不同沙土配比对盆栽平邑甜茶的生长及~(15)N吸收、利用和损失的影响

以当年生盆栽平邑甜茶为试材,应用15↑N同位素示踪技术研究不同沙土配比（不加沙、沙/（沙＋土）=20%、40%、60%、80%、纯沙）对植株的生长及15↑N吸收、利用和损失的影响。结果表明：不同的沙土配比处理,平邑甜茶植株具有不同的生长状况及氮素吸收、利用和损失。沙土配比20%处理的植株生长量（株高、茎粗和总干重）最大（37.54 cm,3.457 mm和16.20 g）,60%处理的全氮和15↑N吸收量最大,分别为189.31,32.39 mg,20%～60%处理下的生长量与氮素吸收、利用要显著高于不加沙和高沙处理（沙土配比〉60%）。各处理的Ndff值和15↑N分配率均为地上部〉地下部,20%～80%处理的植株各部分Ndff值随沙土配比的增大而增大。土壤中15↑N残留量与土壤沙土配比大小呈负相关,随着沙土配比增大,氮素总损失呈现增大的趋势。平邑甜茶植株生长和养分吸收、利用与土壤质地密切相关,适宜的沙土配比有利于植株的生长和氮素吸收、利用,较高的沙土配比加剧了土壤氮素损失。     

供磷水平对平邑甜茶幼苗NO3-吸收、利用特性的影响

运用~(15)N示踪及非损伤微测技术,研究了不同供磷水平(0 mmol×L~(-1)、1.0 mmol×L~(-1)、2.0 mmol×L~(-1)、3.0 mmol×L~(-1)、4.0 mmol×L~(-1)、6.0 mmol×L~(-1)、8.0 mmol×L~(-1)、12.0 mmol×L~(-1)和16.0 mmol×L~(-1) H_2PO_4~-)对平邑甜茶幼苗NO_3~--N吸收及利用特性的影响,为提高果园氮肥利用效率提供理论依据。结果表明,在低磷水平(0~1.0 mmol×L~(-1))时,平邑甜茶根系长度、根系总表面积较小,且根尖数较少。随着供磷水平的增加,在2.0~4.0 mmol×L~(-1)磷浓度处理时,平邑甜茶幼苗生物量、根系长度、根系总表面积及根尖数显著高于其他处理。而在6.0~16.0 mmol×L~(-1)时,过量供磷抑制了根系的生长,使平邑甜茶幼苗根系长度、表面积均大幅降低,根尖数量骤降。非损伤扫描离子选择电极测试表明,当生长介质磷浓度在3.0~6.0 mmol×L~(-1)时,平邑甜茶对NO_3~-有吸收作用,并在3.0 mmol×L~(-1)磷浓度时其吸收速率最高。而在0~2 mmol×L~(-1)及8.0~16.0 mmol×L~(-1)磷浓度处理下,平邑甜茶对NO_3~-有外排作用。随供磷水平的增加,各器官从肥料中吸收分配到的~(15)N量对该器官全氮量的贡献率(Ndff)及植株氮素利用率呈现先升高后降低的趋势,4.0 mmol×L~(-1)磷浓度时植株氮素利用率最大,为42.24%,超过4.0 mmol×L~(-1)植株氮素利用率显著降低。适当充足的供磷刺激了幼苗根系生长,从而促进平邑甜茶对氮素的获取,过量的NO_3~-抑制了平邑甜茶根系的生长,同时叶片硝酸还原酶的活性受到抑制,因此其氮素吸收和利用效率较低。因此,磷浓度在3.0~4.0 mmol×L~(-1)时最有利于平邑甜茶幼苗的生长及氮素的吸收利用。     

