Intensification of Reservoir Fisheries in Tropical and Subtropical Countries

By now, most marine and inland fishery resources have been fully exploited or overexploited. To keep up with the growing demand for fish, only a few avenues for increasing fish production remain open. One of these is the intensification of fisheries in inland waters, such as reservoirs, lakes and small water bodies. Fish species transfer and culture-enhanced fisheries based largely on exotic species, mainly tilapias and cyprinids, is the current common strategy for increasing fishery benefits from tropical and subtropical inland water bodies. The growing human population and rising expectations require a steady growth in the number of reservoirs, both large and small. The development of cage and pen culture, especially in Asia, has substantially increased the reservoir fish production there. In Latin America, tilapias are the mainstay of many reservoir fisheries. By the year 2025, an additional 62 million tonnes of aquatic products will be required to maintain the present consumption of 19.1 kg/person. Much of it will have to come from inland waters, including reservoirs and small water bodies.     

Evaluation of Chalcone Derivatives as Photosynthesis and Plant Growth Inhibitors

We report the evaluation of chalcone derivatives as photosystem II (PSII) and plant growth inhibitors. Chalcone derivatives were evaluated as PSII inhibitors through Chl a fluorescence measurement. (E)-Chalcone ( 6a ) and (E)-3-(4-bromophenyl)-1-(4-fluorophenyl)prop-2-en-1-one ( 6j ) showed the best results, reducing the performance index on absorption basis parameter (PI_abs) by 70 %. Additionally, the decrease of TR₀/RC and ET₀/RC parameters indicates that the chalcone derivatives limited the number of active PSII reaction centers and the amount of trapped energy within them. Compounds 6a and 6j both act as post-emergent herbicides at 50 μM, reducing the root biomass of the Ipomoea grandifolia weed by 72 % and 83 %, respectively, corroborating the fluorescence results. The selectivity against weeds as compared to valuable crops by compounds 6a and 6j were evaluated employing Zea mays and Phaseolus vulgaris plants. In these, our newly synthesized compounds showed no effects on biomass accumulation of roots and aerial parts when compared to the control, providing valuable evidence for the role of these compounds as selective inhibitors of the growth of undesired weeds.     

Interspecific Interactions among Tropical and Subtropical Freshwater Fungi

Abstract Twenty-seven species of tropical and subtropical fungi isolated from freshwater were examined for evidence of interspecific interactions, which are important in determining the ecological roles of fungi. Evidence for interspecific interactions was examined by inoculating paired fungi 25 mm apart on the surface of agar plates. The antagonistic activities were different among different isolates and even between isolates of the same species, for example, Ophioceras dolichostomum isolated from different origins. Pseudohalonectria longirostrum and Kirschsteiniothelia elaterascus, which produced pigment in culture, were strongly inhibitory species. Several aquatic hyphomycetes seems to be less competitive and less likely to produce antagonistic substances. Competitive abilities were also influenced by the range of enzymes that a fungus produced. For example, Verticillium sp. and Diaporthe sp., which produced only one or two kinds of enzyme, were found to exhibit weak competitive abilities and were easily replaced. The results of competition experiments also showed that slow-extending fungi (e.g., Pseudohalonectria longirostrum and Kirschsteiniothelia elaterascus) were more competitive than early fast-extending fungi (e.g., Ophioceras dolichostomum and Nectria haematococca). Received: 13 October 1998; Accepted: 3 March 1999     

Diazotrophic Diversity and Distribution in the Tropical and Subtropical Atlantic Ocean

