Seasonal distribution and changes in the nutritive quality of living,dead and detrital fractions of Zostera marina L.

Samples of eelgrass, Zostera marina L., were collected monthly from December 1974 through December 1975 in a shallow embayment near Beaufort, N.C., and separated into green leaves, dead leaves, and leaf detrital material. Each component was analysed for dry weight, organic matter, inorganic and organic carbon, nitrogen and amino compounds.The standing crop of green and dead blades reached a maximum in April through June, while detrital matter had peaks in December, April and July–September. Inorganic carbon in the three grass fractions showed seasonal variations similar to those observed for epiphytic biomass in previous years, and represented 14, 24, and 30% of the total carbon associated with the green and dead leaves and detrital fragments, respectively. Organic carbon represented a decreasing proportion of the dry weight of these three fractions on a dry weight basis while there was a significant increase in organic carbon on an ash-free dry weight basis in the detrital fragments relative to the head dead blades. During senescence there was a loss of nitrogen from the leaves and an increase in the nitrogen content of the organic matter of the detritus relative to the dead leaves. The latter suggests that there was microbial growth on the detritus and subsequent nitrogen immobilization from the surrounding medium. There were significant decreases of lysine, histidine, arginine, glycine, tyrosine, and glucosamine in the dead leaves relative to the detritus. The glucosamine, derived from N-acetyl-glucosamine, a product of murein which is a component of microbial cell walls, had a seasonal distribution similar to that of the epiphytic community and available inorganic nitrogen in the surrounding water. The relative proportions of N-acetyl-glucosamine, nitrogen and organic carbon were all higher in the fall and winter.     

Relative abundance and growth of mussels (Mollusca: Eulamellibranchia) in pools 8,9 and 10 of the Mississippi River

SUMMARY. Twenty-three species of unionid mussels were sampled during the summer of 1975 from a 76-mile reach of the Upper Mississippi River; this represented eight species fewer than were recorded in a 1930–31 survey for the same section of the river. Of the 244 sites sampled in 1975, mussels were found at 116 sites and the ten most productive sites accounted for 40.8% of the 1205 mussels collected. There were as many as thirteen different mussel species taken from one sampling site. The two most abundant species ( Amblema peruviana and Megalonaias gigantea ) constituted 54.5% of the mussels sampled in 1975; these two species made up only 8.3% of the 1930–31 survey. Individuals of the twelve most abundant mussel species were aged, and shell-length growth equations were determined. In addition, shell-free dry weight growth rate and shell weight growth rate was determined for Amblema peruviana . The calculated annual production for A. peruviana (assuming a mean density of 1 per m²) was 482 mg/m² shell-free dry weight, and 14.471 g/m² shell weight.     

On the early growth of 0+ perch, Perca fluviatilis, in Windermere

SUMMARY. The growth in length and weight (wet and dry) of 0+ perch Perca fluviatilis during their first summer of life in Windermere, has been investigated. Two major stanzas, occurring during and after metamorphosis, characterize the growth of 0+ perch in Windermere. The change from one stanza to another takes place between six and eight weeks after hatching. The exponential rate of growth in length was 0.26 and 0.27 mm mm⁻¹ week⁻¹ for the first stanzas of 1975 and 1976, respectively, and decreased to about 0.08 and 0.07 mm mm⁻¹ week⁻¹ for the second stanzas of the same years. Similarly, the growth in both wet and dry weights decreased from the first to the second stanza. Growth of 0+ perch was found to be logistic, and could not be described by the von Bertalanffy growth curve. The relationship between weight and length was allometric and the power values for length were, for wet weight: 4.154 (in 1975) and 4.033 (in 1976) for the first stanza and 2.400 (in 1975) and 2.734 (in 1976) for the second stanza; for dry weight: 3.988 (1975) and 3.971 (1976) for the first stanza and 3.066 (1975) and 2.651 (1976) for the second stanza. Half of the total growth was completed in 47% (1975) and 40% (1976) of the total growth period to the end of the summer.     

