稻草覆盖还田对直播冬油菜生长及养分积累的影响

[目的]冬油菜产量常受限于季节性干旱、冬季低温以及土壤肥力较低等因素。考虑到秸秆还田有培肥土壤的优势以及长江中下游地区稻草过剩的现实,通过田间试验研究稻油轮作区稻草覆盖还田对直播冬油菜生长的影响,探讨稻草整株覆盖还田对直播油菜生育期内密度、株高、根茎粗的变化特征及其对油菜产量和养分吸收量的影响。[方法]试验于2014 2015和2015 2016年在湖北省武汉市华中农业大学试验场进行,共设置4个处理,分别为:1)对照,不施肥稻草不还田(CK);2)不施肥稻草覆盖还田(S);3)单施化肥(NPK);4)稻草覆盖还田配施化肥(NPK+S)。施肥处理(NPK、NPK+S)肥料用量为N 180 kg/hm^2、P2O5 60 kg/hm^2、K2O75 kg/hm^2、硼砂15 kg/hm^2。分别于油菜苗期、蕾薹期、花期、角果期和成熟期取样,测定油菜地上部生物量,氮磷钾含量和积累量,并在田间监测油菜生育期内密度、株高和根茎粗。[结果]稻草覆盖还田提高土壤最低温度0.6~1.2℃(播后95天),降低土壤最高温度0.8~1.8℃(播后184天),缩小土壤温度变幅2.3℃(播后95~184天),提高土壤平均含水量8.0%~8.9%(播后48~184天)。与稻草不覆盖相比,稻草覆盖还田减少冬油菜80%以上的出苗密度;与出苗密度相比,成熟期CK、S、NPK和NPK+S处理的密度分别降低71.3%、40.3%、69.5%和32.1%,稻草还田处理的油菜生育期内密度降低幅度小于稻草不还田处理。油菜成熟期S处理的根茎粗和株高分别比CK显著提高了22.7%和8.3%,NPK+S和NPK处理株高和根茎粗无明显差异。两年结果表明,S处理的最大生物量较CK平均增加了88.6%,与NPK处理相比,NPK+S处理的地上部苗期生物量降低3.7%~27.9%,角果期生物量平均增加28.1%。CK和S处理氮、磷和钾素积累量均在蕾薹期花期差异较大,成熟期S处理的氮、磷积累量分别较CK高28.6%~268.2%、93.3%~253.1%,两年增产率分别为218.8%和28.5%;施肥处理(NPK、NPK+S)冬油菜氮、磷和钾积累量随生育期持续增加,均在角果期达到最大值,与NPK相比,NPK+S处理分别提高成熟期油菜氮、磷和钾积累量18.1%~19.1%、23.7%~36.9%和28.3%~56.9%,两年分别增产1811和1032 kg/hm^2,增产率分别达到25.6%和20.3%。[结论]稻草覆盖还田能缓解气温骤变对土壤温度的影响,保持土壤含水量,缓解土壤干旱。稻草覆盖还田前期抑制直播冬油菜的出苗密度,后期可维持冬油菜密度的稳定,同时对冬油菜的生长、生物量、产量和养分吸收量有促进作用。     

