汞对玉米、小麦幼苗生长及过氧化物酶同工酶的影响

7ppm Hg~#对玉米、小麦幼苗生长具一定的刺激作用,而10ppm Hg~#则抑制幼苗生长。Hg~#对两种作物根系生长有不同的生理效应,而对玉米、小麦根系过氧化物酶影响表现为谱带减少或活性减弱。     

土壤添加玉米秸秆对小麦Pb毒害缓解效应

采用室内盆栽和网室盆栽的方法研究了Pb污染土壤上玉米秸秆对小麦幼苗生物效应、成熟期籽粒Pb含量和蛋白质含量以及产量性状的影响,探讨了玉米秸秆缓解Pb毒害小麦的生理机制.结果表明,添加3g/kg和6g/kg的玉米秸秆对Pb污染土壤上小麦幼苗生长有明显的促进作用,能有效缓解Pb对小麦的毒害.具体表现为,与对照相比,小麦幼苗根长、芽长、植株干重增大,叶绿素含量和根系活力升高,过氧化物酶(POD)和超氧化物歧化酶(SOD)同工酶活性以及丙二醛(MDA)含量下降,小麦成熟期籽粒Pb含量降低,蛋白质含量以及生物产量升高.     

薄壳山核桃根系水浸提液对2种作物种子萌发及幼苗生长的影响

为探讨薄壳山核桃根系水浸提液对小麦、大豆的影响,采用蒸馏水浸提法收集薄壳山核桃根系化感物质,并运用室内生物测定法检测不同浓度(0.025、0.05和0.1 g·mL~(-1))根系水浸提液对小麦、大豆种子萌发和幼苗生长的影响。结果表明:各浓度处理的根系水浸提液对小麦、大豆萌发及幼苗生长的化感抑制作用较为显著,且具有显著的浓度效应(浓度低抑制作用弱,浓度高抑制作用强);薄壳山核桃根系水浸提液对小麦、大豆种子发芽率、发芽指数、发芽势和活力指数的抑制作用分别依次为:活力指数发芽势发芽指数发芽率和活力指数发芽势发芽率发芽指数;薄壳山核桃根系水浸提液各浓度处理对小麦、大豆幼苗根长、苗高、鲜质量和干质量的化感效应均为:根长苗高鲜质量干质量,其中薄壳山核桃根系水浸提液对2种受体植物幼苗根长均有显著的抑制作用,而对幼苗干、鲜质量的影响则因受体植物种类的不同而不同;薄壳山核桃根系水浸提液对2种受体植物的综合化感效应顺序为:小麦大豆;生长7 d的幼苗体内,SOD活性降低,MDA含量、POD活性和CAT活性与对照相比均随浓度的增加而增加。综合分析认为:小麦对薄壳山核桃根系水浸提液更为敏感。     

淹水解除后玉米幼苗形态及光合生理特征恢复

以郑单958为试验材料,在盆栽条件下研究了淹水及淹水解除后玉米幼苗根系、叶片形态、光合生理及植株的恢复生长.结果表明:(1) 淹水总体上抑制玉米幼苗根系生长,短期淹水(7d)导致根系总长度、根系表面积、根系体积均显著降低,随着淹水时间延长(14d)玉米根系产生大量不定根,使得根系总长度、根系表面积、根系体积显著升高(P＜0.01);(2)淹水条件下叶片生长同样受到抑制,玉米叶面积、叶型指数和可见叶片数均显著下降;(3)淹水条件下玉米幼苗的光合性能下降,光合色素总含量降低,但短期淹水(7d)后叶绿素a/b值提高;气孔限制(Ls)是淹水7d植株光合速率下降的主要因素,而非气孔限制则是淹水14d植株光合速率下降的主要因素.(4)淹水处理7d、14d后的玉米幼苗均能够恢复生长,但恢复生长速率随淹水时间延长而降低;在恢复生长过程中,光合生理指标恢复早于形态恢复,强光对于淹水后幼苗恢复生长具有明显的抑制效应.     