不同剂量VB6、COB对苹果幼树生物学性状和理化性质的影响

以富士/平邑甜茶(M.hupehensis)二年生幼树为试材,研究盆栽条件下土壤中施加不同剂量的维生素B_6(VB_6)和复合维生素B(C_OB)对苹果幼树生物学性状和理化性质的影响。于2016年在山东农业大学园艺科学与工程学院果树根系实验室进行富士苹果盆栽试验。5月26对富士苹果土施VB_6、C_OB,剂量分别为0,0.02,0.03,0.04g/株。6—10月测定外源维生素条件下苹果幼树株高、茎粗,叶面积,叶片抗氧化酶活性,叶绿素相对含量,光合荧光参数以及根系的生长分布状况。研究表明,不同剂量VB_6和C_OB对苹果幼树株高、茎粗,植株生物量,叶面积,叶片抗氧化酶活性,光合荧光参数和根系分布情况有不同程度的影响。盆施不同剂量VB_6、C_OB显著改善了植株生长势,叶面积以VB_6 0.03g增加最显著为22%,植株地上部分以C_OB 0.04g处理对植株株高、茎粗和新梢长度增加最显著,株高、茎粗和新梢长度在10月相比对照分别增加了24%,34%和45%,VB_6 0.03g与C_OB 0.04g两处理间无显著性差异;地下部分,VB_6 0.03g与C_O B 0.04g两处理对根系干鲜重、总长度、总体积和总表面积增加尤为显著,根尖数和根系分叉数也显著增加。VB_6 0.02g和C_OB 0.02g剂量下苹果幼树叶片抗氧化酶活性相比对照无显著性差异,VB_6 0.03g与C_OB 0.04g植株抗性得到显著性增强,抗氧化酶活性显著提高。此外,苹果幼树叶片叶绿素相对含量显著提高、光合荧光特性也得到显著性改善,且VB_6 0.03g与C_OB 0.04g两处理间无显著性差异。综合研究结果,VB_60.03g/株和C_OB 0.04g/株对苹果幼树的生物学性状和理化性质影响最显著,鉴于C_OB的有效施用剂量和市场价格均高于VB_6,推荐施用VB_6来改善土壤营养条件。     

苹果发酵液对Fe2+的螯合能力及对缺铁平邑甜茶幼苗的影响

本试验研究了苹果发酵液对二价铁的螯合能力,并以平邑甜茶（Malus hupehensis var. pingyiensis）幼苗为试材,研究了平邑甜茶幼苗根系对铁的吸收效应以及发酵液和FeSO4混合施用后,对缺铁平邑甜茶幼苗株高和干粗的增长率、 鲜、 干重根冠比、 全量铁与活性铁含量、 叶绿素及净光合速率的影响。结果表明,当苹果发酵液pH为5.5时,对Fe2+的螯合能力最强,其与FeSO4混合根施后,能促进平邑甜茶幼苗根系对铁的吸收; 发酵液300倍稀释液和FeSO4混合处理对缺铁平邑甜茶幼苗株高和干粗的增长率、 鲜、 干重根冠比、 活性铁含量、 叶绿素含量及净光合速率的提高最为显著。由试验结果推论,苹果发酵液具有较强的Fe2+螯合能力,有利于苹果幼苗对Fe2+的吸收,并能有效地改善缺铁植株叶片的光合效率。     

低磷胁迫下五种苹果砧木的磷吸收与利用特性

【目的】磷是植物必需的矿质元素之一,能够促进植株花芽分化,但施入土壤中的磷易被固定从而变成难以利用的闭蓄态磷,使土壤中的有效磷含量降低。因此,研究和发掘磷高效的苹果砧木对于解决低磷胁迫和提高磷利用效率具有重要意义。本研究以5种一年生苹果野生砧木为试材,进行低磷胁迫处理,调查苹果野生砧木对磷的吸收和利用特性。【方法】盆栽试验以正常管理的一年生八棱海棠（M. micromalus Makino）、 平邑甜茶（Malus hupehensis Rehd.）、 东北山荆子（M. baccata Borkh.）、 富平楸子［M. prunifolia（Willd）Borkh.］、 新疆野苹果［M. sievesii（Ledeb.）Roemer］5种苹果砧木为试材。试验分为低磷（LP）和正常施磷（CK）两组处理,每个处理6次重复（6盆）。根总表面积、 根系总长度分析用WinRHIZO 根系分析软件进行; 植株各器官组织烘干粉碎后,用钒钼黄比色法测定其含磷量。离子吸收动力学参数的测定采用平邑甜茶水培幼苗,吸收前置于黑色培养瓶饥饿处理24 h,幼苗吸收24 h后采集营养液10 mL,钼锑抗比色法测定含磷量。【结果】5种砧木的相对磷效率从高到低为富平楸子（93.66%）平邑甜茶（87.69%）东北山荆子（83.44%）八棱海棠（74.54%）新疆野苹果（74.01%）。在低磷及正常施磷条件下,5种砧木的磷吸收效率均为富平楸子平邑甜茶东北山荆子新疆野苹果八棱海棠; 磷利用效率为平邑甜茶富平楸子八棱海棠新疆野苹果东北山荆子。H2PO-4离子最大吸收速率（Vmax）最高的为富平楸子［101.81 mol/(gh)］,其次为平邑甜茶［66.40 mol/(gh)］、 东北山荆子［45.00 mol/(gh)］和新疆野苹果［44.32 mol/(gh)］,八棱海棠的Vmax最低,为41.28 mol/(gh); 平邑甜茶的Km值最低,为4.05 mol/L,富平楸子为8.68 mol/L,东北山荆子为12.29 mol/L,新疆野苹果为12.64 mol/L,八棱海棠最高为13.57 mol/L。吸收根总表面积和总根长均以富平楸子最大,八棱海棠最小。【结论】低磷胁迫下富平楸子的相对磷效率和磷吸收效率最高,在低磷胁迫下生长势最好并且磷吸收能力最强,是一种对低磷胁迫适应能力较好的苹果砧木; 平邑甜茶的相对磷效率仅次于富平楸子,磷利用效率最高,其耐低磷胁迫的能力也仅次于富平楸子。进一步分析发现,砧木对磷的吸收效率与吸收根总表面积和总根长存在显著正相关关系,说明低磷胁迫下植物通过增加吸收根总表面积及总根长等方式,扩大根系吸收面积,从而增加根系对磷的吸收。     