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。     

直播和移栽冬油菜生长和产量形成对氮磷钾肥的响应差异

【目的】直播和移栽是目前长江流域冬油菜的两种主要种植方式,其发展状况对我国油菜产业发展和油料供应安全具有重要意义。直播和移栽冬油菜的栽培过程和植株密度存在显著差异,因此两者的个体形态、 生长发育及产量形成有所差异,对养分的施用响应也可能不同。本研究利用大田试验研究施肥和种植方式对冬油菜生长发育和产量形成的影响,比较不同种植方式下冬油菜的生长特点及其差异。【方法】采用大田试验,研究氮磷钾肥配施(NPK)、 不施氮(-N)、 不施磷(-P)和不施钾(-K)处理下直播和移栽冬油菜各生育期的株高、 根颈粗和叶片数。越冬期低温和干旱逆境发生时测定顶四叶的生理生化指标,包括硝酸还原酶活性、 过氧化物酶活性、 过氧化氢酶活性、 可溶性蛋白含量、 可溶性糖含量、 游离脯氨酸含量和丙二醛含量。角果期调查菌核病的发病率。成熟期调查产量构成因素,包括密度、 分枝数、 单株角果数、 主序角果数、 角粒数和千粒重,最后进行实产统计。【结果】直播冬油菜前期株高相比移栽冬油菜增长较快,薹期后则明显降低,根颈粗和叶片数在各生育时期均显著较低。直播冬油菜越冬期叶片生理生化水平较移栽冬油菜偏低,丙二醛含量显著较高。直播冬油菜角果期菌核病的发病率平均为21.8%,远高于移栽冬油菜的8.5%。两种种植方式冬油菜成熟期表现出显著不同的产量构成,相比移栽冬油菜,直播冬油菜的植株密度显著较高,而个体分枝数、 角果数和角粒数则显著较少,而且主序角果的比例明显较高。最终,直播和移栽冬油菜在NPK处理的产量非常接近,分别为2019和2081 kg/hm2,但直播冬油菜在缺素条件下的产量较移栽冬油菜均显著偏低。相比NPK处理,任一养分缺乏均显著阻碍直播和移栽冬油菜的生长发育和产量形成,其中氮素影响最为显著和全面,其次是磷素,钾素影响相对较小。与移栽冬油菜不同,直播冬油菜成熟期的植株密度在缺素时出现下降,氮、 磷缺乏导致直播冬油菜密度分别降低53.6%和18.7%。养分缺乏条件下较差的个体生长和降低的植株密度是导致直播冬油菜产量降幅偏高的主要原因。【结论】当前栽培方式下,直播冬油菜起始阶段个体发育较差,导致生育期内生长表现和产量形成对养分缺乏更为敏感。相比移栽冬油菜,直播冬油菜应更重视氮磷钾养分的平衡施用,以促进个体健壮和群体稳定而获得高产。直播冬油菜的养分管理研究需进一步加强,尤其是应对逆境发生的施肥调控技术与措施。     

肥料运筹方式对冬油菜生长及产量的影响

以湘杂油763为供试材料,研究了不同肥料运筹方式对冬油菜产量和部分农艺性状的影响。结果表明：氮肥运筹方式对油菜生长的影响较大,以基肥:苗肥:薹肥 = 5:2:3处理的籽粒产量最高,其次是基肥:苗肥:薹肥 = 6:2:2处理,基肥:苗肥:薹肥 = 10:0:0处理的产量最低,其差异达到了显著水平,单株角果数、每角果粒数、绿叶数、茎粗、最大叶长和叶宽、叶片叶绿素含量等指标也有类似的变化趋势,而氮肥运筹方式对千粒重的影响不显著。磷肥和钾肥运筹方式对油菜生长的影响较小,在不同磷钾肥运筹方式下籽粒产量、产量构成因素、茎叶性状均没有显著差异。在本试验所设的8种处理中,以氮肥的基肥:苗肥:薹肥 = 5:2:3、磷肥和钾肥的基肥:苗肥:薹肥 = 10:0:0 处理和氮肥的基肥:苗肥:薹肥 = 5:2:3、磷肥的基肥:苗肥:薹肥 = 6:2:2、钾肥的基肥:苗肥:薹肥 = 10:0:0 处理的籽粒产量并列最高。     

Seed germination and seedling growth parameters in nine tall fescue varieties under salinity stress

ABSTRACT

To assess seed germination parameters and identifying tolerant varieties, seeds of nine tall fescue varieties (Festuca arundinacea Schreb.) were germinated under various salinity levels for 14 days. Tall fescue is considered ‘moderately tolerant’ to salinity stress, but our study revealed a remarkable diversity among the tested varieties. Armani, Essential, Fatcat, and Starlett were found to reach the same final germination (>90%), irrespective of NaCl concentration up to 15 ds m^?1 NaCl; Asterix and Meandre expressed lower germination under the highest salinity level (>75%); and final germination decreased in Eyecandy, Rhizing star, and Thomahawk gradually with increasing salinity (>55%). The main effect of increasing salinity was a delay in germination, and our study suggests that the recording of final germination, which is performed on day-14 in a standard germination test, should be postponed in order to understand the full effect of salinity on germination potential. Nonetheless, a delay in germination will affect turf quality negatively and hence there is good reason to test for salinity tolerance when choosing a variety for sowing on saline soil. Further, our findings indicate a future perspective for breeding for improved salinity tolerance in tall fescue by the identification of salinity-tolerant breeding lines or varieties.     

