Effects of Chilling Stress on Photosynthetic Rate and Chlorophyll Fluorescence Parameter in Seedlings of Two Rice Cultivars Differing in Cold Tolerance

A cold-tolerant cultivar, Xiangnuo 1, and a cold-sensitive cultivar, IR50, were used to study the influence of chilling on photosynthetic rate and chlorophyll fluorescence parameters in rice seedlings. The photosynthetic rates declined dramatically during chilling, and decreased by 48.7% and 67.5% in Xiangnuo 1 and IR50 seedlings, respectively, after being subjected to chilling treatment for two days. Chlorophyll fluorescence measurements showed that relatively higher qp and qNP in Xiangnuo 1 were maintained to dissipate the redundant excitation energy and protect the reaction centers from chill injury; accordingly, redundant excitation energy accumulated less in the reaction centers, and antenna systems were less injured by chilling in Xiangnuo 1. On the contrary, in IR50, qp and qNP declined rapidly while Eg increased, as the chilling persisted. This result indicated that the reaction centers and antenna systems in IR50 were damaged severely by chilling, which led to the lower photosynthetic rate.

NO_3^-/NH_4^+ ratios affect plant growth, chlorophyll content,respiration rate, and morphological structure in Malus hupehensis seedlings

Malus hupehensis （Pamp.） Rehd. is a widely cultivated rootstock in China. We studied the effect of three NO3-/NH4＋ ratios （100/0, 50/50, and 0/100, molar basis） at total nitrogen （N） concentration of 8 mmoL L-1 in a nutrient solution on M. hupehensis seedlings. Plant biomass, NO3- and NH4＋concentrafion, chlorophyll con- tent, respiratory rate, and cellular structure were investi- gated. M. hupehensis seedlings at the NO3-/NH4＋ ratio of 50/50 had the highest level of fresh weight, dry weight, shoot length, and chlorophyll （a, b, and a ＋ b） content, but the lowest respiration rate in the leavesand roots. In addition, thickness and numbers of palisade and spongy tissue cells of the leaves were greater with this treatment than with other treatments. At the NO3-/NH4＋ ratio of 100/0, the leaves and roots had higher NO3- concentration and lower NH4＋ concentration. However, the opposite trend occurred at the NO3-/NH4＋ ratio of 0/100. Chloro- phyll （a, b, and a ＋ b） content was lowest at the NO3-/NH4＋ ratio of 100/0 than at the other ratios. At the NO3-/ NH4＋ ratio of 0/100, oxygen （02） consumption increased in the leaves and roots, and irregular epidermis and cortex cells were observed in the root apical meristematic and mature region. Our results indicated that the NO3-INH4＋ ratio at 50/50 was suitable for growth of M. hupehensis seedling to achieve the highest biomass production and efficiency.

Relationships between chlorophyll a, bacteria, ATP, POC and respiration rates in the Changjiang Estuary and the plume

-Bacteria abundance, chlorophyll a, ATP and POC concentrations and respiration rates of microorganisms in the Changjiang Estuary and the plume were determined in July 1986. The high values of bacteria abundance occurred in the river mouth in association with suspended matter. It is assumed that bacteria were the major contributor to ATP and the main consumer of dissolved oxygen, and that the relationship between ATP and POC was present in that area. In the dilution zone (salinity; 25-30), instead of bacteria, phytoplankton was the major contributor to ATP and respiration rates, due to diatom bloom. Close relationships between Chi a and ATP, and ATP and POC were observed. Contribution of microbial carbon to POC was also estimated.

Effects of Water Stress on Leaf Water and Chlorophyll Fluorescence Parameters of Sugarcane Seedling

[Objective] The aim was to explore the effects of water stress on leaf water and chlorophyll fluorescence parameters of sugarcane seedling,as well as to provide basis for the study on sugarcane production and evaluation. [Method] Seven different sugarcane varieties were studied at the seedling stage under drought stress,and the changes of leaf water and chlorophyll fluorescence parameters under stress conditions were detected. [Result] leaf water potential,leaf relative water content and soil relative water content showed a certain amount of internal relationship,the sugarcane varieties that had more tolerant to drought had higher utilization rate of soil water; the correlation analysis and factor analysis suggested that the survival rate at seedling stage under drought stress,Fv/Fm,leaf water potential and relative water content could be used as drought resistance evaluation indicators. [Conclusion] As a relatively independent influencing factor,water potential had dominating effect on drought resistance,and the reliability of Fv/Fm as drought resistance evaluation indicator had been verified.