To understand the structure of marine diazotrophic communities in the tropical and subtropical Atlantic Ocean, the molecular diversity of the nifH gene was studied by nested PCR amplification using degenerate primers, followed by cloning and sequencing. Sequences of nifH genes were amplified from environmental DNA samples collected during three cruises (November-December 2000, March 2002, and October-November 2002) covering an area between 0 to 28.3°N and 56.6 to 18.5°W. A total of 170 unique sequences were recovered from 18 stations and 23 depths. Samples from the November-December 2000 cruise contained both unicellular and filamentous cyanobacterial nifH phylotypes, as well as γ-proteobacterial and cluster III sequences, so far only reported in the Pacific Ocean. In contrast, samples from the March 2002 cruise contained only phylotypes related to the uncultured group A unicellular cyanobacteria. The October-November 2002 cruise contained both filamentous and unicellular cyanobacterial and γ-proteobacterial sequences. Several sequences were identical at the nucleotide level to previously described environmental sequences from the Pacific Ocean, including group A sequences. The data suggest a community shift from filamentous cyanobacteria in surface waters to unicellular cyanobacteria and/or heterotrophic bacteria in deeper waters. With one exception, filamentous cyanobacterial nifH sequences were present within temperatures ranging between 26.5 and 30°C and where nitrate was undetectable. In contrast, nonfilamentous nifH sequences were found throughout a broader temperature range, 15 to 30°C, more often in waters with temperature of <26°C, and were sometimes recovered from waters with detectable nitrate concentrations.     

Inhibition of Hydrolytic Enzyme Activities and Plant Pathogen Growth by Invertase Inhibitors

The invertase inhibitory protein isolated from Cyphomandra betacea Sendt and Solanum tuberosum inhibited the invertase activity from different species, genera and even plant family. Furthermore, proteinaceous inhibitors are not invertase specific; fungal, bacterial and higher plant enzymes including polygalacturonase, pectinase, pectin lyase, α - l -arabinofuranosidase and β -glucosidase are also shown to be inhibited. Both inhibitors exhibited an in vitro antibacterial action against phytopathogenics strains of Xanthomonas campestris pvar vesicatoria CECT 792, Pseudomonas solanacearum CECT 125, Pseudomonas corrugata CECT 124, Pseudomonas syringae and Erwinia carotovora var carotovora.     

Soilless Plant Growth Media Influence the Efficacy of Phytohormones and Phytohormone Inhibitors

Plant growth regulators, such as hormones and their respective biosynthesis inhibitors, are effective tools to elucidate the physiological function of phytohormones in plants. A problem of chemical treatments, however, is the potential for interaction of the active compound with the growth media substrate. We studied the interaction and efficacy of propiconazole, a potent and specific inhibitor of brassinosteroid biosynthesis, with common soilless greenhouse growth media for rice, sorghum, and maize. Many of the tested growth media interacted with propiconazole reducing its efficacy up to a hundred fold. To determine the molecular interaction of inhibitors with media substrates, Fourier Transform Infrared Spectroscopy and sorption isotherm analysis was applied. While mica clay substrates absorbed up to 1.3 mg of propiconazole per g substrate, calcined clays bound up to 12 mg of propiconazole per g substrate. The efficacy of the gibberellic acid biosynthesis inhibitor, uniconazole, and the most active brassinosteroid, brassinolide, was impacted similarly by the respective substrates. Conversely, gibberellic acid showed no distinct growth response in different media. Our results suggest that the reduction in efficacy of propiconazole, uniconazole, and brassinolide in bioassays when grown in calcined clay is caused by hydrophobic interactions between the plant growth regulators and the growth media. This was further confirmed by experiments using methanol-water solvent mixes with higher hydrophobicity values, which reduce the interaction of propiconazole and calcined clay.     

Vegetation Components of a Subtropical Rural Landscape in China

To assess the overall vegetation changes and their ecological significance, following landscape evolution, plant composition and physical structures of the homegardens (woodlots and vegetation patches with hedgerow fence) and field boundaries were examined in the rural landscape of subtropical China in order to determine their ecological significance. Field surveys on landscape changes and plant composition were carried out in two typical villages in the Yangtze river plain. Analysis of landscape changes and plant composition showed that the rural landscape is diverse both in terms of types of elements and plant species. The vegetation types in the area have undergone frequent alterations by human beings following major changes of landscape management due to economic and social reforms. The plant diversity of the various vegetation types in the area is related to the duration of colonization of the vegetation type, the extent of disturbance by human beings, and the physical structure diversity of the vegetation type. In the discussion, the plant diversity and heterogeneity of the physical environment in any vegetation type is of importance for the ecological sustainability of the landscape.     

