水稻对土壤中DDT及其系列降解物的吸收

在温室条件下,盆栽种植水稻(Oryza sativa,淹水土壤),设老化态DDT残留和新施入DDT两种处理,生长期126 d。研究结果显示:老化残留DDT在土壤中降解十分缓慢,而新施入DDT在土壤中降解相当迅速,GC/MS鉴定结果表明,降解物除DDD外,还有DDMS和DDMU。尽管土壤中老化残留的降解受到明显抑制,但水稻根系仍可吸收利用并向地上组织传输,因此不可低估老化残留的生物有效性。在新施入DDT的处理中,水稻根系对DDD的吸收量高达900 ng g-1,不过,根系向地上部组织传输DDX的能力极为有限。值得注意的是:水稻根系对土壤中DDMS和DDMU吸收的生物富集因子为DDD或DDE的3倍,表明DDMU和DDMS具有较母体化合物更为突出的作物可吸收利用性。DDX各组分从水稻根系向地上组织传输时,其分布状况发生了明显的变化,引起这种变化的主要原因是作物在吸收和传输DDX时具有一定的选择性,或者DDX在这种吸收和传输过程中发生了进一步的降解。     

施硒对冬小麦镉吸收、迁移及分配的影响

为探明施硒对冬小麦镉吸收、迁移及分配的影响,采用盆栽试验,设置镉0 mg·kg~(-1)(Cd_0)、1.5mg·kg~(-1)(Cd_(1.5))、6 mg·kg~(-1)(Cd_6)3个水平和硒0 mg·kg~(-1)(Se_0)、0.5 mg·kg~(-1)(Se_(0.5))、5 mg·kg~(-1)(Se_5)3个水平,研究不同施硒量对冬小麦各部位中镉质量分数的影响。结果表明,冬小麦产量随镉胁迫的增加而下降,Se_(0.5)、Se_5处理均增加冬小麦产量。在Cd_(1.5)水平下,施硒增加冬小麦各部位的镉质量分数,降低籽粒及根中镉分配比例,最大降幅分别为29.0%和23.5%。在Cd_6水平下,Se_5处理显著降低冬小麦籽粒、颖壳、茎秆中镉质量分数以及根到茎秆镉迁移系数;施硒提高根中镉分配比例,最大增幅为51.7%,降低茎秆中镉分配比例,最大降幅为52.3%。Se_5处理可抑制冬小麦对镉的吸收,减少冬小麦中镉向籽粒的转运。     

不同浓度氨源引起的红松苗木根际pH变化及其对Fe、Mn、Cu、Zn有效性和吸收的影响

Dark brown forest soil was collected from the upper 20 cm soil layer in Changbai Mountain Research Station of Ecosystem, Chinese Academy of Sciences. The soil was amended with two different forms of nitrogen fertilizers: NO₃ as Ca(NO₃)₂, NH₄ ⁺ as NH₄Cl at the concentrations of 50, 100, 200 and 400 mg kg⁻¹respectively. The experiment was carried out with 2-yr-oldPinus koraiensis seedlings in pot. The pH change of rhizosphere soil and the contents of available Fe, Mn, Cu, and Zn in soil and leaves were analyzed. The result indicated that the addition of NH₄-N decreased the rhizosphere pH value, while the addition of NO₃-N increased the rhizosphere pH value in contrast with the control treatment. The direction and extent of the pH change mainly depended on N source and its concentrations applied. The rhizosphere pH change had a remarkable influence on the availability of the micronutrients in the rhizosphere, and thereafter affected the nutrient uptake by the seedlings. The contents of available mineral nutrients had a negative correlation with the pH value in the rhizosphere soil. The contents of available mineral nutrients in leaves were positively correlated to the levels of the available nutrients in the rhizosphere soils. Foundation item: This paper was supported by National Natural Science Foundation of China (Grant No. 30170167). Biography: CHEN Yong-liang (1969-), male, Ph. Doctor, lecture of Northeast Forestry University, Harbin 150040, Post-doctor in Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, P. R. China. Responsible editor: Song Funan     

