间作对玉米根系分泌物及团聚体稳定性的影响

通过田间小区试验种植玉米(玉米单作、玉米∥大豆、玉米∥马铃薯),测定3个生育期(拔节期、大喇叭口期、抽雄期)玉米根系分泌总糖含量、总有机酸含量和土壤团聚体状况,分析间作对玉米根系分泌物及团聚体稳定性的影响。结果表明:玉米根系分泌总糖含量和总有机酸含量随生育期的推移而增加,间作显著提高玉米根系分泌总糖含量和总有机酸含量,玉米∥马铃薯玉米∥大豆。在抽雄期,玉米∥大豆、玉米∥马铃薯相比玉米单作0.25mm水稳性团聚体含量(R_(0.25))分别显著提高6.19%,8.17%;平均质量直径(MWD)分别提高5.04%,10.08%;几何平均直径(GMD)分别提高6.12%,12.24%;分形维数(D)分别显著降低0.72%,1.09%;团聚体破坏率(PAD)分别显著降低16.77%,26.08%。在根系分泌物最大的抽雄期,玉米根系分泌总糖含量、总有机酸含量与R_(0.25),GMD,D,PAD呈极显著相关关系(P0.01)。因此,间作可通过增加玉米根系分泌总糖含量和总有机酸含量,进而提高土壤团聚体的稳定性。     

不同环境胁迫对根系分泌有机酸的影响研究进展

综述了根系分泌有机酸种类、组成含量、来源、分析检测方法、影响因素及其作用。根系分泌有机酸是植物应对环境胁迫的一种适应性响应机制,在许多环境胁迫下诸如养分胁迫、水分胁迫和重金属胁迫条件下,植物通过根系释放有机酸到根际土壤中,不仅可以改变土壤的理化性质及微生物活性,还会影响土壤-植物界面的许多生理生化过程。通过深入研究不同环境胁迫对根系分泌有机酸的影响及机制,有助于更深层次地研究植物在逆境胁迫下的适应性机制。     

营养胁迫与根系分泌物

根系不仅是活跃的吸收、代谢器官，而且是强大的分泌器官，营养元素是影响根系分泌的外界因素之一，在营养胁迫条件下，根系分泌物的组成、数量均发生变化。本文介绍了铝毒害及磷，铁。锌缺乏时，根系分泌物研究新进展。     

氮素对不同大豆品种根系分泌物中有机酸的影响

采用室内溶液培养方法,分别研究了接种根瘤菌处理下,两种氮源和两种氮浓度对两个大豆品种根系分泌物中有机酸的影响。结果表明,合丰25号根系分泌的有机酸种类和数量无论苗期或花期,接种或不接种根瘤菌,均表现为硝态氮处理高于酰胺态氮处理,表明合丰25号大豆更喜硝态氮,硝态氮促进了有机酸的分泌。绥农10号在酰胺态氮下的有机酸种类和数量均高于硝态氮处理,表明其更喜酰胺态氮,酰胺态氮下根瘤菌的存在增加其根系分泌物中有机酸种类和数量。可见,大豆根系分泌物中有机酸的种类和数量因品种而异,因品种对氮源的喜好而变化;根瘤菌在不同程度上增强或减弱根系有机酸的分泌作用。柠檬酸受氮素供应浓度影响很大,当氮素供应浓度较低时,大豆根系分泌物中可检测到柠檬酸,供氮浓度升高则检测不到。     

硫营养对小花南芥（Arabis alpinal Var.parviflora Franch）累积铅锌的影响研究

采用盆栽试验方法,研究了硫营养对Pb/Zn富集植物--小花南芥（Arabis alpinal Var.parviflora Franch）生长和铅锌累积能力的影响。结果表明：小花南芥地上部生物量随硫营养质量分数的增加而显著增加,增幅为49.5%~118.6%;64mg·kg^-1硫营养处理,小花南芥植株地下部生物量增加114.5%;硫营养促进小花南芥对铅的累积,植株地上部铅累积量增加1.74-2.92倍,地下部增加2.01-3.86倍;8mg·kg^-1和24mg·kg^-1硫营养处理促进小花南芥对锌的累积。试验揭示适当的硫营养能促进小花南芥生长和对铅锌的累积。     

