锌营养状况对小麦根细胞膜透性的影响

小麦缺锌不仅导致根系K~ 和NO_3~-泌出量增加,而且低分子量有机化合物如氨基酸、糖类化合物和酚类化合物的泌出量也明显提高。重新供锌(ZnSO_4)12h后,根系K~ 、NO_3~-、氨基酸和碳水化合物的泌出量迅速减少,随着时间的延长,泌出量接近对照水平。结果说明锌对根细胞膜结构的稳定性及膜功能的完整性是必不可少的。     

供锌条件下碳酸钙对小麦幼苗生长和锌吸收的影响

通过营养液培养试验,研究了供Zn条件下添加CaCO₃对3种基因型冬小麦（远丰998、中育6号、小偃22）幼苗生长及Zn吸收的影响.结果表明,供Zn和添加CaCO₃对小麦幼苗生长量和根冠比均无显著性影响,3种基因型小麦间亦无显著性差异;添加CaCO₃诱发了小麦叶片失绿黄化.无论供Zn还是不供Zn,添加CaCO₃对3种基因型小麦根、茎、叶各部分的Zn含量及累积量均无显著性影响;与不供Zn处理相比,供Zn会大幅度地提高根、茎、叶的Zn含量和累积量,供Zn使3种基因型小麦植株Zn含量分别增加80.0%、104.8%和139.6%,缺Zn敏感型小麦远丰998植株Zn含量和累积量的增加幅度远小于不敏感型小麦中育6号和小偃22.供Zn和添加CaCO₃对小麦幼苗根、茎、叶中P含量均无显著影响,但远丰998小麦根、茎、叶3部分的P含量均明显低于其它两种非敏感型小麦.供Zn使小麦根、茎、叶3部分的P/Zn大幅度降低,添加CaCO₃也使P/Zn呈现降低的趋势.不供Zn条件下添加CaCO₃能诱发小麦失绿黄化,但Zn吸收量未降低.表明在水培条件下,高含量CaCO₃对小麦Zn吸收并未产生明显的抑制作用.     

小麦种子含锌量在幼苗中的分配与对缺锌敏感性的关系

应用三个种子含锌量不同的小麦品系为实验材料,研究了在缺锌和供锌条件下锌在小麦幼苗中的分配规律。实验证明在缺锌的条件下,小麦幼苗植株含锌量与种子的含锌量成正相关。锌在三个品系小麦不同叶位中的分配规律是一致的,但种子含锌量低的小麦向幼叶中分配的锌量比例大。在供锌的条件下,种子含锌量高的品系地上部的总锌量比低锌品系高。     

小麦种子含锌量在幼苗中的分配与对缺锌敏感性的关系

应用三个种子含锌量不同的小麦品系为实验材料,研究了在缺锌和供锌条件下锌在小麦幼苗中的分配规律。实验证明在缺锌的条件下,小麦幼苗植株含锌量与种子的含锌量成正相关。锌在三个品系小麦不同叶位中的分配规律是一致的,但种子含锌量低的小麦向幼叶中分配的锌量比例大。在供锌的条件下,种子含锌量高的品系地上部的总锌量比低锌品系高。     

低锌和缺锌对玉米生长发育的影响

以玉米沈单10号为材料,用溶液培养的方法研究了缺锌、低锌和正常供锌对玉米生长发育的影响,进一步明确了一定量低锌比缺锌对玉米的伤害更大,并对其POD、SOD、CAT同工酶谱及蛋白质表达进行了分析、结果表明：一定浓度的低锌培养使玉米生长受抑及受害最重,且地上部分比地下部分更敏感。低锌和缺锌处理时3种同工酶的酶谱和蛋白表达与正常供锌时均有明显的差异,尤其在一定量低锌浓度时,有些同工酶的表达增强或被特异性诱导,而另一些酶的合成受阻;低锌和缺锌处理都诱导出了新的蛋白组分,也缺失了部分蛋白组分,且低锌比缺锌时缺失的蛋白组分更多。这些变化可能与玉米生长发育及受害密切相关。     