An investigation into the relations between some growth parameters and yield of barley

Twenty-five field experiments on barley were done at four sites from 1970 to 1975, with an additional site in 1975, comparing five rates of nitrogen application. The crops were sampled at c. 14-day intervals from about the four-leaf stage to maturity to follow changes with time in the dry weights of the constituent plant parts and to measure fertile tiller number, grain number per ear and grain weight. Some data have been selected from this body of information and regression analysis has been used to assess the possible importance of pre- and post-anthesis growth in determining the yield of barley. Ear emergence was taken as an approximate indicator of anthesis. Yield was closely related (r=+0–96) and almost equal to the amount of dry matter accumulated before ear emergence for twenty-one of the experiments, with a regression coefficient of 0–95. In two of the remaining experiments the regression coefficient was greater, 1–14; and smaller in the other two, o-8i. Plant population is also shown to affect the regression coefficient. Despite these anomalies grain yield was more closely related to plant dry weight at ear emergence than to the increase in weight after ear emergence (r =+0–79). The increase in plant dry weight after ear emergence was frequently less than the yield of grain, suggesting that the plant can compensate for inadequate photosynthesis during grain filling. The result of this compensation is a reduction in straw dry weight. This implies that previously assimilated dry matter is transported to the grain, or that respiratory losses from the straw are not replaced by current photosynthesis. These observations suggest that yield may be limited by sink capacity rather than by photosynthesis after ear emergence. The main component of sink capacity, grain number per m² was closely related to yield (r =+0–95) and is known to be determined at or before anthesis. Grain size was shown to be related to grain number per ear (r= 4- 0–99), suggesting that grain size is also, at least partially, determined at ear emergence. Therefore, all the yield components are determined, wholly or partly before ear emergence.     

The life cycle of Chironomus anthracinus in Lough Neagh

Chironomus anthracinus generally had a one year life cycle at 8 m depth in Lough Neagh, during the study period. In spring 1975 however only a proportion of the population emerged as usual, the rest remaining a second year in the benthos to emerge in 1976. The mean dry weight of larvae just before emergence was 2.8 mg in 1971 and 2.6 mg in 1974 but only 1.6 mg in 1975, and it seems that larvae must reach a weight of at least 1.0 mg in the early spring to emerge that year. Considering temperature, oxygen saturation and standing crop of phytoplankton as factors influencing the life cycle, mean monthly chlorophyll a (phytoplankton) was weakly correlated with mean monthly increase in weight and % monthly weight increase could be related to temperature.     

盐胁迫对裸果木幼苗生长和叶片相关生理指标的影响

裸果木起源于古地中海,为亚洲中部荒漠区分布的第三纪孑遗植物种,对研究旱生植物演化过程具有重要的科学价值。以一年生裸果木(Gymnocarpos przewalskii)实生苗为材料,在盆栽条件下用质量浓度为0.4%、0.8%、1.2%和1.6%的NaCl溶液进行盐胁迫处理,测定各NaCl处理下裸果木幼苗叶片的抗氧化酶活性、渗透调节物质含量、叶绿素含量、相对电导率(REC)、丙二醛(MDA)含量以及株高、基径,根、茎、叶、总干重,根冠比变化,探讨裸果木幼苗对盐胁迫的生理耐受性。结果显示,(1)随着盐胁迫程度的加重,裸果木幼苗株高、基径,以及根、茎、叶干重和总干重整体呈下降趋势,而根冠比呈上升趋势;裸果木幼苗株高、基径和根干重在0.4%NaCl处理下较对照变化不显著,但其茎干重、叶干重和总干重在各NaCl处理下均显著低于对照。(2)随着盐胁迫程度的加重,裸果木幼苗叶片的可溶性糖(SS)含量、可溶性蛋白(SP)含量、超氧化物歧化酶(SOD)活性、过氧化物酶(POD)活性均先升高后降低,而脯氨酸(Pro)含量、过氧化氢酶(CAT)活性、REC、MDA含量均呈持续升高趋势;在0.8%NaCl处理...     

