甜高粱茎秆汁液成分分析及浓缩贮藏的试验研究

为提高甜高粱茎秆汁液制取燃料乙醇的原料利用率,延长甜高粱茎秆及其汁液贮藏期限,测定了辽甜1号、早熟1号、醇甜2号三个甜高粱品种茎秆及其汁液的营养成分,采用浓缩法对甜高粱茎秆汁进行了贮藏试验.结果表明,三个品种都含有丰富的糖分,可以为酵母菌发酵制取酒精提供良好的碳源,但总氮和某些矿物质元素(如:Fe3 )不能满足酒精酵母的营养需要;甜高粱茎秆汁浓缩至4～5倍时,可以抑制汁液中大多数微生物的活动,使其中糖分不受损失;在试验设定的真空浓缩工艺条件下(55～60℃,0.15 Mpa)甜高粱茎秆汁中产酸微生物或水解酶类仍保持活性,使得还原糖占总糖的比率随贮藏时间延长而升高,这有利于酒精发酵.     

自然干燥甜高粱茎秆长期贮藏及乙醇发酵研究

为了延长甜高粱乙醇生产原料供应时间,将甜高梁茎秆自然干燥后用于长期贮藏.分别考察干燥和长期贮藏过程糖分变化,结果显示,自然干燥过程中,茎秆的含水率(干基)由80％降低至18％时,总糖损失率为3.85％;不同含水率的茎秆经6个月长期贮藏,含水率为22％以下茎秆中的总糖和还原糖基本保持不变.表明自然干燥过程使总糖损失较小,22％可作为甜高粱茎秆干燥贮藏的“安全含水率”.通过考察干燥的茎秆乙醇发酵的可行性,结果表明,固态发酵24 h即可达到终点,基质中的乙醇质量分数可以达67.06 mg/g(干基),发酵过程基本正常.通过该研究,表明自然干燥可作为甜高粱茎秆长期贮藏的一种较为有效的加工方式,可为解决甜高粱乙醇周年生产的原料供应问题提供一定技术参考.     

陇东山旱地夏播复种饲用甜高粱品种筛选

陇东山旱地区为陇东肉羊肉牛产业的重要生产区，其长期饲草供应不足，困扰产业发展。为探明山旱地夏播复种饲用甜高粱的干草生产力状况，增加饲草生产能力，引进了4个饲用甜高粱品种在陇东山旱地开展试验。结果表明，甜高粱2180收割高度最高，为169.53 cm；其次是陇甜粱1号，为160.87 cm。茎粗以海牛最高，为11.20 mm；陇甜粱1号、甜高粱2180较高，分别为10.20、10.00 mm。鲜草产量、干物质产量均以甜高粱2180最高，分别为35 073.68、14 985.53 kg/hm2；其次是陇甜粱1号，分别为30 797.60、12 385.86 kg/hm2。陇甜粱1号的可溶性糖含量(268.3 g/kg)、干物质采食量(2.24%)、相对饲用价值(110.20)和可消化营养物(57.84)均为最高，其次是甜高粱2180。综合分析，陇甜粱1号和甜高粱2180产草量高，营养价值较高，可在陇东地区山旱地种植。     

高CO2冲击处理对采后蓝莓生理代谢及品质的影响

为了解高CO2处理对采后蓝莓果实生理代谢的影响及其作用机制,该试验采用体积分数为99.9%的高CO2处理蓝莓果实48、96 和144 h,然后装入聚乙烯薄膜袋后松扎口,贮藏在1℃下。贮藏期间,分析测定了果实风味指数、呼吸速率、腐烂率、呼吸商、果肉乙醇含量和pH值、果实硬度以及与自由基形成和清除相关的多酚氧化酶 （PPO）、 过氧化物酶 （POD）、过氧化氢酶（CAT）和脂氧合酶（LOX）等酶活性。结果表明,高CO2处理48 h和96 h降低了蓝莓果肉的pH值,有效控制了腐烂率,保持了较高的果实硬度,诱导了POD活性升高并使LOX活性维持在较低水平,从而降低了蓝莓果实的呼吸速率,并使有效贮藏期延长到50 d 左右。144 h的高CO2处理对果实造成不可逆伤害,导致无氧呼吸发生,诱发了果实异味产生以及腐烂率的增加。研究结果表明,高CO2短时冲击用于采后蓝莓果实贮前的“休克冲击”处理,具有抑制果实生理代谢和保持品质的保鲜效果。     

