Mepiquat chloride priming confers the ability of cotton seed to tolerate salt by promoting ABA-operated GABA signaling control of the ascorbate–glutathione cycle

Background Ensuring that seeds germinate and emerge normally is a prerequisite for cotton production,esp.in areas with salinized soil.Priming with mepiquat chloride(MC)can promote seed germination and root growth under salt stress,but its mechanism has not been fully elucidated.In this study,physiological and biochemical experiments revealed that MC-priming promotes the tolerance of cotton seeds to salt stress by increasing the ability of antioxidant enzymes related to the ascorbate-glutathione(AsA-GSH)cycle to scavenge reactive oxygen species(ROS).Results Results revealed that treatment with inhibitors of abscisic acid(ABA)and γ-aminobutyric acid(GABA)biosynthesis reduced the positive effects of MC-priming.Similarly,MC-priming increased the contents of ABA and GABA under salt stress by stimulating the expression levels of GhNCED2 and GhGAD4 and the activity of calmodulin-binding(CML)glutamate decarboxylase(GAD).Further analysis showed that an inhibitor of ABA synthesis reduced the positive impacts of MC-priming on the content of GABA under salt stress,but the content of ABA was not affected by the GABA synthesis inhibitor.Furthermore,a multi-omics analysis revealed that MC-priming increased the abundance and phosphorylation levels of the proteins related to ABA signaling,CML,and Ca^(2+)channels/transporters in the MC-primed treatments,which resulted in increased oscillations in Ca^(2+)in the MC-primed cotton seeds under salt stress.Conclusion In summary,these results demonstrate that MC-mediated ABA signaling operates upstream of the GABA synthesis generated by GAD by activating the oscillations of Ca^(2+)and then enhancing activity of the AsA-GSH cycle,which ensures that cotton seeds are tolerant to salt stress.

Effects of mepiquat chloride and plant population density on leaf photosynthesis and carbohydrate metabolism in upland cotton

Background Mepiquat chloride(MC)application and plant population density(PPD)increasing are required for modern cotton production.However,their interactive effects on leaf physiology and carbohydrate metabolism remain obscure.This study aimed to examine whether and how MC and PPD affect the leaf morpho-physiological characteristics,and thus final cotton yield.PPD of three levels(D1:2.25 plants·m^(-2),D2:4.5 plants·m^(-2),and D3:6.75 plants·m^(-2))and MC dosage of two levels(MC0:0 g·ha^(-2),MC1:82.5 g·ha^(-2))were combined to create six treatments.The dynamics of nonstructual carbohydrate concentration,carbon metabolism-related enzyme activity,and photosynthetic attributes in cotton leaves were examined during reproductive growth in 2019 and 2020.Results Among six treatments,the high PPD of 6.75 plants·m^(-2)combined with MC application(MC1D3)exhibited the greatest seed cotton yield and biological yield.The sucrose,hexose,starch,and total nonstructural carbohydrate(TNC)concentrations peaked at the first flowering(FF)stage and then declined to a minimum at the first boll opening(FBO)stage.Compared with other treatments,MC1D3 improved starch and TNC concentration by 5.4%~88.4%,7.8%~52.0% in 2019,and by 14.6%~55.9%,13.5%~39.7% in 2020 at the FF stage,respectively.Additionally,MC1D3 produced higher transformation rates of starch and TNC from the FF to FBO stages,indicating greater carbon production and utilization efficiency.MC1D3 displayed the maximal specific leaf weight(SLW)at the FBO stage,and the highest chlorophyll a(Chl a),Chl b,and Chl a+b concentration at the mid-late growth phase in both years.The Rubisco activity with MC1D3 was 2.6%~53.2% higher at the flowering and boll setting stages in both years,and 2.4%~52.7% higher at the FBO stage in 2020 than those in other treatments.These results provided a explanation of higher leaf senescence-resistant ability in MC1D3.Conclusion Increasing PPD coupled with MC application improves cotton yield by enhancing leaf carbohydrate production and utilization efficiency and delaying leaf senescence.