栽培模式对直播油菜生长、产量和养分吸收利用的影响

发展直播油菜对增加我国油菜种植面积和总产有重要意义,但栽培措施尤其是施肥技术的滞后极大地影响了油菜的产量及施肥效果。2009/2010年度在湖北省油菜主产区设置田间试验,研究栽培模式对直播油菜生长、产量、经济效益和养分吸收利用的影响,探讨适合当前生产的高产高效栽培技术。结果表明,各优化模式比农民习惯栽培模式均有增产增收效果,其中在30104 plant/hm2种植密度、秸秆还田和加强病虫草害防治的基础上进行优化施肥（氮、磷、钾肥用量分别为N 195 kg/hm2、 P2O5 90 kg/hm2、K2O 90 kg/hm2,硼砂用量15 kg/hm2,氮肥和钾肥分次施用）的模式Ⅲ表现最好,比农民习惯施肥增产35.9 %、增收1632 Yuan/hm2,地上部干物质量和养分累积也均较高,氮、钾肥偏生产力分别为N 13.7 kg/kg和K2O 29.8 kg/kg,实现高产高效目标。说明当前直播油菜的栽培模式应结合其生长发育进程和养分吸收规律,适当密植以增库促源,加强植保防治病虫草害,更重要的是积极推行平衡施肥和有机、无机配施,并合理安排施肥时期及比例。     

香菇柄水提液对油菜种子活力及抗逆性的影响

在室内用生物学方法研究了不同浓度香菇柄水提液浸种对油菜种子活力的影响。结果表明,0.005 g/mL 的水提液浸种对提高油菜种子活力的效果最佳。进一步研究表明,0.005 g/mL 的水提液浸种处理,使油菜种子在4℃低温下的发芽率显著提高,且幼苗经4℃低温胁迫两天后,叶片中的超氧化物歧化酶（SOD）、 过氧化物酶（POD）活性,可溶性糖、 可溶性蛋白及叶绿素含量显著高于对照组,膜脂过氧化产物丙二醛（MDA）含量显著低于对照组,表明香菇柄水提液浸种处理油菜种子可提高其种苗的抗寒性。试验结果还表明,香菇柄水提液浸种处理油菜种子可提高油菜种苗的耐除草剂能力。     

氮磷钾硼配施对油菜泌蜜量的影响

采用四因素五水平二次正交旋转回归试验方法,在影响甘蓝型中熟品种油菜泌蜜量的施肥诸因素中,选择氮、磷、钾、硼的施用量作为生产上的决策变量,以油菜的泌蜜量为目标函数,所得结果通过计算机数据分析,建立了二次回归数学模型。对模型的主效应和交互效应的分析结果表明,磷素和钾素是影响油菜泌蜜量的主要控制因子;根据试验结果筛选出油菜泌蜜量的最佳施肥方案N 150 kg/hm2,P2O5 126 kg/hm2,K2O 157.5 kg/hm2和H3BO3 7.5 kg/hm2。     

不同硼肥对油菜产量和品质的影响及其在油稻轮作中的后效

通过盆栽土培和田间试验,研究两种具有缓释特性的硼肥Etibor-48(Na2B4O7·5H2O,EB)和Colemanite (Ca2B6O11·5H2O,CB)对油菜产量和品质的影响及其在油稻轮作中的后效.盆栽试验结果表明,EB和CB各处理第一季油菜产量显著高于不施硼处理(-B),与硼砂处理(B)比较也有较大提高;安...     