甜高粱茎秆汁液锤度与可发酵糖含量的关系

甜高粱茎秆富含糖分,是生产燃料乙醇的良好原料。在甜高粱育种或生产中,常用锤度估算汁液含糖量,但锤度与可发酵糖的关系还不是很清楚。本文采用81个甜高粱材料,种植于北京、天津(盐碱地)、河北3个地点,研究了茎秆汁液锤度与可发酵总糖和蔗糖含量的关系。结果表明,北京、河北、天津三个地点甜高粱茎秆汁液总糖/锤度(糖锤比)总平均值分别为0.76、0.74和0.72,其中天津的甜高粱茎秆汁液糖锤比显著低于北京。北京、河北、天津三个地点甜高粱茎秆汁液锤度与总糖、蔗糖含量的相关性均达极显著水平,相关系数分别为0.8911,0.8376和0.9186,其中天津点显著低于河北。适合北京和河北非盐碱地种植的甜高粱茎秆汁液的锤度、可发酵总糖含量的整合回归方程为Y=0.8969X-1.7576(R2=0.8237);天津盐碱地糖锤比低于北京,相关系数显著低于河北,故其回归方程Y=0.9343X-3.1726(R2=0.7015)只可供其它盐碱地区参考。锤度和糖锤比的相关系数显著低于总糖含量和糖锤比的相关系数,说明含糖量高,锤度也高,但锤度高,含糖量不一定高。该结果对于甜高粱育种和加工工艺设计具有重要参考价值。     

植物生长调节剂对甜高粱茎秆贮藏中糖分变化的影响

为降低甜高粱茎秆采后自然贮藏期内含糖量损失,掌握糖分损失与有关酶活性变化的关系,该文研究了采用植物生长调节剂处理甜高粱植株对其采后贮藏含糖量影响,以及有关酶活性的变化情况。结果表明,用适当种类和剂量的植物生长调节剂处理可以将甜高粱茎秆贮藏期延长到3～4个月,贮藏至112d,赤霉素(40mg/L)、马来酰肼钾盐(400mg/L)、萘乙酸钠(70mg/L)处理的茎秆干基含糖量分别为初始值的95%、92%和94%,均显著高于对照组。采用适当种类和剂量的植物生长调节剂对调节与甜高粱茎秆采后衰老及糖代谢有关酶的活性具有显著作用,这3种植物生长调节剂对甜高粱茎秆采后糖分损失的抑制与其调节有关酶活性有关。该项研究为解决大规模使用甜高粱茎秆制取燃料乙醇过程中的茎秆贮藏问题提供了参考。     

气调包装对松籽常温贮藏生理和品质变化的影响

以朝鲜红松带壳松籽和去壳松仁为试材,将其分别放在30 μm紫色聚氯乙烯袋、30 μm白色聚氯乙烯袋和40 μm白色聚乙烯袋中进行自发气调贮藏,研究了常温下（20～30℃）贮藏180 d期间松籽种仁的生理、品质和脂肪酸氧化变化。结果表明：与40 μm聚乙烯袋相比,30 μm紫色聚氯乙烯袋与30 μm白色聚氯乙烯袋可以形成相对低O2高CO2的贮藏条件,能有效降低带壳松籽和去壳松仁的呼吸速率和可溶性总糖的损耗,提高种仁的贮藏优品率;同时可以较好地防止总脂肪的降解,抑制酸价、过氧化值的升高和碘价的降低。综上所述,30 μm聚氯乙烯袋可以较好地保持松籽品质,相同气调包装贮藏下带壳松籽的贮藏品质优于去壳松仁。     