Effects of plant density and mepiquat chloride application on cotton boll setting in wheat–cotton double cropping system

Sowing cotton directly after harvesting wheat in the Yangtze River Valley of China requires early mature of cotton without yield reduction.Boll-setting period synchronisation and more yield bolls distributed at the upper and middle canopy layers are also required for harvesting.The objective of this study is to quantify the individual and interaction effects of plant density and plant growth regulator mepiquat chloride(MC)on temporal and spatial distributions of yield bolls,as well as yield and yield components.During the 2013–2016 cotton growing seasons,the experiments were conducted on a shortseason cotton cultivar CRRI50 at Yangzhou University,China.Various combinations of plant density(12.0,13.5 and 15.0 plants m^(–2))and MC dose(180,270 and 360 g ha^(–1))were applied on cotton plants.The combination of 13.5 plants m^(–2)and 270 g ha^(–1)MC resulted in the greatest boll number per unit area,the highest daily boll setting number and more than 90%of bolls positioned within 45–80 cm above the ground.In conclusion,appropriate MC dose in combination of high plant density could synchronize boll-setting period and retain more bolls at the upper and middle canopy layers without yield reduction in the system of direct-seeded cotton after wheat harvest,and thus overcome the labor-intensive problem in current transplanting cropping system.

Effects of mepiquat chloride on yield and main properties of cottonseed under different plant densities

Background:Cottonseed oil and protein content as well as germination traits are major indicators of seed quality.However,the responses of these indicators to plant density and mepiquat chloride(MC)are still uncertain.To investigate plant density and MC effects on cotto nseed yield and main quality parameters,we con ducted a twoyear field experiment including four plant densities(1.35,2.55,3.75 and 4.95 plants·m^-2)and two closes of MC(0 and 135g·hm^-2)in Dafeng,Jiangsu Province,in 2013 and 2014.Results:The application of MC reduced plant height,fruit branch length and fruiting branch number under different plant densities,resulting in a lower and more compact plant canopy.Cottonseed yield showed a nonlinear increase as plant density increasing and achieved the highest value at 3.75 plants·m^-2,regardless of MC application.No significant interactio ns were found between plant density and MC for cotton seed yield and quality parameters.The 100-seed weight,cottonseed oil content and vigor index significantly decreased as plant density increased,while these parameters significantly increased with MC applying under different plant densities.Seed vigor index was positively correlated with 100-seed weight and seed oil con tent across different plant densities and MC treatments.Conclusions:Thus,application of MC could realize a win-win situation between cottonseed yield and main quality parameters under various densities;and plant density of 3.75 plants·m^-2 combined with 135 g·hm^-2 of MC applying is optimal for high cottonseed yield and quality in this cotton production area.

Cotton maturity and responses to harvest aids following chemical topping with mepiquat chloride during bloom period

Early maturity, complete defoliation and boll opening are essential for the efficient machine harvesting of cotton. Chemical topping, involving one extra application of mepiquat chloride(MC) in addition to its traditional multipleapplication strategy, may be able to replace manual topping. However, it is not known whether this chemical topping technique will influence maturity or cotton responses to harvest aids. In this 2-yr field study, we determined the effects of the timing of chemical topping using various rates of MC on boll opening percentage(BOP) before application of harvest aids(50% thidiazuron··ethephon suspension concentrate, referred to as TE), and the defoliation percentage(DP) and BOP 14 days after TE application. The results indicated that late chemical topping(near the physiological cutout, when the nodes above white flower is equal to 5.0) significantly decreased BOP before TE by 5.9–11.2% compared with early(at peak bloom) or middle(seven days after peak bloom) treatments in 2019, which was a relatively normal year based on crop condition. Also, a high MC rate(270 g ha) showed a significantly lower(22.0%) BOP before TE than low(90 g ha) or medium(180 g ha) rates. In 2020, which was characterized by stronger vegetative growth in the late season, the late chemical topping reduced the number of leaves before TE application relative to early or middle treatments, but had lower DP(23.2–27.2%) 14 days after TE application. The high MC rate showed a leaf count before TE application that was similar to the low and medium rates, but it showed the most leaves after TE and much lower(15.0–21.7%) DP in 2020. These results suggest that late timing of chemical topping and a high MC rate decreased the sensitivity of leaves to harvest aids. Further analysis indicated that the late chemical topping mainly affected the leaf drop from the mainstem and fruiting branches where the late regrowth occurred, and the high MC rate reduced leaf shedding from these parts and also from the vegetative branches. In conclusion, chemical topping with MC during the bloom period affected cotton maturity and responses to harvest aids in different ways according to the crop condition. To avoid the risks of delayed maturity and poor defoliation after the application of harvest aids, chemical topping should not be performed too late(i.e., near the physiological cutout) by using MC at more than 180 g ha. The optimum timing of chemical topping probably varies from peak bloom to around seven days later, and the safest MC rates for chemical topping should be less than 180 g ha.