不同施肥模式对桃幼树根系生长与氮素吸收分配的影响

采用盆栽试验,应用15 N同位素示踪技术,研究了不同施肥模式对桃幼树根系生长与氮素吸收分配的影响。结果表明,与不施肥(CK)相比,单施化肥(MF)、生化黄腐酸钾配施化肥(BFA)及有机肥配施化肥(OF)3种施肥模式均显著提高了根系总长度、平均直径、根系表面积、根系体积、根尖数、分枝数和交叉数,其中BFA处理显著提高了根系平均直径,OF处理增加根系生物量的效果最好,并且OF处理更有利于诱导细根(d≤2mm)的发生和生长,而BFA处理更有利于诱导根系的加粗生长,增加中粗根(2mmd≤4.5mm)和粗根(d4.5mm)的长度。BFA处理的根系活力显著高于其它各处理,且根系SOD、POD、CAT酶活性显著高于其它处理,MDA含量显著低于其它处理,表现为BFA处理延缓根系衰老效果最好。不同施肥模式处理的桃幼树各器官Ndff%差异显著,BFA处理各器官Ndff%显著高于其它处理。BFA处理的15 N利用率为13.53%,显著高于OF(11.77%)和MF(10.60%)处理。不同施肥模式处理均在一定程度上促进了桃幼树地上部的生长,且BFA处理更能显著促进地上部新梢的加粗和加长生长,这与BFA处理对根系加粗生长的影响表现出一致性。综上可见,生化黄腐酸钾配施化肥(BFA)能显著促进根系生长,促进根系加粗生长,增加粗根的长度,提高根系活力,延缓根系衰老进程,同时还能显著提高根系氮素利用效率,促进桃幼树地上部的生长。     

