水稻物质生产与氮、磷、钾、硅素积累特点及其相互关系

大田条件下研究了30个水稻基因型的干物质与N、P、K、Si积累特性及其相互关系.结果表明,水稻干物质积累总量随N、P、K和Si积累总量的增加呈直线增加,其相关系数早季和晚季均达极显著水平.同时,N、P、K、Si积累的平衡有利于干物质积累,干物质积累量随NBI(养分平衡指数)直线增加,随NDI(养分偏离指数)直线下降.30个水稻品种平均N、P、K、Si积累总量比值早季为3.76:1:4.55:7.10,晚季为2.88:1:4.54:8.09.干物质积累能力以中期最强,前期最弱,而N积累能力却以前期最强,后期最弱.水稻抽穗前积累的干物质主要分配在茎鞘中,当抽穗期茎鞘比率达到最大时,茎鞘重约为叶片重的2倍,而抽穗前积累的N主要分配在叶片中,叶片中N的分配比率全生育期均比干物质分配比率高.成熟期积累的干物质、N和P主要分配在穗部,早、晚季稻的平均分配比率分别为58.01%、66.42%和70.06%,而K主要分配在茎鞘中,早、晚季稻的平均分配比率为62.08%.早季Si在茎中的分配比率(43.11%)最大,而晚季却以穗中的分配比率(46.99%)最大.     

水稻物质生产与氮、磷、钾、硅素积累特点及其相互关系

大田条件下研究了30个水稻基因型的干物质与N、P、K、Si积累特性及其相互关系．结果表明,水稻干物质积累总量随N、P、K和Si积累总量的增加呈直线增加,其相关系数早季和晚季均达极显著水平．同时,N、P、K、Si积累的平衡有利于干物质积累,干物质积累量随NBI(养分平衡指数)直线增加,随NDI(养分偏离指数)直线下降．30个水稻品种平均N、P、K、Si积累总量比值早季为3．76：1：4．55：7．10,晚季为2．88：1：4．54：8．09．干物质积累能力以中期最强,前期最弱,而N积累能力却以前期最强,后期最弱．水稻抽穗前积累的干物质主要分配在茎鞘中,当抽穗期茎鞘比率达到最大时,茎鞘重约为叶片重的2倍,而抽穗前积累的N主要分配在叶片中,叶片中N的分配比率全生育期均比干物质分配比率高．成熟期积累的干物质、N和P主要分配在穗部,早、晚季稻的平均分配比率分别为58．01％、66．42％和70．06％,而K主要分配在茎鞘中,早、晚季稻的平均分配比率为62．08％．早季Si在茎中的分配比率(43．11％)最大,而晚季却以穗中的分配比率(46．99％)最大．     

机插秧水稻物质生产与养分积累特性研究

为明确机插水稻的物质生产与养分积累特性,该研究以早季和晚季水稻常规品种(珍桂矮和新香粘)为材料进行大田试验,设置机插秧(行距30 cm×株距12 cm)、手插秧(行距30 cm×株距12 cm)、手抛秧(27.75万蔸·hm~(-2))三种栽培方式。在水稻抽穗期测定各处理叶面积指数,在分蘖期、拔节期、抽穗期和成熟期分别测定各处理干物质积累量,氮、磷、钾养分积累量及成熟期稻谷产量。结果表明:在同一单位面积栽植密度条件下,早晚两季、机插秧水稻在抽穗期的叶面积指数与手插秧水稻、手抛秧水稻间并无显著差异,机插秧水稻成熟期干物质,氮、磷、钾养分积累量等方面与手插秧、手抛秧水稻无显著差异,但其前期积累的干物质及养分积累量较少,后期积累量较大。早晚两季机插秧水稻、手插秧水稻和手抛秧水稻的产量分别是7.73、7.62、6.70 t·hm~(-2)和5.91、5.97、5.90 t·hm~(-2),都未表现出显著差异。这表明机插秧水稻的产量潜力、干物质和养分积累潜力与手插秧、手抛秧水稻的差异较小,但其物质积累过程与手插秧、手抛秧水稻存在明显差异。     