花生重组近交系(RIL)根部性状的遗传分析

利用花生R IL群体,分析了主根长、侧根数、根基粗(1 cm和3 cm处)、根体积、主根鲜重、干重、侧根鲜重和干重、主侧根瘤数等11个花生根部性状的遗传力,估算基因对数及性状间的相互关系,根据偏度系数(g1)和峰度系数(g2)的估算控制性状基因互作情况。结果表明:在11个研究性状中,有6个性状在2个亲本间差异显著或极显著。但不论性状在亲本间的差异显著与否,在R IL群体中基因型间的性状差异均表现为连续变异和明显的超亲分离。同时主根粗(1 cm)和主根长的变异系数较小,分别为11.27%和11.218%。11个花生根部性状都是受多基因控制的数量性状,如影响侧根根瘤数、侧根鲜重和侧根干重的基因均在10对左右;而其它性状的基因估计在5~7对左右,尤其是控制侧根数的基因最少为5对左右。而在R IL群体中,除侧根干重的遗传力最高,达0.569,其次是侧根根瘤和侧根数分别达0.545和0.542外,其它性状的遗传力均较低。同时控制主根长和主根粗(1 cm)的基因间存在重叠作用;而控制侧根根瘤、侧根鲜重和侧根干重基因间存在互作,表现为互补作用;控制其它性状的基因间互补或重叠作用不明显或者不存在。主根干重和侧根干重与根体积、主根粗(1 cm)和主根粗(3 cm)显著相关,根体积与主根粗(3 cm)极显著相关,主根鲜重和侧根鲜重与根体积的相关表现不一致。     

GROWTH AND NUTRITION OF TIMOTHY (PHLEUM PRATENSE L.): IV. THE EFFECT OF NITROGEN, PHOSPHORUS AND POTASSIUM SUPPLY ON GROWTH DURING THE FIRST YEAR

In a sand-culture experiment lasting 21 weeks plants of timothy grown from seed were maintained at all combinations of three levels of nitrogen, phosphorus and potassium. The number and weight of tillers, leaves and ears, and the weight of roots, were determined at the end of the experiment, and for some of the treatments at intervals of 4 weeks. All three nutrients had significant effects, especially N which at its lowest level of supply tended to mask the effect of the other two elements. Potassium influenced tiller numbers least, especially those of primary tillers, but in the presence of high concentrations of N and P it had a large effect on leaf area and dry weight. Relative growth and net assimilation rates responded to varying nutrient supply only in the early stages of growth, so that in general variations in dry weight were associated with nutrient effects on leaf area.     

Local climate, topography and plant growth in Lathkill Dale NNR. II. Growth and nutrient uptake within a single season

Abstract In a 30-week field experiment, observations on growth and nutrient uptake in potted plants were made concurrently with soil and air temperatures on north- and south-facing slopes. Parallel observations were also made in a controlled environment. Growth in the field was slow but steady, declines in shoot weight fraction with time being matched by increases in rate of dry weight increment per unit of shoot. Increases in root weight fraction, however, failed to match low and declining rates of nitrogen uptake per unit of root; hence, nutrient concentrations generally declined with time. Thermal time in the form of degree-day integrals above the base 3°C was found to correlate well with growth, each degree day contributing a 0.16% increase in total dry weight, on average. Soil, locational and moisture effects caused this average to vary ca. two-fold in either direction.     

Population dynamics of two snail species,Planaxis sulcatus and Cerithium moniliferum,and their trematode species at Heron Island,Great Barrier Reef