不同施氮水平苹果矮化中间砧幼树光合产物的周年分配利用

【目的】光合产物在树体内的利用、分配状况直接影响着果树的产量形成,是果树优质、丰产、稳产的重要因素。氮肥的不合理施用易导致树体C/N失衡,造成树体旺长或早衰,直接影响果树的产量、品质形成。因此,研究矮化中间砧苹果在不同氮水平下的光合产物利用、分配特性,为合理协调光合产物在树体内的利用、分配以保证果树稳健生长又及时成花结果打下理论基础。【方法】以生产上最常用的2年生烟富3/M26/平邑甜茶幼树为试材进行盆栽试验。设置不施氮肥(N0)、适宜施氮肥(N100)和过量施氮肥(N200)3个氮素水平,分别于春梢生长期、春梢停长期、秋梢生长期进行13C标记,标记72 h后取样,整株解析为叶、一年生枝条、主干、中间砧、根系,测定了其13C丰度,玉米素核苷(ZR),脱落酸(ABA),可溶性淀粉含量,并测定了叶面积和叶绿素含量。【结果】与N0相比,不同物候期适宜施氮肥(N100)和过量施氮肥(N200)处理均显著促进树体生物量的增加,提高叶片面积和叶绿素含量,N100处理对树体生长的促进作用随着氮肥施入时间的延长逐渐显现。春梢生长期和春梢停长期,N100处理细根生长量最高,其次是N200处理,N0处理最低;至秋梢生长期,N0处理细根生物量迅速升高至最高且显著高于N200处理。N0处理在不同生长期叶片淀粉含量均显著高于N100和N200处理。氮肥施入初期,叶片ZR含量为N200N100N0,施肥30天后,N100处理叶片仍保持较高的ZR含量,但N200处理ZR含量显著下降。氮肥施入初期各处理ABA含量无显著差异,随着生育期延长差异性逐渐显著,施肥后30天,N0处理的叶片ABA含量达到最高并保持较高水平至生长后期。不同施氮处理树体根冠比和光合产物分配规律在不同生长期差异显著。氮肥施入至春梢生长期,N100和N200处理根系13C分配率分别是N0处理的285.35%和217.98%,而N0处理树体会将更多的光合产物用于地上部生长;至春梢停长期N100和N200处理仍保持较高根冠比和根系13C分配率;至秋梢生长期,N0处理根系光合产物分配率升高,而N100和N200处理根系13C分配率分别降低至N0处理根系13C分配率的71.98%和41.26%,表明生长后期N0处理生长中心逐渐向根系转移。【结论】施氮水平对苹果矮化中间砧幼树生长及光合产物利用方式和分配规律的显著影响与玉米素核苷和脱落酸的合成变化密切相关。施氮通过促进ZR大量合成显著促使光合产物向根系大量分配,周年尺度上表现为树体根冠比和根系生物量显著升高,树体地上部快速生长。整个生长期内低氮条件下树体光合产物转化为淀粉在叶片中大量贮存是由ABA的合成差异所造成。     

生物炭介导下磷水平对连作苹果幼苗及土壤环境的影响

苹果连作障碍是制约苹果产业可持续发展的重要因素之一。研究生物炭介导下不同施磷水平对连作条件下平邑甜茶幼苗生物量、根系呼吸速率和土壤环境的影响,探讨生物炭配施磷肥这种措施对苹果连作障碍的防控效果,并筛选出合适磷肥用量,为生产中老果园改造提供理论依据。盆栽条件下,以苹果常用砧木-平邑甜茶为试材,设计了连作土壤(CK)、连作土用溴甲烷熏蒸处理(F)、连作土+2%生物炭(B)、连作土+2%生物炭+0.5‰磷肥(BP0.5)、连作土+2%生物炭+1‰磷肥(BP1)和连作土+2%生物炭+2‰磷肥(BP2)6个处理。采用常规方法测定了不同处理对平邑甜茶幼苗生物量、根系呼吸速率、土壤养分和土壤酶活性的影响。结果表明:溴甲烷灭菌后,幼苗的株高、地径、鲜重和干重均远远高于连作土,分别是连作土中幼苗的1.6,1.5,2.9,2.5倍,幼苗的根系呼吸速率及保护酶也远远高于对照和其他处理。生物炭、或者生物炭配施磷肥,均可提高平邑甜茶幼苗的生物量,幼苗的株高、地径、鲜重和干重分别是连作土中幼苗的1.2,1.1,1.6,1.4倍和1.4,1.2,2.2,1.9倍,2种处理的根系呼吸速率也有大幅度提高;生物炭配施0.5‰磷肥可明显提高幼苗根系SOD、POD和CAT酶活性,同时降低MDA含量;与对照相比,生物炭配施0.5‰磷肥能明显提高土壤中有机质含量,增加硝态氮和速效磷的含量,促进土壤中脲酶、蔗糖酶和磷酸酶的活性。综合分析比较,生物炭配施0.5‰磷肥相比于单施生物炭,能更好的提高连作条件下平邑甜茶幼苗的生长发育,增加土壤有机质含量,增强土壤酶活性。因此,生物炭配施磷肥这一综合措施能更好的防控苹果连作障碍。     