Wheat ear carbon assimilation and nitrogen remobilization contribute significantly to grain yield

The role of wheat ears as a source of nitrogen (N) and carbon (C) in the grain filling process has barely been studied. To resolve this question, five wheat genotypes were labeled with ¹⁵N‐enriched nutrient solution. N remobilization and absorption were estimated via the nitrogen isotope composition of total organic matter and Rubisco. Gas exchange analyses showed that ear photosynthesis contributed substantially to grain filling in spite of the great loss of C due to respiration. Of the total kernel N, 64.7% was derived from the N acquired between sowing and anthesis, while the remaining 35.3% was derived from the N acquired between anthesis and maturity. In addition, 1.87 times more N was remobilized to the developing kernel from the ear than from the flag leaf. The higher yielding genotypes showed an increased N remobilization to the kernel compared to the lower yielding genotypes. In addition, the higher yielding genotypes remobilized more N from the ears to the kernel than the lower yielding genotypes, while the lower yielding genotypes remobilized more N from the flag leaf to the kernel. Therefore, the ears contribute significantly toward fulfilling C and N demands during grain filling.     

Accumulation Characteristics of Protein and Non-Protein Components and Their Correlations with Protein Concentration in Rice Grains

Protein in rice grains is an important source of nutrition for rice consumers. This study mainly aimed to identify the critical factors that determine grain protein concentration in rice. Accumulation parameters, including mean accumulation rate (R_mean) and active accumulation duration (D_active), for protein and non-protein components and their correlations with protein concentration in rice grains were investigated in field experiments conducted over two years with six rice cultivars. Results showed that grain protein concentration ranged from 9.6% to 11.9% across cultivars and years. Accumulation processes of protein and non-protein components were well fitted by the logistic equation for all six rice cultivars in both years, and the ratio of protein to non-protein for R_mean and D_active ranged from 0.08 to 0.12 and 1.01 to 1.33, respectively. Grain protein concentration was significantly correlated with protein to non-protein ratio for R_mean. This study suggests that grain protein concentration is not solely determined by the accumulation of protein or non-protein component, but by the coordination of protein and non-protein accumulation.     

镉和砷在植物中的积累及其分子调控机制研究进展

植物源食物是人类摄入有毒金属元素镉(Cd)和砷(As)的主要途径。深化植物对Cd和As积累途径分子机制的认识,有助于培育可食部分中低有毒金属元素含量的作物新种质。该文基于近年来有关植物Cd和As积累在主要模式植物中所取得的实质性研究进展,对植物介导Cd和As吸收的转运蛋白、As形态和生物转化机制以及控制Cd和As根-地上部转运效率和分配的关键因子等方面的研究进展进行综述,并对未来的研究前景进行了展望。     

Mathematical estimations of hyper-ammonia producing ruminal bacteria and evidence for bacterial antagonism that decreases ruminal ammonia production(1)

Bacteria capable of denitrification are spread among phylogenetically diverse groups. In the present investigation, molecular methods (amplified ribosomal DNA restriction analysis (ARDRA) and partial 16S rDNA gene sequencing) were used to determine the genetic diversity of culturable denitrifying soil bacteria. The purpose of this work was to study the microbial density and diversity of denitrifying communities isolated from two luvisols and a rendosol. The denitrifying bacterial density was significantly higher in the two luvisols (3x10(6) and 4x10(6) bacteria g(-1) dry soil) than in the rendosol (4x10(5) bacteria g(-1) dry soil). Denitrifying isolates from soils were grouped according to the similarity of their restriction patterns into 26 ARDRA types. Interestingly ARDRA analysis suggests that some denitrifying isolates are specific to a soil type while others seem to be geographically widespread. The number of individual isolates found in each ARDRA type appeared to be highly variable between the two sampling dates but some denitrifying types were capable of persisting in soil. The tree obtained from the partial sequences revealed five major branches exhibiting highest identity to the following genera: (i) Burkholderia-Ralstonia, (ii) Pseudomonas, (iii) Xanthomonas-Frateuria, (iv) Bacillus and (v) Streptomyces. Our 16S rDNA-based analysis clearly reveals broad diversity exceeding that previously described in the literature.     

