The Effect of Photoinhibition on Photosynthetic Oxygen Production in the Brown Alga Dictyota dichotoma

Photoinhibition of photosynthesis in the brown alga, Dictyota dichotoma, was studied with a PAM fluorometer (Walz, Effeltrich, Germany) and a homemade oxygen measuring device. As a measure of fluorescence, Fv/Fm, and for the photosynthetic yield, ΔF/Fm', were used. Oxygen measurements show clearly that the observed degree, as well as the time course, of photoinhibition depends on the fluence rate of the light used to measure changes of the production rate. After photoinhibition of photosynthesis the depression of oxygen production caused by non-saturating fluence rates was generally much more pronounced than that caused by saturating or nearly saturating fluence rates. At minimal photoinhibition the initial slope and the convexity of the fluence rate-response curve of oxygen evolution decrease, whereas the level of light saturation decreases only after strong photoinhibition. Nevertheless, at different degrees of photoinhibition, changes in the degree of the upper bending of the fluence rate-response curve of oxygen production are also linearly correlated to changes in the fluorescence ratios (Fv/Fm and ΔF/Fm'). The action spectrum of photoinhibition, calculated on the basis of changes of Fv/Fm, indicates that the reaction center of PS I is not involved in photoinhibition. The lower effectiveness of blue light in comparison to effects of green and red light may be due to chloroplast displacement, as in the so-called strong light position, the light absorbed by the thalli in vivo is decreased.     

The first report on the characterization of a virus isolated from Allomyrina dichotoma in the Republic of Korea

This report reveals the structure of a virus extracted from the Korean horn beetle Allomyrina dichotoma. The purified virus particle was 100% identical to Allomyrina virus lef‐8 sequence registered as KM_233709.1. The structure of this virus was confirmed to be closely related to that of the Nudiviridae family, and it was rod shaped and enveloped, and observed to be of approximately the mean length of a single viral nucleocapsid of 200–210 nm and mean diameter of 100–110 nm. These results provide an insight into the structural characteristics of the Nudiviridae family that can be used for nudiviral identification.     

环境条件对双叉犀金龟成虫存活及繁殖的影响

双叉犀金龟Allomyrina dichotoma是一种重要的森林资源昆虫,本文研究了环境温度（20℃、23℃、26℃、29℃、32℃）及菌糠含水量（35%、45%、55%、65%）对双叉犀金龟成虫寿命及子代数量的影响。结果表明,双叉犀金龟雌雄虫寿命均随温度的升高呈显著缩短,20℃~26℃下雌虫寿命在55~62 d之间,显著长于29℃~32℃处理;20℃~23℃下的雄虫寿命在33~48 d之间,显著长于26℃~32℃处理;环境温度及菌糠含水量均对双叉犀金龟成虫子代数量有显著影响,26℃时,4个菌糠含水量处理的平均子代数量为31.42 头/雌,显著高于其它温度处理,菌糠含水量55%~65%时,5个温度处理的平均子代数量为18.83~19.12 头/雌,显著高于其它菌糠含水量处理,其中以温度26℃、菌糠含水量55%处理的双叉犀金龟子代数量最高,达45.42 头/雌。各温度下双叉犀金龟繁殖子代数量均随时间的延长呈先上升后下降的趋势,各温度下产卵繁殖的高峰时间存在明显差异。在26℃时,双叉犀金龟各时间段子代数量均高于其它温度,在35~45 d时,达到产卵高峰期（12.33 头/雌）,综合各指标,建议利用菌糠饲养双叉犀金龟时,其成虫最佳环境条件为26℃,菌糠含水量55%。     

On the analysis of non‐linear allometries

Abstract 1. Non‐linear allometries are those where a log–log scatterplot of trait size against body size deviates from simple linearity. These are found in many insects, including the horns of beetles, the forceps of earwigs, and the heads of certain castes of ant. 2. Non‐linear allometries are often associated with polyphenism that is itself related to behaviour: for example, the alternative mating tactics displayed by many species of beetle are widely associated with dimorphisms in horn size. 3. This paper critically reviews the current techniques used to analyse these datasets. 4. Recommendations include the use of scatterplots and assessment of the goodness of fit of simple linear models as an initial screen for non‐linear allometry. The use of recently developed algorithms for ‘segmented' regression to analyse continuous allometric relationships, and a pragmatic approach to the analysis of discontinuous relationships that recognises that there is no simple way to distinguish between morphs in some cases, and that all of the proposed methods for doing so have some drawbacks. 5. Worked examples of the analysis of two sets of data from animals that have been the subject of controversy regarding the nature of their allometric relationships are given: further worked examples are provided as online Supporting Information.     