不同施氮水平对返青期水分胁迫下冬油菜 补偿效应的影响

为确定甘蓝型冬油菜在返青期水分胁迫条件下的适宜施氮量及其对水分胁迫的补偿效应,本文采用桶栽试验方法,在返青期设置每桶施纯氮0 g(N0)、0.2 g(N1)、0.4 g(N2)、0.6 g(N3)和0.8 g(N4)5个施氮水平(折合为0 kg·hm~(-2)、30 kg·hm~(-2)、60 kg·hm~(-2)、90 kg·hm~(-2)、120 kg·hm~(-2))及水分亏缺(D,土壤含水率为50%~55%田间持水率)和充分供水(W,土壤含水率为70%~80%田间持水率),研究施氮量对返青期水分胁迫后复水冬油菜生长指标、叶绿素含量、光合速率、籽粒产量和水分利用效率的补偿效应,并对不同处理下各指标利用主成分分析进行评价。结果表明,在相同水分条件下,地上部干物质量、叶绿素含量、光合速率、籽粒产量和水分利用效率均随施氮量的增加呈先增加后降低的趋势,并在N3达到最大。返青期干旱胁迫后复水,各施氮处理冬油菜的地上部干物质量、叶绿素含量、光合速率、产量及产量构成均表现出一定程度的补偿效应,补偿效果随施氮量的增加先增加后降低,在N3施氮量下补偿效果最好。在N3施氮水平下,D处理冬油菜的各生长指标、叶绿素含量和籽粒产量均与W处理无显著差异,表现为等效补偿效果;而D处理冬油菜初花期的光合速率显著大于W处理,表现为超补偿效果。N3D处理的产量比N3W处理降低2.2%,水分利用效率提高3.8%。氮肥偏生产力和油菜籽粒的含油率均随施氮量的增加而降低;油菜籽粒的蛋白质含量随施氮量的增加而增加。与N0相比,2种水分处理下N3的平均氮肥偏生产力降低6.2%,籽粒含油率降低13.0%,但产量提高87.6%,水分利用效率提高32.9%,籽粒的蛋白质含量提高24.6%。对各指标进行主成分分析发现,N3D处理的主成分分析综合得分最高。由此可见,N3D处理对促进冬油菜生长,提高产量和水分利用效率,保证品质的综合效果最好。     

NaCl胁迫下外源腐胺和钙对草莓幼苗离子吸收的影响

在150 mmol/L NaCl 胁迫条件下,以达塞莱克特草莓为试材,利用基质盆栽方法研究了外源腐胺和钙对草莓生长、叶片含水量、脯氨酸含量及Ca2+、Na+ 和 Cl- 吸收的影响。结果表明,在营养液中添加14 mmol/L 硝酸钙和叶面喷施 1×10-5 mol/L 腐胺均可提高盐胁迫草莓植株的地上部和地下部干鲜重,提高叶片含水量、脯氨酸含量,抑制 Na+ 和Cl- 的吸收及运输,提高根系和叶片的 K+/Na+ 值和 Ca2+/ Na+ 值,硝酸钙和腐胺同时处理的效果优于单独处理。缺钙条件下,喷施外源腐胺的 K+/Na+ 值和 Ca2+/ Na+ 值显著或极显著低于腐胺加钙处理,Cl- 含量显著高于腐胺加钙处理。外源腐胺对 Na+ 和 Cl- 吸收的调控作用受到 Ca2+ 的调节。     

