不同水分条件对冬小麦根系时空分布、土壤水利用和产量的影响

为了明确华北严重缺水区晚播冬小麦灌水对根系时空分布和土壤水分利用规律的影响,以冬小麦石麦15为材料,利用田间定位试验研究了不同灌水处理(春季不灌水W0;春季灌拔节水75mm,W1;春季灌起身水、孕穗水和灌浆水共225mm,W3)对根系干重密度(DRWD)、根长密度(RLD)、体积密度、分枝数等在0—200cm土层的垂直分布、动态变化及其对耗水和产量的影响,结果表明:随着春季灌水量的减少,开花后0—80cm土层的根干重密度、根长度密度、体积密度和分枝数密度均显著减少,80cm—200m土层的根干重密度、根长度密度、体积密度和分枝数密度却显著增加,并且显著增加冬小麦在灌浆期间对100cm以下深层土层水分的利用,总耗水量W1和W0分别比W3减少70.9mm、115.1mm,土壤耗水量分别比W3增加79.1mm、108.9mm,子粒产量W1和W0分别比W3减少653.3kg/hm2、1470kg/hm2,水分利用效率(WUE)则分别比W3提高0.09kg/m3、0.06kg/m3。晚播冬小麦春季灌1水(拔节水)可以促进根系深扎,增加深土层的根系分布量,提高对深层土壤贮水的吸收利用量,有利于实现节水与高产的统一。     

不同耕作措施对冬小麦根系时空分布和产量的影响

在田间定位试验的基础上,研究了内陆河绿洲灌区不同耕作措施对冬小麦根系时空分布和产量的影响.结果表明:免耕秸杆覆盖(NTS)和免耕立茬(NTSS)措施下冬小麦根系总干重和总根长都大于传统耕作(T),且差异显著;开花期各处理总根干重和总根长都达到最大,之后开始下降;NTS和NTSS处理0～10cm土层的根长密度和根干重密度显著高于T处理,表现出根系表层分布的特征;拔节期, NTS、NTSS和NT处理10～30cm的根长密度和干重密度都小于T,而拔节后NTS 和NTSS各土层根长密度和根干重密度增长幅度大于T.产量研究结果表明,NTS和NTSS能显著提高冬小麦产量,与T 相比,产量分别提高16.84%～30.59%和12.76%～24.32%.     

根修剪对黄土旱塬冬小麦(Triticum aestivum)根系分布、根系效率及产量形成的影响

通过田间试验研究了不同时期根修剪处理对冬小麦（Triticum aestivum）根系大小与分布、根系效率、水分利用效率及产量形成的影响。设置4个根修剪处理：越冬期小剪根（WS）、越冬期大剪根（WB）,返青期小剪根（GS）、返青期大剪根（GB）,未剪根小麦作为对照（CK）。结果表明,到花期时,各根修剪处理小麦的在0～120cm总根量均显著小于对照。与对照相比各根修剪处理主要是显著地减少了上层土壤中的根量。但WS和GS两小剪根处理和对照相比在中层土壤中有较大的根量;花后各处理小麦旗叶的气孔导度和蒸腾速率均显著大于对照。这说明根修剪处理减少了小麦表层的根量,从而削弱了表土干旱信号对作物与外界气体交换的抑制作用。花期时各根修剪小麦的净光合速率均显著高于对照,而单位面积上的根呼吸速率均显著小于对照,根修剪处理提高了小麦的根系效率,使更多的光合产物用于籽粒生产,从而提高了小麦的收获指数。根修剪还提高了小麦的水分利用效率,其中WS、WB、GS处理的水分利用效率显著高于对照。但是GB处理的水分利用效率却没有显著提高。因此,本研究进一步证明了由不同年代品种得到的推测,认为在旱地农业中,通过遗传育种或采用适当农艺措施优化根系分布,既可以减少生长前期作物对水分的过度消耗,又能够削弱花后表土过度干旱对作物生长抑制作用,同时降低根系对同化产物的消耗,对作物产量及水分利用效率的提高具有积极的作用。     