不同施氮水平对烟富3/M26/平邑甜茶幼树当年及翌年氮素吸收、利用、分配的影响

以2年生烟富3/M26/平邑甜茶幼树为试材,研究了不同施氮水平对苹果矮化中间砧幼树当年及翌年15N 吸收、 利用和分配的影响。结果表明,适量施氮肥利于幼树生长和氮肥利用率的提高,更利于翌年树体生长及氮肥利用率的提高。以不施氮肥（N0）处理为对照,适量施氮肥（N100）或过量施氮肥（N200）条件下均通过促进根系生长进而促进地上部生长,且 N100处理对地上部生长的促进作用较N200更为显著。氮肥施入至春梢旺长期和春梢停长期,N100处理对根系生长的促进作用显著,根冠比由高到低分别为 N100＞N200＞N0,且春梢旺长期根系15N 分配率为 N100(42.93%)＞N200(37.10%)＞N0(26.39%),春梢停长期各处理根系15N分配率由高到低仍为 N100(28.61%)＞N200(20.30%)＞N0(14.27%)。至秋梢旺长期,N100处理生长势显著高于N0,但各器官15N分配率无显著差异;N100与N200处理树体生长势无显著差异,但N100处理地上部15N分配（85.93%）显著高于N200处理(77.28%),根系15N 分配率(14.07%)显著低于N200 处理(22.72%)。至翌年春梢旺长期,N100树体生物量迅速增高至N0 的175.83% 和N200 的176.41%,根冠比和根系15N 分配率显著低于N0和 N200。N200处理始终保持较高的根冠比和根系15N分配率但不利于地上部生长。冬季叶片脱落是苹果矮化中间砧幼树最大的氮流失途径,流失量为当年氮吸收量的44.56%~51.25%。     

不同钾肥种类对苹果产量、 品质及耐贮性的影响

【目的】苹果需钾量高,而果农普遍忽视钾肥的施用,随近年来密植栽培的推广,苹果单产大幅提升,使得陕西苹果园土壤面临缺钾现状,故合理补充钾肥对苹果生产至关重要。本文通过比较两种钾肥(KCl与K2SO4)对树体生长、 矿质养分吸收、 果实产量品质及采后贮藏特性的影响,为苹果树钾肥的合理施用提供科学指导。【方法】以陕西凤翔8年生红富士苹果树为研究对象,连续两年(2011~2013)对果树进行3种施肥处理,分别为不施钾(CK)、 KCl和K2SO4。在果树生长期间测定新梢生长量、 新梢叶片及果实矿质元素含量、 果实产量品质并定期测定采后贮藏期果实品质的变化(包括硬度、 可溶性固形物、 可滴定酸、 腐烂率)。【结果】1)CK、 KCl、 K2SO4 3个处理的平均新梢生长量分别为18.25 cm、 17.83 cm、 19.39 cm,无显著差异。与CK相比,施KCl 和K2SO4 7月中旬新梢叶片的氮、 磷含量均有所提高,其中K2SO4处理的叶片氮、 磷含量显著高于CK,但钙、 镁含量降低。2)年均苹果产量表现为KCl K2SO4CK,且3者之间差异显著。3)CK、 KCl、 K2SO4的年均单果重分别为267.42 g、 304.72 g、 287.73 g,其中KCl处理的单果重显著高于其它处理。施用KCl和K2SO4,横径80 mm以上的果实比例分别比CK提高14.9%和11.5%; 4)与对照相比,两种钾肥均提高了果实的氮、 磷含量和累积量,且KCl处理果实氮、 磷累积量高于K2SO4。果实中的钾含量和累积量3个处理之间无显著差异。施钾与对照相比均降低了果实中的钙、 镁含量及累积量。5)施钾与否对果实采收时的硬度无显著影响,但施钾可提高果实的可滴定酸、 可溶性糖及Vc含量。在室温下贮藏,90 d内不同处理果实可滴定酸含量降低,并趋势一致; KCl和K2SO4处理可溶性固形物含量呈上升趋势,而不施钾处理的可溶性固形物逐渐降低。贮藏结束后,果实软化率CK、 KCl、 K2SO4分别为19.23%、 6.96%、 22.19%,腐烂率分别为11.11%、 9.25%、 5.55%。【结论】短期内施KCl肥在增加产量,促进果实膨大,改善采收时果实品质方面效果稍好于K2SO4; 而K2SO4在促进新梢生长、 树体养分吸收,提高果实贮藏性能方面优于KCl。     

Adaptive attributes of tropical forage species to acid soils I. Differences in plant growth,nutrient acquisition and nutrient utilization among C4 grasses and C3 legumes