Summary The population dynamics of the prosobranch snail Planaxis sulcatus and its trematode parasites on 600 m of beachrock on the southern side of Heron Island, Great Barrier Reef, were studied. Populations of Planaxis show little mixing, due to lack of long-distance movements. From March 1973 to June 1975, an increase in the numbers of small and medium-sized snails occurred, but the biomass (dry tissue weight) of the snail population did not change. Snails were infected with one species of Aspidogastrea and six species of cerariae. Infections with cercariae did not significantly affect the relative weight of the snails. Multiple infections were random, i.e. neither negative nor positive interactions between trematode species could be demonstrated. Proportions of uninfected snails and snails infected with various trematode species remained more or less constant from July 1973 to February 1975.The population dynamics of the prosobranch snail Cerithium moniliferum and its 11 species of cercariae and one species of Aspidogastrea in a small area at Heron Island were studied. Numbers of large snails decreased and numbers of small snails increased from August 1973 to June 1975. The biomass of the Cerithium population increased only slightly. Prevalence of infection changed significantly only in large snails.Infections of Cerithium moniliferum and Peristernia australiensis with an aspidogastrid species decreased strongly from January 1971 to March/April 1972 and had not recovered by mid 1975.Seasonal fluctuations could not be demonstrated for any of the snails or parasites.The data for Planaxis suggest equilibrium conditions and saturation of the habitat.     

Influence of season on birth weight and weaning age of indigenous Balami and imported Sudan Desert sheep in the Sahel region of Northeastern Nigeria

Data on birth weight and age at weaning for 1,092 (609 indigenous Balami and 483 imported Sudan Desert) sheep born from 1975 to 1979 in a Government farm near Maiduguri were analysed to study the influence of season on birth weight and age at weaning in sheep reared in the sahel region of Northeastern Nigeria. The suitability of the Sudan Desert for replacing or upgrading the indigenous Balami was considered.Season, breed, sex and type of birth significantly (P<0.001) influenced birth weight, age at weaning and the average daily gain from birth to weaning of lambs. Heaviest lambs were born during the rainy season-June–August. Birth weight was lowest during the dry hot season. Balami lambs were heavier at birth and were weaned earlier with greater average daily gain than the Sudan Desert (P<0.001). Ram lambs were heavier at birth and had greater daily gain than the ewes (P<0.001). Also single-born lambs were heavier at birth and were weaned earlier (P<0.001) than twins. Twining rate in Balami was almost double that in the Sudanese. Survival tended to be greater in Sudanese than in Balami. Birth, twining and survival rates were highest for the dry cold season-born lambs. The dry cold season seems the best lambing season here. In all, the local Balami proved far superior in almost all traits considered. The use of the Sudan Desert here is definitely not econmically justifiable or rational.     

Assessing daily tropical rainfall variations using a neuro-fuzzy classification model

Rainfall variations in tropical areas like Indonesia are dependent upon the tropical climate variability that has two seasons, the dry and wet seasons. However, the significant variations inherent in tropical climate are frequently affected by the combination of the atmosphere phenomena such as the El Niño-southern oscillation (ENSO) influence and tropical cyclone. This in turn lead to uncertainty of rainfall, making it difficult to develop an analysis technique that adequately assesses and interprets variations in rainfall periodicity. Many previous studies of rainfall variation have used techniques such as artificial neural networks and fuzzy methods. Each method uses a different rationale for the way in which the analysis purposes are preserved during analysis. The current study presents the use of a supervised learning of the neuro-fuzzy classification model in order to assess the rainfall variations in a tropical area. This method is a special example of a model within the field of neuro-fuzzy systems that enables the construction of the model output that could be represented by fuzzy classification rules. The classification procedures were started to derive the cluster information for the datasets by using the fuzzy C-means (FCM) clustering. Here, the process of clustering was arranged to provide two clusters of datasets, by adapting to the rainfall of dry (small rainfall) and wet (large rainfall) seasons over the study areas. Based on the prior clusters from the FCM, a neuro-fuzzy algorithm was trained to develop a set of the rule base of the classification models. The pruning strategies for the given rule base in the trained classifier were then exploited to improve the accuracy of the resulting model. The results of analysis gave strong performance by yielding a simpler rule base with a high accuracy. This enabled improved interpretability of variation in rainfall.     