Tropical Plant Extracts Modulating the Growth of Mycobacterium ulcerans

Mycobacterium ulcerans, the etiologic agent of Buruli ulcer, has been detected on aquatic plants in endemic tropical regions. Here, we tested the effect of several tropical plant extracts on the growth of M. ulcerans and the closely related Mycobacterium marinum. M. ulcerans and M. marinum were inoculated on Middlebrook 7H11 medium with and without extracts from tropical aquatic plants, including Ammannia gracilis, Crinum calamistratum, Echinodorus africanus, Vallisneria nana and Vallisneria torta. Delay of detection of the first colony and the number of colonies at day 7 (M. marinum) or day 16 (M. ulcerans) were used as endpoints. The first M. ulcerans colonies were detected at 8 ± 0 days on control Middlebrook 7H11 medium, 6.34 ± 0.75 days on A. gracilis-enriched medium (p<0.01), 6 ± 1 days on E. africanus- and V. torta-enriched media (p<0.01), 6 ± 0 days on V. nana-enriched medium (p<0.01) and 5.67 ± 0.47 days on C. calamistratum-enriched medium (p<0.01). Furthermore, the number of detected colonies was significantly increased in C. calamistratum- and E. africanus-enriched media at each time point compared to Middlebrook 7H11 (p<0.05). V. nana- and V. torta-enriched media significantly increased the number of detected colonies starting from day 6 and day 10, respectively (p<0.001). At the opposite, A. gracilis-enriched medium significantly decreased the number of detected colonies starting from day 8 PI (p<0.05). In conclusion, some aquatic plant extracts, could be added as adjuvants to the Middlebrook 7H11 medium for the culturing of M. marinum and M. ulcerans.     

Synthesis of Novel Plant Growth Inhibitors Structurally Related to Abscisic Acid

When paraffin wax is dispersed in medium as emulsion, some kinds of bacteria and yeasts readily grow on it. This paper presents a study on microbial cell production from solid paraffin. In this study a paraffin wax which contains 91% of normal paraffins ranging from C₂₅ to C₃₇ with the melting point of 62.5°C was used as a substate, but no solvent was used for the dispersion of the wax.

As a result of this study, the following have been found out. (1) Many strains of liquid normal paraffin assimilating bacteria and yeasts can assimilate paraffin wax. (2) Dried cell yields on added hydrocarbons of Corynebacterium hydrocarboclastus S-12-B2 and Candida tropicalis S-315-Y1 are 70% and 56% respectively, when they are cultured by wax emulsion of 0.6% concentration. (3) When nonion surface-active agent (Plysurf A210G) was added as an emulsifing agent, highly concentrated wax emulsion was obtained, but the growth of microorganisms on it was slower. Further investigation is needed to obtain better strains of bacteria and yeasts and also to find out optimum culture conditions.     

Coumarin-related Compounds as Plant Growth Inhibitors from Two Rutaceous Plants in Thailand

Chemical investigation of naturally occurring plant growth inhibitors from Rutaceous plants in Thailand led us to identify five 7-methoxycoumarins and one 5,7-dimethoxycoumarin from Murraya paniculata, and six furanocoumarins from Citrus aurantifolia. Of these compounds, murranganon senecioate (1) is a new natural compound found in M. paniculata. Minumicrolin (6) was found to be highly active against the 2nd leaf sheath elongation of rice seedlings.     

关于华南的热带与亚热带分界线问题

关于华南的热带与亚热带的分界线问题,地理学工作者和植物学工作者都发表过一些文章,从各个角度进行讨论。华南的地植物学工作者多赞成以雷州半岛北部作为华南热带与亚热带的分界线,把广东大陆的亚热带分为两个亚带,即华南南亚热带常绿季雨林亚带和南岭山地中亚热带常绿阔叶林亚带。侯宽昭、徐祥浩(1955年)首先从地植物学角度提出,华南的热带与亚热带的分     

Investigations on Growth and Metabolism of Plant Cells: III. Evidence for Growth Inhibitors in Certain Mature Tissues

Using the carrot explant technique, with added coconut-milkfactor, evidence has been obtained of inhibitors of growth inpotato tubers, onion bulbs, and maple buds. In discussion itis suggested that the regulation of growth in such tissues asmature parenchyma may thus be due to absence of necessary growth-factorsor the presence of growth inhibitors.     