Effects of soil drought stress on photosynthetic gas exchange traits and chlorophyll fluorescence in Forsythia suspensa

To clarify the changes in plant photosynthesis and mechanisms underlying those responses to gradually increasing soil drought stress and reveal quantitative relationships between photosynthesis and soil moisture,soil water conditions were controlled in greenhouse pot experiments using 2-year-old seedlings of Forsythia suspensa（Thunb.） Vahl. Photosynthetic gas exchange and chlorophyll fluorescence variables were measured and analyzed under 13 gradients of soil water content. Net photosynthetic rate（PN）, stomatal conductance（gs）, and water-use efficiency（WUE） in the seedlings exhibited a clear threshold response to the relative soil water content（RSWC）. The highest PNand WUEoccurred at RSWCof51.84 and 64.10%, respectively. Both PNand WUEwere higher than the average levels at 39.79% B RSWCB 73.04%. When RSWCdecreased from 51.84 to 37.52%,PN, gs, and the intercellular CO2 concentration（Ci）markedly decreased with increasing drought stress; the corresponding stomatal limitation（Ls） substantially increased, and nonphotochemical quenching（NPQ） also tended to increase, indicating that within this range of soil water content, excessive excitation energy was dispersed from photosystem II（PSII） in the form of heat, and the reduction in PNwas primarily due to stomatal limitation.While RSWCdecreased below 37.52%, there were significant decreases in the maximal quantum yield of PSII photochemistry（Fv/Fm） and the effective quantum yield of PSII photochemistry（UPSII）, photochemical quenching（qP）, and NPQ; in contrast, minimal fluorescence yield of the dark-adapted state（F0） increased markedly. Thus,the major limiting factor for the PNreduction changed to a nonstomatal limitation due to PSII damage. Therefore, an RSWCof 37.52% is the maximum allowable water deficit for the normal growth of seedlings of F. suspensa, and a water content lower than this level should be avoided in field soil water management. Water contents should be maintained in the range of 39.79% B RSWCB 73.04% to ensure normal function of the photosynthetic apparatus and high levels of photosynthesis and efficiency in F.suspensa.

Differences in Chlorophyll Fluorescence Parameters, Yield and Its Components Between Different Genotypes of Wheat Under Waterlogging Conditions at Anthesis

Waterlogging is one of the most factors limiting wheat production in the middle and lower reaches of the Yangtze River Plain of China,especially in the middle and late stages of wheat.Wheat varieties‘Jingmai102’(JM102)and‘Yangmai158’(YM158)were planted to study the dynamic changes of photosynthetic characteristics in flag leaf and the influence of waterlogging at anthesis on the yield and components and dry matter accumulation and remobilization of winter wheat in above ground.The results showed that the SPAD values slightly increased at 1 day after anthesis(d),and then kept decreasing with the increase of waterlogging time.The decrease in SPAD value was more remarkably in YM158 than that in JM102.As for the chlorophyll fluorescence parameters,the photochemical efficiency(Fv/Fm),potential activity(Fv/Fo)of photosystem II,and electronic transmission(Fm/Fo)on photosystem II increased first and then decreased with the increase of waterlogging days after anthesis.The quantum ratio of heat dissipation(Fo/Fm)had a tendency opposite to that of Fv/Fm,and the change range of JM102 was lower than that of YM158.For the grain yield and components,waterlogging at anthesis decreased the dry weight of single stem,grain yield,1 000-kernel weight,spikelet per panicle,and harvest index,and the reduction of JM102 was smaller than that of YM158.As for the accumulation and remobilization of dry matter,the accumulation of dry matter after anthesis decreased significantly under waterlogging condition(WL),and the reduction of JM102 was smaller than that of YM158.In conclusion,waterlogging at anthesis significantly affected the photosynthetic characteristics,yield and components in both varieties,but different varieties exhibited different tolerances to waterlogging stress and YM158 was more sensitive to water stress than JM102.