印度芥菜对土壤中难溶态铅的吸收与活化

[目的]研究了印度芥菜对石灰性土壤中难溶态铅的吸收、活化和积累规律。[方法]采用盆栽试验,研究了印度芥菜对石灰性土壤中难溶态Pb吸收的影响和对石灰性Pb污染土壤的修复效率。[结果]印度芥菜能够吸收石灰性土壤中难溶态铅并正常生长。印度芥菜吸收的铅80%以上累积在根部,根际与非根际土壤中DTPA提取的铅含量差异不显著。在该试验条件下,印度芥菜对土壤中铅的净化率为0.01~0.02%。[结论]印度芥菜对模拟石灰性污染土壤中难溶态Pb的净化效果不理想。     

不同耐低磷水稻基因型秧苗对难溶性磷的吸收利用

选取4个典型耐低磷水稻基因型99011、508、580和99112,并以2个磷敏感基因型99012和99056为参照,采用营养液培养和砂培的方法,研究不同磷处理对秧苗生长的影响以及不同耐低磷基因型对3种难溶性磷源(有机磷、铝磷和磷矿粉)吸收利用能力的差异。结果表明,不同无机磷处理,6个基因型生物量和根干重基本上均为全磷处理（P）>对照+铝磷（CK+Al-P）>对照+磷矿粉（CK+RP）> 对照（CK）;4个耐低磷基因型根干重和根冠比均大于2个磷敏感基因型;对于根冠比,耐低磷基因型580和99011为对照+磷矿粉（CK+RP）>对照+铝磷（CK+Al-P）> 对照（CK）> 全磷处理（P）,耐低磷基因型508、99112和磷敏感基因型99012为CK> CK+RP> CK+Al-P > P,磷敏感基因型99056为CK+Al-P > CK+RP > P>CK;缺磷处理,秧苗活化吸收难溶性磷源的能力均为OP> Al-P> RP,且不同基因型的分解吸收能力对OP为99011> 508> 580> 99012> 99112> 99056（表2）,对Al-P为580> 99011> 99112> 508> 99056> 99012（表3）,对RP为580> 99112> 99011> 508> 99012> 99056（表2）。此外,缺磷即CK处理,508对低浓度的磷吸收最多(表2和表3),而580对磷的利用效率显著高于其他基因型（表3）,这些特征可能也是它们耐低磷的重要贡献因子之一。     

不同磷源及其配比对铜绿微囊藻生长和摄磷效应的影响

在实验室条件下研究了无机磷(磷酸氢二钾)与2种有机磷(β-甘油磷酸钠、三磷酸腺苷钠)不同配比对铜绿微囊藻(Microcystis aeruginosa)的生长效应以及微囊藻摄取不同磷形态[总溶解磷(total dissolved phosphorus,TSP)、溶解反应磷(soluble reactive phosphorus,SRP)和溶解有机磷(dissolved organic phosphorus,DOP)]的规律。结果表明,当无机磷与有机磷配比为6∶1时,对铜绿微囊藻生长最有利,对数生长期可维持6～8d,其最大生物量达2.586×106个/mL;培养基中以有机磷作为唯一磷源时,铜绿微囊藻的生长最差;2种有机磷(β-甘油磷酸钠、三磷酸腺苷钠)对铜绿微囊藻生长的效果相似,铜绿微囊藻对SRP的摄取速度越快,其生长速率也越高(R=0.9995);待水中可利用磷耗尽后,β-甘油磷酸钠会在碱性磷酸酶作用下转化成可利用磷供藻生长,而三磷酸腺苷可直接分解成磷酸基供铜绿微囊藻生长。     

Influence of ambient acidity on the absorption of NO3 − and NH4 + by tomato punts

Abstract

The effects of ambient acidity on NO₃ ^? and Nh₄ ⁺ absorption by 26‐day‐old tomato plants (Lycopersicon esculentum Mill.) were examined in solution culture. The absorption rate per unit root mass was measured for 6 hr. The NO₃ ^? absorption rate from 0.4 mM NaNO, was 36% greater at pH 4.5 than at pH 6.5. In contrast, the NhY absorption rate was approximately 42% greater at pH 5.5 or 6.5 than at pH 4.5. The presence of equimolar NHr from 0.4 mM NH^NO, decreased the NO, absorption rate at pH 5.5 or 6.5 but did not reduce the rate at pH 4.5. The NO, absorption rate was inhibited less at pH 5.5 when equimolar NHr was supplied from 0.2 mM (NH₄)₂S0₄ as opposed to NH₄NO₃. At pH 5.5, the N0₃ ^? absorption rate increased with increased #OPNH₄#CP₂SO₄ concentration. The presence of equimolar NO₃ ^? supplied as either NaNO₃ or NH₄NO₃ had no effect on the NH₄ ⁺ absorption rate at pH 5.5 or 6.5. However, at pH 4.5, the NH₄ ⁺ absorption rate was slightly reduced from NH₄NO₃ solutions relative to that from a (NH₄)₂S0₄ solution.     