续断菊与玉米间作的铅累积及根系低分子量有机酸分泌特征研究

为探明间作作物根系分泌低分子量有机酸对土壤重金属生物有效性的影响,采用矿区周边农田土壤进行室内盆栽试验,研究了云南本土超累积植物续断菊(Sonchus asper L. Hill)和玉米(Zea mays L.)间作下,植物生长、根系低分子量有机酸分泌量、根际土壤Pb提取形态以及植物Pb积累特点。结果表明:与单作相比,间作续断菊地上部和根部生物量、根长、根内径和根系体积均显著增加(P0.05);间作玉米根部生物量、根长、根内径和根系体积显著增加(P0.05)。柠檬酸、草酸是续断菊和玉米根系分泌的主要低分子量有机酸,间作导致续断菊根系低分子量有机酸的分泌量增加,玉米根系低分子量有机酸的分泌量降低。续断菊根际土壤生物有效态Pb含量增加85.2%(P0.05),而玉米根际土壤生物有效态Pb含量降低26.1%(P0.05)。续断菊体内Pb含量显著增加18.0%～43.2%(P0.05),富集系数提高26.0%,而转运系数降低42.0%;玉米地上部Pb含量显著降低24.3%(P0.05),转运系数降低43.1%。续断菊根系分泌的柠檬酸和草酸数量,均与土壤生物有效态Pb含量呈显著正相关,且土壤有效态Pb含量分别与续断菊地上部和根部的Pb含量呈显著正相关。表明间作增加了续断菊对Pb的吸收积累量,与间作体系植物根系分泌的低分子有机酸介导下的土壤有效态Pb含量增加密切相关。     

不同磷水平下玉米-大豆间作对根系有机酸分泌特征及磷吸收的影响

通过盆栽试验,探讨不同磷水平下玉米-大豆间作根系分泌物中有机酸以及磷吸收的变化特征。结果表明：与单作相比,在P50和P100水平下,间作种植显著提高了玉米和大豆籽粒产量70.82%、52.67%和22.46%、16.62%。2个磷水平下,玉米-大豆间作具有明显的磷吸收优势,磷吸收土地当量比（LERP）为1.32～1.56,且LERp不受磷水平调控。与常规磷水平（P100）下的单作相比,玉米-大豆间作在磷肥减施1/2 (P50)的条件下,并未降低玉米和大豆的磷素吸收量。间作改变了玉米和大豆根系有机酸分泌的种类,显著提高了有机酸的分泌速率,并且在P50水平下间作处理有机酸的分泌速率最大。因此,间作诱导根系有机酸分泌增加是驱动不同磷水平下玉米和大豆磷高效吸收的重要机制之一,玉米-大豆间作具有减施磷肥并维持作物产量和磷吸收的潜力。     

根系分泌物对镉生物有效性的影响

通过凝胶色谱分析和吸附，解吸，扩散，盆载试验研究表明：玉米根系水溶性有机分泌物与镉的络合可达１２８ｍｍｏｌｅ／１００ｇ，新鲜根系分泌物减少土壤对镉的吸附，提高其扩散性，但经培养分解后则起相反作用。施用铵态氮显著降低根际土壤ｐＨ，增加土壤可解吸性镉和株吸镉量，施用硝态氮肥则相反。     

Cd胁迫下长白落叶松幼苗根系有机酸的分泌研究

用A1层暗棕壤栽植长白落叶松幼苗(1 a生和2 a生),1个月后用CdCl2溶液对土壤进行Cd胁迫处理,使土壤Cd2+浓度分别达1、2、4、8 mg kg-1,在胁迫处理后第3 d、10 d和30 d,分别采集上述两种幼苗的根际土壤样品,研究不同Cd胁迫程度(水平)和胁迫时间处理后,长白落叶松幼苗根系分泌的有机酸种类和数量,以期为系统研究有机酸在森林生态系统中的作用提供理论依据。结果表明,Cd胁迫促进1 a生苗根系分泌有机酸种类和数量增加,增加量因胁迫时间和胁迫程度而异;增加有机酸种类数量的胁迫时长顺序为30 d 3 d 10 d,即在一定胁迫程度范围内,苗木受胁迫时间较短、胁迫较重时新检出有机酸的种类较多。同样,在一定胁迫程度和胁迫时长内,苗木根系分泌有机酸总量随胁迫程度提高而增加,达到最大值后胁迫程度继续提高则分泌有机酸的总量降低。在其它条件一定时,随胁迫时间延长,根系有机酸分泌总量降低。在不同的胁迫时间,有机酸分泌量大多以3 d增幅最大;对于不同种类有机酸,苹果酸分泌量增幅最大,其次为柠檬酸或草酸。对于2 a生苗,大多数Cd胁迫处理也增加其根系分泌的有机酸种类数量,且在一定胁迫程度内有机酸分泌总量随胁迫程度增加而增加。     