不同盐处理对玉米幼苗根系质子分泌及细胞膜透性的影响

以玉米品种郑单958为实验材料,分别用100 mmol/L NaCl、100 mmol/L KCl和50 mmol/L Na2CO3处理其幼苗3 d,研究不同盐类对玉米根系质子分泌和细胞膜透性的影响.结果表明:不同盐处理都显著抑制玉米幼苗根系的生长,抑制程度依次为Na2CO3>KCl>NaCl;不同盐处理均使玉米幼苗根系Na 含量显著增加,NaCl和Na2CO3处理显著降低根系K 含量而导致其Na /K 升高,但KCl处理却显著提高根系K 含量使其Na /K 降低;不同盐处理均能显著增加细胞膜透性而降低根系质子分泌能力,影响程度依次为Na2CO3>KCl>NaCl.研究发现,相同阳离子浓度条件下,KCl处理对玉米根系质子分泌的抑制作用强于NaCl,碱性盐的抑制作用大于中性盐;盐胁迫可能通过改变玉米幼苗根系质膜的稳定性来影响质子分泌,从而抑制根系生长.     

外来杂草反枝苋对农作物的化感作用及其风险评价

利用改进的差时播种共培法,以麦田伴生恶性杂草播娘蒿为对照,在实验室条件下研究反枝苋根系分泌物及其不同浓度残枝浸提液对小麦、玉米、油菜种子萌发及生长的影响.结果显示:(1)反枝苋幼苗的根系分泌物能够显著抑制作物根长和苗高的生长;(2)反枝苋不同浓度浸提液均能抑制作物种子的萌发,其抑制作用随浓度的增加而增强;(3)除0.025 g·mL-1处理对小麦根长和苗高、玉米苗高有促进作用外,其余各浓度反枝苋浸提液对作物幼苗的根长和苗高有不同程度的抑制,且对根长的抑制作用更强;(4)反枝苋对作物幼苗的抑制作用强于恶性杂草播娘蒿,风险评估定量分析结果认定反枝苋为陕西省高度危险性植物.     

铜胁迫对玉米幼苗生长、叶绿素荧光参数和抗氧化酶活性的影响

本文研究了铜(Cu)胁迫下玉米(Zeamays)幼苗生长、叶绿素含量、叶绿素荧光参数和抗氧化酶活性的变化。研究结果表明,5￣20μmol.L-1Cu处理10天明显抑制玉米幼苗根系生长,并减少玉米幼苗的干物重,以及增加玉米幼苗地上部和根系含Cu量;玉米幼苗吸收的Cu大部分积累在根系,在地上部分布较少。Cu处理还降低玉米叶片的叶绿素含量和Fv/Fm、ETR、qP和qy值。在10天的Cu处理期间,根系中SOD、POD、CAT和GR活性呈现先上升后下降的趋势。而叶片中的SOD、POD、CAT和GR活性在处理前期不受Cu胁迫的显著影响,处理后期则因Cu胁迫而增强。实验表明抗氧化酶在抵御过量Cu引起的氧化胁迫中发挥了一定的作用。     

CO2倍增对不同氮水平下小麦幼苗根系及叶片NR活性的影响

以小麦品种'小偃22'幼苗为材料,采用开顶式气室和水培实验研究了不同供氮水平(2.5、5.0、10.0和 15.0 mmol·L-1)下小麦幼苗植株生长量、根系形态、有机碳分泌速率和硝酸还原酶(NR)活性对大气CO2浓度升高的响应.结果显示,大气CO2浓度倍增均增加了小麦幼苗各生长阶段根冠生物量以及根系长度、面积、有机碳分泌速率和叶片NR活性.随供氮水平的提高,各生长阶段幼苗根冠生物量、根长和面积以及叶片NR活性呈上升趋势,而有机碳分泌速率呈下降趋势;根冠比变化不同阶段表现不一致,一叶一心期呈下降趋势,二叶一心期和三叶一心期分别以15.0和10.0 mmol·L-1氮水平较高.研究表明,大气CO2浓度升高可促进小麦幼苗根系生长和有机碳分泌速率,提高其氮素同化能力;增加介质供氮有利于高CO2浓度条件下小麦幼苗根冠生长和氮素同化,提高根冠比,减少根系有机碳过度分泌引起的碳损耗.     

