富钾基因型烤烟根系形态和生理特性研究

在水培条件下,以富钾基因型烤烟'农大202'和一般型品种'NC89'、'净叶黄'为材料,研究了不同供钾水平下烟草根系形态和生理特性的基因型差异.结果显示:与低钾水平相比,各品种烤烟在常钾水平下的根系鲜重、体积、干重、总吸收面积、活跃吸收面积、比表面积、根系活力、H+分泌量、阳离子交换量(CEC)、可溶性蛋白和ATPase活性均明显升高,但根系比表面积有所下降,并以'农大202'烤烟的变化幅度较大;在常钾水平下,'农大202'表现出良好的根系形态和较强的生理特性,但其在低钾胁迫下却低于一般型品种,耐低钾能力较弱.研究表明,烟草的根系形态和生理特性及其对环境供钾水平的响应存在明显的基因型差异;提高环境供钾水平能明显促进各基因型烟草根系的形态发育和生理活性,从而增强其对钾的吸收、转运能力.     

低磷胁迫下磷高效基因型大麦的根系形态特征

在根袋土培盆栽条件下,以磷高效基因型DH110+、DH147和低效基因型DH49大麦为试验材料,利用根系分析系统分析不同施磷(P₂O₅)水平(极低磷25 mg·kg^-1、低磷50 mg·kg^-1和正常磷75 mg·kg^-1)下,磷高效基因型大麦的根系形态特征及其与植株磷素吸收的关系.结果表明： 低磷胁迫显著降低大麦生物量和磷吸收量,其中磷高效基因型的生物量和磷吸收量在各施磷水平下分别为低效基因型的1.24～1.70和1.18～1.83倍;大麦的总根长、总根表面积、平均根系直径、不定根长及其根表面积、侧根长及其根表面积均随施磷水平的降低而显著降低,其中磷高效基因型大麦在各施磷水平下的总根长、总根表面积、比根长、侧根长及根表面积分别为低效基因型的1.46～2.06、1.12～1.51、1.35～1.72、1.69～2.42和1.40～1.78倍,而平均根系直径为低效基因型的70.6%～90.2%;主成分分析表明,平均根系直径、比根表面积和比根长受基因型差异的影响较为明显,是区分两类磷效率基因型大麦根系形态差异的主要指标;偏最小二乘回归分析表明,各施磷水平下,总根长、总根表面积对大麦植株磷素吸收贡献均较大,随施磷水平降低,不定根长、不定根表面积对大麦植株磷素吸收的贡献明显降低,而平均根系直径、比根长、侧根长及其根表面积的贡献明显增加.磷高效基因型大麦可通过维持侧根的生长、根细度和比根长的增加来适应低磷胁迫.     

干旱胁迫对不同烤烟品种根系生长和生理特性的影响

以抗旱型烤烟品种‘农大202'及一般型烤烟品种‘NC89'和‘K326'为材料,采用盆栽试验研究了干旱胁迫对根系生长和生理特性的影响,以明确各烟草品种的抗旱能力及其与根系生长和生理特性的关系.结果显示:严重干旱胁迫之后各烤烟品种根系鲜重、干重上升,而根系活力、根系吸收面积以及根系SOD和POD活性等根系生理指标则呈下降趋势.在干旱胁迫条件下,‘农大202'的根系总吸收面积、活跃吸收面积、根系活力、SOD活性和POD活性均显著高于两对照品种‘NC89'和‘K326',但其根系鲜重和干重等生物量并不具有太大的优势.研究表明,烟草的根系生长和生理特性对环境水分条件的响应存在明显的基因型差异;在干旱胁迫条件下, ‘农大202'根系能保持较高总吸收面积、活跃吸收面积、根系活力和保护酶活性,是其具有较强抗旱性的生理基础.     

缺磷条件下不同水稻品种磷素吸收特性的研究

缺磷条件下,供试粳稻品种植株的单株鲜重、干重、全磷含量和单株磷累积量等具有较大差异,从中筛选出磷高效品种TP309和优质8号,其中TP309较磷低效品种早88-1的全磷含量和单株磷累积量分别增加37.50%~40.00%和82.76%~102.00%。单株根数、平均根长和根系体积与单株磷素吸收量的相关程度较小,光合速率(Pn)、叶片可溶蛋白含量和叶片可溶性糖含量均表现为随着吸磷量的增加而不断增大。     