缺锌和HCO_3~-处理对诸葛菜和油菜有机酸特征的影响

以诸葛菜和油菜为材料,水培环境下设置4个不同的缺锌和碳酸氢根离子胁迫处理,分别为+Zn0(含Zn且不加HCO3-的处理组),+Zn10(含Zn且加10 mmol·L-1HCO3-的处理组),-Zn0(缺Zn且不加HCO3-的处理组)和-Zn10(缺Zn且加10 mmol·L-1HCO3-的处理组),利用离子色谱法分析了4个处理的两种植物幼苗器官(根、茎、叶)及根系分泌物中的有机酸特征。结果表明:(1)高浓度碳酸氢根离子处理显著增加了两种植物器官及根系分泌的有机酸总量,尤其是在缺锌和高浓度碳酸氢根离子双重胁迫下(-Zn10处理),诸葛菜器官和根系分泌的有机酸比油菜更敏感,草酸、柠檬酸和苹果酸是诸葛菜器官和根系分泌物中的优势酸,这三种有机酸的含量分别占其有机酸总量的75%及以上;(2)叶片是两种植物有机酸产生的主要器官,有机酸的含量和分配比例从地上部分(叶和茎)到地下部分(根)减少;(3)两种植物器官和根系分泌物中的有机酸变化趋势一致,叶片中有机酸主要来源于暗呼吸过程和光呼吸过程,其他器官和根系分泌物中的有机酸主要来源于暗呼吸过程;(4)诸葛菜对缺锌和高浓度碳酸氢根离子的适应能力强于油菜,为诸葛菜的喀斯特适生性和低锌和高浓度碳酸氢根离子环境(如喀斯特环境)的生态修复提供了理论依据。     

氮锌配施对小麦锌转运、分配与累积的影响

通过田间试验,研究不同氮锌肥运筹方式对小麦植株不同器官中锌的转运、分配与累积的影响。结果表明: 不同处理植株器官中锌浓度和锌累积量的差异达显著水平。与N₃(120 kg·hm^-2)相比,N₁(240 kg·hm^-2)和N₂(180 kg·hm^-2)的籽粒锌浓度分别提高22.0%和8.9%;与未施锌(CK)相比,ZnS(土施锌肥)、ZnF(喷施锌肥)和ZnS+ZnF(土施结合喷施锌肥)处理的籽粒锌浓度分别提高15.4%、60.5%和72.8%,籽粒锌累积量分别提高21.3%、82.5%和102.4%。籽粒中锌主要来自花后吸收锌的再分配,在ZnF和ZnS+ZnF处理中的累积贡献率分别为89.9%和100.0%,锌肥回收率分别较ZnS提高4.8和1.1倍,锌肥利用率分别提高7.9和2.2倍。当前生产条件下,当施氮量<240 kg·hm^-2时,小麦不同器官锌浓度和锌累积量均随施氮量的增加而提高,喷施锌肥可显著提高籽粒中的锌浓度和锌累积量。因而,生产中可通过维持高产施氮方案并结合生育后期喷施锌肥的措施来提高籽粒中的锌浓度和锌累积量,从而提高小麦籽粒锌营养品质。     

内生真菌感染对宿主植物高羊茅锌耐受性的影响

以感染内生真菌(Neotyphodium coenophialum)和未感染内生真菌的高羊茅(Festuca arundinacea Schreb.)为实验材料,在营养液中加入ZnSO4进行锌胁迫实验,分析内生真菌对宿主植物锌耐受性的影响。与未感染内生真菌的植株相比,内生真菌感染对高羊茅的总生物量没有显著增益作用,但增加了分蘖数和叶片延伸生长累积值。内生真菌感染降低了高羊茅中Zn2+的总含量,改变了锌在高羊茅中的分配,增加叶鞘中锌的含量,减少叶片中锌的含量。在高锌浓度下,内生真菌感染对净光合速率的变化没有影响,但是显著提高了其宿主的PSⅡ光化学效率(Fv/Fm)。总体来看,内生真菌感染改善宿主高羊茅的锌耐受性。     

不同农业利用方式下土壤铜和锌的累积

通过对山东寿光表层农业土壤(0～20cm)铜和锌的调查研究,了解不同农业利用方式下土壤铜和锌含量的差异,揭示其空间分布规律及其累积特征.从研究区域采集来自设施菜地、露天菜地、小麦/玉米/棉花地和自然土壤等4类当地主要农业利用方式的土壤(n=127),样点覆盖寿光整个农业生产区域.结果表明,山东寿光农业土壤的铜含量均值为26.43mg · kg-1,极差69.11 mg · kg-1,锌含量均值为80.50mg · kg-1,极差210.8 mg · kg-1.不同农业利用方式的土壤铜锌含量从高至低的顺序均为:设施菜地>露天菜地>小麦/玉米/棉花地>自然土壤,不同农业土壤铜锌含量均出现了明显累积趋势,其中,以设施菜地的累积问题最为突出,其铜锌含量分别为33.91、124.2mg · kg-1,显著高于其它农业利用土壤类型, 但均未超过国家土壤环境质量II级标准;从研究区域铜锌含量的空间分布看,当地农业土壤铜锌含量均表现为北部、南部区域较低、中部地带较高的趋势;在集约化种植模式下,设施菜地铜锌含量随着设施年限的延长显著增加(p<0.05),其累积速率分别为1.49mg · kg-1 · a-1和2.59mg · kg-1 · a-1,这可能与铜锌含量相对较高的有机肥大量施用有关.     

施锌对石灰性褐土上小白菜光合作用及保护酶活性的影响

通过田间试验的方法,采用30(低锌)、75(中锌)和120kg/hm2ZnSO4(高锌)3个施锌水平,研究施锌对山西省石灰性褐土上小白菜叶片叶绿素含量、净光合速率、硝酸还原酶(NR)活性、抗氧化酶活性及丙二醛(MDA)含量的影响.结果表明:随着施锌量的提高,小白菜叶片各叶绿素组分含量、总叶绿素含量、净光合速率和NR活性均呈先升后降的变化趋势,并均以中锌处理最大,且中、高锌处理显著高于对照(不施锌);小白菜叶片过氧化物酶(POD)和过氧化氢酶(CAT)活性也呈先升后降的趋势,而超氧化物歧化酶(SOD)活性持续增加,CAT、POD和SOD活性分别在低锌、中锌和高锌处理时达到最大值,所有施锌处理的3种保护酶活性均显著高于缺锌对照;各处理小白菜叶片MDA含量随着施锌量增大而逐渐降低,且所有施锌处理均显著低于缺锌对照.研究发现,施锌能有效增强石灰性褐土上小白菜叶片光合能力和氮同化能力,显著提高其抗氧化酶系活性,并以75kg/hm2ZnSO4效果最佳.     

Tolerance to Zinc Deficiency in Rice Correlates with Zinc Uptake and Translocation

To study variation in zinc efficiency (ZE) among current Chinese rice genotypes, a pot experiment was conducted with 15 aerobic and 8 lowland rice genotypes. Aerobic rice is currently bred by crossing lowland with upland rice genotypes, for growth in an aerobic cultivation system, which is saving water and producing high yields. A Zn deficient clay soil was used in our screening. Zn deficiency resulted in a marked decrease in shoot dry matter production of most genotypes after 28 days of growth. Genotypes were ranked according to their tolerance to Zn deficiency based on ZE, expressed as the ratio of shoot dry weight at Zn deficiency over that at adequate Zn supply. Substantial genotypic variation in ZE (50–98%) was found among both lowland and aerobic genotypes. ZE correlated significantly (P < 0.05) with Zn uptake (R ² = 0.34), Zn translocation from root to shoot (R ² = 0.19) and shoot Zn concentration (R ² = 0.27). The correlation with seed Zn content was insignificant. In stepwise multiple regression analyses, variation in Zn uptake and Zn translocation explained 53% of variation in ZE. Variation in Zn uptake could be explained only for 32% by root surface area. These results indicate that Zn uptake may be an important determinant of ZE and that mechanisms other than root surface area are of major importance in determining Zn uptake by rice.     