土壤盐胁迫降低后甜高粱的补偿生长和盐离子分布特征

逆境补偿效应在作物中普遍存在,对作物生长发育与产量产生重要的影响。为阐明土壤盐度降低后甜高粱的补偿生长效应,本研究采用盆栽方法,将甜高粱拔节期的土壤含盐量设置3个梯度:5 g×kg~(-1)(高盐处理)、由5 g×kg~(-1)降低到2 g×kg~(-1)(盐度降低处理)、2 g×kg~(-1)(低盐对照),测定2个甜高粱品种地上部器官(茎秆、叶片、叶鞘)干物质生长速率与积累,以及盐离子(Na~+、Cl~-、K~+)在不同器官的含量。结果表明:高盐处理甜高粱地上部干物质增长速率一直显著低于对照;土壤盐度降低后,各器官干物质生长速率明显升高,并超过对照,产生了超补偿效应。成熟期高盐处理株高与地上部干物质大幅下降;土壤盐度降低后‘辽甜1号’的株高与地上部干物质较低盐对照分别下降7.69%和33.21%,而‘中科甜3号’的株高和地上部干物质重与对照没有差异。高盐处理后各器官干物质中Na+和Cl-含量较对照大幅度提高,K+含量增加幅度较小。土壤盐分降低后的35 d,甜高粱Na+和Cl-在各器官中含量虽仍高于对照,但比高盐处理已大幅下降;茎秆与叶鞘K+的含量较对照有小幅提高,而叶片K+含量与对照无显著差异。本研究表明:甜高粱盐胁迫降低后离子毒害减轻、生长速率加快直至超过对照,耐盐甜高粱品种补偿效应尤为明显,成熟期干物质产量可与对照相当。本研究结果可为盐碱地甜高粱栽培提供理论依据。     

薄膜气调包装对枇杷果实冷藏期间呼吸和品质性状的影响

通过对呼吸速率、总可溶性固形物、可滴定酸、pH值、果肉硬度、维生素C、失重率和品质及感官指标的变化进行分析，研究了薄膜气调包装对枇杷(Eriobotrya japonica Lindl.，品种：解放钟）果实冷藏期间呼吸和品质特性的影响，气调包装用的薄膜为低密度聚乙烯薄膜(LDPE，厚度20 μm)，以打孔的低密度聚乙烯薄膜包装为对照。结果表明，低密度聚乙烯薄膜包装枇杷果实后，3～4 d后可维持一个相对稳定的适宜枇杷贮藏的O₂和CO₂的气体浓度，即CO₂(4.8±0.67)%，O₂(11.5±0.85)%；薄膜气调包装结合低温可明显地降低枇杷果实的呼吸速率；薄膜气调包装可以最大限度地减小冷藏期间的枇杷果实的失重率、果肉硬度、维生素C、总可溶性固形物、可滴定酸和固酸比的变化，维持枇杷的新鲜品质，延长货架期。因此，低密度聚乙烯薄膜（LDPE，厚度20 μm）气调包装可用于枇杷的贮藏保鲜。     

叶面喷施硫酸锌对马铃薯淀粉合成和积累的影响

"克新13号"马铃薯品种用不同浓度的硫酸锌叶面喷施后,测定叶片与块茎中淀粉、蔗糖和还原糖含量以及相关酶活性。结果表明,适量硫酸锌(2~4 g.L-1)叶面喷施处理后马铃薯叶中蔗糖磷酸合成酶、蔗糖转化酶以及块茎蔗糖转化酶和蔗糖合成酶活性均提高,促进马铃薯叶和块茎中的蔗糖、还原糖的合成,块茎中淀粉合成和积累提高。     

低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响

【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。     

Pasture Vegetation Elemental Analysis by Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Assessing the effectiveness of conservation measures: Resolving the “wicked” problem of the Steller sea lion

“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.     

Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage

Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.     

Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass

The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.     

Variation in quality parameters between and within 14 Nordic tree fruit and berry species

Abstract

A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species.     