不同氮水平下冬油菜光合氮利用效率与光合器官氮分配的关系

【目的】氮是限制作物光合作用的重要因子,除含量之外,氮在光合器官各组分间的分配可能也是影响光合作用的重要因素。本研究从叶片尺度探究冬油菜苗期氮素在光合器官中的分配,分析不同氮水平下光合氮素利用特征及其与光合氮利用效率的关系,以揭示氮素营养影响光合氮利用效率的机制。【方法】采用田间试验,设3个施氮水平(0、 180、 360 kg/hm2,分别以N0、 N180、 N360表示),在苗期测定最新完全展开的叶净光合速率(Pn)、 氮含量、 光合氮利用效率(PNUE)以及最大羧化速率(Vc max)、 最大电子传递速率(Jmax)等相关生理、 光合参数,并计算叶片氮素在光合器官(羧化系统、 生物力能学组分和捕光系统)的分配比例。【结果】施氮明显改善冬油菜苗期的生长,显著增加了叶片数、 叶面积和叶片干重,但单位叶面积干重低于不施氮处理。与N0相比,N180和N360处理的冬油菜最新完全展开叶的氮含量和Pn显著升高,其中叶片氮含量分别增加了155.0%、 157.3%,Pn则增加57.6%、 56.1%,N180与N360处理间无显著差异; 而PNUE随施氮水平的提高而降低,与N0相比,N180和N360处理分别下降了35.6%和39.6%。施氮提高了冬油菜苗期叶片的光合能力,N180和N360处理的最大净光合速率(Pn max)、 羧化效率(CE)、 最大羧化速率(Vc max)及最大电子传递速率(Jmax)显著高于N0处理。氮肥用量同样影响氮素在光合器官中的分配,与N0相比,N180和N360处理的氮素在叶片光合器官投入的比例显著降低,降低幅度分别为29.3%、 34.5%; 其分配比例在羧化系统(PC)、 生物力能学组分(PB)及捕光系统(PL)分别降低了24.1%、 23.3%、 34.6%和31.0%、 26.7%、 38.5%。相关分析表明,叶片中羧化和生物力能学组分及光合组分氮的分配比例与PNUE均呈显著正相关关系,而与非光合组分氮分配比例呈显著负相关关系。【结论】随施氮量的升高,油菜苗期光合氮利用效率呈下降趋势。氮素在光合器官(羧化系统、 生物力能学组分和捕光系统)分配的差异是影响冬油菜苗期叶片光合氮利用效率的重要原因。在保证苗期适宜氮素供应的情况下,通过协调氮素在光合器官的分配对进一步提高作物光合氮素利用效率具有重要意义。     

Seed priming in nanoparticles of water treatment residual can increase the germination and growth of cucumber seedling under salinity stress

Abstract

A laboratory experiment was carried out to evaluate the impact of the nanoparticles of water treatment residuals (nWTRs) and salt stress on germination and growth parameters of cucumber seedling. The interaction between three nWTRs treatments (0, 500, and 1000 mgL^?1) nWTRs and five saline solution (fresh water: sea water) treatments had 0.70, 2, 3, 6, and 11?dSm^?1 were studied. The results revealed that increasing salinity levels significantly reduced the percentage of germination (GP) for the primed seeds treated in fresh water and nWTRs. The GP reduction was higher in seeds primed in fresh water compared to which primed in nWTRs. Salt stress negatively affected radicle length of cucumber seedling for both priming treatments. However, this impact was more pronounced for the primed seeds treated in fresh water than which treated in nWTRs at high salinity stress. Priming in nWTRs significantly decreased the root radius of cucumber seedlings, and the1000 mgL^?1 priming treatment obtained a lowest value of radicle radius. Increasing salt concentration in culture medium reduced total biomass of cucumber seedling, however for the primed seeds treated in nWTRs, the total biomass was increased in comparison with which treated in fresh water. Salt tolerance and vigor indices were significantly (p?<?0.01) affected by salinity levels, nWTRs treatments and their interaction. It can be concluded that nWTRs are ameliorating materials for plant growth under salt stress conditions.     

Effects of humic acid and Ca(NO3)2 on nutrient contents in pepper (Capsicum annuum) seedling under salt stress

This study was carried out in order to determine the effects of calcium nitrate (Ca(NO₃)₂) and humic acid (HA) applications on nutrient uptake of pepper seedling under salt stress in a plant growth room. Before sowing Demre variety of pepper seeds, 60?mM NaCI was added to each 300?cm³ pot. The experiment was ended at eighth week after the sowing. Applications of HA significantly affected K, Ca, Fe, Mn, Zn (p?p?3)₂ applications did not show a significant effect on Fe and Cu contents of pepper seedling. However, Ca(NO₃)₂ applications significantly affected N and P contents (p?<.05) and K, Ca, Mn, and Zn contents (p?相似文献   

