning to cellulose synthesis

This article discusses the importance and implications of regulating carbon partitioning to cellulose synthesis, the characteristics of cells that serve as major sinks for cellulose deposition, and enzymes that participate in the conversion of supplied carbon to cellulose. Cotton fibers, which deposit almost pure cellulose into their secondary cell walls, are referred to as a primary model system. For sucrose synthase, we discuss its proposed role in channeling UDP-Glc to cellulose synthase during secondary wall deposition, its gene family, its manipulation in transgenic plants, and mechanisms that may regulate its association with sites of polysaccharide synthesis. For cellulose synthase, we discuss the organization of the gene family and how protein diversity could relate to control of carbon partitioning to cellulose synthesis. Other enzymes emphasized include UDP-Glc pyrophosphorylase and sucrose phosphate synthase. New data are included on phosphorylation of cotton fiber sucrose synthase, possible regulation by Ca²⁺ of sucrose synthase localization, electron microscopic immunolocalization of sucrose synthase in cotton fibers, and phylogenetic relationships between cellulose synthase proteins, including three new ones identified in differentiating tracheary elements of Zinnia elegans. We develop a model for metabolism related to cellulose synthesis that implicates the changing intracellular localization of sucrose synthase as a molecular switch between survival metabolism and growth and/or differentiation processes involving cellulose synthesis. Abbreviations: CesA, cellulose synthase; Csl, cellulose-like synthase (genes); DCB, dichlobenil; DPA, days after anthesis; SPS, sucrose phosphate synthase; SuSy, sucrose synthase; P-SuSy, particulate SuSy; S-SuSy, soluble SuSy     

Effects of potassium deficiency on the enzymatic changes in developing cotton fibers

Although effects of potassium (K) on cotton growth have been explored extensively, the effects of K deficiency on the physiological changes closely related to cotton fiber development are lacking. Thus, a 2-year field experiment was conducted with two cotton cultivars (Simian 3 and Siza 3) under 0 kg K₂O ha^?1 (K deficiency) and 300 kg K₂O ha^?1 (K sufficiency). The results showed that tonoplast adenosine triphosphatase (V-ATPase), pyrophosphatase (PPase), plasma membrane H⁺-ATPase (PM H⁺-ATPase), phosphoenolpyruvate carboxylase (PEPC), sucrose synthesis (SuSy) and vacuolar invertase (V-INV) were highly sensitive to K deficiency. The decreases in those enzymes resulted in low malate and soluble sugar contents, which together with low K concentration declined the driving force for fiber elongation, leading to significantly lower fiber length in the 0 kg K₂O ha^?1 treatment. The activity of sucrose phosphate synthase (SPS) was obviously increased by K deficiency before 20 days post anthesis (DPA), which could partly explain the acceleration of fiber cellulose synthesis and the increase in fiber strength in the 0 kg K₂O ha^?1 treatment in the early stage. However, SPS activity was decreased by K deficiency after 20 DPA and SuSy activity was reduced by K deficiency at any sampling date, resulting in low fiber strength in the end. Compared with Simian 3, the enzymes V-ATPase, PPase, PM H⁺-ATPase, PEPC and SuSy during fiber elongation stage were more sensitive to K deficiency in Siza 3, and the enzymes SuSy and SPS during fiber-thickening stage were more sensitive to K deficiency in Siza 3, which were the important reasons causing greater decreases in final fiber length and final fiber strength for Siza 3 than Simian 3 under K deficiency.     

Regulation of the beta-1,3-glucanase system in Penicillium italicum: glucose repression of the various enzymes.

The microscopic fungus Penicillium italicum when grown in a synthetic liquid medium produced at least three enzymes with beta-1,3-glucanase activity which were separated by diethylaminoethyl-Sephadex column chromatography. These were named beta-1,3-glucanases I, II, and III respective to their order of elution from the column. A tentative characterization of these three enzymes indicated that they have different modes of action; the first one is an endoglucanase, the second is an exoglucanase, and the third probably has both mechanisms of action. Glucose had a repressive effect on all three enzymes. Only small amounts of beta-1,3-glucanases II and III were present in the cells when they were actively growing in the presence of this sugar. However, when the cells were transferred to a medium low in glucose, a significant increase in the specific activity of beta-1,3-glucanase took place; this was due in part to a much more active production of beta-1,3-glucanases II and III and in part to the appearance of beta-1,3-glucanase I, which could only be detected after more than 12 h of incubation in this medium. The results are discussed in the context of possible beta-1,3-glucanase functions in the fungal cells.     

The accumulation of pigment in fiber related to proanthocyanidins synthesis for brown cotton

Brown cotton is a kind of naturally colored cotton. Because of less processing and little dying, it is more friendlier to environment than white cotton. For brown cotton, pigment accumulation in fiber is one of the most important characteristics. In this study, we selected a brown fiber line and a white fiber cultivar to determine the factor that affects the pigmentation in brown fiber. Accordingly, fibers were collected to verify the presence of PAs by p-dimethylaminocinnamaldehyde (DMACA) and toluidine blue O (TBO) staining. The PAs content and related genes expressions were determined. As a result, there were obvious differences on the aspect of PAs synthesis in fiber between white cotton and brown cotton. For white fiber, the PAs content reached maximum at 5 DPA, and then gradually decreased to zero. But for brown fiber, the PAs content was increased from 5 to 15 DPA stage, and reached the maximum at the 15 DPA stage, then gradually decreased from 15 to 40 DPA stage. On the contrary, in white cotton, PAs were synthesized in the whole developmental stage from 5 to 40 DPA. And PAs content in brown fiber were far more than that in white fiber, which may be the reason why the brown pigment accumulated in brown fiber.