铝胁迫下大豆根系分泌物对根际土壤微生态的影响

通过对19个不同基因型大豆品种的耐铝性筛选实验,选择耐铝型的浙春2号和敏感型的浙春3号作为实验材料;设置5个铝处理浓度(0,0.2,0.4,0.6,0.8 g kg-1,即土壤总Al3+浓度分别为0.293,0.493,0.693,0.893,1.093 g kg-1)土壤,大棚种植大豆30d后,取大豆根际、非根际土壤和外源根系分泌物作用下的土壤样品,对各类微生物生理群进行分析,同时测定土壤呼吸速率、纤维分解作用、氨化作用、硝化作用,以及酸性磷酸酶、过氧化氢酶和蔗糖酶等土壤重要酶类的活性。结果显示,土壤铝含量较低条件下(0.2,0.4g kg-1),大豆根系分泌物的应激分泌促使土壤微生物数量增多、微生物物质转化能力增强和土壤酶活性增大;土壤铝含量较高(0.8 g kg-1)时,根系分泌物的分泌相对受抑制,土壤微生物活性和土壤酶活性相应地受到抑制。实验结果还表明,外源根系分泌物也能影响土壤微生态,引起土壤微生物数量和土壤酶活性的变化,以及各种土壤生化作用(如硝化作用等)的改变,显示出一定的缓解铝毒能力,从而减少铝毒对植物的伤害。     

玉米生育期的海拔效应研究

为使高海拔地区的玉米生产布局和品种类型利用更加合理,采用作物生态学的田间试验方法,于2006～2007年间,在甘肃省和云南省各设5个试验点,研究了北、南异地不同玉米品种在不同海拔高度的生态效应.结果表明,在播期大体相同的条件下,玉米拔节期、抽雄期、成熟期随海拔的升高而相应延迟,即播种～拔节、拔节～抽雄、抽雄～成熟的"三段生长"时间相应延长.反映生育期长短的出苗～成熟天数与海拔之间呈0.01水平的正相关.本试验条件下,海拔每升降100 m,参试玉米品种的生育期延长或缩短4～5 d,株高和穗上叶数呈随海拔升高而降低趋势.     

Effects of soil compaction and arbuscular mycorrhiza on corn (Zea mays L.) nutrient uptake

Soil compaction is of great importance, due to its adverse effects on plant growth and the environment. Mechanical methods to control soil compaction may not be economically and environmentally friendly. Hence, we designed experiments to test the hypothesis that use of plant symbiotic fungi, arbuscular mycorrhiza (AM) may alleviate the stressful effects of soil compaction on corn (Zea mays L.) growth through enhancing nutrient uptake. AM continuously interact with other soil microorganisms and its original diversity may also be important in determining the ability of the fungi to cope with the stresses. Hence, the objectives were: (1) to determine the effects of soil compaction on corn nutrient uptake in unsterilized (S1) and sterilized (S2) soils, and (2) to determine if inoculation of corn with different species of AM with different origins can enhance corn nutrient uptake in a compacted soil. Using 2 kg weights, soils (from the field topsoil) of 10 kg pots were compacted at three and four levels (C1, C2, C3 and C4) (C1 = non-compacted control) in the first and second experiment, respectively. Corn (cv. 704) seeds were planted in each pot and were inoculated with different AM treatments including control (M1), Iranian Glomus mosseae (M2), Iranian G. etunicatum (M3), and Canadian G. mosseae, received from GINCO (Glomales In Vitro Collection), Canada (M4). Corn leaf nutrient uptake of N, P, K, Fe, Mn, Zn and Cu were determined. Higher levels of compaction reduced corn nutrient uptake, however different species of AM and soil sterilization significantly increased it. The highest increase in nutrient uptake was related to P (60%) and Fe (58%) due to treatment M4S2C3. Although it seems that M3 and M4 may be the most effective species on corn nutrient uptake in a compacted soil, M2 increased nutrient uptake under conditions (C3 and C4 in unsterilized soil) where the other species did not. Through increasing nutrient uptake AM can alleviate the stressful effects of soil compaction on corn growth.     

麦茬处理方式对机播夏玉米的生态生理效应

为探求适合黄淮海平原机播夏玉米的最佳麦茬处理方式,采用大田试验,研究了麦茬处理方式(平茬、立茬、除茬)对机播夏玉米的生态生理效应.结果表明,平茬有利于提高土壤含水率、平衡和改善耕层土壤温度,较好地满足玉米生长对土壤温度和水分的需求.3展叶时,玉米叶面积、干物质重等指标都以除茬处理最好;6展叶时,平茬处理玉米的株高、单株干重、叶面积、光合速率均表现最优,产量也最高.所以平茬处理为机播夏玉米的生长提供了较好的生态条件,促进了夏玉米的生长发育和产量的提高,有很大的推广价值.     