Arbuscular Mycorrhizal Fungi Enhance Zinc and Nickel Uptake from Contaminated Soil by Soybean and Lentil

Generally, soils in Pakistan are deficient in P and N. Due to intensive cropping and irrigation, Pakistani soils have also become deficient in micronutrients such as Zn, Fe, Cu, and Mn. Arbuscular mycorrhizal fungi, which form symbiotic associations with roots of most land plants, are known to enhance uptake of P and trace elements such as Cu, Ni, Pb, and Zn. The present study was conducted to investigate the role of arbuscular mycorrhizae (AM) in uptake of nickel (Ni) and zinc (Zn) by crops viz. soybean (Glycine max (L.) Merrill) and lentil (Lens culinaris Medic). Zn and Ni were applied as ZnSO₄ 7H₂O and NiCl₂ respectively, in four concentrations (0.0, 1.0, 3.0, and 5.0 g kg^-1 soil). AM inoculum consisted of sand containing sporocarps, spores, and AMF infected root pieces from a pot culture of Glomus mosseae. Control plants received pot culture filtrate containing soil microflora minus AM fungal propagules. A significant difference (p < 0.05) was observed in the dry weights of roots and shoots of the mycorrhizal (M) and nonmycorrhizal (NM) cereal plants. The sievate-amended treatments did not stimulate plant growth to the same extent as the AM fungal amended treatments. Trace metals inhibited the extent of mycorrhizal colonization of the cereal roots. The concentrations of the trace metals in the plant tissues of 12-week old cereal plants were found significantly (p < 0.05) higher in M than NM plants. These results indicate that mycorrhize can be used as effective tools to supply sufficient Zn in generally Zn-deficient Pakistani soils and to ameliorate the toxicity of trace metals in polluted soils. The contents of Ni in mycorrhizal soybean plant tissues were higher than those in the mycorrhizal lentil plant tissues. The implications of these results in mycorrhizo remediation of agricultural soils are discussed.     

Zinc Mobility in Wheat: Uptake and Distribution of Zinc Applied to Leaves or Roots

Little is known about transport of Zn from leaves to other plantorgans. The present study tested a range of Zn forms appliedfoliarly for their suitability to provide adequate Zn nutritionto wheat (Triticum aestivum L.). Transport of⁶⁵Zn applied eitherto leaves or to one side of the root system was also studied.Inorganic (ZnO, ZnSO₄) and chelated sources of Zn (ZnEDTA, glycine-chelatedBiomin Zn) applied foliarly provided sufficient Zn for vigorousgrowth. Zinc concentrations in roots and shoots were in thesufficiency range, except in the -Zn control. Foliar treatmentswith ZnSO₄and chelated Zn forms resulted in shoot Zn concentrationsin 7-week-old plants being about two-fold greater than thosein plants supplied with Zn in the root environment or via foliarspray of ZnO. Adding surfactant to foliar sprays containingchelated forms of Zn did not cause negative growth effects,but surfactant added to ZnO or ZnSO₄foliar sprays decreasedshoot growth. Adding urea to the ZnO foliar spray had no effecton shoot growth. Foliarly-applied⁶⁵Zn was translocated to leavesabove and below the treated leaf as well as to the root tips.Stem girdling confirmed that⁶⁵Zn transport toward lower leavesand roots was via the phloem. Split-root experiments showedintensive accumulation of⁶⁵Zn in the stem and transport to allleaves as well as to the root tips in the non-labelled sideof the root system. Foliar application of Zn in inorganic ororganic form is equally suitable for providing adequate Zn nutritionto wheat. Phloem transport of Zn from leaves to roots was demonstrated.Copyright 2001 Annals of Botany Company Foliar spraying, phloem, surfactant, urea, xylem, wheat, zinc     

Effect of iron plaque outside roots on nutrient uptake by rice (Oryza sativa L.). Zinc uptake by Fe-deficient rice

This solution culture study examined the effect of the deposition of iron plaque on zinc uptake by Fe-deficient rice plants. Different amounts of iron plaque were induced by adding Fe(OH)₃ at 0, 10, 20, 30, and 50 mg Fe/L in the nutrient solution. After 24 h of growth, the amount of iron plaque was correlated positively with the Fe(OH)₃ addition to the nutrient solution. Increasing iron plaque up to 12.1 g/kg root dry weight increased zinc concentration in shoots by 42% compared to that at 0.16 g/kg root dry weight. Increasing the amount of iron plaque further decreased zinc concentration. When the amounts of iron plaque reached 24.9 g/kg root dry weight, zinc concentration in shoots was lower than that in shoots without iron plaque, implying that the plaque became a barrier for zinc uptake. While rice plants were pre-cultured in –Fe and +Fe nutrient solution in order to produce the Fe-deficient and Fe-sufficient plants and then Fe(OH)₃ was added at 20, 30, and 50 mg Fe/L in nutrient solution, zinc concentrations in shoots of Fe-deficient plants were 54, 48, and 43 mg/kg, respectively, in contrast to 32, 35, and 40 mg/kg zinc in shoots of Fe-sufficient rice plants. Furthermore, Fe(OH)₃ addition at 20 mg Fe/L and increasing zinc concentration from 0.065 to 0.65 mg Zn/L in nutrient solution increased zinc uptake more in Fe-deficient plants than in Fe-sufficient plant. The results suggested that root exudates of Fe-deficient plants, especially phytosiderophores, could enhance zinc uptake by rice plants with iron plaque up to a particular amount of Fe.     