Effect of salt stress on tomato plant and the role of calcium

Abstract

Salinity is one of the serious abiotic stresses that has adverse effects on plant growth. The aim of this study was to investigate the effect of sodium chloride (NaCl) on germination and growth parameters of tomato plant as well as the role of Ca²⁺as an ameliorating agent. 100?mM NaCl and two concentrations of calcium (5 and 10?mM) were applied to tomato seeds and seedlings. This study was carried out in a Completely Randomized Design (CRD) with a total of six treatments each comprising of three replicates. The application of 100?mM of NaCl delayed the germination time by 27.6%, reduced the seedling length and seedling vigor by 24.33% and germination stress tolerance by 27.6% as compared to control. Salinity also reduced the plant growth (root and shoot length, root fresh and dry weight, shoot fresh and dry weight, membrane stability, relative water content and leaf area), whereas the application of calcium mitigated the negative effects of salinity on germination and growth to a greater extent. With increased calcium concentration, growth and germination increased significantly both alone and in the salt-affected plant. 10?mM calcium showed best results and enhanced the promptness index by 20.7%, seedling length and vigor by 15.1% and GSI by 20.7%. It also improved root fresh and dry weight, shoot fresh and dry weight, relative water content and leaf area. Similarly, 5?mM calcium also increased plant height and membrane stability index. The present study suggests that application of Ca²⁺ enhanced the growth of tomato plant under saline conditions.     

Seed priming and soil incorporation with silicon influence growth and yield of maize under water-deficit stress

Silicon (Si) has been known to enhance plant tolerance against biotic and abiotic stresses besides its beneficial effects on plant growth and yield. Two experiments were conducted to evaluate the effect of Si against water-deficit stress in maize (Zea mays) applied through seed priming and soil incorporation methods, and to find out the optimum dose of Si under each method. In the seed priming experiment, seeds were exposed to different Si levels, up to 2 mM l^–1, germinating under three soil moisture regimes (100%, 75% and 50% field capacity-FC). In the soil incorporation study, the treatments included were six Si doses from 0 to 600 kg ha^–1 under the same soil moisture regimes. Grain yield was reduced by 59% and 69% in the seed priming and soil incorporation study, respectively, at 50% FC. Si application was effective irrespective of the application methods with higher cob length, 100-kernel weight and grain yield than the control. Application of Si at 1 mM l^–1 as seed priming and 300 kg ha^–1 as soil incorporation was more effective than other doses and could be recommended as optimum dose for Nakhon Sawan 3 hybrid maize variety under water-deficit stress.     

盐胁迫下柚实生苗生长、矿质营养及离子吸收特性研究

以坪山柚为材料,对盐胁迫下实生苗生长、矿质营养及离子吸收特性进行了研究。结果表明,沙培30d,80～200mmol/L盐胁迫,随盐浓度提高,坪山柚实生苗株高、叶面积、地上部干重和根部干重明显降低。溶液培养8d,坪山柚实生苗地上部及根Na+、Cl-含量随盐浓度的增加而增加,根及地上部K+、Ca2+、Mg2+以及P和Mn含量下降,Fe、Zn、Cu含量的变化因器官而异。其中,地上部Fe含量对盐胁迫敏感,可作为柚耐盐性鉴定指标。40mmol/L盐胁迫,坪山柚地上部K+/Na+、Ca2+/Na+、Mg2+/Na+值均显著下降,且Mg2+/Na+值+/Na+值>1;浓度≥160mmol/L盐胁迫,K+/Na+值+吸收、运转效率比Cl-高。     

Anatomical responses of root tips to boron deficiency II. Effect of boron deficiency on the cellular growth and development in root tips

Changes induced in the tissue structure and the cellular patterns of young tomato root tips by the absence of boron in the nutrient solution were investigated.

Boron deficiency caused primarily the inhibition of cell division and cell elongation in root apices, and the cells of boron-deficient root tips were fully vacuolated. The cell wall in the apical region was thickened by boron deficiency and the intercellular spaces insufficiently developed.

Boron deficiency also caused the radial enlargement of cortical cells, especially of endodermis, but this enlargement was not accompanied by an increase in water imbibition. In the advanced stage of boron deficiency, the disintegration of tissue structure had occurred.