水杨酸对锌胁迫下小麦幼苗生长抑制的缓解效应

以小麦品种‘新麦18’为材料,采用室内水培实验研究了不同浓度水杨酸(SA)处理对300 mg.L-1锌胁迫下小麦种子萌发和幼苗生长的影响。结果表明:在Zn2+胁迫下,小麦种子的发芽势和发芽率、幼苗根长、芽长以及幼苗叶片的可溶性蛋白含量、根系活力显著降低,而脯氨酸和丙二醛(MDA)含量显著增加(P<0.05);外施SA显著提高了Zn2+胁迫下小麦种子的发芽势和发芽率,同时也使Zn2+胁迫7 d后的小麦幼苗的根长、芽长,幼苗叶片的脯氨酸和可溶性蛋白含量以及根系活力显著升高,膜脂过氧化产物MDA含量却显著降低(P<0.05)。由此可见,外施SA可通过提高小麦幼苗根长和芽长来增加幼苗根系活力,通过提高小麦幼苗可溶性蛋白含量、脯氨酸含量来维持细胞膜的稳定性,降低膜脂过氧化伤害程度,从而缓解了Zn2+胁迫对幼苗生长的抑制,并以14 mg.L-1外源水杨酸缓解效果最好。     

铜胁迫对玉米幼苗生长、叶绿素荧光参数和抗氧化酶活性的影响

本文研究了铜(Cu)胁迫下玉米(Zea mays)幼苗生长、叶绿素含量、叶绿素荧光参数和抗氧化酶活性的变化。研究结果表明, 5~20 μmol.L-1 Cu处理10天明显抑制玉米幼苗根系生长, 并减少玉米幼苗的干物重, 以及增加玉米幼苗地上部和根系含Cu量; 玉米幼苗吸收的Cu大部分积累在根系, 在地上部分布较少。Cu处理还降低玉米叶片的叶绿素含量和Fv/Fm、ETR、qP和qy值。在10天的Cu处理期间, 根系中SOD、POD、CAT和GR活性呈现先上升后下降的趋势。而叶片中的SOD、POD、CAT和GR活性在处理前期不受Cu胁迫的显著影响, 处理后期则因Cu胁迫而增强。实验表明抗氧化酶在抵御过量Cu引起的氧化胁迫中发挥了一定的作用。     

Toxic levels of soil and plant zinc for maize and wheat

Summary Maize and wheat crops grown for 60 days and maturity respectively in soils with a range of available zinc (0.4 to 109 ppm DTPA extractable) indicated 7 ppm Zn in soil and 60 ppm in plant being toxic for wheat. These limits for maize were 11 ppm Zn in soil and 81 ppm Zn in plant. Wheat crop is more susceptible to Zn toxicity as compared to maize.     

The role of maize root size in phosphorus uptake and productivity of maize/faba bean and maize/wheat intercropping systems

Interspecific root/rhizosphere interactions affect phosphorus (P) uptake and the productivity of maize/faba bean and maize/wheat intercropping systems. The aim of these experiments was to determine whether manipulation of maize root growth could improve the productivity of the two intercropping systems. Two near isogenic maize hybrids (the larger-rooted T149 and smaller-rooted T222) were intercropped with faba bean and wheat, under conditions of high- and low-P availability. The larger-rooted T149 showed greater competitive ability than the smaller-rooted T222 in both maize/faba bean and maize/wheat intercropping systems. The higher competitive ability of T149 improved the productivity of the maize/faba bean intercropping system in P-sufficient conditions. In maize/wheat intercropping systems, root growth, shoot biomass, and P uptake of maize were inhibited by wheat, regardless of the P-supply. Compared with T222, the larger-rooted T149 suffered less in the intercropping systems. The total biomass of the maize/wheat intercropping system was higher for wheat/T149 than for wheat/T222 under low-P conditions. These data suggested that genetic improvement of maize root size could enhance maize growth and its ability to compete for P resources in maize/faba bean and maize/wheat intercropping systems. In addition, depending on the P availability, larger maize roots could increase the productivity of intercropping systems.     

Using competitive and facilitative interactions in intercropping systems enhances crop productivity and nutrient-use efficiency