Differential regulation of phenylalanine ammonia-lyase genes during anthocyanin synthesis and by transfer effect in carrot cell suspension cultures

Phenylalanine ammonia-lyase (PAL; EC 4.3.1.5) catalyses the first step in the phenylpropanoid pathway and is induced during differentiation and by various stimuli. In carrot ( Daucus carota L. cv. Kurodagasun) suspension culture cells, PAL is slowly induced during anthocyanin synthesis which occurs in a medium lacking 2,4-dichlo-rophenoxyacetic acid and is also induced rapidly and transiently by transferring and diluting cells to fresh medium. Analyses of nucleotide sequences derived from PAL cDNAs revealed that the PAL mRNAs induced by transfer were transcribed from different carrot PAL genes than the PAL mRNAs induced during anthocyanin synthesis. Northern blotting using probes derived from 3'non-coding regions for PAL cDNAs confirmed that different PAL genes were induced during anthocyanin synthesis and after transfer. Induction of different PAL genes occurs in response to differences in the induction trigger.     

Cellular compartmentation of cadmium and zinc in relation to other elements in the hyperaccumulator Arabidopsis halleri

The cellular compartmentation of elements was analysed in the Zn hyperaccumulator Arabidopsis halleri (L.) O'Kane & Al-Shehbaz (=Cardaminopsis halleri) using energy-dispersive X-ray microanalysis of frozen-hydrated tissues. Quantitative data were obtained using oxygen as an internal standard in the analyses of vacuoles, whereas a peak/background ratio method was used for quantification of elements in pollen and dehydrated trichomes. Arabidopsis halleri was found to hyperaccumulate not only Zn but also Cd in the shoot biomass. While large concentrations of Zn and Cd were found in the leaves and roots, flowers contained very little. In roots grown hydroponically, Zn and Cd accumulated in the cell wall of the rhizodermis (root epidermis), mainly due to precipitation of Zn/Cd phosphates. In leaves, the trichomes had by far the largest concentrations of Zn and Cd. Inside the trichomes there was a striking sub-cellular compartmentation, with almost all the Zn and Cd being accumulated in a narrow ring in the trichome base. This distribution pattern was very different from that for Ca and P. The epidermal cells other than trichomes were very small and contained lower concentrations of Zn and Cd than mesophyll cells. In particular, the concentrations of Cd and Zn in the mesophyll cells increased markedly in response to increasing Zn and Cd concentrations in the nutrient solution. This indicates that the mesophyll cells in the leaves of A. halleri are the major storage site for Zn and Cd, and play an important role in their hyperaccumulation. Received: 4 April 2000 / Accepted: 16 May 2000     

Selenium and sulfur accumulation and soil selenium dissipation in planting of four herbaceous plant species in soil contaminated with drainage sediment rich in both selenium and sulfur

Four selenium (Se) nonaccumulator plant species, including a forage grass species, Tall Fescue (Festuca arundinacea Schreb.), a forage legume species, Alfalfa (Medicago sativa L.), a wetland species, Rush (Juncus tenuis Wild.), and a dry-land alkaline soil species, Saltgrass (Distichlis spicata L.), were grown in soil contaminated by agricultural drainage sediment having elevated levels of Se and sulfur (S). The above-ground plant tissues were consecutively harvested five times and examined for Se and S accumulation. Plant tissue Se concentrations ranged from 23.0 mg kg-1 to 8.3 mg kg-1. Tissue S concentrations ranged from 3239 mg kg-1 to 7034 mg kg-1. Both tissue Se and S concentrations were significantly different between harvests, species, and species/harvest interactions. Total Se accumulation by the plant biomass harvested ranged from 0.3 to 1.3 mg per soil column and total S accumulations ranged from 87.5 to 321.1 mg per soil column. The reduction in the percentage of total soil Se after 24 weeks growth of the plant species ranged from 12.0% in the Tall Fescue planting to 17.3% in the Rush planting. Over 90% of the soil Se losses were unidentified losses and leaching of Se was prevented. The accumulations of Se and S in the plant biomass were very small compared with the total soil Se and S losses, but substantial amounts of total soil Se (12.0 to 15.0%) and S (28.0 to 50.9%) inventories were dissipated by the growing and harvesting of the plants. The soil S concentration was several hundred times higher than the soil Se concentration, but Se accumulation by the plants and Se dissipation from the soil were not impaired by the high level of soil sulfur. For natural grassland habitat restoration, such as at the Kesterson Wildlife Refuge in the Central Valley of California, or for restoration of large-scale Se contaminated agricultural lands, Se nonaccumulator plant species are favorable candidates, because the possibility of introducing Se toxicity into the food chain can be minimized.     