Citrus rootstock and carbon dioxide enriched irrigation influence on seedling emergence,growth, and nutrient content 1

Seeds of Carrizo citrange (Citrus senensis (L.) Osb. X Poncirus trifolliata (L.), Cleopatra mandarin (C. reticulata Blanco), Sour orange (C. aurantium L.), and Rough lemon (C. Union (Buna f.) were sown in trays, irrigated without or with enriched Carbon dioxide (CO₂) (1,362 mg L^‐1) and evaluated for seedling emergence, growth, and nutrient contents. Rough lemon had a faster rate and higher percent emergence than the other rootstocks. Carrizo citrange had thicker stem diameters and taller seedlings than other rootstocks. Cleopatra mandarin had the smallest seedling shoot and root weights and larger shootrroot ratios than Rough lemon and Sour orange. Carrizo citrange and Cleopatra mandarin had higher leaf chlorophyll‐a and total chlorophyll content than Rough lemon or Sour orange. Carbon dioxide enriched irrigation had no effects on emergence or seedling growth variables except lower root weight. Lower media pH (6.90 versus 5.65), attributed to CO₂ enriched irrigation, may have adversely affected root growth as compared to shoot characteristics. Leaf nutrient contents generally differed between rootstocks but were not affected by CO₂ enriched water except for higher Zn and lower Mn contents. These results indicate that citrus seedling emergence, subsequent growth and leaf nutrient content differred between rootstocks but there are no beneficial effect from CO₂ enriched irrigation.     

Puccinellia tenuiflora Exhibits Stronger Selectivity for K+ over Na+ than Wheat

Abstract

The characteristics of selectivity for K⁺ over Na⁺ by the roots of the halophyte Puccinellia tenuiflora were investigated in comparison with the glycophyte wheat (Triticum aestivum). Under various NaCl concentrations, the concentrations of K⁺ in the shoots of P. tenuiflora were 16–24% lower than those of wheat, whereas the concentrations of K⁺ in Puccinellia roots were 2.8–4.0 times higher than those of wheat. In 200 mM NaCl, the concentrations of Na⁺ in shoots of P. tenuiflora and wheat were similar under high K⁺ levels, but the concentrations of Na⁺ in wheat were 1.6 times higher than those in Puccinellia under low K⁺ levels. The concentrations of K⁺ in roots of P. tenuiflora were 1.5–2.0 times higher than those of wheat under low K⁺ levels. Formulas are given for calculating net selective absorption (SA) capacity and selective transport (ST) capacity by roots for K⁺ over Na⁺. We interpret SA as the net capacity of selectively absorbing K⁺ over Na⁺ by epidermal and cortical cells of whole plant roots into the root symplast. ST could reflect the net capacity of selection for K⁺ over Na⁺ transport from whole root stelar symplast to the xylem vessels. The lower ST value of P. tenuiflora might be the reason for accumulation of K⁺ in its roots. The SA values of P. tenuiflora and wheat were approximately equivalent in the low-affinity K⁺ uptake range. The SA values of the former were about two times higher than that of the latter in the high-affinity K⁺ uptake range, showing the root high-affinity K⁺ uptake system of the halophyte P. tenuiflora has a stronger capacity for K⁺ uptake.     

The Yields and Carbon and Nitrogen Balances in the Polyfactorial Field Experiments

The polyfactorial long-term field experiments have been founded in 1979 in several experimental stations located in different soil and climatic conditions, representing a climate and pedosequence of arable soils in the Czech Republic. Four of these experiments exist till the present time. Essentially, the same experimental design that includes different fertilisation with farmyard manure and/or with mineral fertilisers (N, P, K), liming and stand density, each in five levels with four replications, have been applied for all these experiments. Practically, the same eight year crop rotations were applied during the first and second rotations. A conventional tillage has been applied. Organic carbon and nitrogen contents in soil, dry matter of the main and second products, nitrogen uptake by the main and second products and carbon and nitrogen balances have been evaluated in six selected variants of organic and mineral fertilisation over the time period 1996 to 2000.