Enhanced establishment and growth of giant cardon cactus in an eroded field in the Sonoran Desert using native legume trees as nurse plants aided by plant growth-promoting microorganisms and compost

To evaluate the feasibility of long-term desert reforestation technology of mixed vegetation, cardon cactus (Pachycereus pringlei) seedlings from indoor and outdoor nurseries were planted in the field adjacent to one seedling of potential legume nurse trees: mesquite amargo (Prosopis articulata), yellow palo verde (Parkinsonia microphylla), and blue palo verde (Parkinsonia florida). Some of the planting holes were also supplemented with common dairy compost. Additionally, the combinations of legume tree–cactus were inoculated with either a consortium of desert arbuscular mycorrhizal (AM) fungi, plant growth promoting bacteria (PGPB; the diazotroph Azospirillum brasilense Cd, and the phosphate solubilizer Paenibacillus sp.), or a mixture of all. The field experiments were evaluated periodically during 30 months for survival and growth. Cardons reared in an outdoor screen house survived better in the field than those reared in a controlled growth chamber and hardened later outdoors. Association with any legume nurse tree increased survival and enhanced growth of untreated cardons. For cardons growing alone, application of either compost, AM fungi, and all the treatments combined increased survival. For these plants, no treatment affected plant growth during the first 3 months after transplanting. Later, all treatments, except for AM fungi, enhanced plant growth. However, only 2 years after transplanting the enhanced growth effect of AM fungi was also significant. In the presence of the legume nurse trees, transient positive effects on cardon growth were recorded. General evaluation after 30 months of cultivation showed that the treatments positively affected cardon growth when growing alone or in combination only with mesquite amargo but not with the other two legume trees. This study proposes that young legume trees have the capacity to enhance survival and growth of cardon cactus, depending on the legume cactus combination. Additional treatments such as compost or PGPB can either amplify the effect or else attenuate it.     

Karyotypic and genome size variation in Cajanus cajan (L.) Millsp. (pigeonpea) and some wild relatives

Detailed karyotypes and 4C DNA amounts have been studied in five cultivars of Cajanus cajan and 20 species belonging to Cajanus, Rhynchosia, Dunbaria, Flemingia and Paracalyx. C. cajan shows intraspecific variability and its karyotype is most similar to that of C. cajanifolius (sect. Cajanus) in the morphology and number of satellite chromosomes and the lack of any correlation between chromosome size within the complement and asymmetry. Karyotypes of C. lineatus and C. sericeus belonging to sect. Atylia are similar with respect to maximum r-index and the ratio of longest and shortest chromosomes in their respective complements. C. acutifolius (sect. Frutocosa) is distinct in having a very low ratio (1.44) between the longest and the shortest chromosomes, while in C. albicans, C. goensis, C. scarabaeoides (sect. Cantharospermum) there is no chromosome pair with r-index >2.0. C. mollis and C. volubilis (sect. Volubilis) show similarity with regard to ratio between the longest and the shortest chromosomes and a distinct chromosome pair with an arm ratio of 2.7 and C. platycarpus is distinct (sect. Rhynchosoides) in having the smallest ratio (1.36) between the longest and the shortest chromosomes. 4C DNA amounts in Cajanus and Rhynchosia vary between 3.28 pg to 11.69 pg and 4.92 pg to 11.13 pg respectively, while in Dunbaria, Flemingia and Paracalyx these vary between 4.70 and 7:06 pg. In the genus Cajanus karyotypic features and 4C DNA amounts agree with the sectional classification and bring out a close relationship between C. cajan and C. cajanifolius. This is supported by studies based on seed protein patterns, isozyme analysis, trypsin and chymotrypsin inhibitor patterns, RFLP and RAPD data and crossability relationships. A clear relation between DNA amount and abnormalities effecting the extent of pairing and recombination in interspecific hybrids shows the importance of this study in developing future breeding programme involving C. cajan and its wild relatives that are of potential value.     

Potassium Fixation and Release Characteristics in Rhizosphere and Nonrhizosphere Soils for a Rapeseed–Rice Cropping Sequence

Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L^?1 nitric acid (HNO₃) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L^?1 ammonium acetate (NH₄OAc) and 1.0 mol L^?1 HNO₃ extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils.