Estimation of the primary productivity of Spartina alterniflora using a canopy model

A comprehensive canopy productivity model was built to study the productivity of a primary salt marsh grass, Spartina alterniflora. in Georgia, USA The canopy model was unique in employing plant demographic data to reconstruct canopy profiles and dynamics, which showed many growth processes that are otherwise difficult to discern in the field By linking canopy dynamics and leaf photosynthesis, the net total primary productivity of S alterniflora m a Georgia salt marsh was estimated to be 1421, 749, and 1441 g C m^-2 yr^-1 for the tall, short, and N-fertilized short populations respectively These estimates are reasonable in terms of the physiological capacity of S alterniflora and well below the range of 3000–4200 g C m^-2 yr^-1 as reported by some recent harvest studies Our detailed analysis suggested the net total productivity of S alterniflora might be greatly overestimated in the past This is mainly because of 1) failure to consider the translocation of photosynthate between aboveground and belowground parts, and 2) possible overestimates of belowground production We estimated the net belowground production to be 872, 397, and 762 g C m^-2 yr^-1 for the tall, short, and N-fertilized populations respectively After receiving nitrogen fertilizer, the net leaf carbon fixation in the short population increased from 1489 to 2487 g C m^-2 yr^-1, and our simulation showed the contribution of elevated leaf N to this increase was small, 21%, compared with that of increased leaf area, 79% Both tall and short populations allocated ca 48-49% of their annual gross leaf carbon fixation to belowground structures Nitrogen enrichment caused more allocation to aboveground parts in the short population, mainly for increasing leaf area The canopy model assumed that there was no leaf photosynthesis under tidal submergence, but if this assumption was relaxed, then leaf carbon fixation might increase 7–13% for different S alterniflora populations Although this research focused only on a salt marsh species, our general approaches, especially the coupling of leaf physiology with the reconstructed canopies, should be applicable to the study of production processes of many other plant populations     

Insertional Mutation on Mouse Chromosome 18 with Vestibular and Craniofacial Abnormalities

A dominant mutation was generated in transgenic mice as a consequence of insertional mutation. Heterozygous mice from transgenic line 9257 (Tg(9257)) are hyperactive with bidirectional circling behavior and have a distinctive facial appearance due to hypoplasia of the nasal bone. Morphological analysis of the inner ear revealed asymmetric abnormalities of the horizontal canal and flattening or invagination of the crista ampullaris, which can account for the circling behavior. The sensory epithelium appeared to be normal. The transgene insertion site was localized by in situ hybridization to the B1 band of mouse chromosome 18. Genetic mapping in an interspecific backcross demonstrated the gene order centromere--Tg(9257)--8.8 +/- 3.4--Grl-1, Egr-1, Fgf-1, Apc--14.7 +/- 4.3--Pdgfr. The phenotype and the mapping data suggest that the transgene may be inserted at the Twirler locus. Homozygosity for the transgene results in prenatal lethality, but compound heterozygotes carrying the Tw allele and the transgene are viable. The function of the closely linked ataxia locus is not disrupted by the transgene insertion. This insertional mutant will provide molecular access to genes located in the Twirler region of mouse chromosome 18.     

Photoinhibition and light-dependent turnover of the D1 reaction-centre polypeptide of photosystem II are enhanced by mineral-stress conditions

The function of photosystem II (PSII) and the turnover of its D1 reaction-center protein were studied in spinach (Spinacia oleracea L.) plants set under mineral stress. The mineral deficiencies were induced either by supplying the plants with an acidic nutrient solution or by strongly reducing the supply of magnesium alone or together with sulfur. After exposure for 8–10 weeks to the different media, the plants were characterized by a loss of chlorophyll and an increase in starch content, indicating a disturbance in the allocation of assimilates. Depending on the severity of the mineral deficiencies the plants lost their ability to adapt even to moderate iradiances of 400 mol photons·m^–2·s^–1 and became photoinhibited, as indicated by the decrease in F_v/F_m (the ratio of yield of variable fluorescence to yield of maximal fluorescence when all reaction centers are closed). The loss of PSII function was induced by changes on the acceptor side of PSII. Fast fluorescence decay showed a loss of PSII centers with bound Q_B, the secondary quinone acceptor of PSII, and a fast reoxidation kinetic of q _a ^- , the primary quinone acceptor of PSII, in the photoinactivated plants. No appreciable change could be observed in the amount of PSII centers with unbound Q_B and in Q_B-nonreducing PSII centers. Immunological studies showed that the contents of the D1 and D2 proteins of the PSII reaction center and of the 33-kDa protein of the water-splitting complex were diminished in the photoinhibited plants, and the occurrance of a new polypetide of 14 kDa that reacted with an antibody against the C-termius of the D1 protein. As shown by pulse-labelling experiments with [¹⁴C]leucine both degradation and synthesis of the D1 protein were enhanced in the mineral-deficient plants when compared to non-deficient plants. A stimulation of D1-protein turnover was also observed in pH 3-grown plants, which were not inhibited at growth-light conditions. Obviously, stimulation of D1-protein turnover prevented photoinhibition in these plants. However, in the Mg- and Mg/S-deficient plants even a further stimulation of D1-protein turnover could not counteract the increased rate of photoinactivation.Abbreviations amp_(f,m,s) amplitude of the fast, (medium and slow) exponential component of fluorescence decay - F_m yield of maximum fluorescenc when all reaction centers are closed - F_o yield of intrinsic fluorescence at open PSII reaction centers in the dark - F_v yield of variable fluorescence, (difference between F_m and F_o) - LHC light-harvesting complex - PFD photon flux density - Q_A primary quinone acceptor of PSII - Q_B secondary quinone acceptor of PSII Dedicated to Professor Dr. Dres. hc. Achim Trebst on the occasion of his 65th birthdayThis work was supported by grants from the BMFT and the Ministerium für Umwelt, Raumordnung and Landwirtschaft, Nordrhein-Westfalen. The authors thank H. Wietoska and M. Bronzel for skilful technical assistance.     