适宜氮肥和缩节胺配合施用显著提高棉花“四桃”种子的播种和营养品质

【目的】研究棉花“四桃”种子品质及其对氮肥和缩节胺(DPC)配合施用的响应,为高质量棉花种子高效生产提供科学依据。【方法】2015—2017年,在郑州市黄河滩区进行双因素裂区设计田间试验。主区为3个氮肥用量,即:不施氮肥(N0)、施用常量氮肥(N1,225 kg/hm^(2))和过量氮肥(N2,450 kg/hm^(2));副区为3个DPC用量,即:不喷施DPC(D0)、喷施常量DPC(D1,75 g/hm^(2))和过量DPC(D2,150 g/hm^(2))。测定了棉花“四桃”种子的播种品质(籽指、发芽势和发芽率)和营养品质(总蛋白、粗脂肪、总淀粉、可溶性蛋白和可溶性糖含量)。【结果】“四桃”种子的播种品质和营养品质差异显著,伏桃和早秋桃的籽指以及发芽势和发芽率没有显著差异,二者均显著高于伏前桃和晚秋桃。伏桃和早秋桃的总蛋白和可溶性蛋白含量显著高于伏前桃和晚秋桃,但总淀粉和可溶性糖含量显著低于伏前桃和晚秋桃,“四桃”的粗脂肪含量差异不显著。施用氮肥与DPC均可显著提升“四桃”种子的发芽品质和营养品质。N1处理“四桃”种子的平均籽指与N2没有显著差异,发芽势和发芽率显著高于N2处理;N1处理的种子总蛋白、可溶性蛋白和粗脂肪平均含量显著高于N2处理,但总淀粉、可溶性糖显著低于N2处理。D1处理的种子平均籽指低于D2处理,平均发芽势和发芽率高于D2;D1处理的种子总蛋白、可溶性蛋白、粗脂肪平均含量高于D2,总淀粉、可溶性糖平均含量低于D2。在氮肥与DPC的9个用量组合中,N1D1组合的发芽势、总蛋白、可溶性蛋白和粗脂肪含量均最高,较其他8个处理组合分别增加了3.35%~40.86%、3.80%~43.01%、13.75%~54.86%和1.11%~13.48%。种子的发芽势和发芽率与总蛋白、粗脂肪和可溶性蛋白含量呈极显著正相关,与总淀粉和可溶性糖含量呈极显著负相关。【结论】在黄河流域棉区,棉花伏桃和早秋桃的种子质量明显优于伏前桃和晚秋桃。适宜氮肥与DPC用量组合可显著提高种子总蛋白、粗脂肪和可溶性蛋白含量,降低总淀粉和可溶性糖含量,进而提升发芽势和发芽率。施用常量氮肥(225 kg/hm^(2))配合常量DPC(75 g/hm^(2)),并采收早秋桃和伏桃有利于提升棉花种子质量。