水肥空间组合对成熟期冬小麦各器官氮磷养分分配的影响

以肥熟土垫旱耕人为土为供试土壤,冬小麦(Triticum aestivum L.)小偃22为供试植物,在全生育期人工控制土壤水分条件下,采用分层隔水土柱法研究了与田间土层分布相同土柱不同土层水分、氮、磷组合对冬小麦不同器官氮、磷养分累积及分配的影响.结果表明:(1)冬小麦不同器官氮、磷累积量表现为籽粒茎秆、叶>穗余部>根系.(2)与整体湿润处理相比,上干下湿水分处理可降低小麦各器官氮、磷累积量,但仅籽粒氮、磷累积量所占比例减少,而营养器官氮累积量所占比例均增加.(3)从肥料处理看,单施氮、单施磷和氮磷配施处理的小麦植株各器官氮、磷累积量均比对照增加,但籽粒氮、磷累积量所占比例均减小.(4)施肥层根系氮、磷累积量比对照相对增加,并以0～30cm土层根系氮、磷累积量为最高.(5)单施氮条件下,以0～90cm土层施肥各器官氮、磷累积量最高,0～30cm土层施肥最低;单施磷和氮磷配施时,以0～90cm土层施肥处理籽粒氮、磷累积量最高,其次是0～30cm土层施肥.由于石灰性土壤中肥料氮终产物以硝态氮为主且容易移动,而磷肥不易在土壤中迁移,在生产实践中仍以氮磷配施入0～30cm土层为佳.     

大气NH3和介质供氮水平对不同氮效率玉米基因型叶绿素荧光参数的影响

采用开顶式气室(Open Top Chambers)进行水培试验,以两种氮效率玉米(Zea mays L.)基因型为供试作物,通过不同大气NH3浓度处理,测定苗期各叶绿素荧光动力学参数.结果表明,供氮介质和大气NH3浓度升高对两种氮效率玉米基因型的初始荧光值(Fo)不存在显著影响.高供氮介质下,在NH3浓度升高时,氮高效5号基因型的最大荧光产量(Fm)和可变荧光(Fv)均显著减小(p<0.05),而氮低效基因型四单19的Fm、Fv值显著增加;低供氮介质下,大气NH3浓度升高对2种基因型Fm、Fv值的影响结果与高供氮介质时相反.说明大气NH3浓度升高对生长在高供氮介质下的氮高效5号基因型有一定的抑制作用,而对氮低效基因型四单19有一定程度的促进作用.在不同供氮介质下,大气NH3浓度升高时,两种氮效率玉米基因型的qN、qP值减小,说明大气NH3浓度升高时,作物对光合机构的保护能力比大气背景NH3浓度时弱.     

磷高效利用野生大麦基因型筛选及其根际土壤无机磷组分特征

通过土培盆栽试验,研究了16份野生大麦种质资源在相同供磷水平下磷素吸收利用的基因型差异,探讨磷高效野生大麦根际土壤无机磷组分特征.结果表明：拔节期和扬花期磷素干物质生产效率（CV=11.6%、12.4%）、成熟期磷素籽粒生产效率（CV=13.7%）基因型间差异较大.不同生育时期磷高效基因型IS-22-30和IS-22-25生物量、磷积累量和磷素干物质生产效率均显著高于低效基因型IS-07-07,且高效基因型的籽粒产量分别是低效基因型的3.10和3.20倍.不施磷、施磷30 mg·kg^-1条件下,不同磷素利用效率野生大麦根际土壤有效磷和水溶性磷含量均显著低于非根际土壤,且高效基因型较低效基因型根际土壤水溶性磷亏缺量更大.根际与非根际土壤无机磷组分含量为Ca₁₀-P＞O-P＞Fe-P＞Al-P＞Ca₂-P＞Ca₈-P.在拔节期和扬花期,施磷30 mg·kg^-1条件下,磷高效基因型根际土壤Ca₈-P含量显著高于低效基因型,而Ca₂-P含量显著低于低效基因型;不施磷条件下,高效基因型根际土壤Ca₂-P和Ca₈-P含量均显著高于低效基因型,且根际土壤Ca₁₀-P均减少.施磷30 mg·kg^-1条件下,根际土壤Fe-P和O-P含量均表现为高效基因型显著高于低效基因型,Al-P含量则呈现相反的趋势;不施磷条件下,高效基因型根际土壤Al-P、Fe-P和O-P含量均显著低于低效基因型.低磷胁迫下,高效基因型活化吸收Ca₂-P、Al-P的能力强于低效基因型.     