This paper reviews recent research on the processes involved in the yield advantage in wheat (Triticum aestivum L.)/maize (Zea mays L.), wheat/soybean [Glycine max (L.) Merr.], faba bean (Vicia faba L.)/maize, peanut (Arachis hypogaea L.)/maize and water convolvulus (Ipomoea aquatica Forsk.)/maize intercropping. In wheat/maize and wheat/soybean intercropping systems, a significant yield increase of intercropped wheat over sole wheat was observed, which resulted from positive effects of the border row and inner rows of intercropped wheat. The border row effect was due to interspecific competition for nutrients as wheat had a higher competitive ability than either maize or soybean had. There was also compensatory growth, or a recovery process, of subordinate species such as maize and soybean, offsetting the impairment of early growth of the subordinate species. Finally, both dominant and subordinate species in intercropping obtain higher yields than that in corresponding sole wheat, maize or soybean. We summarized these processes as the `competition-recovery production principle'. We observed interspecific facilitation, where maize improves iron nutrition in intercropped peanut, faba bean enhances nitrogen and phosphorus uptake by intercropped maize, and chickpea facilitates P uptake by associated wheat from phytate-P. Furthermore, intercropping reduced the nitrate content in the soil profile as intercropping uses soil nutrients more efficiently than sole cropping.     

Efficacy of diatomaceous earth to control internal infestations of rice weevil and maize weevil (Coleoptera: Curculionidae)

Densities of 10, 20, and 30 hard red winter wheat kernels, Triticum aestivum L., were infested with different life stages of the rice weevil, Sitophilus oryzae (L.), mixed with 35 g of wheat treated with 300 ppm of the Protect-It (Mississauga, Ontario, Canada) formulation of diatomaceous earth (DE), and held at 22, 27, and 32 degrees C. A similar test was conducted by exposing densities of 6, 12, and 18 corn kernels infested with different life stages of the maize weevil, Sitophilus zeamais Motschulsky, mixed with 30 g of corn, Zea mays L., treated with 300 ppm of DE. Mortality of adults emerging from kernels in wheat treated with DE was always greater than controls, and ranged from 56 to 90% at 22 degrees C and was >90% at 27 and 32 degrees C. In most treatment combinations, exposure to DE suppressed F1 progeny by 60-90% relative to untreated controls. Mortality of adult maize weevils on treated corn held at 22 and 27 degrees C was lower than mortality of rice weevils on wheat, and ranged from 4 to 84%. F1 production was low in corn held at 22 degrees C, and no F1s were produced in either the controls or the treatments at 32 degrees C. In treated corn held at 27 degrees C, exposure to the DE suppressed F1 progeny by approximately 70-80% relative to the untreated controls. Results of this study show that rice weevils and maize weevils emerging from infested kernels as adults are susceptible to DE, and these results are comparable to other studies in which adult weevils were exposed directly on wheat or corn treated with DE. Although adult weevils will be killed by exposure to DE, some oviposition could still occur and progeny suppression may not be complete; however, application of DE to commodities already infested with internal feeders, such as the rice weevil and the maize weevil, could help eliminate or suppress the infestation.     

The Production of Haploid Wheat Plants via Wheat X Maize Hybridization

The intergeneric cross between wheat and maize are characterized by a high frequency of formation of hybrid embryos, but maize chromosomes are rapidly eliminated in the first few cell division cycles to produce haploid wheat embryos. If left the embryos on the plants they will soon abort, as a result of the absence or poor development of the endosperm. Embryo rescue techniques should not enable these embryos to grow to plants because of the embryos were extremely young for embryo culture. Viable embryos were obtained at much higher frequenc, if spikes containing cross-pollinated florets were dipped in 100 ppm 2,4-D solution 4 hours after pollination. Of the 382 florets treated, 64(16.8%) embryos were obtained 10 days after treatment, and 47 plants recovered on the culture medium. In control (2,4-D not applied) only 1 (0.96%) embryo and 1 plant was obtained from 104 florets. This simplified technique should enable haploid wheat plants production through wheat - maize to apply to practical breeding.     