内蒙古中东部草原不同生境克氏针茅（Stipa krylovii Roshev.）种群的形态差异分析

对内蒙古中东部草原分布的克氏针茅进行了种群内和种群间的形态差异分析。结果表明：（1）种群内不同的形态性状存在不同程度的差异;（2）种群间生殖枝中的一部分形态性状以及营养枝高度和营养枝干重均存在较大差异;（3）每穗小花数、每穗籽粒数、每穗小穗数、生殖枝高、穗干重、生殖枝干重、每穗种子重、种子重/生殖枝重比等性状的变化趋势相同,均表现为随生境条件变差而增加,即在生殖上投入增加以增大适合度;（4）主成分分析表明穗长、种子重/生殖枝重比、每穗小花数、每穗籽粒数、生殖枝高、基盘长、第二芒柱长、营养枝高、千粒重、芒针长是不同种群差异的主要指标。这些形态性状的差异可以看作克氏针茅对不同生境的适应性表现。     

Conditional and unconditional QTL mapping of drought-tolerance-related traits of wheat seedling using two related RIL populations

For discovering the quantitative trait loci (QTLs) contributing to early seedling growth and drought tolerance during germination, conditional and unconditional analyses of 12 traits of wheat seedlings: coleoptile length, seedling height, longest root length, root number, seedling fresh weight, stem and leaves fresh weight, root fresh weight, seedling dry weight, stem and leaves dry weight, root dry weight, root to shoot fresh weight ratio, root-to-shoot dry weight ratio, were conducted under two water conditions using two F_8:9 recombinant inbred line (RIL) populations. The results of unconditional analysis are as follows: 88 QTLs accounting for 3.33–77.01% of the phenotypic variations were detected on chromosomes 1A, 1B, 1D, 2A, 2B, 2D, 3A, 3B, 4A, 4B, 4D, 5A, 5B, 5D, 6A, 6B, 6D, 7A, 7B and 7D. Among these QTLs, 19 were main-effect QTLs with a contribution rate greater than 10%. The results of the conditional QTL analysis of 12 traits under osmotic stress on normal water conditions were as follows: altogether 22 QTLs concerned with drought tolerance were detected on chromosomes 1B, 2A, 2B, 3B, 4A, 5D, 6A, 6D, 7B, and 7D. Of these QTLs, six were main-effect QTLs. These 22 QTLs were all special loci directly concerned with drought tolerance and most of them could not be detected by unconditional analysis. The finding of these QTLs has an important significance for fine-mapping technique, map-based cloning, and molecular marker-assisted selection of early seedling traits, such as growth and drought tolerance.     

Investigations into the soil mycoecology of Chambal ravines of India

Summary The present investigation deals with the seasonal succession of fungal communities in wheat fields. The studies were performed during the year 1975–76 and involved four study seasons,viz. winter (1975), summer (1975), rainy (1975) and winter (1976). The observations during two winter seasons were done to find out whether or not fungal communities exhibit definite cyclic pattern. Of the 69 isolated species, 25 showed wider ecological amplitude whereas some species were specific of a particular season. Each season was marked by different fungal mycoflora. The population ofAspergillus terreus, a dominant member of the community, along with many other autochthonous species, exhibited a definite periodicity during various seasons. Seasonal variations in the fungal communities, variations in the extent of similarity among the fungal communities during various seasons and the impact of climatic conditions on the components of fungal communities are discussed.     

Daily changes in population structure and production of Eudiapomus gracilis (G.O. Sars) (Copepoda, Calanoida) during summer in a shallow lake (Balaton, Hungary)