Immunofluorescence and electron microscopic studies of microtubule organization during the cell cycle ofDictyota dichotoma (Phaeophyta,Dictyotales)

Summary Interphase cells ofDictyota dichotoma (Hudson) Lamour. lack cortical microtubules (Mts) but display an impressive network of cytoplasmic microtubules (c-Mts). These are focussed on two opposed perinuclear centriolar sites where centrin or a centrin-homologue is localized. Some of the Mts surround the nucleus, but the majority traverse the cytoplasm as bundles variously directed towards the plasmalemma. In apical cells, and to a lesser extent in the square or slightly elongated meristematic cells, Mts are more or less evenly arranged. In elongated cells they form thick bundles longitudinally traversing the cytoplasm; a pattern maintained in differentiated cells. In early prophase the non-perinuclear Mts disappear but by late prophase a bi-astral arrangement of short Mts is observed. They enter polar nuclear depressions and attach to differentiated regions of the nuclear envelope where polar gaps open. By metaphase the spindle Mts converge on the centrioles at the polar gaps. At anaphase, interzonal Mts are evident and the asters start to reassemble. After telophase disruption of the interzonal Mts, the daughter nuclei approach each other, but move apart again before cytokinesis. The latter movement keeps pace with the development of two interdigitating Mt systems, ensheathing both daughter nuclei. The partition membrane bisects this Mt cage. Between telophase and cytokinesis the centrosomes separate, finally occupying opposed perinuclear sites. New Mts arise at the new centrosomes, some terminating on the consolidating partition membrane. Our data show thatD. dichotoma vegetative cells display a prominent cytoplasmic Mt cytoskeleton, which undergoes continual, but definite, change in organization during the cell cycle.     

芒萁植株浸出液对几种植物生长的影响

 芒萁在天然植物群落中具有较强的竞争能力和对其它植物的排斥作用。在研究中必须注意其化学分泌物对其它植物的抑制作用,以利荒山灌木草丛的经济利用。作者选取马尾松、猪屎豆、天兰苜蓿、紫苜蓿、葛藤、红车轴草、白车轴草及禾本科的牛尾草、块茎虉草进行栽培试验证明,芒萁植株的浸出液对马尾松以外的其它试验植物均有抑制作用。     

FATTY ACIDS,AMINO ACIDS,MINERAL CONTENTS,AND PROXIMATE COMPOSITION OF SOME BROWN SEAWEEDS1

This study was conducted to create a nutritional database on brown seaweeds and to popularize their consumption and utilization in Iran. The fatty acid contents, amino acids profiles, and certain mineral elements composition of some brown seaweeds, Padina pavonica (L.) Thivy, Dictyota dichotoma (Huds.) J. V. Lamour., and Colpomenia sinuosa (Mert. ex Roth) Derbés et Solier were determined. Total lipid content ranged from 1.46 ± 0.38 to 2.94 ± 0.94 g · 100 g^?1dry weight (dwt), and the most abundant fatty acids were C16:0, C18:1, C20:4 ω6, and C20:5 ω3. The unsaturated fatty acids predominated in all species and had balanced sources of ω3 and ω6 acids. Highest total polyunsaturated fatty acid (PUFA) levels occurred in C. sinuosa. The protein content of D. dichotoma was 17.73 ± 0.29 g · 100 g^?1dwt, significantly higher than the other seaweeds examined. Among amino acids essential to human nutrition, methionine (Met; in D. dichotoma and P. pavonica) and lysine (Lys; in C. sinuosa) were present in high concentrations. The crude fiber content varied by 9.5 ± 11.6 g · 100 g^?1dwt in all species. Chemical analysis indicated that ash content was between 27.02 ± 0.6 and 39.28 ± 0.7 g · 100 g^?1dwt, and that these seaweeds contained higher amounts of both macrominerals (7,308–9,160 mg · 100 g^?1dwt; Na, K, Ca) and trace elements (263–1,594 mg · 100 g^?1dwt; Fe, Ni, Mn, Cu, Co) than have been reported for edible land plants. C. sinuosa had the highest amount of Ca, Fe, and a considerable content of Na was measured in P. pavonica.