李果实甲哌鎓与烯效唑残留量的差异及膳食风险评估

建立甲哌鎓和烯效唑在李果实中的残留检测方法,分析甲哌鎓和烯效唑残留量差异,评估2种农药残留长期和急性膳食摄入风险。样品前处理为QuEChERS方法,残留检测采用高效液相色谱-三重四极杆串联质谱法。李果实甲哌鎓和烯效唑在储藏183 d时,降解率分别为13%和14%,残留量在本试验条件下储藏较为稳定。李果实甲哌鎓和烯效唑在2个采样间隔期时残留量均小于0.01 mg/kg。甲哌鎓和烯效唑的普通人群国家估算每日摄入量(national estimated daily intake,NEDI)每千克体重分别是0.355 918、0.033 007 mg,分别占每日允许摄入量的2.90%和2.62%。李果实甲哌鎓和烯效唑的所有人群和儿童的国家估算短期摄入量(national estimated short term intake,NESTI)每千克体重均为0.000 095 4 mg;育龄妇女和普通人群及成年群体的国家估算短期摄入量每千克体重均为0.000 127 mg。李果实甲哌鎓的所有人群和儿童的国家估算短期摄入量占急性参考剂量的百分比(ARfD%)均为0.031 8%,育龄妇女和普通人群及成年群体的ARfD%均为0.042 3%;烯效唑的所有人群和儿童的ARfD%均为0.190 8%,育龄妇女和普通人群及成年群体的ARfD%均为0.254 0%。当基质、施药剂量和采收间隔期一致时,采收间隔期2 h时甲哌鎓与烯效唑的残留量有显著性差异,采收间隔期7 d和14 d时2种农药残留量差异不显著,原始沉积量(采样间隔2 h)与农药类型相关,最终残留量与农药消解半衰期和采样时间相关。

不同甲哌鎓滴施剂型筛选及其对棉花生长发育调控效果研究

棉田滴施甲哌鎓一直备受关注,为研究新型缓释甲哌鎓滴施剂型及其对棉花调控的作用效果,探寻缓释甲哌鎓滴施可行性。设5种剂型(H1、H2、H3、H4、H5)处理,普通缩节胺(S)和清水对照(CK),开展盆栽试验,大田设低(90.0 g hm^(-2))、高(180.0 g hm^(-2))2个浓度水平,进行剂型筛及棉花农艺性状与产量调控效果调查。结果表明,盆栽条件下,5种不同剂型甲哌鎓滴施出苗整齐度基本在66%以上,壮苗率受品种影响差别较大,在40%~70%之间;除H3外,各剂型甲哌鎓滴施均有控高效果,与CK和S相比,株高分别降低32%~41%和24%~35%,25 d后株高直观差异明显。大田条件下,处理S控高效果最好,CK增高最快,缓释甲哌鎓高浓度时各处理均有较好控高效果且与CK差异显著,低浓度时H5株高61.0 cm,与S效果相近且无显著差异,其他处理与CK无显著差异。棉花株宽、茎粗、主茎叶数、果枝台数等农艺性状各剂型处理分别在26.0~35.0 cm、9.5~11.5 mm、13~14片、7~8台之间,与CK和S比均没有显著影响。新型缓释甲哌鎓可促进现蕾,使蕾铃数增加,到6月28日(盛花期)H1低、高浓度下蕾铃花总数分别为12.7个和11.5个比S多2.0个和0.8个。最终产量表现为低浓度各处理均高于高浓度,H5产量最高,为7267.26 kg hm^(-2),分别高出CK和S 40%和33%,其次为H1。综合分析,H1、H5控高塑型及产量表现比较好,可进一步展开相关试验研究。

