玉米根系形态对光照、氮水平反应的基因型差异

用溶液培养的方法，研究了光照、以及氮水平对不同氮效率玉米自交系奶系形态养分吸收的影响，研究结果表明，提高光照水平有助于光合产物向根系分配，表现为总根长、根体积、根系重量等显著增加，在不同光照水平低氮胁迫时，氮低效品种白瓷与其它三个品种相比，根系的形态指标均有不同程度的降低。在高光强，0.4mmol/L氮水平胁迫时，与氮高效品种478相比，根系体积减少27.54%，根干重减少21.24%，并降低了根系的吸收效率，同时也表明，光照与氮水平对光合产物的分配具有耦合效应。     

不同养分配比对高粱根系生长及养分吸收的影响

为探明高粱养分吸收和根系生长对氮、磷、钾胁迫的响应,通过长期定位试验,在高粱/玉米轮作条件下研究了不同养分配比NPK、PK、NK、NP、CK对高粱根系生长及养分吸收的影响。结果表明:与NPK相比,长期不施氮肥(PK)条件下高粱总根长增加18.29%,总根体积降低26.52%,且根系主要分布在0~10 cm土层,直径小于0.5 mm细根所占比例显著增加。不施磷肥(NK)显著抑制了高粱根系生长,总根长、总根表面积和总根体积分别降低24.03%、27.48%和41.29%。不施钾肥(NP)对细根生长有明显抑制作用。不施氮、磷、钾均降低高粱对相应养分的吸收和累积,不施氮促进了营养器官中氮和钾素向籽粒转运,不施磷或钾肥抑制了氮、磷及钾的转运。高粱对养分的吸收、积累和转运与根系形态有关,不同养分积累与运转与根系形态关系表现不尽相同:氮素、钾素积累和转运与根系形态具有较好的相关性,氮素的积累和转运与植株生物量和产量的相关性大于磷素和钾素。综上,高粱根系形态及养分吸收对氮、磷及钾胁迫响应不同,该研究可为不同养分瘠薄地高粱高效栽培提供理论依据。     

低氮胁迫对不同耐低氮性玉米品种幼苗根系形态和生理特征的影响

采用水培方法,以2个耐低氮品种和2个不耐低氮玉米品种为材料,以正常氮处理B3[15 mmol(N)·L?1]为对照,研究2个低氮胁迫水平B1[0.05 mmol(N)·L?1]、B2[0.5 mmol(N)·L?1]对不同耐低氮性玉米品种苗期根系形态和伤流量及氮代谢关键酶活性的影响。结果表明:与正常供氮处理相比,在B1和B2低氮胁迫处理下,玉米幼苗根系伤流量和硝酸还原酶(NR)、谷氨酰胺合成酶(GS)、谷氨酸脱氢酶(GDH)活性均下降,耐低氮品种上述各指标的降幅(29.8%和8.7%、46.9%和39.6%、7.3%和4.4%、31.3%和19.8%)均小于不耐低氮品种(37.0%和27.5%、68.8%和56.6%、24.5%和18.7%、60.7%和42.7%),且在B1处理下耐低氮品种根系NR、GDH活性分别是不耐低氮品种的1.4倍、1.35倍。低氮胁迫对玉米苗期地上部生长的影响大于对地下部生长的影响,使地上部干重显著降低,根冠比显著增大,根数减少;在B1和B2处理下,不耐低氮品种根冠比增幅(81.6%和25.4%)、根数降幅(22.2%和31.1%)均大于耐低氮品种(61.0%和21.1%、19.8%和19.4%)。随着低氮胁迫程度的增大,耐低氮品种根长增长,根粗减小,对低氮胁迫的响应能力增大,表现为根系伸长变细以增加对氮的吸收面积。与不耐低氮品种相比,低氮胁迫下耐低氮品种根系形态较好,根系生理活性和对低氮胁迫的耐性较强,能维持较稳定的生长;随着低氮胁迫时间的延长,耐低氮品种对低氮胁迫的适应性增强,不耐低氮品种则降低。     