Low supply of nutrients is a major limitation of forage adaptation and production in acid soils of the tropics. A glasshouse study was conducted to find differences in plant growth, nutrient acquisition and use, among species of tropical forage grasses (with C₄ pathway of photosynthesis) and legumes (with C₃), when grown in two acid soils of contrasting texture and fertility. Twelve tropical forage legumes and seven tropical forage grasses were grown in sandy loam and clay loam Oxisols at low and high levels of soil fertility. After 83 days of growth, dry matter distribution among plant leaves, stems, and roots, leaf area production, shoot and root nutrient composition, shoot nutrient uptake, and nutrient use efficiency were measured. Soil type and fertility affected biomass production and dry matter partitioning between roots and shoots. The allocation of dry matter to root production was greater with low soil fertility, particularly in sandy loam. The grasses responded more than the legumes to increased soil fertility in both shoot and root biomass production. Leaf area production and the use of leaf biomass for leaf expansion (specific leaf area) were greater in legumes than in grasses, irrespective of soil type and fertility. But soil type affected shoot biomass production and nutrient uptake of the grasses more than those of the legumes. There were significant interspecific differences in terms of shoot nutrient uptake. The grasses were more efficient than legumes in nutrient use (grams of shoot biomass produced per gram of total nutrient uptake) particularly for nitrogen (N) and calcium (Ca).     

施用磷、钙对红壤上胡枝子生长和矿质元素含量的影响

采用红壤土培试验,研究了施用P、Ca对耐Al性不同的两个胡枝子品种的生长和矿质元素含量的影响.结果表明,单独 +P处理显著增加了耐Al 品种根和地上部生物量,而对Al敏感品种无影响;单独 +Ca处理显著促进了Al敏感品种根部的生长,而对耐Al品种的生长无影响;+P+Ca处理显著增加了两个品种根和地上部生物量.耐性品种地上部Al含量显著低于敏感品种,而根部Al含量无显著差异.两个品种体内P含量在 +P处理时耐性品种显著高于敏感品种,其他处理品种间无显著差异.整体上,胡枝子体内Ca、K、Mn和Mg含量耐性品种大于敏感品种,Fe含量反之.结果表明,低P胁迫是酸性土壤上耐Al胡枝子品种生长的主要限制因子,增施P肥效果明显,而对于Al敏感品种,Al毒是其生长的首要限制因子,只有施用石灰后对其加P,生物量才能提高.耐性品种根部有阻碍Al 向地上部运输的机制,而这种机制与体内P含量较高有着直接或间接的关系.另外,推测耐Al胡枝子品种对其他养分的吸收利用能力也较强.     

Effects of excess aluminum on mineral uptake in mycorrhizal sorghum

Soil acidity is often associated with toxic aluminum (Al), and mineral uptake usually decreases in plants grown with excess Al. This study was conducted to evaluate the effects of Al (0, 35, 70, and 105 μM) on Al, phsophorus (P), sulfur (S), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), zinc (Zn,) and copper (Cu) uptake in shoots and roots of sorghum [Sorghum bicolor (L.) Moench, cv. SC283] colonized with the vesicular‐arbuscular mycorrhizal (VAM) fungi isolates Glomus intraradices UT143–2 (UT143) and Glomus etunicatum UT316A‐2 (UT316) and grown in sand (pH 4.8). Mycorrhizal (+VAM) plants had higher shoot and root dry matter (DM) than nonmycorrhizal (‐VAM) plants. The VAM treatment had significant effects on shoot concentrations of P, K, Ca, Fe, Mn, and Zn; shoot contents of P, S, K, Ca, Mg, Fe, Mn, Zn, and Cu; root concentrations of P, S, K, Ca, Mn, Zn, and Cu; and root contents of Al, P, S, K, Ca, Mg, Fe, Mn, Zn, and Cu. The VAM effects on nutrient concentrations and contents and DM generally followed the sequence of UT316 > UT143 > ‐VAM. The VAM isolate UT143 particularly enhanced Zn uptake, and both VAM isolates enhanced uptake of P and Cu in shoots and roots, and various other nutrients in shoots or roots.     

Biochar properties and soil type drive the uptake of macro‐ and micronutrients in maize (Zea mays L.)