高温干旱下缩节胺通过调节碳和氨基酸代谢提高Bt棉杀虫蛋白含量的生理机制

【目的】探讨高温干旱胁迫下缩节胺(mepiquat chloride,DPC)调控Bt(Bacillus thuringiensis)棉杀虫蛋白含量的生理机制,为高抗虫性Bt棉品种选育及高产高效栽培提供理论依据。【方法】2020—2021年以转Bt抗虫基因抗虫棉品种泗抗3号为材料,采用盆栽法,在人工气候室进行高温干旱胁迫,胁迫开始后立即用20 mg·L^(-1) DPC和清水(对照)喷施。7 d后测定铃壳杀虫蛋白含量、α-酮戊二酸含量、丙酮酸含量以及谷氨酸合酶活性、谷氨酸草酰乙酸转氨酶活性、可溶性蛋白含量、游离氨基酸含量。并进行转录组测序,利用DESeq进行差异基因分析,通过GO富集和KEGG Pathway数据库注释参与DPC调节杀虫蛋白含量的差异表达基因。【结果】与清水对照相比,DPC可显著提高高温干旱条件下Bt棉铃壳中杀虫蛋白含量,提高幅度达4.7%—11.9%。在碳代谢方面,α-酮戊二酸含量、丙酮酸含量提高46%—57%和25%—29%;在氨基酸代谢方面,谷氨酸合酶活性、谷氨酸草酰乙酸转氨酶活性、可溶性蛋白含量、游离氨基酸含量分别提高32%—44%、30%—40%、28%和22%—27%。转录组分析结果表明,DPC处理后上调基因7542条,下调基因10449条。GO和KEGG结果显示,差异基因主要涉及氨基酸代谢、碳代谢等生物过程。其中编码6-磷酸果糖激酶和丙酮酸激酶、谷氨酸丙酮酸转氨酶、丙酮酸脱氢酶、柠檬酸合酶、异柠檬酸脱氢酶和α-酮戊二酸脱氢酶、谷氨酸合酶、吡咯啉-5-羧酸脱氢酶、谷氨酸草酰乙酸转氨酶、N-乙酰谷氨酸合成酶、乙酰鸟氨酸脱乙酰酶基因表达显著上调。【结论】高温干旱下,DPC通过调节碳、氨基酸代谢增加丙氨酸、α-酮戊二酸含量,提高天冬氨酸、谷氨酸、丙酮酸和精氨酸合成能力,进而提高Bt棉杀虫蛋白含量。

不同施氮水平下化学调控对棉花光合特征及产量的影响

为探明不同施氮水平与缩节胺对棉花光合特性及产量的互作效应,以“新陆中88号”为试材,采用双因素裂区试验设计,设置320(N1)、480 kg/hm^(2)(N2)2个施氮(纯氮)水平和67.0(F1)、150.0(F2)、260.5(F3)、371.0 g/hm^(2)(F4)4个缩节胺喷施剂量,研究不同施氮水平下缩节胺喷施剂量对棉花光合特征及产量构成因素的影响。结果显示,施氮水平与缩节胺剂量对棉花净光合速率(Pn)、蒸腾速率(Tr)、干物质积累、氮素积累与产量构成因素均存在互作效应。氮肥与缩节胺对棉花Pn与Tr的促进作用主要在棉花盛铃期与吐絮期,且Pn与Tr均以N1F3处理较高。N1最终生殖器官干物质积累量、氮素积累与皮棉产量均高于N2,各指标依次高出5.6%、11.32%、7.68%。同一施氮水平下,F3剂量能够显著提高棉花生殖器官干物质及氮素积累量,增加棉花单株结铃数、单铃质量与皮棉产量,亦均以N1F3处理较高,但其与N1F2处理相比均未达显著差异水平,其中N1F3皮棉产量为2803.32 kg/hm^(2),但其仅较N1F2处理增产0.3%。因此,综合考虑各测定指标表现,在本试验条件下,推荐南疆棉田适宜施氮量为320 kg/hm^(2),同时配合喷施缩节胺剂量150.0 g/hm^(2)为宜,节本的同时可保证较高的棉花产量。

植物生长延缓剂对藜麦抗倒伏能力及产量的影响

为提高藜麦抗倒伏性,选出降低藜麦倒伏率的最佳植物生长延缓剂水平,采用随机区组试验,以喷施清水为对照,探究多效唑(PP333)、烯效唑(S3307)和缩节胺(MEP)3种植物生长延缓剂在50、100、200和350 mg·L^(-1)时对藜麦生长发育及其产量的影响。结果表明,3种植物生长延缓剂都能有效降低藜麦株高,在一定范围内提高抗折力,降低倒伏指数和倒伏率。其中,烯效唑效果最好,以100 mg·L^(-1)为宜,株高较相同水平的多效唑和缩节胺分别降低6.8%和4.2%,抗折力增加17.4%和25.2%;多效唑在100 mg·L^(-1)时提高抗倒伏能力效果高于其他处理,倒伏率较CK显著降低79.9%;缩节胺在100~200 mg·L^(-1)范围内效果较好。以上结果为藜麦优质种植的化控措施提供了理论参考。