聚磷茵JPA1菌株的生长特性和聚磷条件的优化

以YG培养基为基础,考察不同条件对聚磷菌JPA1菌株生长及聚磷效率的影响。结果表明：JPA1菌株生长的对数期为3-9h,9h后进入稳定期,12h到达衰亡期。在单因素试验中,麦芽糖为JPA1菌株最适生长和聚磷的C源,最适生长温度为30-35℃,pH为8,Na＋、Ca2＋、Mg2＋、Mn2＋和K＋等离子有利于JPA1菌株的生长;最适聚磷温度为30-35℃,pH为7,Fe2＋、Na2＋、Mg2＋、Mn“和K＋等离子有利于JPA1菌株的聚磷。正交试验结果表明：JPA1菌株去磷培养基的最优组合为麦芽糖1．5g／L,温度37℃,pH6．5,装液量50mL（300mL摇瓶）;菌株最适扩增培养基为麦芽糖1．5g/L,温度37℃,pH6．5或7．5,装液量150mL（300mL摇瓶）。     

Infection with Phloem Limited Abutilon Mosaic Virus Causes Localized Carbohydrate Accumulation in Leaves of Abutilon striatum: Relationships to Symptom Development and Effects on Chlorophyll Fluorescence Quenching During Photosynthetic Induction

Abstract: Infection with phloem limited Abutilon Mosaic Virus caused localized carbohydrate accumulation (high levels of starch, sucrose, and hexoses) in leaves of Abutilon striatum during early symptom development. In mature leaves with attenuated symptoms, tissues showing faint vein-clearing had markedly higher carbohydrate contents than uniformly green areas of the same leaf. A similar pattern of carbohydrate accumulation was found in pale-green mosaics in mature leaves with overt symptoms when compared to green-islands of the same leaf, but overnight carbohydrate loses were comparable to controls. Because leaves with attenuated symptoms showed no further symptom development whereas the pale-green mosaics became yellow and eventually necrotic in leaves with overt symptoms, it seems unlikely that carbohydrate accumulation following impaired translocation was responsible for symptom expression. High carbohydrate status in leaves with attenuated symptoms had little effect on nonphotochemical quenching during early stages of photosynthetic induction. In leaves with overt symptoms, areas of high carbohydrate status with pale-green mosaics showed markedly slower nonphotochemical quenching. Early symptom areas of young leaves, and advanced symptom areas of mature leaves had low starch contents but were otherwise similar to controls in carbohydrate status. Impaired nonphotochemical quenching in these tissues tended to reflect the state of symptom development, rather than carbohydrate status. Plants with overt symptoms grew about half as fast as plants with attenuated symptoms.     

Selection and characterization of sodium chloride-tolerant callus of Glycine max (L.) Merr cv. Acme

Callus cultures were initiated from soybean (Glycine max (L.) Merr cv. Acme) cotyledons onMiller's basal medium supplemented with 2 mg L^–1NAA and 0.5 mg L^–1 kinetin. Growing cells wereexposed to increasing concentrations of NaCl in themedium. A concentration of 100 mM NaCl completelyinhibited callus growth. After incubation for 28 d,cells which could tolerate this concentration of NaClgrew to form cell colonies. A NaCl-tolerant line wasobtained through continuous subculturing on 100 mMNaCl. Salt tolerance in this culture was characterizedby an altered growth behavior, reduced cell volume, and accumulation of Na⁺, Cl^–, proline and sugars when grown under salt stress, as well as on normal media. These characteristics, which proved tobe stable after the culture was transferred to asalt-free medium, is commonly associated with halophytes. Presented data suggest that this salt tolerance is the result of a shift towards a halophytic behavior.     