Primordia of lateral roots arose closely in root apices. Maturation of the vascular system, especially of the primary xylem, was exasperated abnormally, and frequently there occurred a differentiation of cambial layers close to the apical initials.

Anatomical effects of boron deficiency appeared particularly in the root apex and not clearly in the region of successive maturation. The results are discussed with regards to the role of boron in cellular growth at apical growing points.

The results are discussed with regards to the role of boron in cellular growth at apical growing points.     

水分状况及硼素营养对油菜苗期根系生长及硼营养效率的影响

采用温室盆栽试验 ,研究了不同土壤水分条件下施硼对油菜苗期根系生长、硼吸收、利用及其移动性的影响。结果表明 ,随土壤含水量、施硼量的下降 ,油菜根长、根体积、根系生长速率、根 /冠比减小 ,根系及地上部干物质积累降低 ,植株地上部硼浓度及含硼量下降。而硼利用效率、硼运移指数则随土壤含水量、施硼量的下降而升高。不同油菜品种的根系形态参数 (包括根长、根体积、根干重、根冠比及根系生长速率 )、硼利用效率及运移指数存在明显差异 ,即在相同条件下 ,V1根系较发达 ,硼利用效率、运移指数均高于V4 。研究认为 ,根系发达程度、硼利用效率及硼移动性大小是不同基因型油菜耐缺硼差异的重要因素。     

Root growth and N‐uptake activity of oilseed rape (Brassica napus L.) cultivars differing in nitrogen efficiency

Nitrate‐N uptake from soil depends on root growth and uptake activity. However, under field conditions N‐uptake activity is difficult to estimate from soil‐N depletion due to different loss pathways. We modified the current mesh‐bag method to estimate nitrate‐N‐uptake activity and root growth of two oilseed‐rape cultivars differing in N‐uptake efficiency. N‐efficient cultivar (cv.) ‘Apex' and N‐inefficient cv. ‘Capitol' were grown in a field experiment on a silty clayey gleyic fluvisol near Göttingen, northern Germany, and fertilized with 0 (N₀) and 227 (N₂₂₇) kg N ha^–1. In February 2002, PVC tubes with a diameter of 50 mm were installed between plant rows at 0–0.3 and 0–0.6 m soil depth with an angle of 45°. At the beginning of shooting, beginning of flowering, and at seed filling, the PVC tubes were substituted by PVC tubes (compartments) of the same diameter, but with an open window at the upper side either at a soil depth of 0–0.3 or 0.3–0.6 m allowing roots to grow into the tubes. Anion‐exchange resin at the bottom of the compartment allowed estimation of nitrate leaching. The compartments were then filled with root‐free soil which was amended with or without 90 mg N (kg soil)^–1. The newly developed roots and nitrate‐N depletion were estimated in the compartments after the installing period (21 d at shooting stage and 16 d both at flowering and grain‐filling stages). Nitrate‐N depletion was estimated from the difference between NO ‐N contents of compartments containing roots and control compartments (windows closed with a membrane) containing no roots. The amount of nitrate leached from the compartments was quantified from the resin and has been taken into consideration in the calculation of the N depletion. The amount of N depleted from the compartments significantly correlated with root‐length density. Suboptimal N application to the crop reduced total biomass and seed‐yield formation substantially (24% and 38% for ‘Apex’ and ‘Capitol’, respectively). At the shooting stage, there were no differences in root production and N depletion from the compartments by the two cultivars between N₀ and N₂₂₇. But at flowering and seed‐filling stages, higher root production and accordingly higher N depletion was observed at N₀ compared to N₂₂₇. Towards later growth stages, the newly developed roots were characterized by a reduction of root diameter and a shift towards the deeper soil layer (0.3–0.6m). At low but not at high N supply, the N‐efficient cv. ‘Apex’ exhibited higher root growth and accordingly depleted nitrate‐N more effectively than the N‐inefficient cv. ‘Capitol’, especially during the reproductive growth phase. The calculated nitrate‐N‐uptake rate per unit root length was maximal at flowering (for the low N supply) but showed no difference between the two cultivars. This indicated that the higher N‐uptake efficiency of cv. ‘Apex’ was due to higher root growth rather than higher uptake per unit of root length.