Induction of Haploid Durum Wheat Plants Through Pollination of Maize Pollen

When tetraploid wheat (Triticum durum Desf. ) variety DR147 was crossed with maize (Zea mays L. ) variety suppersweet ss 7700, pollen readily germinated on the stigma and one or more pollen tubes reached the embryo sac in 83.4% of wheat florets. The frequency of fertilization and embryo formation was 44.5% and 42. 6% respectively. The hybrids were karyotypically unstable and the maize chromosomes were eliminated early in the development. Thus haploid wheat embryos were form. Although the double fertilization frequency of durum wheat X maize was high (32.7%) to form embryos and endosperms, yet the endosperms were highly abnormal. It was very difficult to produce viable mature seeds from the mother durum wheat plants. The survival of hybrid embryos produced by durum wheat X maize could be improved or prolonged by treatment with 100 ppm 2, 4-D (either by dipping inflorescences in solution or injecting 0.3 to 0.5 mL 2, 4-D solution into the uppermost internodes of the wheat stem). 9 to 13 days after pollination, caryopsis were excised from the pollinated spikes and surface sterilized for peeling of the embryos in different developing stages. The embryos were plated on MS solid medium containing 3% sucrose, 200 mg/L casein hydrolysate for embryo rescue. The experimental results revealed that the well developed embryos (larger than 0. 5 mm with scutellum structure) were easy to produce calli by callus induction or produce haploid wheat plants by embryo rescue, whereas the poorly developed embryos (globular, pear or torpedo-shaped embryos smaller than 0.3 mm) responsed very poorly. The germination frequencies of well and poorly developed embryos were 83.3 % and 12.5 %, respectively. Chromosome counts of root tip cells of the rescued plants proved their haploid nature (2n= 2x= 14).     

Differences between maize and wheat in growth-related nutrient demand and uptake of potassium and phosphorus at suboptimal root zone temperatures

The effects of low root zone temperatures (RZT) on nutrient demand for growth and the capacity for nutrient acquisition were compared in maize and wheat growing in nutrient solution. To differentiate between direct temperature effects on nutrient uptake and indirect effects via an altered ratio of shoot to root growth, the plants were grown with their shoot base including apical shoot meristem either within the root zone (low SB), i.e. at RZT (12°, 16°, or 20°C) or, above the root zone (high SB), i.e. at uniformly high air temperature (20°/16° day/night).At low SB, suboptimal RZT reduced shoot growth more than root growth in wheat, whereas the opposite was true in maize. However, in both species the shoot growth rate per unit weight of roots, which was taken as parameter for the shoot demand for mineral nutrients per unit of roots, decreased at low RZT. Accordingly, the concentrations of potassium (K) and phosphorus (P) remained constant or even increased at low RZT despite reduced uptake rates.At high SB, shoot growth at low RZT in both species was higher than at low SB, whereas root growth was not increased. At high SB, the shoot demand per unit of roots was similar for all RZT in wheat, but increased with decreasing RZT in maize. Uptake rates of K at high SB and low RZT adapted to shoot demand within four days, and were even higher in maize than in wheat. Uptake rates of P adapted more slowly to shoot demand in both species, resulting in reduced concentrations of P in the shoot, particularly in maize.In conclusion, the two species did not markedly differ in their physiological capacity for uptake of K and P at low RZT. However, maize had a lower ability than wheat to adapt morphologically to suboptimal RZT by increasing biomass allocation towards the roots. This may cause a greater susceptibility of maize to nutrient deficiency, particularly if the temperatures around the shoot base are high and uptake is limited by nutrient transport processes in the soil towards the roots.     

Effect of vanadium on the growth,yield and chemical composition of maize (Zea Mays L.)

Summary The effects of application of vanadium on the growth, yield, and chemical composition of maize were compared in a series of pot experiments during several years. It was concluded that above a threshold value (0.05 ppm) vanadium was injurious to maize crop, but at milder dose it increased the yield of maize crop significantly. Quality of produce was also affected markedly by vanadium application.     

平原农区幼龄杨树间作农作物的产量表现

通过1~2年与3~4年树龄杨树间作冬小麦和夏玉米,探讨了杨树对农作物产量及产量形成因子的影响。结果表明,1~2年树龄杨树间作冬小麦其产量有所增加,与夏玉米间作使其产量降低31.3%~33.7%。3~4年树龄杨树间作冬小麦的产量降低了36.9%~42.5%,间作夏玉米的产量降低了80.8%~87.4%,且距树越近产量越低。产量形成因子分析表明,杨树对冬小麦产量的影响主要为穗数。因此保证冬小麦分蘖期的肥水管理,在群体建立的基础上保证营养器官建成期所需的各种资源,为正常的穗粒数形成及粒重的充实奠定基础。对夏玉米的影响,随着杨树的生长,表现不一样,由穗粒数逐渐转变为穗数。复合系统建立初期应保证玉米拔节期到吐丝期所需资源,确保较多的穗粒数形成,而杨树生长2~3年后必须对杨树进行合理的管理,保证穗数的建立,减小夏玉米产量的降低。针对农林复合系统的复杂性,今后应综合考虑杨树和农作物光、热、水、肥等生物学特性,对其进行合理管理,尽可能做到杨树与作物的和谐共生。