Effect of shock-loading of heavy metals on total organic carbon and phosphate removal in an anaerobic-aerobic activated sludge process

The effect of shock-loading of zinc, copper and cadmium ions on the removal of total organic carbon (TOC) and phosphate in an anaerobic-aerobic activated sludge process was investigated. TOC removal was not sensitive to shock-loading of Zn²⁺ and Cd²⁺ ions, and complete removal was achieved even at 20 mg Zn²⁺/l and 20 mg Cd²⁺/l. However, with over 1 mg Cu²⁺/1 TOC removal efficiency decreased. PO _inf4 ^sup3- removal, in contrast, was extremely sensitive to these metal ions, with the threshold being 1 mg Zn²⁺/l and 1 mg Cd²⁺/l. Higher concentrations adversely affected PO _inf4 ^sup3- removal. Copper again proved detrimental; no PO _inf4 ^sup3- removal was achieved even at 1 mg Cu/l. These results highlight the sensitivity of the removal efficiencies of TOC and PO _inf4 ^sup3- to shock loadings of these heavy metals.Y.P. Ting is with the Department of Chemical Engineering, National University of Singapore, Kent Ridge, 0511, Singapore; H. Imai and S. Kinoshita are with the Department of Chemical Process Engineering, Hokkaido University, Sapporo 060, Japan.     

水分胁迫对小麦光系统Ⅱ的影响

水分胁迫可降低小麦叶绿体的室温荧光产量和Ｍｇ２＋ 在两个光系统间的调节能力、叶片的可变荧光产量、可变荧光猝灭速率以及荧光上升互补面积,表明光系统Ⅱ受到了伤害。光系统Ⅱ氧化侧的人工电子供体ＤＰＣ能部分恢复受到抑制的叶绿体可变荧光,说明水分胁迫对光系统Ⅱ的损伤部位不仅位于氧化侧,也可能在反应中心上     

质体醌重组的D1／D2／Cytb559复合物的荧光衰减动力学和光破坏作用

光系统Ⅱ反应中心Ｄ１／Ｄ２／Ｃｙｔｂ５５９ 在分离纯化过程中失去了电子受体ＱＡ 和ＱＢ,人工合成的质体醌可以与Ｄ１／Ｄ２／Ｃｙｔｂ５５９ 复合物发生重组。癸基质体醌（ＤＰＱ）与Ｄ１／Ｄ２／Ｃｙｔｂ５９９ 复合物的重组导致该复合物的荧光强度下降及发射光谱蓝移,同时两个与光化学活性相关的长寿命（２４ ｎｓ和７３ ｎｓ）荧光衰减组分占整个荧光的百分数下降,这些结果表明ＤＰＱ作为Ｐｈｅｏ－ 的电子受体,限制了Ｐ６８０＋ ·Ｐｈｅｏ－ 的电荷重组。ＤＰＱ 的加入对Ｄ１／Ｄ２／Ｃｙｔｂ５５９复合物中Ｃｈｌａ 分子的光破坏敏感性影响不大,但β－胡萝卜素在加入ＤＰＱ 之后可以被光照破坏,这个过程可能与β－胡萝卜素的生理功能相关。     

大蒜中期染色体内的核糖核蛋白物质

研究了大蒜（Ａｌｌｉｕｍ ｓａｔｉｖｕｍ Ｌ．）中期染色体的超微结构和ＲＮＰ物质。常规染色表明,大部分染色体内部有低电子密度区,有的染色体中低电子密度区域较大而似孔洞。银染结果也证明了有大小不等的孔洞存在。Ｂｅｒｎｈａｒｄ 染色显示,在染色体周边和染色体内部都有ＲＮＰ分布。用ＮａＯＨ 处理证明了Ｂｅｒｎｈａｒｄ 染色法所显示的深染区确实含有ＲＮＡ。ＲＮＰ量的多少与ＥＤＴＡ 的分化时间呈负相关     

Purification,and characterization of a β-mannanase of Trichoderma reesei C-30

Trichoderma reesei was studied for its ability to produce -mannanase activity on a variety of carbon sources. The highest -mannanase activity was produced on cellulose, whereas -mannan-containing carbon sources (such as kojac powder or locust bean gum) gave lower enzyme titres. The enzyme responsible for the major -mannanolytic activity from T. reesei was purified to physical homogeneity by preparative chromatofocusing and anion exchange fast protein liquid chromatography. This -mannanase is a glycoprotein, with a molecular mass of 46 (±2) kDa and an isoelectric point of 5.2. It has an optimal pH at 5.0 and broad pH stability (2.5–7.0). It is stable for 60 min at 55° C, and has an optimal temperature for activity at 75° C. During incubation with locust bean gum, the enzyme releases mainly tri- and disaccharides. Correspondence to: C. P. Kubicek