Subcellular Localization of Zinc and Calcium in Bean (Phaseolus vulgaris L.) Tissues

Two bean (Phaseolus vulgaris L.) cultivars differing in growth responses to zinc were examined for differences in uptake and subcellular localization of ⁶⁵Zn during a 15-day growth period. The zinc-sensitive cultivar Sanilac showed initially a much higher rate of absorption, which declined after 24 hours. The zinc-tolerant cultivar Saginaw showed a slow but steady rate of absorption for 10 days. In roots as well as in stem callus tissues of both cultivars, three-fourths of the absorbed ⁶⁵Zn was localized in the “cytoplasmic” supernatant fractions (containing ribosomes and vacuolar sap). Very little (less than 7%) ⁶⁵Zn was localized in the cell wall fraction. There was a much greater proportion of the absorbed ⁶⁵Zn localized in root mitochondria and nuclei of the zinc-sensitive Sanilac than in the zinc-tolerant Saginaw. Stem callus tissues, however, did not show such cultivar differences in zinc accumulation at the sub-cellular level.     

Ecotypes of Holcus lanatus Tolerant to Zinc Toxicity also Tolerate Zinc Deficiency

Genotypes tolerant to zinc (Zn) toxicity, if they accumulateZn in their roots, may grow better than Zn-sensitive genotypes,even in Zn-deficient soil. In the present study, Holcus lanatusL. ecotypes differing in tolerance to Zn toxicity were grownin Zn-deficient Laffer soil which was amended with Zn to createa range of conditions from Zn deficiency to Zn toxicity. IncreasingZn additions to the soil, up to the sufficiency level, improvedgrowth of all ecotypes. At toxic levels of added Zn, the Zn-sensitiveecotype suffered a greater decrease in growth than the Zn-tolerantecotypes. All ecotypes accumulated more Zn in roots than inshoots, with root concentrations exceeding 8 g Zn kg^-1dry weightin extreme cases. When grown in Zn-deficient or Zn-sufficientsoil (up to 0.5 mg Zn kg^-1soil added), ecotypes tolerant toZn toxicity took up more Zn, grew better and had greater rootand shoot Zn concentration than the control (Zn-sensitive ecotype).Zn-tolerant ecotypes transported more Zn, copper (Cu) and iron(Fe) from roots to shoots in comparison with the Zn-sensitiveecotype. The average Zn uptake rate from Zn-deficient soil (noZn added) was greater in the Zn-tolerant ecotypes than in theZn-sensitive ecotype. In conclusion, ecotypes of H. lanatusthat are tolerant to Zn toxicity also tolerate Zn deficiencybetter than the Zn-sensitive ecotype because of their greatercapacity for taking up Zn from Zn-deficient soil. This is thefirst report of the coexistence of traits for tolerance to Zntoxicity and Zn deficiency in a single plant genotype. Copyright2000 Annals of Botany Company Copper, heavy metal, Holcus lanatus, iron, zinc deficiency, zinc toxicity     

Dietary Zinc Glycine Chelate on Growth Performance,Tissue Mineral Concentrations,and Serum Enzyme Activity in Weanling Piglets