大气NH3和介质供氮水平对不同氮效率玉米基因型叶绿素荧光参数的影响

采用开顶式气室（Open Top Chambers）进行水培试验,以两种氮效率玉米(Zea mays L.)基因型为供试作物,通过不同大气NH3浓度处理,测定苗期各叶绿素荧光动力学参数。结果表明,供氮介质和大气NH3浓度升高对两种氮效率玉米基因型的初始荧光值（Fo）不存在显著影响。高供氮介质下,在NH3浓度升高时,氮高效5号基因型的最大荧光产量(Fm)和可变荧光(Fv)均显著减小(p<0.05),而氮低效基因型四单19的Fm、Fv值显著增加;低供氮介质下,大气NH3浓度升高对2种基因型Fm、Fv值的影响结果与高供氮介质时相反。说明大气NH3浓度升高对生长在高供氮介质下的氮高效5号基因型有一定的抑制作用,而对氮低效基因型四单19有一定程度的促进作用。在不同供氮介质下,大气NH3浓度升高时,两种氮效率玉米基因型的qN、qP值减小,说明大气NH3浓度升高时,作物对光合机构的保护能力比大气背景NH3浓度时弱。     

缺磷胁迫下的小麦根系形态特征研究

研究了缺磷条件下不同基因型小麦（Triticum aestivum L.)苗期根系形态学适应特征,以明确环境因子对根系不同组分（根轴和侧根）生长发育调控作用的强度和根系形态与磷营养效率关系。在缺P环境中,小麦根轴数量和侧根长度明显减小,同化物向根部的分配比例增加,根轴长度、侧根数量和根系长度等均有显著提高。供试基因型小麦的根轴数量及其长度的差异在每个供磷水平及不同供磷水平之间均呈显著,说明这两种性状的差异是由基因型和环境因素共同决定的;而侧根特征的差异只在不同供磷水平间显著,表明侧根性状主要受环境因素的控制。对6种基因型小麦的研究表明,根轴数量、根轴长度、根生长角度和根系长度根角之间存在着显著的基因型差异。相关分析表明,小麦的相对产量与缺磷条件下的小麦苗期根系形态指标的交互作用之间具有显著的线性关系。这种关系说明根系形态性状可作为早期有效地筛选磷高效小麦品种的指标。     

高肥力土壤条件下不同基因型花生对氮素利用的差异

在桶栽条件下,利用¹⁵N示踪技术,选用20个基因型花生为供试材料,研究了高肥力土壤条件下不同基因型花生对氮素利用的差异.结果表明:高肥力土壤条件下花生氮素营养以土壤氮为主,根瘤固氮次之,肥料氮最低.不同基因型间花生对全氮、肥料氮、土壤氮和根瘤固氮的吸收和积累均存在显著差异,基因型间遗传变异以根瘤固氮最大,肥料氮和土壤氮相当.氮素荚果生产效率和氮肥利用率基因型间差异显著,最高值分别为最低值的3.6和2.1倍.全氮、肥料氮、土壤氮和根瘤固氮的氮素收获指数基因型间均存在显著遗传变异,且以根瘤固氮的氮素收获指数基因型间遗传变异最大.花生荚果产量与不同氮源氮素积累量及氮素收获指数、氮素荚果生产效率和氮肥利用率呈显著或极显著正相关.依据花生对不同氮源氮素吸收积累和荚果产量筛选出全氮高积累高产型、肥料氮高积累高产型、土壤氮高积累高产型和根瘤固氮高积累高产型四大类型花生,其中四大类型特征兼有的有4个花生基因型.     

Distribution of Lateral Root Primordia in Root Tips of Musa

The distribution of lateral root primordia in the root tipsof four Musa landraces (Grande Naine, Pisang Berlin, Ngok Egomeand Yangambi Km5) grown in the field has been investigated toevaluate the range of genetic variation of lateral root initiation.In banana (Musa sp.), lateral roots are initiated in the roottip, 0.6–4 mm behind the root/cap junction and arise inseveral protoxylem-based longitudinal rows or ‘ranks’.Significant differences were observed among landraces for theposition of the most distal primordium, however the longitudinalspacing between successive primordia along the ranks was similarfor all landraces. All ranks were involved in lateral root initiation.The number of ranks also showed significant variations amonglandraces and was proportional to the stelar diameter. Hencethe density of lateral roots (roots cm^-1) was affected by stelardiameter variations. Finally, root elongation in the root tipwas landrace-specific and not necessarily exponential, unlikesuggested in previous studies. It is concluded that lateralroot initiation in Musa is not involved in the genetic variationsof root architecture in the field. A dissection of root architectureinto components which may account for these variations is proposedin relation to the improvement of root system architecture.Copyright 1999 Annals of Botany Company Lateral root initiation, root architecture, Musa, banana.     

Root Growth, Secondary Root Formation and Root Gravitropism in Carotenoid-deficient Seedlings of Zea mays L.