不同糜子品种对低氮胁迫的生物学响应

采用溶液培养的方法,研究了低氮胁迫下不同糜子品种苗期生物学性状、 氮素吸收利用效率差异及与根系形态生理指标之间的相关关系。 结果表明, 低氮胁迫下,糜子地上部生长受抑程度大于根部,植株氮累积量降低但氮利用效率明显提高。晋黍7号株高、 叶面积、 茎叶干重、 根干重、 总根数、 总吸收面积和活性吸收面积下降幅度在所测试品种中均最小, 其总氮累积量分别是晋黍1号、 晋黍5号、 晋黍8号的1.35、 1.50、 1.39倍,根系氮累积量/总氮量的百分率增加的幅度和地上部氮累积量/总氮量的百分率下降的幅度均最低,分别为9.75% 和 3.47%; 植株氮利用效率比晋黍1号、 晋黍5号、 晋黍8号分别高20.92%、 12.44%、 14.83%。晋黍7号较其他品种更耐低氮胁迫。低氮胁迫下,糜子根系干重、 总根长、 总吸收面积与总氮累积量呈显著线性相关,表明低氮胁迫下,根系形态生理指标对氮素吸收效率起重要作用。     

不同氮效率小麦品种根系特征及根际土壤酶活性的分析

为探明不同氮效率小麦（Triticum aestivum L.）品种根系特征及其对根际土壤酶活性的响应,以30年的长期定位试验为平台,于2018—2020年采用大田试验的方法,在不同氮效率品种筛选的基础上,以氮高效小麦品种郑麦113、偃高21和氮低效小麦品种丰德存5号、周麦27为试验材料,在不施氮肥（N0）和正常施氮肥（N1）条件下研究其根系特征、氮素吸收利用及根际土壤酶活性的差异。结果表明,各品种小麦的根系活力均在孕穗期达到最大值,N0、N1水平下氮高效小麦品种根系活力的平均值分别比氮低效小麦品种增加了16.13%～24.22%、10.22%～62.49%。N1水平下小麦根长、根表面积和根体积明显高于N0水平。郑麦113、偃高21、周麦27的氮吸收效率显著高于丰德存5号,而周麦27的氮利用效率较低。两种氮水平处理下,郑麦113和偃高21的根际土壤β-葡萄糖苷酶（BG）、亮氨酸氨基肽酶（LAP）和多酚氧化酶（POX）活性整体显著高于丰德存5号和周麦27(P<0.05),且根际土壤酶活性与根系形态指标均呈正相关关系。这说明郑麦113和偃高21较高的根系活力、根长、根表面积和根体积促...     

不同铁效率玉米品种苗期适应低铁胁迫的根系特征与铁积累差异

  【目的】  石灰性土壤高pH和高重碳酸盐含量严重影响土壤中有效铁含量,导致作物缺铁黄化、减产,铁高效玉米品种的推广应用是实现石灰性土壤玉米高产稳产的重要途径。 本研究探讨不同铁效率玉米品种适应低铁胁迫的根系特征与铁积累差异,旨在为铁高效玉米品种的推广应用提供科学依据。  【方法】  试验以铁高效玉米品种正红2号 (ZH2)、正大619 (ZD619) 和铁低效玉米品种川单418 (CD418)、先玉508 (XY508) 为材料,设置极低铁处理 (Fe0,Fe浓度为0 μmol/L)、低铁处理 (Fe10,Fe浓度为10 μmol/L) 和正常供铁 (Fe100,Fe浓度为100 μmol/L) 3个处理,通过砂培试验,研究不同铁效率玉米品种适应低铁胁迫的根系形态特征、干物质重、铁积累及铁吸收利用差异。  【结果】  低铁胁迫下,玉米幼苗的根干重、单株干重、铁积累量、根系相对铁吸收效率均显著降低,而根冠比与铁素生理效率均显著升高,且随胁迫程度的增加变幅加大;总根长、根表面积、根体积和根直径则表现出明显的品种差异,与正常铁处理 (Fe100)相比,低铁处理下铁低效品种的总根长、根表面积和根体积显著降低,根直径显著增加,而铁高效品种的总根长和根表面积差异不显著,根体积显著增加,根直径在极低铁处理(Fe0)下显著降低,低铁处理 (Fe10)下差异不显著;铁高效品种总根长、根表面积、根体积、根干重、单株干物重、铁积累量和根系铁吸收效率的降幅及根冠比的增幅均明显低于铁低效品种,而铁生理效率的增幅高于铁低效品种。相关性分析结果表明,玉米幼苗铁积累量与总根长、根表面积、根体积和根干重均呈显著正相关,而与根冠比呈负相关,其中与总根长 (R2 = 0.8546) 和根表面积 (R2 = 0.8983) 相关性最强。  【结论】  与铁低效玉米品种相比,铁高效玉米品种低铁胁迫下具有较优的总根长、根表面积及较高的根系铁吸收效率与铁生理效率,促进了其对铁的高效吸收与利用,提高了其对低铁环境的适应能力。     