Estimation, variation and importance of leaf curvature in Zea mays hybrids

Maize leaves are curved but this curvature cannot be described by a single system of equations based on conic sections. We made comparisons of curvature between hybrids, leaf positions and planting density using measures of maximum leaf height and leaf tip:maximum leaf height ratio. With these measures a modern hybrid released in 1991 (Pioneer 3394) shows less curvature compared with hybrids released in 1963 (Pioneer 3306) and 1936 (Pioneer 307). The greater uprightness of 3394's leaves was apparent for all leaves measured. Curvature is a plastic character. While all hybrids developed less curvature in higher density plantings the effect was greatest for 3394. 3394 had shorter, more lanceolate leaves with smaller leaf area, a lower estimated torque around the point of leaf attachment to the stem, and a significantly smaller auricle base and smaller angle between the leaf blade and auricle base. These results support suggestions that the pattern of curvature may be produced by the progression of irreversible bending during leaf development. We found no consistent relationships between differences in curvature and measurements of leaf midrib morphology or anatomy.A frequently used approach in modeling foliage area distribution by angle is to use an approximation provided by the angular distribution of an ellipsoid. We show that for leaves in this study this approach is biased and that a Richards function describes the cumulative frequency distribution of leaf area by inclination angle more effectively. The importance of an unbiased estimator is discussed in relation to the variation in photon flux density received by surfaces of different inclinations.     

Effect of heavy metals contamination on root-derived and organic matter-derived CO2 efflux from soil planted with Zea mays

The CO₂ efflux from loamy Haplic Luvisol and heavy metal (HM) uptake by Zea mays L. were studied under increased HM contamination: Cd, Cu, and Ni up to 20, 1000, and 2500 mg kg⁻¹ soil, respectively. Split-root system with contrasting HM concentrations in both soil halves was used to investigate root-mediated HM translocation in uncontaminated soil zones. To separate root-derived and soil organic matter (SOM)-derived CO₂ efflux from soil, ¹⁴CO₂ pulse labeling of 15-, 25-, and 35-days-old plants was applied. The CO₂ evolution from the bare soil was 10.6 μg C–CO₂ d⁻¹ g⁻¹ (32 kg C–CO₂ d⁻¹ ha⁻¹) and was not affected by HM (except 2500 mg Ni kg⁻¹). The average CO₂ efflux from the soil with maize was about two times higher and amounted for about 22.0 μg C–CO₂ d⁻¹ g⁻¹. Portion of assimilates respired in the rhizosphere decreased with plant development from 6.0 to 7.0% of assimilated C for 25-days-old Zea mays to 0.4–2.0% for 45-days-old maize. The effect of the HM on root-derived ¹⁴CO₂ efflux increased with rising HM content in the following order: Cd < Cu < Ni. In Cu and Ni contaminated soils, shoot and root dry matter decreased to 70% and to 50% of the uncontaminated control, respectively. Plants contained much more HM in the roots than in the shoots. A split-root system with contrasting HM concentrations allowed to trace transport of mobile forms of HM by roots from contaminated soil half into the uncontaminated soil half. The portion of mobile HM forms in the soil (1 M NH₄NO₃ extract) increased with contamination and amounted to 9–16%, 2–6% and 1.5–3.5% for Cd, Cu, and Ni, respectively. Corresponding values for the easily available HM (1 M NH₄OAc extract) were 22–52%, 1–20% and 5–8.5%. Heavy metal availability for plants decreased in the following order: Cd > Cu ≥ Ni. No increase of HM availability in the soil was found after maize cultivation.     

Mulch effects on rainfall interception, soil physical characteristics and temperature under Zea mays L.

Application of organic amendment to the soil surface is widely used in order to ameliorate topsoil physical conditions, especially with respect to temperature, evaporation and water content. Water intercepted by mulch and crop canopy involves loss through evaporation that never replenishes the soil water. In this study, hydrological and temperature conditions beneath mulches of manufactured materials, organic waste, wheat straw (Tritium aestivum L.) and soybean straw (Glycine max L. Merrill) applied at different thickness were investigated in glasshouse and field conditions in southern England. Interception loss by a maize (Zea mays L.) canopy and mulch modified the soil water balance by adversely affecting soil water content beneath thicker application. Mulching had a beneficial effect on soil water and temperature regimes. These findings are important for identifying mulching practices for dryland agriculture and under scenarios of climatic change that predict lower rainfall and higher temperatures in summer.     