The use of biochar in agriculture is a promising management tool to mitigate soil degradation and anthropogenic climate change. However, biochar effects on soil nutrient bioavailability are complex and several concurrent processes affecting nutrient bioavailability can occur in biochar‐amended soils. In a short‐term pot experiment, the concentration of N, P, K, S, Ca, Mg, Cu, Zn, Mn, B, Fe, and Na in the shoots of maize grown in three different soil types [sandy soil (S1), sandy loam (S2), and sandy clay loam (S3)] was investigated. The soils were either unamended or amended with two different biochars [wheat straw biochar (SBC) or pine wood biochar (WBC)] at two P fertilizer regimes (–/+ P). We used three‐way ANOVA and Principal Component Analyses (PCA) of transformed ionomic data to identify the effects of biochar, soil, and P fertilizer on the shoot nutrient concentrations. Three distinct effects of biochar on the shoot ionome were detected: (1) both biochars added excess K to all three soils causing an antagonistic effect on the uptake of Ca and Mg in maize shoots. (2) Mn uptake was affected by biochar with varying effects depending on the combined effect of biochar and soil properties. (3) WBC increased maize uptake of B, despite the fact that WBC increased soil pH and added additional calcite to the soil, which would be expected to reduce B bioavailability. The results of this study highlight the fact that the bioavailability of several macro and micronutrients is affected by biochar application to soil and that these effects depend on the combined effect of biochar and soils with different properties.     

有机肥缓解小麦铝毒效果的研究

以交换性Al为1.83［1／3Al3+］cmol／kg的淋溶型水田砂质土（低Al毒）和交换性Al为6.05［1／3Al3+］cmol／kg的黄筋泥（红壤,高Al毒）为供试土壤,研究了有机肥对缓解小麦铝毒的效果。盆栽试验（均有充足N、P、K基肥）结果表明,小麦（扬表5号）在这两种土壤上均发生Al毒。在前一种土壤上生育不良,减产约一半左右,后一种土壤上几近绝收。施用生产中常量猪厩肥（约22.5／hm2）,与施用石灰比较,在低Al毒土壤上,产量接近施石灰处理（90％～100％）,能基本消除Al毒;在高Al毒土壤上,同样表现出一定的解Al毒效果,但还不够明显,产量只为石灰处理的1／4。土壤测定表明,施用猪厩肥使交换性Al下降18.1％～38.7％。植株分析也表明,吸收的Al相应减少。土壤Al毒明显抑制小麦对K、Ca、Mg的吸收;对S则有促进吸收的趋势;对N、P、Fe、Zn的吸收影响不大。在Al毒土壤上施用猪厩肥,不仅降低Al的吸入,并可减缓Al对小麦Ca、Mg、K吸收的抑制作用,有利于体内营养元素间的平衡。     

Influence of soil strength on root growth: experiments and analysis using a critical-state model

Roots grow thicker in compacted soil, even though it requires greater force for a large object to penetrate soil than it does for a small one. We examined the advantage of thickening in terms of the stresses around a root penetrating with constant shape, rather than the stresses around an expanding cylinder or sphere, as has been studied previously. We combined experiments and simulations of the stresses around roots growing in compacted soils. We measured the diameter of pea roots growing in sandy loam and clay loam at four different densities, and the critical‐state properties of the soils. At a penetration resistance of about 1 MPa the diameter of the roots in the sandy loam was about 40% greater than that at 0.7 MPa, and at 2 MPa it was about 60% greater. In the clay loam, there was less thickening – about 10% greater at 1 MPa and about 20% greater at 1.5 MPa. The maximum axial stresses were predicted using a critical‐state finite‐element model to be at the very tip of the root cap. When there was friction between the root and the soil, shear stresses were predicted with smaller values at the tip than just behind the tip. When the interface between the soil and the root was assumed to be frictionless, there were by definition no shear stresses. In the frictionless case the advantage of root thickening on relieving peak stress at the root tip was diminished. The axial and shear stresses were predicted to be smaller in the clay loam than in the sandy loam and may explain why the roots did not thicken in this soil although its resistance to penetration was similar. Our results suggest that the local values of axial and shear stresses experienced by the root near its tip may be as important in constraining root growth as the total penetration resistance.     