Population structure and production of Eudiaptomus gracilis(G.O. Sars) have been calculated from daily measurements inLake Balaton for one month during each summer in 1975 and 1977.Fecundity was different in the two years 6.98 ? 1.16 and 10.68? 1.42 in 1975 and 1977, respectively. A total of 80% and 64%of the population were made up of larvae in 1975 and 1977, respectively.The ratio of males to females was 1:1.63 and 1:1.1, respectively.In 1975 it was possible to follow the development of cohorts,19 –20 days in the former year, 17 –20 days in thelatter. In both years of examination 80 – 83% of naupliiand 12–15% of copepodites were eliminated. Daily net biomassproduction was 6.88 mg (dry wt.)/m³ in 1975 and 1.94 mg (drywt.)/m³ in 1977. Ratios of eggs, nauplii and copepodites indaily production was 1:2.4:1.4 in 1975 and 1:1.0:1.0 in 1977.The daily potential biomass production were 34.40 mg (dry wt.)/m³ and 10.28 mg (dry wt.)/m³ and the elimination were 80 and81 wt.%, respectively. P/B ratio — allowing for net productionvalues — was nearly the same in both periods of investigation(0.12 and 0.099 respectively).     

Spatial variations in size, weight and condition factor of the females of Acartia clausi (Copepoda: Calanoida) along a salinity gradient in two contrasting estuaries of the Basque coast (Bay of Biscay)

Variations in prosome length and width, dry weight and condition factor of female Acartia clausi copepods were studied at three salinities (35, 34 and 33 psu) in the euhaline region of two estuaries (Bilbao and Urdaibai) of the Basque coast, with different level of anthropogenic impact. Effect of the environmental variables upon the morphology of A. clausi females on a small geographic scale is discussed. In general, biometric variables showed no significant differences between the two estuaries, but dry weight and condition factor were significantly higher in the estuary of Urdaibai at 35 and 34 psu, whilst at 33 psu they were higher in Bilbao. Body dimensions decreased significantly with decreasing salinity in both estuaries, however, no similar trends were observed for dry weight and condition factor. Temperature appeared the main variable to account size variations, but once eliminated seasonal effect of the temperature body size was related with oxygen concentration in the estuary of Bilbao and with salinity in Urdaibai. This study reveals that morphological characteristics of A. clausi not are only dependent on the temperature, but also, within a limited geographical zone, on local differences in environmental variables, mainly salinity and oxygen concentration.     

Alkaloid variability in Leucojum aestivum from wild populations

Leucojum aestivum (summer snowflake) is a plant species used for the extraction of galanthamine, an acetylcholinesterase inhibitor for the treatment of Alzheimer's disease. Extracts from bulbs collected from 18 Bulgarian populations and from shoot-clumps obtained in vitro from 8 different populations showed variations in their alkaloid composition. Nineteen alkaloids were detected in the studied samples by GC-MS. Typically, the alkaloid fractions of L. aestivum bulbs were dominated by galanthamine type compounds, but lycorine, haemanthamine and homolycorine type alkaloids were also found as dominant compounds in some of the samples. Extracts from the shoot-clumps obtained in vitro were found to contain galanthamine or lycorine as main alkaloids. The galanthamine content ranged from 28 to 2104 microg/g dry weight in the bulbs, and from traces to 454 microg/g dry weight in the shoot-clumps.     

Annual variations in length–weight relationship of Gymnogobius isaza (Tanaka, 1916) from Lake Biwa,Japan

The study describes length–weight relationships (LWRs) of Gymnogobius isaza (Tanaka, 1916) collected from Lake Biwa, Japan, between 1975 and 2002. Annual values of the allometric exponent of LWRs ranged from 2.47 to 3.42. This study is one of the few to report annual variations in LWR.     

The influence of water supply on the growth and phosphorus uptake of italian ryegrass and white clover in pot culture

Summary White clover appears to be much more sensitive, in terms of dry-matter production, to variations of soil moisture than Italian ryegrass. The results show that a variation of 5 in the percentage of water (moist-soil basis) on either side of the field-capacity figure can cause a statistically significant effect in the dry weight of Italian ryegrass in pot culture, although a slightly larger percentage may be necessary for white clover to be affected as standard errors in pot culture with this crop tend to be higher.With an adequate supply of soil phosphorus the greater the amount of readily available water the greater the percentage of P₂O₅ in Italian ryegrass; with white clover it rises to a maximum then falls off under very wet Statistically significant differences in percentage P₂O₅ for both crops can be obtained whit those variations in the water supply which caused significant differences in dry weight.