One hundred twenty crossbred piglets (Duroc × Landrace × Yorkshire) were used to determine the effects of dietary zinc glycine chelate on growth performance, tissue mineral concentrations, and serum enzyme activity. All pigs were allotted to four treatments and fed with basal diets supplemented with 0, 50, and 100 mg/kg Zn as zinc glycine chelate or 3,000 mg/kg Zn as zinc oxide (ZnO). After the 35-day feeding trial, results of the study showed that, compared to the control, average daily gain was improved (P < 0.05) for pigs fed 100 mg/kg Zn from zinc glycine chelate or 3,000 mg/kg Zn from ZnO and Zn concentrations in serum and M. longissimus dorsi were significantly enhanced by 100 mg/kg dietary zinc glycine chelate and 3,000 mg/kg ZnO. In addition, supplementation of 100 mg/kg zinc glycine chelate decreased (P < 0.05) the liver Fe level, liver Zn level, spleen Cu level, and kidney Cu level compared to that of the 3,000-mg/kg ZnO group. For feces mineral excretion, 3,000 mg/kg Zn from ZnO greatly increased the concentration of fecal Zn (P < 0.01) and Mn (P < 0.05) compared to that of the control or the 100-mg/kg zinc glycine chelate group. Moreover, alkaline phosphatase and Cu/Zn superoxide dismutase activities of pigs in 100 mg/kg zinc glycine chelate and ZnO treatments were greatly higher than that of the control. The results of present study showed that supplementation with zinc glycine chelate could improve growth and serum enzyme activities and could also decrease zinc excretion in feces in weanling pig compared to high dietary ZnO.     

Localization of phytosiderophore release and of iron uptake along intact barley roots

Under iron deficiency the release of so-called phytosiderophores by roots of barley plants ( Hordeum vulgare L. cv. Europa) was greater by a factor of 10 to 50 compared to iron-sufficient plants. This enhanced release occurred particularly in apical zones of the seminal roots and in the lateral root zones. Under iron deficiency, uptake rates for iron, supplied as FeIII phytosiderophore, increased by a factor of ca 5 as compared to iron-sufficient plants. This enhanced uptake rate for iron was also much more pronounced in apical than in basal root zones. In contrast, with supply of the synthetic iron chelate, FelII EDDHA (ferric diaminoethane-N, N-di- o -hydroxyphenyl acetic acid), the Fe deficiency-enhanced uptake rates for iron were only small and similar along the roots, except for the lateral root zones. The high selectivity of barley roots for uptake and translocation of FeIII phytosiderophores compared with FeIII EDDHA is reflected by the fact that, at the same external concentration (2 μ M ), rates of uptake and translocation of iron from FeIII phytosiderophores were between 100 (Fe-sufficient) and 1 000 times higher (Fe-deficient plants) than from FeIII EDDHA. The relatively high rates of uptake and particularly of translocation of iron supplied as FeIII EDDHA in the zone of lateral root formation strongly suggest an apoplastic pathway of radial transport of the synthetic iron chelate into the stele in this root zone.
The results demonstrate that apical root zones are the main sites both for Fe deficiency-enhanced release of phytosiderophores and for uptake and translocation of iron supplied as FeIII phytosiderophores.     

Decrease in nitrate uptake and increase in proton release in zinc deficient cotton,sunflower and buckwheat plants

The effect of varied Zn supply on the pH of the nutrient solution and uptake of cations and anions was studied in cotton (Gossypium hirsutum L.), sunflower (Helianthus annuus L.) and buckwheat (Fagopyrum esculentum Moench) plants grown under controlled environmental conditions in nutrient solutions with nitrate as source of nitrogen. With the appearance of visual Zn deficiency symtoms, the pH of the nutrient solutions decreased from 6 to about 5 whereas the pH increased to about 7 when the plants were adequately supplied with Zn. In Zn deficient plants the pH decrease was associated with a shift in the cation-anion uptake ratio in favour of cation uptake. Of the major ions, uptake of Ca²⁺ and K⁺ was either not affected or only slightly lowered whereas NO₃ ^- uptake was drastically decreased in Zn deficient plants. Although the Zn nutritional status of plants hardly affected the NO₃ ^- concentrations in the plants, the leakage of NO₃ ^- from roots of Zn deficient plants into a diluted CaCl₂ solution was nearly 10 times higher than that of plants adequately supplied with Zn. In contrast to Zn deficiency, Mn deficiency in cotton plants neither affected NO₃ ^- uptake nor the pH of the nutrient solution.The results indicate that, probably as a consequence of the role of Zn in plasma membrane integrity and nitrogen metabolism, when Zn is deficient in dicotyledonous species net uptake of NO₃ ^- is particularly depressed which in turn results in an increase in cation-anion uptake ratio and a corresponding decrease in external pH. The ecological relevance of this rhizosphere acidification is discussed.