Short-term Response of Photosynthesis and Chlorophyll Content to Salinity Stress in Two Mangrove Species:Aegiceras corniculatum and Kandelia candel

There were fewer comparative studies on the adaptability of mangrove plants with two different salt secretion mechanisms to salinity stress. In this study,the seedlings of mangrove plants Aegiceras corniculatum and Kandelia candel were selected as the research objects,and the methods of hydroponics with different salinity gradients were used. The salinity of 0‰,10‰,and 30‰ was applied respectively to simulate the adaptability of seedlings at low,moderate,and severe salinity stresses. Based on the results,the short-term responses of photosynthesis and chlorophyll content to salinity stress in two mangrove species with different salt secretion mechanisms were analyzed and discussed. The results show that A. corniculatum was more tolerant to10‰ salinity than K. candel,and the net photosynthetic rate(Pn),transpiration rate(Tr),stomatal conductance( Gs) and water use efficiency(WUE)were also relatively higher;both A. corniculatum and K. candel could acclimate the low salinity(0‰),but showed severe osmotic stress at 30‰ salinity;A. corniculatum was more sensitive to severe salinity(30‰) than K. candel. These results can be of help to provide a theoretical support for the selection of species for mangrove wetlands restoration and seedlings acclimatization in tidal flats.

烟剂对大棚藜麦菜光合作用和叶绿素含量的影响

在藜麦菜的温室大棚种植中,用12%百菌清烟剂与12%速克灵烟剂防治病害较为常用。为了研究这两种烟剂对藜麦菜的叶绿素含量和光合作用的影响,施用烟剂后第3天和第5天分别进行藜麦菜叶片叶绿素含量和光合速率的检测。结果显示,施用烟剂可以提高藜麦叶绿素的含量,提高光合速率,进而提高生产率。

不同施氮量对皂荚幼苗生长及光合特性的影响

以长势一致的2年生皂荚嫁接苗为试验材料,研究不同施氮量对2年生皂荚幼苗生长、光合特性及叶绿素荧光参数的影响,以期找出适合2年生皂荚嫁接苗快速生长的最适施氮量。结果表明:(1)施氮肥显著提高了皂荚树幼苗株高、地径、刺长及刺茎的净增长量,并且均在N3(纯氮90 g/株)处理下达到最大值,试验结束后,与CK相比,株高和地径增长量分别提高了59.71%和50.10%;(2)N3处理下可以较大幅度的促进皂荚叶片叶绿素的合成,增大叶片净光合速率和气孔导度等,进而提高皂荚幼苗的光合能力。(3)随着施肥量的增加,皂荚叶片最大荧光(F_(m))和PSⅡ最大光化学效率(F_(v)/F_(m))随施氮肥量的增加呈先上升后下降的趋势,而初始荧光(F_(o))与二者变化趋势相反,并且均在N3处理下达到极值。(4)在PSⅡ反应中心活性方面,合理施氮肥可以使得单位反映中心吸收的光能(ABS/RC)、捕获的光能(TRo/RC)和用于传递电子的能量(ETo/RC)上升,降低用于热耗散的能量(DIo/RC)。综合各参数来看,适宜2年生皂荚嫁接苗生长的最适施氮量为60~90 g/株。

