Filtration rate capacities in 6 species of European freshwater bivalves

Summary Filtration rate capacities in undisturbed freshwater bivalves were determined by means of two different methods (indirect clearance and suction methods) in Anodonta anatina (L.), Unio tumidus Philipsson, Unio pictorum (L.), Unio crassus Philipsson, Dreissena polymorpha (Pallas) and Sphaerium corneum (L.). In A. anatina, D. polymorpha, and S. corneum the filtration rate (FR, 1 h^-1) at 19–20°C as a function of dry tissue weight (DW, g) or ash-free dry weight (AFDW, g) could be expressed by the equations: 1.10 DW^0.78, 6.82 DW^0.88, and 2.14 AFDW^0.92, respectively. In U. tumidus, U. pictorum, and U. crassus filtration rates were comparable with those of A. anatina. In D. polymorpha the b value of the corresponding regression of gill area on dry weight was 0.87. The rates of water transport in freshwater bivalves are 2–8 times lower than in marine bivalves of comparable size. A corresponding difference in the filtration rate per gill area unit is found. The measured filtration rates in undisturbed bivalves are substantially higher (at least 4 times) than previously reported. This indicates that the impact of bivalve water processing on freshwater ecosystems is greater than hitherto suggested.     

Cultivar differences in the rate of nitrate uptake by intact wheat plants as related to growth rate

Six Argentinian wheat ( Triticum aestivum L.) cultivars grown in nutrient solutions in controlled environment were compared for their nitrate uptake rates on a root dry weight basis. Up to 3-fold differences were observed among the cultivars at 16, 20 and 24 days from germination, either when measured by depletion from the nutrient solution in short-term experiments, or by total N accumulation in the tissue during 8 days.
No differences in total N concentration in root or shoots were found among cultivars. Although the different cultivars showed significant differences in shoot/root ratio and nitrate reductase activity (EC 1.6.6.1) in the roots, none of these parameters was correlated with the nitrate uptake rate. However, nitrate uptake was found to be positively correlated (r = 0.99) with the shoot relative growth rate of the cultivars. The three cultivars with the highest nitrate uptake rates and relative growth rates showed a positive correlation between root nitrate concentration and uptake. However, this correlation was not found in the cultivars with the lowest growth and uptake rates.
Our results indicate that the difference in nitrate uptake rate among these cultivars may only be a consequence of their differences in growth rate, and it is suggested that at least two mechanisms regulate nitrate uptake, one working when plant demand is low and another when plant demand is high.     

温度对亚东璃眼蜱发育的影响

亚东璃眼蜱的卵、饱食的幼虫和若虫分放在四个等级的温度、相对湿度90%和黑暗的条件下,观察温度对各期发育的影响.在20°、25°、30°和35℃条件下,卵期发育的平均日数分别为71.87±0.05、31.55±0.03、21.02±0.03和16.47±0.03天;幼虫蜕化期分别为25.02±0.05、13.01±0.03、8.75±0.02和6.40±0.02天;若虫蜕化期分别为47.32±0.22、24.2±0.13、14.36±0.08和10.78±0.06天.在各种温度条件下若虫蜕化为成虫的时间,雄虫比雌虫长.卵期发育的积温为321.77日度,而幼虫和若虫蜕化期分别为129.97和212.39日度.卵期发育的温度低阈为15.07℃,而幼虫和若虫蜕化期分别为14.88和15.58℃.     

玉米不同叶位叶片叶绿体超微结构与光合性能的研究

对玉米植株基部（第3叶）,中部（果穗叶）和上部（倒2叶）叶位叶片,进行叶绿体超微结构的观察,并测定了叶绿素含量和光合强度,结果表明,不同叶位叶片叶肉细胞中叶绿体的超微结构,随叶位上升而渐趋复杂化,果穗叶最为显著,向上又趋简单,具体表现为基粒片层的数目随叶位上升而增多基质片层和基质也随之增加,果穗叶最多,向上又趋减少,不同叶位叶片叶绿素含量和光合强度,果穗叶高于其它叶位。     

我国沙漠中部地区主要不同生态类型植物脯氨酸的累积、光合、呼吸和叶绿素含量

中生植物脯氨酸含量为0．42mg/g.dw, 低于少浆旱生植物（1．73mg/g.dw)。多浆旱生植物脯氨酸含量最高（7．22mg/g.dw),为前两者的17倍和4倍,两类旱生植物在干旱条件下（非灌溉）脯氨酸含量均高于灌水处理。少浆与多浆旱生植物的光合强度（16．74,14．04CO2mg/g.dw.h)差异不大,而中生植物（37．57mg/g.dW.h)略高于多浆旱生植物（4．73CO2Mg/g.dw.h),与中生植物（7.60Co2mg/g.dw.h)接近,光合／呼吸值,少浆,多浆与中生植物分别为2．50,3．09和4．59,说明中生植物的合成明显大于消耗,季节动态中,中生植物显著高于两类旱生植物,叶绿素总量三类植物差异甚微。     

Artificial incubation of California condor Gymnogyps californianus eggs removed from the wild

The currrent California condor (Gymnogyps californianus) recovery plan entails increasing the reproductive rate via replacement-clutch manipulation of eggs. During the period from 1983 to 1985, 15 eggs were removed from wild nesting pairs for artificial incubation. The eggs were incubated at a dry bulb temperature of 36.4°C in modified forced-air Lyon Electric incubators. The incubation humidity was adjusted for individual eggs based on weight loss data (water = weight), 25.6–30.0°C wet bulb (41.0–63.0% Relative Humidity (RH)). The chicks were hatched initially under forced-air conditions of 36.1°C dry bulb, 31.1–01.7°C wet bulb (70.0–73.0% RH). In 1984, hatching parameters were changed to still-air conditions, 36.1°C dry bulb (top of the egg), 35.0°C dry bulb (bottom of the egg), 31.1–31.7°C wet bulb (70.0-73.0% RH). Tactile and auditory stimulation was utilized during the pip-to-hatch interval. From among 15 eggs collected, 13 hatched, and 12 condor chicks were raised successfully (hatchability: 86.7%; survivability: 92.3%).     

锰重组钙调蛋白水质子弛豫速率的研究

钙调蛋白(CaM)是一种多功能调节蛋白,它含有4个Ca~(2+)结合域.晶体研究表明所有Ca~(2+)都与主链氧原子及酸性残基侧链氧原子配位,但Ca~(2+)的配位层中是否有水分子存在尚未确定.木文利用核磁共振技术,以Mn~(2+)为探针,通过测定水质子的核磁弛豫速率T_(1P)_(-1)建立了有关Ca~(2+)配位层中水分子数目的模型,该模型指出Cam中高、低亲和位上Ca~(2+)结合水的能力不同,高亲和位上Ca~(2+)的配位层中没有水分子存在,而低亲和位上Ca~(2+)配位层中含两个水分子.     

1,4—二取代酰氨基硫脲化合物A导致黄瓜增产的生理基础的初步研究

用0.1ppm的1—异烟酰—4-(4′-氯代苯基)—氨基硫脲(以下用A代表)喷施3—4叶期的黄瓜(Cucumis sativus L.)幼苗,可以提高叶片光合速率并导致黄瓜增产。进一步的实验结果表明:经0.1ppm A处理后,黄瓜叶片的叶绿素含量(a+b)增加约50%,叶绿素a/b比值降低约30%,叶黄素含量增加近2倍,光合磷酸化活性增强。这些变化可能是黄瓜增产的生理基础。