施氮对大豆根系形态和氮素吸收积累的影响

采用框栽试验方法研究了不同施氮水平对大豆根系形态和氮素吸收积累的影响,结果表明:不同施氮水平对大豆植株生物量、氮素吸收积累量及根系形态有显著影响,随施氮量增加,植株干重、氮素积累量、单株产量等均呈先增加后降低趋势,其中以N100[100 kg(N)·hm-2]处理效果最佳,总体表现为N100>N200>N50>N25>N0.无N(NO)和适量偏低的氮(N25、N50)增加了大豆的根冠比,但过多的氮(N200)反而降低了大豆的根冠比,说明低氮胁迫促进了大豆根系的生长.大豆根长、根表面积和根体积随施氮量的增加表现为先降后增而后又降低的规律,不施氮(N0)情况下,根长、根表面积和根体积均高于低氮处理(N25、N50),之后随施氮量增加而增加,当超过一定施氮量(N200)时又呈降低趋势.不同生育时期植株生物量、氮素积累、根长、根表面积和根体积等表现为花期>苗期>鼓粒期.因此施用一定量氮肥对大豆植株生物量、氮素积累以及根系形态等产生显著影响,进而影响大豆氮素转运量和转运效率,最终影响大豆籽粒产量和品质.     

氮磷养分胁迫下小麦幼苗期生物学响应研究

为了阐明小麦苗期耐低氮、低磷胁迫的生物学响应特征,以矮抗58品种为试验材料,采用水培试验法研究了小麦在不同营养环境中(全营养、低氮胁迫、低磷胁迫)的地上部生物学特性(地上部干重、株高、叶面积)、根系形态学特性(最大根长、总根数、根系总长度、根系干重和根冠比)和根系生理特性(根系活力、根系吸收面积),以及小麦苗期氮、磷素吸收与根系形态之间的关系。结果表明,在低氮和低磷胁迫下,小麦的株高、叶面积、茎叶干重、含氮量、根系干重、总根长、总根数及根冠比均明显降低,其中低磷胁迫下根系干重、总根长及根冠比的下降幅度大于低氮胁迫,低氮下最大根长的增加幅度较低磷增加7.3%;在低磷条件下小麦的含氮量下降了57.7%。低氮、低磷胁迫下小麦根系的总吸收面积、活性吸收面积及根系活力均明显降低;正常条件下的小麦氮、磷素吸收量与根系形态指标之间相关性较差,在低氮和低磷条件下小麦的氮、磷吸收量与根系干重、总根长、总吸收面积、活性吸收面积及根系活力呈极显著正相关。总之,该小麦品种根系对低磷环境反应较为敏感,而对低氮胁迫具有较好的适应性,小麦通过改变根系形态增加对低氮、磷胁迫的适应。     

油菜NO3-的吸收、分配及氮利用效率对低氮胁迫的响应

【目的】探究油菜NO3-的吸收、分配和对低氮胁迫的响应及其氮利用效率,为理解油菜在不同低氮胁迫下相关生理变化及其氮素利用效率提供科学依据。【方法】以常规油菜品种814为研究材料,采用砂培试验,在正常供氮水平（10 mmol/L）和低氮胁迫水平（3 mmol/L、1 mmol/L）下,研究油菜的根系特性、蒸腾作用对低氮胁迫的响应及其氮素吸收效率,并研究油菜NO3-的运输分配与同化对低氮胁迫的响应及其氮素利用效率。【结果】与正常供氮处理（10 mmol/L）相比,低氮胁迫处理（3 mmol/L、1 mmol/L）的油菜NO3-含量、全氮含量均显著下降,但（NO3-）叶/根、（全氮（%））叶/根显著升高,植株根系干物质重、根系吸收面积均显著下降,但根冠比显著升高。油菜植株在低氮胁迫下气孔导度和蒸腾速率显著增加,一方面促进植株对NO3-的捕获,另一方面也促使更大比例的NO3-分配在植物的地上部分,但植株的水分散失加剧,水分利用效率显著下降。低氮胁迫处理油菜根和叶中NR、GS活性与正常供氮处理之间的差异不显著或有增加,其叶绿素含量、光合速率均显著下降,但光合氮素利用率显著升高。【结论】在低氮胁迫条件下,油菜植株的氮素和干物质累积均显著下降,但NO3-在植株的地上部分分配比例的增加以及光合氮素利用率的升高促使植株的氮素利用效率显著提高。     