UPLC-MS/MS检测小麦中甲哌鎓的残留量

本研究建立了采用超高效液相色谱-串联质谱(UPLC-MS/MS),测定小麦籽粒和秸秆中甲哌鎓残留量的分析方法。样品采用乙酸铵-0.1%甲酸水溶液和甲醇提取,提取液经分散固相萃取净化,采用多反应监测模式(MRM),外标法定量测定。结果表明:在0.05~5 mg/L范围内,甲哌鎓的质量浓度与其峰面积呈良好的线性关系(相关系数大于0.999)。添加水平为0.05、0.5、1 mg/kg时,检测方法的平均回收率为78%~103%,相对标准偏差为2.3%~8.9%。此分析方法的线性关系良好,灵敏度和精确性满足农药残留分析要求,可用于生产上小麦中甲哌鎓残留检测分析。

甲哌鎓原药及其制剂的高效液相亲水色谱分析

采用默克ZIC-HILIC亲水色谱柱进行分离,DAD或VWD检测器进行检测,利用外标法定量。流动相为80%的乙腈+20%的25 mM乙酸铵,柱温30℃,检测波长210 nm。制剂回收率98.87%~101.14%,满足《NY/T 2887-2016农药产品质量分析方法确认指南》相关要求。方法操作简便,定量准确。

多效唑、缩节胺和矮壮素对花生化学调控效应的比较研究

【目的】筛选出适宜花生生长的植物生长调节剂及其最佳喷施浓度,为花生生产提供技术指导。【方法】以桂花771为试材,设不同浓度3种植物生长调节剂为处理,分别为多效唑（150、250、350、400mg/L）、缩节胺（200、250、300mg/L）和矮壮素（100、150、200mg/L）,调查花生农艺性状和产量。【结果】3种植物生长调节剂对花生植株生长的抑制程度顺序为：多效唑〉缩节胺〉矮壮素。多效唑、缩节胺和矮壮素分别在400、250和200mg/L时对花生植株生长的抑制程度最大。经多效唑处理的桂花771单株荚果数、单株生产力、产量分别较对照降低。250mg/L缩节胺处理花生单株生产力和产量均高于对照,但差异不显著。200mg/L矮壮素处理花生单株荚果数、单株生产力、产量达到最大值,分别比对照增加了15.7%、23.5%和17.0%。【结论】250mg/L缩节胺和100-200mg/L矮壮素可适当降低花生植株的伸长量,提高花生产量,其中200mg/L矮壮素对花生的化学调控增产效应最好。

氮肥和DPC用量对棉花叶片叶绿素含量和SPAD值的影响

在大田条件下研究了氮肥和缩节胺(DPC)用量对中早熟棉花品种豫杂35和早熟品种银山1号叶片叶绿素含量、SPAD值的影响。结果表明,随着施氮量或DPC用量的增加,两个品种的叶片叶绿素含量和SPAD值均呈增加趋势。叶片叶绿素含量和SPAD值呈正相关关系,但生育后期叶绿素含量的下降明显快于SPAD值,表现为吐絮期的叶绿素含量显著低于盛铃期,而吐絮期的SPAD值与盛铃期差异不显著。因此,在DPC化控条件下,仍可使用SPAD值进行棉花叶色诊断,但应注意生育后期SPAD值与叶绿素含量的不同趋势。

乙烯利-甲哌鎓复配剂对夏玉米生育及产量的影响

在玉米大喇叭口期叶面喷施乙烯利 -甲哌复配剂 ,能起到改善株型结构、促进同化物分配转运和提高产量的综合效果。具体表现为 :1)增加气生根数和根系干重 ;2 )缩短节间长度、增加茎粗 ,降低株高和穗位高 ,提高茎粗系数 ;3)促进灌浆初期同化物向根系分配、灌浆中期在地上部营养器官内积累、灌浆后期向产量器官转运 ,并有利于玉米提早成熟 ;4 )提高双穗率、增加穗数 ,减少秃尖、增加行粒数 ,显著提高玉米单产。上述结果表明 ,乙烯利 -甲哌复配剂能起到防止倒伏、提早成熟的作用 。