有机肥对小麦根系生长及根系衰老进程的影响

采用土柱栽培与室内分析相结合的方法,研究了有机肥对小麦根系生长及根系衰老进程的影响。结果表明,有机肥可促进小麦根系的生长和根系在深层土壤中的分布,使小麦根系的总鲜重和深层土壤根系鲜重明显增加;提高不同土层、特别是深层土壤中根系的活力,使小麦生长后期保持较高的根系吸收养分的能力。有机肥可促进根系对氮、磷、钾的吸收和向子粒中的转移,使氮、磷、钾在子粒中的分配量增加;而且能抑制根系的膜脂过氧化作用,使不同土层小麦根系SOD活性提高、MDA含量降低,从而延缓了根系的衰老。     

Differential response of citrus rootstocks to aluminum levels in nutrient solutions: II. Plant mineral concentrations 2

The objective of this study was to determine relations between Al effects and mineral concentrations in citrus seedlings. Six‐month‐old seedlings of five citrus rootstocks were grown for 60 days in supernatant nutrient solutions of Al, P, and other nutrients. The solutions contained seven levels of Al ranging from 4 to 1655 μM. Al and similar P concentrations of 28 μM P. Aluminum concentrations in roots and shoots increased with increasing Al concentration in the nutrient solution. Aluminum concentrations in roots of Al‐tolerant rootstocks were higher than those of Al‐sensitive rootstocks. When Al concentrations in nutrient solution increased from 4 to 178 μM, the K, Mg, and P concentrations in roots and the K and P levels in shoots increased. Conversely, Ca, Zn, Cu, Mn, and Fe in the roots and Ca, Mg, Cu, and Fe in the shoots decreased. The more tolerant rootstocks contained higher Fe concentrations in their roots than did the less tolerant ones when Al concentrations in solution were lower than 308 μM. Concentrations of other elements (Ca, K, P, Mg, Zn, and Mn) in roots or shoots exhibited no apparent relationship to the Al tolerance for root or shoot growth of the rootstocks. Calcium, K, Zn, Mn, and Fe concentrations in roots and Mg and K concentrations in shoots of all five rootstocks seedlings had significant negative correlations with Al concentrations in corresponding roots or shoots.     

Influence of thigmic stress or chlormequat chloride on tomato morphology and elemental uptake

Root dry weight and leaf number were not affected by thigmic stress or chlormequat chloride. Shoot dry weight, shoot:root dry weight ratio, shoot height, leaf area, and root surface area were decreased by both thigmic stress and chlormequat chloride. However, root length was decreased and root radius increased only by chlormequat chloride. Total element uptake was decreased by both thigmic stress and chlormequat chloride. In the shoot and root, N was not affected, P was increased in the shoots, K decreased in the shoots but increased in the roots, and Mg decreased in the roots as a result of thigmic stress and chlormequat chloride. Whereas, Ca was decreased in the roots and Mg increased in the shoots by chlormequat chloride. The uptake of N, P, Ca, or Mg was not affected by thigmic stress or chlormequat chloride, however, K uptake per root surface area decreased. Thigmic stress decreased K in both the upper and lower stem but did not affect leaf concentration of K. However, chlormequat chloride decreased K in both the stem and leaves. Thigmic stress because of the role of K in cell elongation. Chemical name used: (2‐chloroethyl)trimethyl‐ammonium chloride (chlormequat chloride).     

The effect of salinity and iron application on growth and mineral uptake of sunflower (helianthus annuus L.)

In a greenhouse experiment, the effect of salinity and Fe chelate on growth and mineral uptake of sunflower (Helianthus annuus L. c.v. Record) was studied.

Sunflower plants were grown in nutrient solution with four levels of salinity (0, 1.5, 3.0 and 4.5 atm), induced by NaCl and four rates of Fe chelate (0, 0.5, 1.0 and 1.5, ppm Fe) as FeEDDHA. The experiment was a completely randomized design with treatment combinations arranged in a factorial manner with three replications.

Dry matter yield, shoot‐root ratio, leaf area, plant height and transpiration decreased as salinity increased, the effect of salinity being depressed by iron applications. Salinity reduced P, K, Ca and Mg uptake by roots as well as that of N, P, K, Ca, Mg by shoots, while Fe applications increased uptake of these elements in roots and shoots. Both salinity and iron applications increased Cl, Na and Fe uptake by roots and shoots, as expected. In most instances salinity reduced uptake of Fe, Mn and Zn by the plants while iron applications improved uptake of these elements.

The sunflower plant used in this experiment was found to be, at least partly, tolerant to salinity and decreased water availability as well as toxicity of ions. Nutritional disorders were the cause of decreased plant growth by increasing salinity of the nutrient solution. The decreased plant growth and mineral uptake, induced by salinity, were partially offset by increased iron levels in the nutrient solution.