不同水分条件下施磷对冬小麦穗花结实及光合特性的影响

为探究不同水分条件下施磷肥对冬小麦光合及结实特性的调控效应,明确施磷调控光合生产力促进穗花发育成粒的机制,于2020—2022年设置3种水分处理(W0:重度干旱;W1:中度干旱;W2:正常水分)和2种磷肥处理(P0:不施磷;P1:施磷)的盆栽试验,以大穗型品种周麦16(V1)和多穗型品种豫麦49-198(V2)为试验材料,通过测定不同穗位(基部、中部和顶部)的可孕小花数、结实数以及叶片净光合速率、叶绿素、叶绿素荧光参数、蔗糖含量等,分析不同水分条件下磷素对两类型品种冬小麦光合及结实特性的影响。结果表明,施磷肥可以有效增加冬小麦开花期(W10时期)可孕小花数,尤其对基部穗位的可孕小花数提升效果最显著(13.74%—27.01%),其次是顶部(9.57%—20.19%),再次是中部(6.97%—14.01%)。对成熟期的结实粒数而言,施磷肥可以提高干旱胁迫下每穗的小穗数以及各小穗的结实数,进而显著提高每穗的结实粒数。此外,施磷肥可以有效提高两类型品种叶片净光合速率、叶绿素含量、光系统Ⅱ最大光化学效率(F_(v)/F_(m))和实际光化学效率(Φ_(PSII));对蔗糖含量的影响因水分而异,干旱处理下增施磷肥降低了蔗糖含量,正常水分条件下则增加了蔗糖含量。将两类型品种光合指标分别与可孕小花数和穗粒数进行通径分析发现,5个光合指标与可孕小花数和穗粒数均呈正相关,其中净光合速率和蔗糖与可孕小花数的直接通径系数为1.001和0.435,与穗粒数的直接通径系数为0.996和0.626,远高于其他指标。最终,施磷通过增加穗数、穗粒数以及千粒重来显著增加产量,其中穗粒数在不同水分下均达到显著水平,穗数在W1和W2处理下显著,千粒重提升效果不显著。综上所述,在不同水分条件下施磷肥均可以通过调控冬小麦的光合性能提高其光合生产力,以维持正常的生理代谢功能,从而减少可孕小花的退化和败育以促进穗花成粒,最终达到缓解干旱胁迫危害以实现高产稳产的目的。研究结果为小麦生产中合理施用磷肥缓解干旱胁迫提供理论依据和技术支撑。

油菜籽粒叶绿素降解速率对菜籽油关键品质的影响

油菜籽粒中的叶绿素是阻碍高品质菜籽油生产的关键因素。压榨制油时叶绿素进入菜籽油,菜籽油叶绿素含量高不仅外观品质差,且易引发光氧化反应。因此,提高籽粒成熟过程中叶绿素降解速率,对改善菜籽油外观及营养品质具有重要意义。试验利用281份来自国内外的栽培品种、品系组成的自然群体,在武汉试验点连续进行2年田间小区试验,考察油菜籽粒叶绿素降解速率、油脂外观及营养品质等指标,分析籽粒叶绿素降解与千粒重、含油量、油脂色泽、抗氧化能力等指标的内在联系,以期为优质菜籽油原料的生产提供理论与技术支撑。结果表明,不同品系籽粒叶绿素降解速率存在差异,供试群体品系间存在广泛变异;相关性分析显示,籽粒叶绿素降解速率与种子千粒重、含油量无显著相关性,与菜籽油叶绿素含量显著负相关;菜籽油叶绿素含量与菜籽油红值、黄值及过氧化值显著正相关,与菜籽油抗氧化能力显著负相关,籽粒叶绿素降解速率快的类别,菜籽油色泽更浅,菜籽油过氧化值较低且具有较高的总酚含量与抗氧化能力;花后40 d,叶绿素降解快的品系籽粒POR酶的活性低于叶绿素降解慢的品系,但花后53 d PAO酶的活性高于叶绿素降解慢的品系,因此籽粒成熟后期叶绿素降解速率快,种子叶绿素含量低。

十五个鲜食枣品种光合特性和产量的比较

以15个鲜食枣品种为试材,采用单因素方差分析和相关性分析法,研究不同鲜食枣品种光合特性、叶绿素含量及产量之间差异,以期为新疆鲜食枣品种的选择和引种提供参考依据。结果表明:15个鲜食枣品种净光合速率、蒸腾速率、气孔导度和胞间CO_(2)浓度之间均达极显著差异(P<0.01)。相关性分析得出15个鲜食枣品种净光合速率与气孔导度和蒸腾速率有关联;水分利用效率与气孔导度、胞间CO_(2)浓度和蒸腾速率呈极显著负相关;15个鲜食枣产量与净光合速率呈极显著正相关。由此可见,鲜食枣品种‘蜂蜜罐’‘冬枣’‘香脆’‘赛蜜酥1号’和‘伏脆蜜’光合特性和产量等指标较高于其他品种,适合南疆喀什地区引种和种植。

不同施氮处理对百农207光合特性及氮肥利用效率的影响

为探究百农207(BN_(2)07)在不同氮肥管理下的光合特性和氮肥利用效率,从而建立最优氮肥管理、实现绿色高产高效栽培,以BN_(2)07为试验材料,设置5种不同氮肥梯度,即0(N0)、120(N120)、180(N180)、240(N_(2)40)及360(N360)kg/hm^(2),分析灌浆中后期小麦光合性能、叶绿素荧光参数和叶面积指数(LAI)的变化,及其对生物量、氮肥利用效率和产量的影响。结果表明,与NO相比,N180、N_(2)40及N360组BN_(2)07叶绿素荧光参数中的F_(V)/F_(M)(暗适应下PSⅡ的最大量子产额)、ET_(O)/RC(单位反应中心捕获的用于电子传递的能量)、LAI、籽粒氮素积累量、生物量及产量分别上升0.71%~4.87%、3.45%~5.70%、117.22%~157.64%、62.67%~63.98%、39.30%~57.01%及27.87%~28.92%,OJIP曲线中各特征位点的峰值和氮肥利用效率均下降,但施氮组间无显著差异。此外,BN_(2)07在N180组的净光合速率(P_n)显著高于其他组,表明BN_(2)07在N180组更有利于实现绿色高产高效的目标。线性加平台结果表明,当施氮量达到172.14 kg/hm^(2)时,小麦的产量达到平台值。综上所述,BN_(2)07的最佳施肥量为172.14 kg/hm^(2),该结果可为BN_(2)07在华北平原地区高产栽培管理提供理论依据。

扁核木不同直径茎干的光合生理特征

植物的绿色茎干能在叶片缺失时有效地利用阳光进行光合作用,为植物的生长发育提供额外的能量来源,使其更好地适应极端环境。本研究以分布于西南地区具有绿色茎干的植物——扁核木为对象,比较了扁核木不同直径茎干的光合特性及其与叶绿素含量之间的差异,为扁核木的育种和高效栽培提供依据。结果显示:(1)扁核木茎干具有较强的光合能力,且与叶绿素含量存在显著相关性;(2)不同直径的茎干叶绿素含量和光合能力存在差异,随着扁核木茎干直径的增加,叶绿素含量、净光合速率、光补偿点和光饱和点呈现逐渐下降的趋势,但扁核木不同直径的茎干净光合速率均较高。研究表明:茎干的光合作用功能有助于扁核木在早春无叶期间完成开花的生理过程,提高了其对极端环境的适应性。

濒危植物柳州异裂菊和凹脉异裂菊扦插技术研究

[目的]筛选珍稀濒危植物柳州异裂菊(Heteroplexis incana)和凹脉异裂菊(Heteroplexis impressinervia)扦插繁殖最优组合,为其种质保育及开发奠定基础。[方法]选择健康的柳州异裂菊和凹脉异裂菊枝条进行扦插,采用正交试验设计,探究插穗粗度、基质类型、植物生长调节剂种类和浓度4个因素对柳州异裂菊和凹脉异裂菊扦插苗生长性状的影响,并筛选出最优组合。[结果]柳州异裂菊9个组合的成活率差异较大,组合③成活率最高,为40%;9个组合的根长和根粗均不存在显著差异(P>0.05),而9个组合根数存在显著差异(P<0.05),组合③有利于根生长。凹脉异裂菊组合①的成活率最高,达20%,凹脉异裂菊的枝数、枝高、枝粗、叶片数、叶长9个组合间均不存在显著差异(P>0.05),而叶宽存在显著差异(P<0.05)。[结论]粗度为6.0~10.0 mm的穗条使用150 mg/L NAA浸泡后扦插于肥土基质中利于柳州异裂菊扦插成活及苗木生长,而同样粗度的凹脉异裂菊穗条使用50 mg/L SGJ浸泡后扦插于黄土基质中扦插效果较佳。

高温干旱复合胁迫下冬小麦叶片和冠层尺度SIF与光合作用的关联变化特征研究

为探究高温干旱复合胁迫下叶片和冠层尺度日光诱导叶绿素荧光(solar-induced chlorophyll fluorescence,SIF)与植物光合作用的关系,开展冬小麦高温干旱复合胁迫田间试验,共设置三种水分条件[严重干旱(50%~60%田间持水量)、轻度干旱(65%~75%田间持水量)和正常供水对照组(80%~90%田间持水量)]和三个温度水平(半包式增温、全包式增温和大田环境温度对照组),分析不同胁迫处理下冠层和叶片尺度SIF、冠层总初级生产力(gross primary productivity,GPP)和叶片净光合速率(net photosynthetic rate,P_(n))的日变化和季节变化特征,探讨小麦叶片SIF与P_(n)和冠层SIF与GPP之间的关联性。结果表明,高温干旱复合胁迫下日尺度和季节尺度叶片和冠层SIF总体均呈现出单峰型变化特征,季节尺度冠层SIF对干旱胁迫的响应比叶片SIF明显,且高温干旱复合胁迫对叶片和冠层SIF的影响均大于单一高温或干旱胁迫。P_(n)和GPP总体分别呈现出双峰型和单峰型变化特征。高温干旱复合胁迫下叶片SIF与P_(n)的相关性(R^(2)=0.42)小于冠层SIF与GPP的相关性(R^(2)=0.52),随着单一胁迫的增强,二者之间的相关性逐渐降低,且干旱胁迫对二者关系以及P_(n)和GPP的影响均大于高温胁迫。此外,环境变量中温度对SIF与P_(n)关系的影响最大,其次是饱和水汽压差(vapor pressure deficit,VPD),光合有效辐射(photosynthetic active radiation,PAR)影响最小,且SIF与P_(n)之间的相关性随温度的增加逐渐降低,随VPD的增大先降后升,随PAR的增加先升后降。高温干旱复合胁迫下冠层和叶片SIF大小与植物光合作用强弱有一定关联性,并受环境变量影响。

不同水分管理对小麦各品种光合特性及产量的影响

不同水分管理影响小麦各品种光合特性,进而影响小麦产量.为了提高小麦产量,研究以百农207(BN207)、百农307(BN307)和洛旱27(LH27)为试验材料,设置灌溉(I)和雨养(R)两种水分处理,研究不同水分管理对小麦旗叶净光合速率(P_(n))、叶绿素荧光参数及产量的影响.与雨养处理相比,BN207、BN307、LH27的P_(n)在灌溉处理下分别增加53.48%、81.45%、42.83%.单位反应中心吸收的光能(ABS/RC)、单位反应中心捕获的用于电子传递的能量(ET_(O)/RC)和单位反应中心捕获的用于还原Q_(A)的能量(TR_(O)/RC)在灌溉处理下3个小麦品种均高于雨养处理,而单位反应中心耗散掉的能量(DIO/RC),BN207和LH27更高,BN307在灌溉条件下反而更低.3个小麦品种的叶绿素荧光诱导曲线(OJIP)变化趋势相同,但荧光值具有差异:BN207和LH27在灌溉条件下O点荧光强度高于雨养条件,J、I、P点荧光强度低于雨养条件;BN307在灌溉条件下O、J、I点荧光强度高,P点强光强度低.在灌溉处理下,BN207产量提高20.12%、穗粒数降低14.66%、穗数提高51.98%,千粒质量降低3.11%;在灌溉条件下,BN307产量提高53.71%、穗粒数提高5.03%、穗数提高51.74%、千粒质量降低7.99%;在灌溉条件下,LH27产量、穗粒数和穗数分别提高了14.83%、0.68%和20.43%,而千粒质量则降低了3.15%.灌溉处理能提高小麦光系统中电子传递链的能量传递、提高旗叶净光合速率,主要通过增加穗数来提高小麦产量.BN307、BN207在灌溉处理下产量提高最显著,更适合在灌溉条件充足的条件下种植,而LH27对灌溉不足的条件的适应性更强.

Effects of Paclobutrazol Seed Priming on Seedlings Quality,Physiological and Bakanae Disease Index Characteristics of Rice(Oryza sativa L.)

Rice(Oryza sativa L.)is one of the most important cereal crops in the world.Bakanae disease is a significant rice disease widely distributed in rice-growing regions worldwide.Therefore,the present investigation aimed to assess the optimal concentrations of paclobutrazol(PBZ)as a treatment for rice grains(cv.Sakha 108)to control bakanae disease,also evaluating its impact on grain germination,seedling growth parameters as well as disease index.Paclobutrazol concentrations had no significant impact on seed germination,regardless of whether the seeds were incubated with Fusarium fujikuroi or not.Application of PBZ,either alone or in combination with fungal pathogens,negatively impacted the rice seedlings’height.Paclobutrazol at 25,50 and 100 mg/L,combined with the fungal pathogen positively impacted root length.Paclobutrazol at 3 and 6 mg/L mitigated the adverse impact on chlorophyll pigments content in infected seedlings.The highest proline contents were achieved by 100 mg/L PBZ alone or in combination with fungal pathogens.It has been observed that the application of PBZ,either alone or in combination with a fungal pathogen,leads to the enhancement of catalase,peroxidase,and polyphenol oxidase activities.The median lethal concentration of PBZ was 0.874 mg/L;applying low concentrations of paclobutrazol effectively increased the percentage of fungal growth suppression.Application of PBZ,at higher concentrations(50 and 100 mg/L),decreased infection percentage and disease severity index(DSI)significantly.These findings suggest that PBZ can be an effective treatment for controlling bakanae disease and enhancing resistance in rice plants.

重金属Pb^(2+)对早熟禾种子萌发的影响

[目的]探究重金属铅对早熟禾种子萌发的影响。[方法]用不同浓度Pb^(2+)(20、40、60、80 mg/L)处理早熟禾种子,测定Pb2+对早熟禾种子萌发、叶绿素以及生根等指标的影响。[结果]随着Pb2+浓度的增加,草籽的萌发率、发芽指数降低,但降低趋势不明显。逐日萌发率在第3天出现高峰,早熟禾的根茎长度呈下降趋势。叶绿素a、叶绿素b含量降低明显,类胡萝卜素含量在Pb^(2+)浓度80 mg/L时增加。[结论]早熟禾种子的萌发率在Pb^(2+)浓度20~80 mg/L范围内受影响较小,而叶绿素含量、类胡萝卜素含量以及幼苗根茎的生长受到一定的抑制。

氮肥后移对玉米灌浆、光合特性与氮效率的影响

为提高氮肥利用率,以郑单958为材料,2021-2022年在施氮总量250 kg·hm^(-2)条件下,设置4个施氮处理,传统施氮(全部基施,N1)为对照、拔节期后移30%+灌浆期后移10%(N2)、拔节期后移20%+灌浆期后移20%(N3)、拔节期后移10%+灌浆期后移30%(N4),以及不施氮区(N0),分析不同施氮处理对玉米灌浆,光合特性和氮效率的影响。结果表明,氮肥后移处理可显著促进籽粒灌浆,增加籽粒干物质量,灌浆高峰提前,延长了灌浆活跃期,平均灌浆速率和最大灌浆速率增加。与常规施氮不后移相比,氮肥后移处理可使玉米维持较高的叶绿素相对含量(SPAD)、净光合速率(Pn)和蒸腾速率(Tr)。氮肥后移能够显著提高成熟期氮素累积量、氮肥利用率、氮肥农学效率和氮肥偏生产力。氮肥后移还能够显著增加夏玉米穗粒数和百粒重,使籽粒产量平均提高了16.32%~34.67%,生物产量平均提高了12.81%~25.89%。在施氮总量250 kg·hm^(-2)的水平下,拔节期后移20%+灌浆期后移20%(N3)可有效提高河南砂姜黑土区夏玉米氮素供需吻合度,是实现夏玉米增产、增效的有效措施。