市政污泥直接施用对玉米生长和品质的影响

[目的]研究市政污泥施用后对土壤和作物生长与品质的影响,为市政污泥的直接土地利用提供科学依据。[方法]以玉米为试验材料,利用田间试验研究了污泥不同的施用方式(沟施、撒施、表土下20 cm施用)和施用量(30,90,200 t/hm~2)对玉米生长和品质以及土壤重金属含量的影响。[结果]适量的污泥对玉米个体的生长有促进作用,施用量为30 t/hm~2时株高、单株生物量、叶片叶绿素含量、籽粒蛋白质含量均显著高于对照。表土下20 cm施用污泥在整体上较其他两种施用方式有更高的出苗率和籽粒产量,在施用量为30 t/hm~2时籽粒产量最高,为656.70 kg/667m~2,高出对照29.64%。3种施用方式下,土壤中的Cu,Zn,Pb含量及玉米籽粒中的Cu,Zn含量均随污泥施用量的增加而增加,而玉米籽粒中Pb含量与对照相比差异不显著,土壤和籽粒中重金属含量均未超过国家相关标准。以重金属浓度满足土壤环境质量标准为限制条件,推算出当地的市政污泥施用量为30 t/hm~2可以连续施用5 a。[结论]施用30 t/hm~2的污泥具有良好的效果和环境效应;为了降低污泥在土壤中的局部累积而导致的胁迫效应,表土下20 cm施用和地表撒施是相对较好的方式。     

外源乙烯对镉处理下玉米幼苗生理代谢的影响

为探讨外源乙烯缓解玉米（Zea mays）幼苗镉（Cd）毒害的生理机制,通过水培试验研究了Cd处理下,外源乙烯对玉米幼苗相关生理指标与Cd的亚细胞分布的影响,以不做任何处理为空白对照,以Cd处理和（NH₄）₂SO₄处理为试验对照。结果显示,相对Cd处理,乙烯和（NH₄）₂SO₄处理可显著降低Cd胁迫下玉米幼苗H₂O₂和丙二醛（MDA）含量,使净光合速率分别提升1.23倍和1.22倍;显著降低抗氧化物酶[超氧化物歧化酶（SOD）、过氧化氢酶（CAT）]活性,抗氧化物质[抗坏血酸（AsA）、谷胱甘肽（GSH）]含量则显著上升。另外,相对于Cd处理,乙烯+Cd处理可使玉米幼苗ATP硫酸化酶活性、谷胱甘肽还原酶（GR）活性、半胱氨酸和还原型谷胱甘肽（GSH）含量分别上升54.43%、27.93%、50.77%和49.85%,而对非蛋白硫醇（NPT）和植物螯合素（PCs）含量无显著性影响。在乙烯+Cd处理的基础上添加GSH合成抑制剂BSO（buthionine sulfoximine）可导致玉米叶片GSH含量显著降低,H₂O₂含量上升,光合速率下降。外源乙烯可显著降低Cd胁迫下玉米叶片Cd含量,而显著提升根部细胞壁和液泡中Cd含量。因此,外源乙烯一方面通过提升玉米叶片GSH和AsA含量,增强叶片非酶促抗氧化能力,而非通过抗氧化酶促反应和NPT、PCs的螯合作用;另一方面则通过根细胞壁的固定作用和液泡区室化作用,减少Cd向玉米叶片中的转移,从而缓解Cd毒害。研究结果可为乙烯作为潜在的作物重金属拮抗剂提供理论依据。     

水稻与美人蕉间作对水稻生长、病虫害发生及产量的影响

间作是一类提高农田生物多样性、增加农业生态经济效益的农田种植模式。本研究通过一年两季的田间试验,探讨了水稻与美人蕉间作对水稻生长性状、病虫害防控以及产量的影响。结果表明:与水稻单作相比,水稻与美人蕉间作在早稻分蘖末期、抽穗期降低了水稻株高,而在早稻抽穗期、成熟期及晚稻分蘖末期和成熟期提高了水稻叶片的叶绿素含量;间作下水稻分蘖数明显提高,在早稻分蘖末期、抽穗期和晚稻成熟期水稻分蘖数分别提高25.20%、11.20%和26.01%。在病虫害防控方面,水稻与美人蕉间作降低了纹枯病和稻纵卷叶螟的发生,其中在早稻分蘖中期、末期以及晚稻分蘖末期、抽穗期纹枯病的病情指数分别显著降低35.61%、19.55%、24.83%和16.05%;在晚稻分蘖中期和末期,稻纵卷叶螟卷叶率显著降低46.35%和60.31%;水稻与美人蕉间作显著提高了水稻单位面积产量,增幅达11.16%。研究表明,水稻与美人蕉间作是一种能促进水稻生长、降低水稻病虫害、提高水稻产量和经济效益的新型生态种植模式。