Proteinase Inhibitors in Plant Seed

Three different types of proteinase inhibitors, I, II and III, were fractionated from Japanese radish seed by repeated column chromatographies on SE- and CM-cellulose. The finally purified preparation of inhibitor III was found to be homogeneous by both chromatographic and electrophoretic analyses. All three of them strongly and stoichiometrically inhibited trypsin whereas they showed weak inhibition on other proteinases, such as chymotrypsin, Nagarse and Pronase. From nitrogen content and ultraviolet absorption spectra, each of the inhibitors I and III was confirmed to be a protein. The molecular weights of inhibitors I and III were calculated to be 8000 and 12,000, respectively. These inhibitors were stable at temperatures above 90°C in an acidic pH.     

Syntheses and Biological Activities of New Plant Growth Inhibitors Structurally Related to Abscisic Acid

Several analogs of abscisic acid (ABA) were prepared and their biological activities were assayed. Among the compounds tested, 5-(l, 2-epoxy-2, 6, 6-trimethyl-l-cyclohexyl)-, 5-(l-hydroxy-2, 6, 6-trimethyl-2-cyclohexen-l-yl)- and 5-(l-hydroxy-2-methylene-6, 6-dimethyl-l-cyclohexyl)-3-methyl-cis, trans-2, 4-pentadienoic esters (V, IX, XXIII and XXV) were found to be potent plant growth inhibitors. Their activities were superior or comparable to that of ABA.     

Proteinase Inhibitors in Plant Seeds

The proteinase inhibitors I (R-I) and III (R-III) isolated from Japanese radish seed were characterized in terms of their N-terminal amino acids, amino acid composition and reacting groups. The amino acid composition of two proteins differed from each other, while histidine, methionine and tryptophan contents were all low. N-Terminal amino acids of these inhibitors determined by Edman degradation were the same; valine.

By modifying free amino groups in the inhibitors with trinitrobenzenesulfonic acid, R-III was greatly inactivated in proportion to the modification of amino groups, but the activity of R-I was not affected.

However, modification of arginyl residues of R-I by cyclohexanedione reduced its activity. These results indicate that R-I is an arginine-type and R-III is a lysine-type inhibitor.     

A New Method for Separation of Gibberellins and Growth Inhibitors in Plant Extracts using Sephadex Columns

A method is described for estimating gibberellin levels in plantmaterial, using a separation method avoiding organic solvents.High molecular weight inhibitors were separated from growth-promotingfractions by column chromatography on Sephadex. Of the severalgrades of Sephadex tried, G15 was found to give the sharpestseparation. Ammonium chloride was included in the sample appliedto the column to increase the retention of anionic substances.The inhibitory effect of other substances, probably abscisicacid, which are eluted from the gel together with the gibberellins,was reversed by addition of kinetin to test solutions in thelettuce hypocotyl bioassay. Using this method an increase ingibberellin level in cotyledons of Phaseolus multiflorus duringgermination was measured in terms of GA₃ activity, with referenceto the lettuce hypocotyl bioassay.     

Growth and Germination Inhibitors in Hog-weed

Properties of a glutathione transport system in T. ferrooxidans strain AP-44 were investigated using a reduced form of ³⁵S-glutathione (³⁵S-GSH). About 71.2% of the total radioactivity taken up into the cells was distributed in the cytosol fraction. The amount of GSH taken up into the cells was in proportion to the amount of ferrous iron oxidized. However, a high concentration of silver ions (50 mm), which completely inhibited an iron-oxidizing activity, did not inhibit the GSH transport. The results suggest that GSH was transported by using a proton electrochemical gradient formed across the cytoplasmic membrane. Since growth inhibition by silver nitrate was decreased by the addition of GSH to both silver ion sensitive-cells and resistant-cells, the GSH transport system may play some role in the silver ion resistance mechanism of the bacterium.