超高效液相色谱-质谱法快速分析番茄及其制品中矮壮素和缩节胺残留量

采用超高效液相色谱-串联质谱（UPLC／MS—MS）研究了番茄及其制品中矮壮素和缩节胺残留量的测定方法。样品用水提取，无需经过任何净化过程；在粒径为1．7μm的超高压亲水作用色谱柱上以V（乙腈）：V（含0．1％甲酸的10mmol／L乙酸铵溶液）=6：4为流动相，等度洗脱分离；电喷雾正离子检测（ESI’），多反应监测模式（MRM）对定性和定量离子进行MS测定。结果表明：矮壮素和缩节胺的添加水平在5、10和20μg/kg时，回收率范围分别为78．5％～90．1％和80．0％～104．0％；相对标准偏差在9．5％-11．3％和10．5％～13．2％之间；方法检出限均为0．8ng／kg。本方法仅需约2min的检测时间，且灵敏、准确，完全满足番茄及其制品中矮壮素和缩节胺残留量的快速、高灵敏度的分析要求。

黄河流域北部棉区棉花缩节胺化学封顶技术

【目的】探讨黄河流域北部棉区应用缩节胺(1,1-dimethyl-piperidinium chloride,DPC)对棉花进行化学封顶的可行性。【方法】于2012—2014年在河北省河间市瀛州镇国欣科技园和北京市中国农业大学上庄实验站进行,共包括6个独立试验。供试棉花品种为国欣棉3号(GX3)、欣抗4号(XK4)、石抗126(S126)和欣试17(XS17)。DPC化学封顶技术分为单独应用常规DPC化控技术(简称DPC)、将常规DPC化控技术与增效型DPC(简称DPC+)相结合(简称DPC+DPC^+)两种方式,以在常规DPC化控基础上进行人工打顶(简称DPC+MT)为对照。【结果】2012和2013年花铃期(7—8月份)多雨,应用DPC化学封顶技术的棉株较高、新生果枝数较多,其中株高较DPC+MT增加10.6—12.3 cm,果枝数增加5.8—7.9台。2014年花铃期干旱少雨,DPC化学封顶的株高与DPC+MT相比无显著差异,新生果枝数不超过3台。DPC化学封顶对棉花产量的影响不显著,但可发现2012年DPC+DPC^+的产量表现出降低趋势,且上部果枝成铃少、新生果枝成铃多,群体熟期有推迟现象。2013和2014年DPC+DPC^+的产量和熟期则与对照相当或略有增减。DPC+的应用时间(7月中旬至7月底)和剂量(750—1 500 m L·hm^(-2))对棉花株型及产量的影响无显著差异,但应避免在结铃盛期(7月底)应用大剂量DPC+(1 500 m L·hm^(-2)),以防延长后期棉铃的成熟。与DPC+DPC^+相比,单独应用常规DPC化控技术进行化学封顶在多雨年份或高密度下对棉株的控长强度较弱,而且存在减产风险。【结论】应用DPC进行化学封顶在黄河流域北部棉区基本可行,实际应用时需要根据气象因子和种植密度决定单独应用常规DPC化控技术还是将常规DPC化控技术与增效型DPC的应用相结合。

缩节胺浸种提高棉花幼苗根系活力中的活性氧代谢

以国欣棉3号为材料,研究200 mg L–1缩节胺(DPC)浸种12 h对棉花子叶苗根系活力的影响,并从活性氧(ROS)代谢的角度揭示相关的生理机制。结果表明,DPC浸种显著增强了棉花幼苗的根系活力,根尖部位氯化三苯基四氮唑(TTC)染色光密度为清水对照的1.3倍,TTC法测定的根系活力和呼吸速率分别较对照增加167%和90%,非损伤微测技术(NMT)测定的K+净内流速率(距根尖300μm处)较对照提高36%。吖啶橙染色结果显示,DPC处理根尖伸长区的凋亡细胞数目较对照减少。此外,DPC处理使根系的过氧化氢酶(CAT)、抗坏血酸氧化酶(APX)和谷胱甘肽还原酶(GR)活力显著高于对照,超氧化物歧化酶(SOD)活力则降低;H2O2含量和超氧阴离子(O2-)产生速率较对照分别降低56%和65%,H2O2原位染色结果也显示其根尖部分的褐色较对照明显减弱。根系组织的ROS代谢得到改善可能是DPC浸种提高棉花幼苗根系活力的机制之一。