低氮胁迫下玉米幼苗氮素和蔗糖分配特性

  【目的】  明确玉米自交系幼苗氮素吸收、转运与利用特性，探究低氮胁迫下其不同表型和生理性状的变化规律。  【方法】  以玉米自交系XY4和PH4CV为供试材料，进行了水培试验。设置正常氮 (N 2 mmol/L，NN) 和低氮 (N 0.04 mmol/L，LN) 两个氮水平，从培养3 h起，每3天测定一次幼苗生物量、光合特性、根系性状及氮素和蔗糖含量，直至第12天。  【结果】  玉米幼苗根系对低氮胁迫的反应早于地上部，与NN处理相比，LN处理PH4CV和XY4的根干重分别在培养第3和第6天时增加了65.15%和84.63%，而从培养第9天开始，LN处理下两自交系幼苗地上部干重显著低于NN处理，由此导致根冠比增加；与NN处理相比，LN处理下除了胞间CO₂浓度 (Ci) 和水分利用效率 (WUE) 外，两自交系幼苗叶片的SPAD值、净光合速率 (Pn)、蒸腾速率 (Tr) 和气孔导度 (Gs) 等光合特性均显著降低，且XY4下降幅度均大于PH4CV；LN处理下两自交系幼苗根干重的变异来源并不一致，XY4根干重的增加与总根长、根表面积、根体积、侧根数和初生根长增加有关，而PH4CV主要与侧根数目增加有关；与NN处理相比，LN处理两自交系幼苗地上部的氮素积累量和蔗糖含量显著降低，且XY4老叶的氮素含量下降速率明显快于PH4CV，而根系的氮素积累量、单株氮素生理利用效率和根中蔗糖含量均显著增加，且XY4增加的幅度均大于PH4CV。  【结论】  低氮胁迫促使玉米幼苗分配给地上部的氮素和蔗糖相对较少，因此限制地上部生物量积累及叶片光合能力的发挥，而分配给根系的氮素和蔗糖相对较多，从而促进根系形态建成，以利于吸收更多的氮素。     

Nitrogen Use Efficiency in Cacao Genotypes

Cacao (Theobroma cacao L) is mostly grown on soils with low natural fertility. On such soils nitrogen (N) is one of the most yield limiting nutrients for cacao. Information is lacking on N use efficiency in cacao. A greenhouse experiment was conducted to evaluate growth response and N use efficiency by two cacao genotypes. The genotypes used were TSH-565 and ICS-9 and N rates adapted were 0, 120, 240, 360, and 480 mg N /pot. In both genotypes, increasing levels of applied N improved growth (stem girth, dry weight of shoot and roots and shoot/root ratio), and concentration and uptake of N. Genotypes differed significantly for stem girth and ICS -9 produced greater stem girth compared with TSH-565. Nitrogen uptake had a linear relationship with root dry weight of the two genotypes. In both genotypes, increasing levels of applied N overall increased N-uptake efficiency (NEFF = N concentration in shoot x shoot/root), but decreased N-use efficiency by shoot and roots (NUE = g dry matter of shoot or root/mg N) and N-use efficiency of carbohydrate (NUEC = mg of total carbohydrates in shoot/mg of N in shoot). Both genotypes responded differently to applied N, despite the existence of close genetic relatedness between them. The method used here appears to be suitable method for identification of cacao genotypes that are efficient in uptake and utilization of N.     