Silver tolerance and accumulation in yeasts

Summary Debaryomyces hansenii (NCYC 459 and strain 75-21),Candida albicans (3153A),Saccharomyces cerevisiae (X2180-1B),Rhodotorula rubra (NCYC 797) andAureobasidium pullulans (IMI 45533 and ATCC 42371) were grown on solid medium supplemented with varying concentrations of AgNO₃. Although Ag⁺ is highly toxic towards yeasts, growth on solid media was still possible at Ag concentrations of 1–2 mM. Further subculture on higher Ag concentrations (up to 5 mM) resulted in elevated tolerance. The extent of Ag tolerance depended on whether Ag-containing plates were exposed to light prior to inoculation since light-mediated reduction of Ag⁺ to Ag⁰ resulted in the production of a less toxic silver species. Experimental organisms exhibited blackening of colonies and the surrounding agar during growth on AgNO₃-containing medium especially at the highest Ag concentrations tested. All organisms accumulated Ag from the medium; electron microscopy revealed that silver was deposited as electron-dense granules in and around cell walls and in the external medium. X-ray microprobe analysis indicated that these granules were metallic Ag⁰ although AgCl was also present in some organisms. Volatile and non-volatile reducing compounds were produced by several test organisms which presumably effected Ag⁺ reduction to Ag⁰.     

The accumulation and metabolism of plant growth regulators during organogenesis in cultures of thin cell layers of Nicotiana tabacum

The accumulation and metabolism of exogenously applied and endogenously produced auxins and cytokinins were studied in relation to organogenesis in thin cell layers of Nicotiana tabacum L. It was shown that, in order to obtain maximal flower bud formation, both exogenous auxin and cytokinin needed to be present during the first 4 days of culture (to the formation of a subepidermal meristematic zone) whereas cytokinins needed to be present for at least 4 days more (until formation of organogenic centres). Explants taken from floral branches have higher endogenous indole-3-acetic acid (IAA) levels compared with explants from the basal part of the stem which form only vegetative buds. This might be related to a different IAA metabolism in these two types of explants as was shown by the different accumulation of exogenously applied IAA. Both 'floral' and 'vegetative' cells layers contained comparable amounts of zeatin riboside (ZR) as their major cytokinin. Free bases, zeatin (Z) and dihydrozeatin [(diH)Z], given exogenously, were largely metabolised to their respective ribosides. The observation that Z was less effective than (diH)Z in the induction of flower buds could be related to (diH)ZR apparently not being a substrate for cytokinin oxidase.     

几种蔬菜对外源碘的吸收与积累特性

在盆栽条件下研究了小白菜、芹菜、辣椒和萝卜4种蔬菜对2种外源碘(海藻固体碘肥和KI)的吸收与积累特性.结果表明:蔬菜体内的碘含量均随外源碘浓度的提高而逐渐增加;不同蔬菜种类对碘的吸收与积累能力存在较大差异,叶菜类的小白菜对碘的积累能力最强,其次为茎菜类的芹菜,而根菜类的萝卜和果菜类的辣椒吸收与积累碘的能力较弱;碘在蔬菜体内的分布一般为根>叶>茎>果实,但萝卜地下块根的碘含量低于地上部分.低浓度碘处理(0～25mg.kg-1)对蔬菜生长没有明显的影响,但高浓度的外源碘(≥50mg.kg-1)对蔬菜生长有抑制作用,导致蔬菜生物量减少.不同蔬菜对碘的敏感反应表现为辣椒>小白菜>芹菜>萝卜.与海藻固体碘肥相比,KI处理的第1茬蔬菜生物量下降明显(P<0.05),而2种外源碘对第2茬蔬菜的生长均无显著影响.蔬菜对2种外源碘的吸收和积累效果同样存在很大差异(P<0.05),第1茬蔬菜对KI的吸收能力强于海藻碘肥(P<0.05),第2茬蔬菜对KI的吸收量迅速下降,而对海藻固体碘肥的吸收下降不明显,说明海藻固体碘肥比KI具有更长的持效性.     