不同抗旱性冬小麦根系时空分布与产量的关系

为明确不同抗旱性冬小麦品种(Triticum aestivum L.)根系时空分布及其与产量的关系,以抗旱性品种长武134、长旱58和干旱敏感性品种小偃22、西农979为材料,采用根箱试验研究干旱胁迫和充分供水条件下4个品种在拔节期、开花期和成熟期根系总生物量、总根长密度、根系在表层(0—20 cm)和深层(20 cm以下)土壤中的垂直分布、动态变化及其对产量的影响。结果表明,干旱胁迫下抗旱性品种产量显著高于干旱敏感性品种,其中长旱58产量最高,西农979最低;充分供水条件下,西农979产量最高,长武134最低,长旱58与小偃22之间没有差异。相关分析表明,产量与各生育时期根系性状均有显著关系。多元逐步回归分析的结果显示,干旱胁迫和充分供水条件下,拔节期深层根生物量对产量有正效应,而成熟期总根长密度对产量表现为负效应。通径分析表明,干旱胁迫下,根系性状对产量的直接贡献大小为开花期总根长密度(|0.54|)拔节期深层根生物量(|0.36|)成熟期总根长密度(|-0.31|);充分供水时,成熟期总根长密度(|-1.56|)拔节期深层根生物量(|0.83|)。研究表明,减少成熟期总根长密度,增加拔节期深层根生物量对抗旱性及干旱敏感性冬小麦品种产量均有显著的正效应,增加开花期根长密度有利于提高抗旱性冬小麦产量。     

EFFECTS OF ROOT PRUNING AT THE REGREENING STAGE ON DROUGHT TOLERANCE AND WATER USE EFFICIENCY OF WINTER WHEAT IN LATE GROWING STAGE

 通过盆栽试验研究了返青期根修剪对冬小麦(Triticum aestivum)后期耐旱性及水分利用效率的影响。在返青期设置了两个根修剪处理: 1)小剪根, 在植株一侧切去部分侧生根; 2)大剪根, 在主茎四周切去部分侧生根。不剪根者设为对照(CK)。研究结果显示, 两个根修剪处理均显著减少了小麦的根系, 但对根冠比没有显著影响。在花期, 两个根修剪处理的小麦旗叶的叶绿素荧光参数最大光化学效率(The maximum photochemical efficiency of PSⅡ, F_v/F_m)、 PSⅡ潜在活性 (PSⅡ potential activity, F_v/F_o)、实际光化学量子产量(Effective PSⅡ quantum yield, Φ_PSⅡ)、表观光合电子传递速率(Apparent rate of photosynthetic electron transport, ETR)、光化学淬灭系数( Coefficient of photochemical quenching, q_P)和非光化学淬灭系数(Coefficient of non-photochemical quenching, NPQ)值, 在停止供水7 d后, 均显著高于对照, 这表明根修剪小麦的耐旱性强于对照, 因此在干旱胁迫下有较高的光化学活性。小剪根处理在高水条件下对小麦产量无显著影响, 而在中度干旱条件下显著提高了小麦的产量, 因此, 小剪根处理显著提高了小麦的抗旱系数; 小剪根处理在高水分处理(土壤水分含量为田间持水量的85%)和中度干旱胁迫处理(土壤水分含量为田间持水量的55%)条件下, 均显著提高了小麦的水分利用效率。但大剪根处理由于严重影响了群体数量和产量, 水分利用效率和抗旱系数均没有提高。可见, 适当地减少根系有助于小麦的耐旱性和水分利用效率的提高。     

冬小麦播种密度和施肥方式对麦田杂草群落组成及生长的影响

在半湿润地区的土垫旱耕人为土上,以冬小麦品种小偃22为指示作物,通过田间小区试验研究了不同施肥条件下冬小麦田间杂草种群的组成以及在4个生育期(越冬期、返青期、拔节期、成熟期)田间杂草密度和生物量的变化.结果表明:(1)在冬小麦全生育期内共发现以猪殃殃、麦家公、婆婆纳、播娘蒿、泽漆、荠菜等为主的17种杂草,不同生育期杂草的优势种群不同,而且杂草总密度表现为越冬期>返青期>拔节期,生物量表现为拔节期>返青期>越冬期;(2)与不施肥处理(P0N0)比较,单施氮肥增加了杂草密度和生物量,在氮磷配施条件下,氮肥对生物量有极显著影响且随施氮量增加表现为减小趋势,其中PN45处理的杂草生物量最大并比P0N0增加51.8%;施磷对杂草生物量有极显著影响,其中单施磷比P0N0处理增加44.0%,PN135处理比P0N135处理增加24.0%.(3)低密度播种比正常密度播种能显著增加杂草生物量,平均增加幅度达82.9%.结果表明,通过增施氮肥和适当增加种植密度,可在一定程度上控制杂草发生,促进作物良好生长.     

施氮和垄膜沟播种植对晋南旱地冬小麦水分利用的影响

通过2008—2010年两年的大田试验,研究了基施氮、追氮和垄膜沟播种植对晋南雨养区冬小麦生育期0～2m土层土壤水分、冬小麦产量和水分利用效率的影响.结果表明:不同处理下冬小麦生育期土壤水分变化趋势一致,表现为播前至返青期稳定升高,返青至抽穗期急剧降低,之后至成熟期又逐渐回升,其中返青期到抽穗期土壤耗水量最大.增施氮肥或追氮可增加土壤耗水量,试验年份生育期间土壤水分变幅较大的活跃层逐渐加深,水分变幅较小的相对稳定层也相对下移,追氮可显著提高旱地冬小麦产量.垄膜沟播种植可减少土壤水分损耗,提高水分利用效率,两年分别比传统种植模式高23.4%和39.1%(P<0.05).垄膜沟播+追氮处理的小麦籽粒产量为3643kg·hm-2,显著高于单一垄膜沟播处理和追氮处理,水肥耦合效应较好.     

黄土旱塬冬小麦返青期断根对根冠比、水分利用及产量的影响

采用适当的农艺措施来影响根系生长以提高作物水分利用效率是节水农业研究的一项重要内容。通过田间试验研究了旱作冬小麦‘长武135’(Triticum aestivum cv. Changwu135)返青期切断部分侧生根对根冠比、水分利用效率及产量的影响。与不断根处理相比,冬小麦切断部分侧根后,极显著地减少了表层的根量,花期时断根和不断根小麦在0~20 cm土层根量分别249.70和307.52 g·m^-2,100 cm以上总根量分别为305.53和368.73 g·m^-2。断根比不断根处理根呼吸速率下降了25.57%。断根也抑制了小麦的群体数量,断根和不断根处理单位面积的穗数分别为590.33和646.33 m^-2,但断根显著增加了千粒重,断根和不断根分别为45.99和41.47 g,收获指数也有一定提高。断根对籽粒产量没有显著影响,但断根后土壤含水量显著增加,水分消耗减少。以生物量计算的水分利用效率和以产量计算的水分利用效率分别提高了32.52%和29.98%。因此,在旱地农业中,通过返青期人工断根措施削减根系降低根系对同化产物的消耗和减少耗水量来达到提高冬小麦水分利用效率的方法,是可行的。但今后还需对断根措施作进一步研究,以期实现产量和水分利用效率的同步提高。     

基于双稳定同位素和MixSIAR模型的冬小麦根系吸水来源研究

灌溉和施肥措施对农田水文循环具有重要影响,根系吸水是联系植物蒸腾和土壤水分运动的关键水文过程,定量识别灌溉施肥影响下作物根系吸水来源对农业用水优化管理具有重要意义。氘氧稳定同位素(D和18O)是追溯农田水分运移过程的理想天然示踪剂。基于2013—2015年北京市典型农田不同灌溉施肥处理冬小麦水分运移试验,利用D和18O双稳定同位素和MixSIAR贝叶斯混合模型,量化冬小麦主要根系吸水深度及其贡献比例,阐明作物水分来源的季节变化及不同处理间的差异,分析根系吸水与土壤水分分布变化的相互关系。研究结果表明:两季冬小麦返青-拔节、拔节-抽穗、抽穗-灌浆和灌浆-收获期主要根系吸水深度均值分别为0—20 cm(67.0%)、20—70 cm(42.0%)、0—20 cm(38.7%)和20—70 cm(34.9%),但季节变化差异显著,2014季主要吸水深度随作物的生长发育而逐渐增加,2015季则主要集中于浅层土壤(0—70 cm)。返青-抽穗期仅灌水20 mm或施肥105 kg/hm2N促使拔节-抽穗期深层(70—200 cm)土壤水分利用率平均增加29%,而前期充分灌水且大量施肥(≥当地施肥量210 kg hm-2N)时拔节-抽穗期根系吸水深度为土壤表层0—20 cm。在干旱少雨的冬小麦生长季内作物吸水来源与土壤水分消耗变化基本一致。     

土壤深松和补灌对小麦干物质生产及水分利用率的影响

研究一次深松耕作后土壤水分对冬小麦籽粒产量和水分利用率的影响,为小麦节水高产栽培提供理论依据.于2008-2009和2009-2010两个小麦生长季,选用高产小麦品种济麦22,采取测墒补灌的方法,研究了深松+旋耕和旋耕2种耕作方式下土壤水分对小麦0-200 cm土层土壤含水量、干物质积累与分配、籽粒产量及水分利用率的影响.结果表明,(1)深松+旋耕40-180 cm土层土壤含水量低于旋耕处理;旗叶光合速率和水分利用率,开花后干物质积累量及其对籽粒的贡献率显著高于旋耕处理.(2)W3(补灌至0-140 cm土层土壤相对含水量播种期为85％,越冬期80％,拔节和开花期75％)成熟期0-200cm土层土壤含水量与W1(播种期80％,越冬期80％,拔节和开花期75％)和W2处理(播种期80％,越冬期85％,拔节和开花期75％)无显著差异;W3和W'3(播种期85％,越冬期85％,拔节和开花期75％)60-140 cm土层土壤含水量分别低于W4(播种期85％,越冬期85％,拔节和开花期75％)和W'4(播种期90％,越冬期85％,拔节和开花期75％)处理;W3和W'3灌浆中后期旗叶光合速率较高,开花后干物质积累量及其对籽粒的贡献率显著高于其他处理,获得高的籽粒产量和水分利用率.综合考虑籽粒产量、水分利用率和灌溉效益,在深松+旋耕条件下,两年度分别以W3和W'3为节水高产的最佳处理.     

Canine root development and morphology inMacaca nemestrina

Recently,Yoshikawa andDeguchi (1992) reported an unusually high frequency (40%) of two-rooted maxillary canines inMacaca fuscata females and a complete absence of this trait in males. In the present study, canine root development and morphology was examined using cephalographs taken on 50 male and 50 femaleMacaca nemestrina, and 20 male and 20 femalePapio cynocephalus for comparison with the Japanese macaque. The results showed no double-rooted canines present in either species in the upper or lower canines. This supports the general rule that, among primates, canines possess a single-root. It was further suggested that the two-rooted canines inM. fuscata may be the result of the founder effect, i.e. that the genes for this trait may have been carried by the initial populations when they arrived on the islands sometime during the middle to late Pleistocene.     

Intracellular magnetophoresis of amyloplasts and induction of root curvature

High-gradient magnetic fields (HGMFs) were used to induce intracellular magnetophoresis of amyloplasts. The HGMFs were generated by placing a small ferromagnetic wedge into a uniform magnetic field or at the gap edge between two permanent magnets. In the vicinity of the tip of the wedge the dynamic factor of the magnetic field, (H²/2), was about 10⁹ Oe² · cm^–1, which subjected the amyloplasts to a force comparable to that of gravity. When roots of 2-d-old seedlings of flax (Linum usitatissimum L.) were positioned vertically and exposed to an HGMF, curvature away from the wedge was transient and lasted approximately 1 h. Average curvature obtained after placing magnets, wedge and seedlings on a 1-rpm clinostat for 2 h was 33 ± 5 degrees. Roots of horizontally placed control seedlings without rotation curved about 47 ± 4 degrees. The time course of curvature and changes in growth rate were similar for gravicurvature and for root curvature induced by HGMFs. Microscopy showed displacement of amyloplasts in vitro and in vivo. Studies with Arabidopsis thaliana (L.) Heynh. showed that the wild type responded to HGMFs but the starchless mutant TC7 did not. The data indicate that a magnetic force can be used to study the gravisensing and response system of roots.Abbreviations HGMF high-gradient magnetic field - emu electromagnetic units - Oe Oersted We thank Dr. John Kiss, Miami University, Ohio for providing the Arabidopsis seeds. This work was supported by NASA grant NAGW-3656     

An unusual root tip formation in hairy root culture of Hyoscyamus muticus

Summary Hairy root cultures of Hyoscyamus muticus were established using Agrobacterium rhizogenes ATCC 15834. In one out of 8 clones established, an unusual root tip formation was observed after transfer of cultures from half-strength Murashige and Skoog (1962) to White's medium (1939). This phenomenon was associated with the production of a fine brownish cell suspension culture. Hairy root development resumed after transfer of the root tips from White to half-strength Murashige and Skoog medium. After plating the isolated brownish cells on hormone-free half-strength Murashige and Skoog or White solid medium, callus proliferation was observed, and then redifferentiation of hairy roots occurred. The polymerase chain reaction analysis of the H. muticus hairy root (clone Z2) revealed that only the tl region of the T-DNA was integrated. The growth and the production of five tropane alkaloids by this clone were examined.Abbreviations PCR Polymerase Chain Reaction - MS medium Murashige and Skoog Medium - 1/2 MS medium half-strength MS medium - WP medium Woody Plant medium - RC medium Root Culture medium - WH medium White medium - HPLC High Performance Liquid Chromatography - wt. weight     

1,8-Cineole inhibits root growth and DNA synthesis in the root apical meristem ofBrassica campestris L.

1,8-cineole is a volatile growth inhibitor produced bySalvia species. We examined the effect of this allelopathic compound on the growth of other plants usingBrassica campestris as the test plant. Cineole inhibited germination and growth ofB. campestris in a dosedependent manner. WhenB. campestris was grown for 5 days with various concentrations of cineole, the length of the roots was found to be shorter as the concentration of cineole increased, whereas the length of the hypocotyl remained constant up to 400 μM cineole, indicating that cineole specifically inhibited growth of the root. The mitotic index in the root apical meristem of 3-day-old seedlings decreased from 5.6% to 1.6% when exposed to 400 μM cineole, showing that cineole inhibits the proliferation of root cells. We then examined the effect of cineole on DNA synthesis by indirect immunofluorescence microscopy using antibody raised against 5-bromo-2′-deoxyuridine (BrdU, an analogue of thymidine) in thin sections of samples embedded in Technovit 7100 resin. The results clearly demonstrated that cineole inhibits DNA synthesis in both cell nuclei and organelles in root apical meristem, suggesting that cineole may interfere with the growth of other plant species by inhibiting DNA synthesis in the root apical meristem.     

Response of root and sediment phosphatase activity to increased nutrients and salinity

Wetlands of northern Belize, distributed along a salinity gradient, are strongly phosphorus limited and dominated largely by three species of emergent macrophytes: Eleocharis cellulosa, Cladium jamaicense, and Typha domingensis. We assessed changes in root and sediment phosphatase activities of each species to simultaneous changes of nutrients (N, P) and salinity in a mesocosm experiment. Phosphorus and nitrogen treatment effects on both root and sediment phosphatase were highly significant for all the species, while salinity significantly affected root phosphatase activity in Cladium only. All species showed a significant negative correlation between root phosphatase activity and increasing tissue P content until a threshold of 0.2% P, 0.15% P and 0.12% P in Eleocharis, Cladium and Typha, respectively. There was also a significant negative correlation between soil available P and root and sediment phosphatases in all species. Activity of root phosphatases of Eleocharis and Typha were positively correlated with root tissue N. Both root and sediment phosphatases of all three species were positively correlated with soil available N. The strongest (positive) correlation was found between phoshatase activites and N/P ratios. The results confirmed that these systems are P-limited and that extracellular phosphatases respond to P enrichment by decreasing their activities. Expression of root phosphatase activity by dry root weight, sediment volume, or whole plant biomass gave very different relative results across nutrient treatments and species, suggesting that root phosphatase activities need to be interpreted in a wider context that considers root density.     

Effects of irrigation frequency on germination and on root and shoot yields ofAcacia species

Summary Maximum germination response and root + shoot yields of Acacias were obtained at daily irrigation. Any deviation from daily irrigation resulted in variations of performance (germination and growth yield) between the six Acacia species studied. Species of relatively dry habitse.g. A. nubica andA. seyal were more sensitive to water supply compared with those of relatively wet habitatse.g. A. nilotica andA. albida. This was reflected at the establishment phase by the greater production of root + shoot yields of species of drier zones than by those of wetter ones. It is concluded that variations in water supply may account for species adaptation and distribution in semi-arid zones.     

Phage sensitivity and host range of Rhizobium strains isolated from root nodules of temperate legumes

Twenty-five Rhizobium strains were isolated from root nodules of Astragalus spp. (10), Hedysarum alpinum (7), Glycyrrhiza pallidiflora (3) and Ononis arvensis (5). The sensitivity of these strains to bacteriophages of Rhizobium loti, R. meliloti, R. galegae and R. leguminosarum was studied. Phages specific to R. loti strains were shown to induce the phage lysis of several Astragalus, Hedysarum and Ononis rhizobia. Ten R. loti strains tested for nodulation abilities on the plant hosts under investigation were able to develop nitrogen-fixing nodules on the Ononis arvensis roots. On the other hand, rhizobia from Ononis and Glycyrrhiza could form an effective symbiosis with Lotus corniculatus plants, so these bacteria are considered to belong to the Rhizobium loti taxon. Bacterial strains isolated from Astragalus and Hedysarum were observed to cross-nodulate their plant hosts as well as Oxytropis campestris, Glycyrrhiza uralensis and Ononis arvensis plants, whereas they could not nodulate Lotus plants. It is concluded that these Rhizobium strains comprise a cross-inoculation group related to Rhizobium loti. ei]{gnR O D}{fnDixon}     

Nitrogen in shoot litter,root litter and root exudates from nitrogen-fixingAlnus incana

Summary A pot experiment withAlnus incana (L.) Moench growing in sand was set up to compare the amounts of nitrogen released from plants shoot litter with that released below ground as root litter and/or root exudation. No nitrogen fixation by free-living microorganisms was found in the sand and the increased nitrogen content of the plant + soil system was therefore due to nitrogen fixation byFrankia in the alder root-nodules. Most of the nitrogen released from the plants was in the nitrogen-rich leaf and other shoot litter. Only small amounts of nitrogen were found in the drainage water from the pots and were recorded as increased nitrogen content of the sand.     

Identification of ononitol and O-methyl-scyllo-inositol in pea root nodules

Ononitol (4-O-methyl-myo-inositol) and O-methyl-scyllo-inositol were identified in pea (Pisum sativum L.) root nodules formed by twoRhizobium leguminosarum strains. Ononitol was the major soluble carbohydrate in nodules formed by strain 1045 while O-methyl-scyllo-inositol and two unidentified components were dominant in the carbohydrate pattern of the nodules formed by strain 1 a. The cyclitols were also present in the denodulated roots, but to a much smaller extent; in the above-ground plant parts only traces were found. The identification of ononitol and O-methyl-scyllo-inositol was established by gas chromatography and gas chromatography-mass spectrometry utilizing trimethylsilyl- and acetyl-derivatives.Abbreviations GC-MS gas chromatography-mass spectroscopy - TLC thin-layer chromatography