基因型影响磷镁互作下大豆生长及根瘤和菌根性状

  【目的】  明确施加镁肥在不同磷处理的土壤上对不同基因型大豆生长及根瘤和菌根性状的影响。  【方法】  田间试验采用三因素试验设计,设置施P₂O₅ 40 kg/hm2 (P40)和100 kg/hm2 (P100)两个水平,施MgO 0 kg/hm2 (Mg0)和75 kg/hm2 (Mg75)两个水平,磷高效基因型粤春03-3 (YC03-3)和磷低效基因型本地2号(BD2)两个大豆基因型。测定了大豆植株干重、单株结荚数、根系性状、根瘤性状、菌根侵染率以及植株氮、磷、镁含量。  【结果】  P100处理显著增加了两个大豆基因型的植株干重、单株结荚数、总根长、根表面积和体积以及植株氮、磷、镁积累量。施用镁肥,YC03-3在P40和P100处理下植株干重、单株结荚数、植株氮和镁积累量均显著增加,在P100条件下植株磷积累量以及根表面积、根体积、根平均直径显著增加;BD2在P40和P100处理下植株镁积累量显著增加,P40条件下植株氮积累量显著增加。磷和镁处理显著影响大豆与有益微生物的共生。P40条件下,两个大豆基因型的根瘤数和根瘤干重在Mg0和Mg75处理间无显著差异;P100条件下Mg75处理BD2和YC03-3的根瘤数分别较Mg0处理增加了135%和178%,根瘤干重分别增加了308%和197%。Mg0条件下P40处理YC03-3的菌根侵染率较P100增加了31.6%;Mg75条件下P40处理的BD2菌根侵染率较P100增加了15.0%。P40条件下,Mg75提高了BD2菌根侵染率16.3%;P100条件下,Mg75提高了YC03-3菌根侵染率32.1%。主成分分析发现,P100条件下,Mg0与Mg75处理之间差异显著,而P40条件下镁处理之间差异不明显。  【结论】  增施磷肥显著促进了两个大豆基因型的生长,改善了植株氮、磷、镁养分状况。增施镁肥可增加磷高效大豆基因型YC03-3的地上部和根部干重、单株结荚数、植株氮积累量,对磷低效型基因BD2没有显著作用。YC03-3的根瘤密度对施磷和施镁响应较BD2显著。BD2的菌根侵染率在低磷条件下对施镁的反应敏感,而YC03-3的菌根侵染率在P100条件下对施镁反应敏感。由此可见,磷和镁养分之间的互作效应受到大豆基因型的影响。     

不同氮效率茄子基因型及其杂种F1的氮素吸收特性

为阐明杂种一代在氮素吸收方面的优势,研究了不同氮效率茄子基因型及其杂种 F1的氮素吸收特性。试验以3个典型氮效率的茄子基因型及其F1代为材料,研究其在正常供氮和低氮胁迫条件下的根系体积、根系干重、氮素吸收总量、根系活力、硝酸还原酶活性及谷氨酰胺合成酶活性。结果表明,与高氮低效-低氮低效基因型L相比,氮高效基因型H1、H2的单株根系体积、根系干重、根系活力以及氮素吸收总量均较大; 且具有较高的硝酸还原酶与谷氨酰胺合成酶活性。三个杂交组合F1-1（L×H1）、F1-2（L×H2）和F1-3（H1×H2）的单株根系体积、根系干重、根系活力、硝酸还原酶活性、谷氨酰胺合成酶活性以及氮素吸收总量的中亲优势（Hm）和超亲优势（Hp）多为正向优势; 其中,组合F1-3杂种优势最为明显。利用杂种在氮素吸收方面的优势,对于改善植株体内的氮代谢水平进而提高氮效率具有重要意义。     

Influence of Nitrogen on Growth,Yield, and Yield Components and Nitrogen Uptake and Use Efficiency in Dry Bean Genotypes

Dry bean is an important legume and nitrogen (N) deficiency is one of the most yield-limiting factors in most of the bean-growing regions. A greenhouse experiment was conducted with the objective to determine influence of N on growth, yield, and yield components and N uptake and use efficiency of 23 dry bean genotypes. Straw yield, grain yield, yield components, maximum root length, and root dry weight were significantly increased with the addition of N but varied with genotypes. The N × genotype interactions were also significant for most of these traits, indicating variation in responses of genotypes with the variation in N levels. There was significant difference in N uptake and use efficiency among genotypes. Most of growth and yield components were significantly and positively associated with grain yield. Based on grain yield efficiency index (GYEI), genotypes were classified into efficient, moderately efficient, or inefficient group in N-use efficiency. Nitrogen concentration was greater in grain compared to straw, indicating greater N requirement of dry bean genotypes.     