Biodiversity growth on the volcanic ocean islands and the roles of in situ cladogenesis and immigration: case with the reptiles

Models for biodiversity growth on the remote oceanic islands assume that in situ cladogenesis is a major contributor. To test this, we compiled occurrence data for 194 terrestrial reptile species on 53 volcanically‐constructed middle‐ to low‐latitude landmasses worldwide. Despite 273 native island‐species records, there are only 8–12 cases of the phenomenon, including just two radiations. Diversification frequencies are largely uncorrelated with island area, age, maximum altitude, and isolation. Furthermore, there is no indication that the presence of non‐sister congeners on an island stymies the process. Diversity on individual oceanic islands therefore results primarily from immigration and anageneis, but this is not a simple matter. Clusters that are difficult to reach (far or challenging to get to) or thrive upon (e.g. Canaries, Galápagos) have relatively few clades (3–8), some of which have many species (6–14), and all host at least one endemic genus. In these settings, diversity grows mainly by intra‐archipelago transfer followed by within‐island anagenetic speciation. In contrast, those island groups that are easier to disperse to (characterized by short distances and conducive transit conditions) and harbour more benign habitats (e.g. Comoros, Lesser Antilles) have been settled by many ancestor‐colonizers (≥ 14), but each clade has few derived species (≤ 4). These archipelagoes lack especially distinctive lineages. Models explaining the assembly and growth of terrestrial biotic suites on the volcanic ocean islands thus need to accommodate these new insights.     

HMW-GS组成不同小麦品种各种亚基形成和积累规律研究

以3个HMW—GS组成不同的冬小麦品种为材料,研究了籽粒形成过程中亚基形成及积累表达规律。结果表明,不同亚基形成时间存在差异,Glu—D1、Glu—B1编码的亚基约在开花后第13天最早出现,Glu—A1编码的1亚基形成较晚。在灌浆期亚基已基本全部形成,但积累较慢;花后第20天后进入成熟过程,高分子量麦谷蛋白亚基大量迅速积累,开花第28～31天积累量达最高,之后含量有所下降。同一品种内不同亚基积累量不同,形成较早的Glu—D1、Glu—B1编码的亚基积累量最多,Glu—D1编码的X型亚基在所有供试品种中都有最多量的积累。     

Uptake and distribution of selenium in different fern species

There has been an interest in using hyperaccumulating plants for the removal of heavy metals and metalloids. High selenium (Se) concentrations in the environment are detrimental to animals, humans, and sustainable agriculture, yet selenium is also an essential nutrient for humans. This experiment was conducted to screen fern plants for their potential to accumulate selenium. Eleven fern species, Pteris vittata, P. quadriaurita, P. dentata, P. ensiformis, P. cretica, Dryopteris erythrosora, Didymochlaena truncatula, Adiantum hispidulum, Actiniopteris radiata, Davallia griffithiana, and Cyrtomium fulcatum, were grown under hydroponic conditions for one week at 20 mg L(-1) selenate or selenite. Root Se concentrations reached 245-731 and 516-1082 mg kg(-1) when treated with selenate and selenite, respectively. The corresponding numbers in the fronds were 153-745 and 74-1,028 mg kg(-1) with no visible toxicity symptoms. Only three fern species were able to accumulate more Se in the fronds than the roots, which were D. griffithiana when treated with selenate, P. vittata when treated with selenite, and A. radiata regardless of the forms of Se. A. radiata was the best species overall for Se accumulation. More research is needed to further determine the potential of the fern species identified in this study for phytoremediation of the Se contaminated soils and water.