The effect of ABA on root growth, secondary-root formation androot gravitropism in seedlings of Zea mays was investigatedby using Fluridone-treated seedlings and a viviparous mutant,both of which lack carotenoids and ABA. Primary roots of seedlingsgrown in the presence of Fluridone grew significantly slowerthan those of control (i.e. untreated) roots. Elongation ofFluridone-treated roots was inhibited significantly by the exogenousapplication of 1 mM ABA. Exogenous application of 1 µMand 1 nM ABA had either no effect or only a slight stimulatoryeffect on root elongation, depending on the method of application.The absence of ABA in Fluridone-treated plants was not an importantfactor in secondary-root formation in seedlings less than 9–10d old. However, ABA may suppress secondary-root formation inolder seedlings, since 11-d-old control seedlings had significantlyfewer secondary roots than Fluridone-treated seedlings. Rootsof Fluridone-treated and control seedlings were graviresponsive.Similar data were obtained for vp-9 mutants of Z. mays, whichare phenotypically identical to Fluridone-treated seedlings.These results indicate that ABA is necessary for neither secondary-rootformation nor for positive gravitropism by primary roots. Zea mays, gravitropism, carotenoid-deficient, Fluridone, root growth, vp-9 mutant     

Springback in Root Gravitropism

Conditions under which a gravistimulus of Merit corn roots (Zea mays L.) is withdrawn result in a subsequent loss of gravitropic curvature, an effect which we refer to as `springback.' This loss of curvature begins within 1 to 10 minutes after removal of the gravistimulus. It occurs regardless of the presence or absence of the root cap. It is insensitive to inhibitors of auxin transport (2,3,5-triiodobenzoic acid, naphthylphthalmaic acid) or to added auxin (2,4-dichlorophenoxyacetic acid). Springback is prevented if a clinostat treatment is interjected to neutralize gravistimulation during germination, which suggests that the change in curvature is a response to a `memory' effect carried over from a prior gravistimulation.     

Effect of Main Root Decapitation on Root Branching in Flax Seedlings

Root branching patterns in intact and decapitated flax (Linum usitatissimumL.) roots were compared. The number of initiated primordia in the control and decapitated roots was similar, but decapitated roots produced an increased number of lateral roots owing to an increase in the number of primordia developed into the laterals. It is suggested that the apical meristem influences lateral root development only at the stage of root emergence from the parent root.     

Root Cap Inhibitor Formation in Isolated Root Caps of Zea mays

Root caps were isolated and cultured aseptically on variousdefined media. Under appropriate culture conditions plus suitableillumination a substance able to produce a positive geotropicresponse (i.e. a downward bending of roots) was formed in isolatedroot caps. The presence of this substance, or root cap inhibitor,was assessed by substituting cultured caps in place of capsof dark-grown roots. Normally these roots if kept in continuousdarkness will not respond to gravity (i.e. no bending). Optimalroot cap inhibitor production occurs on a relatively simplemedium, lacking sucrose, but supplemented with 10^–9 MIAA. Protein synthesis is necessary for inhibitor productionand/or expression, whereas DNA synthesis is not.     

Effect of Root Position on Measured Root Position on Measured Root Membrane Potentials

Root membrane potentials were measured by interposing a plantroot between two KCI solutions of different concentrations.The potentials measured across the two calomel electrodes werefound to depend on the position of the root. The potentialswere found to be lower when the root tip rather than the rootbase was in contact with the more concentrated solution. Thisindicates that the two parts of the root do not have the samein transport properties. Using an approximate theoretical treatmentthe observed potentials could be accounted for.     

Cytokinin Inhibits Lateral Root Development at the Earliest Stages of Lateral Root Primordium Initiation in Maize Primary Root

Root architecture is basically controlled by auxin and cytokinin, which antagonize in the formation of lateral roots (LRs) along the primary root (PR) axis. Several mechanisms have been proposed to explain the interaction between these two hormones, cytokinin being the hormone that inhibits LR formation. The analysis of the cytokinin effect on LR formation using LRs in several stages of development could indicate which steps of LR formation are more sensitive to cytokinin. The application of cytokinin to maize PRs showed that the inhibitory effect of cytokinin on LR formation was greater in the zones in which the initial events to form new LRs are taking place. In the presence of cytokinin, the PR is not able to produce new LRs in the initiation zone; this inhibitory effect is permanent as this zone did not recover the capability to form LRs after removing cytokinin. However, the LR density in zones with appreciable LR primordia when cytokinin was applied was only slightly inhibited when a high concentration was used. These results showed that LR formation is more sensitive to the inhibitory effect of cytokinin in the earliest stages of LR development. However, the elongation of a LR primordium to emerge and the subsequent elongation of the new LR were only slightly affected by cytokinin.

     

水培球根花卉根的负向光性与根系造型

在已有水培风信子根系负向光性生长研究的基础上,与在光照条件下生长的郁金香、水仙根系进行比较的结果表明：3种球根的根系均表现负向光性生长,水仙根系对光照反应最敏感,3d可以表现明显负向光性;光强越大,根系的负向性反应越明显;蓝光对球根的负向光性诱导最明显,红光则无效;在同样的光强和光质条件下,水仙表现负向光性的倾角最大,风信子次之,郁金香最小。