ADAPTABILITY MECHANISM OF NITROGEN-EFFICIENT GERMPLASM OF NATURAL VARIATION TO LOW NITROGEN STRESS IN BRASSICA NAPUS

Previous studies showed that wide genotype differences in nitrogen (N) efficiency exists among cultivars of rapeseed (Brassica napus L.), but the mechanisms behind those differences are still unknown. In the present study, our aim was to analyze the adaptability mechanism of N-efficient rapeseed to low-N stress by employing two genotypes of natural variation in N efficiency. Nitrogen-efficient genotype, ‘BG51’, and N-inefficient genotype, ‘BG88’, were grown in a solution culture experiment under conditions of high-N (6.0 mM N) and low-N (0.6 mM N) supply. After growing 30 d, roots and shoots were sampled for the analysis of dry weight, N concentration and accumulation, N use efficiency (NUE), N transport efficiency (NTE), root system vigor parameters, nitrate redutase (NR) activity, and glutamine synthetase (GS) activity. Nitrogen deficiency decreased shoot and root dry weight significantly, but ‘BG51’ exhibited a significantly lower decrease in shoot dry weight and had significantly higher biomass production than ‘BG88’. Under low N supply ‘BG51’ accumulated more N in shoot, root and whole plant than ‘BG88’, and presented higher NUE in both shoot and root. Low-N stress induced an increase in maximum root length by 28.3% for ‘BG88’ and 55.1% for ‘BG51’ compared with the high-N treatment. And ‘BG51’ presented larger root volume, higher root vigor, larger root total absorbing area and root active absorbing area than ‘BG88’ in low-N treatment. Furthermore, ‘BG51’ had significantly higher NR and GS activity in both leaf and root in low N treatment than ‘BG88’, while there was no evident difference between them in high N treatment. These results suggested that N-efficient rapeseed germplasm of natural variation involves an integrated adaptability mechanism responding to low-N stress. Namely, N-efficient genotype could form more developed root system to accumulate more N, and presented efficient N assimilation by higher NR activity and GS activity than N-inefficient genotype. These ultimately resulted in high tolerance of N-efficient genotype to low-N stress and high biomass production.     

Effect of root morphological traits on zinc efficiency in Iranian bread wheat genotypes

Zinc (Zn) has a vast number of functions in plant metabolism, the lack of which had dramatic effects on growth and yield of plants. Plants have morphological and biochemical responses to enhance mineral solubility in the soil and facilitate uptake, such as root plasticity, secretion processes and symbioses. Root architecture modification is an important plant response to nutrient availability. The aim of this study was to identify root morphological reactions to Zn efficiency in Iranian bread wheat genotypes. Soil and solution cultures were used to survey Zn efficiency. In soil culture, six and seven genotypes with high and low Zn contents were selected among 110 Iranian bread wheat genotypes, respectively. The solution culture experiments were set up in a completely randomized block design and plants fed with Johnson’s grass solution. All traits were assessed at 30 and 60 DAPs (days after planting). Our results showed a significant difference between two groups of efficient and inefficient genotypes only at 60 DAP, and Zn-efficient genotypes showed 1.63-, 1.50-, 1.69- and 1.92-fold increases in root diameter, surface area density, shoot and root dry weight, respectively, compared to inefficient genotypes. In contrast, Zn-inefficient genotypes had 1.20- and 2.62-fold more root length and fineness, respectively, than efficient genotypes. The positive significant correlations were observed between shoot and Zn uptake as well as root dry weight and Zn uptake at both stages. Furthermore, shoot and root dry weight showed a significant correlation with root fineness, diameter and surface area density at both stages. The path analysis showed indirect effects on Zn uptake through root traits. Our results showed that roots have a major role in Zn efficiency. Therefore, the better growth and greater Zn uptake in efficient genotypes, compared to inefficient ones, can be attributed to greater root diameter and surface area density, and lower root fineness in these genotypes.     

ROOT GROWTH OF UPLAND RICE GENOTYPES AS INFLUENCED BY NITROGEN FERTILIZATION

The plant root system is an important organ which supplies water and nutrients to growing plants. Information is limited on influence of nitrogen fertilization on upland rice root growth. A greenhouse experiment was conducted to evaluate influence of nitrogen (N) fertilization on growth of root system of 20 upland rice genotypes. The N rate used was 0 mg kg^?1(low) and 300 mg kg^?1(high) of soil. Nitrogen X genotype interactions for root length and root dry weight were highly significant (P < 0.01), indicating that differences among genotypes were not consistent at two N rates. Overall, greater root length, root dry weight and tops-roots ration were obtained at an N fertilization rate of 300 mg kg^?1compared with the 0 mg N kg^?1soil. However, genotypes differ significantly in root length, root dry weight and top-root ratio. Nitrogen fertilization produced fine roots and more root hairs compared with absence of N fertilizer treatment. Based on root dry weight efficiency index (RDWEI) for N use efficiency, 70% genotypes were classified as efficient, 15% were classified as moderately efficient and 15% were classified as inefficient. Root dry weight efficiency index trait can be incorporated in upland rice for improving water and nutrient efficiency in favor of higher yields.     

Variation of morpho-physiological traits in geographically diverse pigeonpea [Cajanus cajan (L.) Millsp] germplasm under different phosphorus conditions

Genotypic variation for morpho-physiological parameters, phosphorus (P) content and root acid phosphatase activity was studied in 52 pigeonpea genotypes. Data related to shoot (length, dry weight, number of leaves, and leaf area), root (volume, length, dry weight, area, perimeter, and number of root tips), acid phosphatase activity, and P content (root, stem, and leaf) were recorded at 60 days after sowing (DAS). The P use efficient genotypes showed high root length, root area, root perimeter, root dry weight, P content in leaves, and root to shoot dry weight ratio under the P not added condition. Significant variation was found among genotypes for root- and shoot-associated characteristics under both P treatments. The P use efficient genotypes with improved root morphological phenes have potential to acquire and utilize more P from immobile soil bound P sources may be of additional factor for increasing efficiency of acquisition and utilization of supplied P fertilizer.     

玉米苗期根系对氮胁迫反应的配合力分析

研究利用7个玉米自交系,采用NC-Ⅱ设计,分析了玉米苗期根系性状对氮胁迫反应的配合力及遗传参数变化。结果表明,在2个氮水平下,玉米苗期根系性状的一般配合力、特殊配合力都存在显著的基因型差异,而且不同的基因型在氮胁迫下的反应也不尽相同。高氮下,根系性状除轴根长以外均以非加性遗传为主;氮胁迫下,除轴根数以外的根系性状以加性遗传为主。2个氮水平下,根干重、总根长和侧根长的广义遗传力均较高;与高氮处理相比,在低氮胁迫下,根系性状的广义遗传力表现为下降趋势,根干重、总根长和侧根长的狭义遗传力有上升的趋势。     

NITROGEN USE EFFICIENCY IN DRY BEAN GENOTYPES

Dry bean is an important legume crop for Latin American people and nitrogen is one of the most yields limiting nutrients for bean crop. A greenhouse experiment was conducted to evaluate nitrogen (N) use efficiency of 20 dry bean genotypes. Genotypes were grown on an Oxisol and two N levels used were without N application (low level) and an application of 400 mg N kg^?1 (high level). Shoot dry weight, grain yield and yield components, N concentration and uptake in shoot and grain were significantly affected by N and genotype treatments. Grain yield had a highly significant (P < 0.01) association with shoot dry weight, pod number, grains per pod and 100 grain weight. Among the 20 genotypes tested, Perola, CNFR 7847, CNFR 7865, CNFP 7777 and CNFM 6911 were found to produce reasonably good yield at low N rate as well as responded well to applied N. Whereas, some genotypes like BRS Radiante, CNFP 7624, CNFM 7875, CNFM 7886, CNFC 7813, CNFC 7827, CNFP 7677 and CNFP 7775 produced very good yields at higher N rate but very low yields at lower N rate. Hence, these genotypes are good for farmers using higher technology. Nitrogen concentration and uptake were higher in dry bean grains compared with shoot and 63% of N accumulated at zero N rate and 75% N accumulated at 400 mg N rate were translocated to grain across 20 genotypes. Nitrogen uptake efficiencies were having highly significant (P < 0.01) quadratic relationship with grain yield. This indicates that improving N uptake in dry bean plants can increase grain yield.