Seasonal changes in net photosynthesis rates and photosynthetic capacity in leaves of Cistus salvifolius,a European mediterranean semi-deciduous shrub

Summary During five different periods between Nov. 1982 and Aug. 1983, the diurnal patterns exhibited in photosynthetic CO₂ uptake and stomatal conductance were observed under natural conditions on twigs of Cistus salvifolius, a Mediterranean semi-deciduous shrub which retains a significant proportion of its leaves through the summer drought. During the same periods, net photosynthesis at saturating CO₂ partial pressure was measured on the same twigs as a function of irradiance at different temperatures. From these data, photosynthetic capacity, defined here as the CO₂- and light-saturated net photosynthesis rate, was obtained as a function of leaf temperature. C. salvifolius is a winter growing species, shoot growth being initiated in Nov. and continuing through May. Photosynthetic capacity was quite high in Nov., March and June, exceeding 40 mol m^-2 s^-1 at optimum temperature. In Dec., photosynthetic capacity was somewhat reduced, perhaps due to low night-time temperatures (<5°C) during the measurement period. In Aug., capacity in oversummering shoots at optimum temperature fell to less than 8 mol m^-2 s^-1, due to water trees and perhaps leaf aging. Seasonal changes in maximal photosynthetic rates under ambient conditions were similar, and like those found in co-occurring evergreen sclerophylls. Like the evergreens, Cistus demonstrated considerable stomatal control of transpirational water loss, particularly in oversummering leaves. During each measurement period except Aug. when capacity was quite low, the maximum rates of net photosynthesis measured under ambient conditions were less than half the measured photosynthetic capacities at comparable temperatures, suggesting an apparent excess nitrogen investment in the photosynthetic apparatus.     

The fate of15N labeled nitrogen applied to mature citrus trees

Summary The efficiency and balance of nitrogen from one year's application was studied in a long-term fertigation experiment. Enriched nitrogen fertilizer, K¹⁵NO₃, was applied to a 22-year-old Shamouti orange tree with a history of high N applications (N₃) and to an N-starved tree (N₁). The distribution of N in the different parts of the trees and in the soil was determined after the experimental trees were excavated. Similar total recovery of the labeled fertilizer N was found in the trees and soil in both treatments (N₁−61.7% N₃−56%). However, the distribution between tree and soil was different. The amount of recovered residual fertilizer in the soil was much larger in the N₃ treatment than in N₁. The highest percentage of fertilizer N was found in the new organs,i.e. fruits, twigs and leaves. The roots and branches took up only 6–14% from the labeled fertilizer. Only 20.9% of the leaf N and 23.4% of the fruit N in the N₃ tree originated in the labeled fertilizer, indicating translocation of N from older parts of the tree to new growth. Evidence was found of storage of N in the wooded branches, while the roots contained a surprisingly small part of labeled fertilizer. Contribution 1599E.     

A comparative study of ammonium toxicity at different constatn pH of the nutrient solution

Seedlings of 14 species were grown for 14–28 days on nutrient solution with 6 mmol.l⁻¹ NH₄ as the sole nitrogen source. Solutions acidity was were kept constant at pH 4.0, 5.0, 6.0 and 7.0 by continuous titration with diluted KOH. The following species were used: barley, maize, oats sorghum, yellow and white lupin, pea, soybean, carrot, flax, castor-oil, spinach, sugarbeet and sunflower. Most plant species grew optimally at pH 6.0 with slight reductions at pH 5.0. Growth of many species was severely inhibited at pH 4.0, but this inhibition was not observed with the legume and cereal species. Yield depressions at pH 4.0 relative to pH 6.0 were well correlated with the respective relative decreases of the K concentration in their roots (P<0.002). In the roots of two species (sunflower and flax) total N concentrations were also strongly reduced at pH 4.0. apparently, the interactions between uptake of K, NH₄ and H ions become the prevalent problem at suboptimal pH. At pH 7.0, yields were also considerably decreased, with the exception of the lupines. At this pH, the roots of the growth inhibited plants were characterized by increased levels of total N and free NH₄. It is thought that the binding capacity of the roots for NH₄ is an important factor in preventing NH₄/NH₃ toxicity at supraoptimal pH.     

澜沧江的沙鳅属鱼类(英文)

通过最近的整理,澜沧江共有沙鳅属鱼类3种,它们是斑鳍沙鳅Botia beaufortiSmith、中华沙鳅B.superciliaris Gnther、黑线沙鳅(新种)B.nigrolineata.黑线沙鳅为新种,鉴别特征是沿背中和体侧有显著的黑色纵条,起自头后止于尾鳍基。首次提出云南沙鳅Botia yunnanensis Chen可能是斑鳍沙鳅的次异名,中华沙鳅是在澜沧江的首次纪录。在附录中记录了突吻沙鳅B.rostrata Gnther,是国内首次纪录,也是萨尔温江和伊洛瓦底江水系的首次纪录。文中每个种均有插图,对新种作了详细的描述,对老种的有关名称作了(林厂里)订或讨论。     

Competition between Dunaliella species at high salinity

Information on the distribution of more than 225 species of planktonic, periphytic, and benthic rotifers from diverse waters in south and central Sweden was analyzed for pH preference. No particularly strong correlation was found between pH and any other environmental factor, with regards to rotifer distribution. However, species indicating oligotrophy generally have their pH optima at or below 7.0, while those indicating eutrophy occur at or above this level. Rotifers found in acidic waters are often non-planktonic or semiplanktonic.     

Succession in zooplankton and hydrophytes of a seasonal water on the west coast of South Africa

Paramesochra mielkei sp.n. is described and figured from the interstices of subtidal sandy sediments off the SW Dutch coast. Kunz' (1981) phylogenetic scheme of the Paramesochridae Lang, 1948 is re-examined and it is suggested that the family comprises two phyletic lines which originated early in paramesochrid evolution. Translation into Linnean hierarchies implies the establishment of two new sub-families. Within the primitive Diarthrodellinae subfam. n., Tisbisoma Bozic, 1964 is ancestral to Diarthrodella Klie, 1949 s.l. and Rossopsyllus Soyer, 1975. Remanea Klie, 1929 is transferred to the Paramesochrinae subfam. n. which comprises the genera of both the Scottopsyllus- and the Paramesochra-group. The aberrant genus Caligopsyllus Kunz, 1975, standing close to Apodopsyllus, is removed from the Paramesochra-group. P. brevifurca Galhano, 1970 is splitted into two subspecies and replaced in the genus Paramesochra. An attempt is made to assess the phyletic interrelationships of the Paramesochra-species and the resulting cladogram splits the genus into four species-groups. P. mielkei sp.n. is referred to the dubia-group and seems to be closely related to P. borealis Geddes, 1981. Finally, an amended diagnosis and a revised key to the species of the genus Paramesochra are presented.     

Aquatic Oligochaeta in some tributaries of the Río de La Plata,Buenos Aires,Argentina

The Oligochaeta of some streams flowing into the Rio de La Plata, Buenos Aires, Argentina, were investigated. Twenty nine taxa (twenty four naidids, five tubificids) were identified. Most species are cosmopolitan, but Dero evelinae, Pristina leidyi, Slavina isochaeta and Bothrioneurum sp. are neotropical. Bratislavia unidentata, Haemonais waldvogeli and Nais pardalis are reported for the first time in Argentina. Variants occurr in the shape of the distal end of the penial sheaths of Limnodrilus hoffmeisteri. The dominant Naidid genera are Dero and Pristina. In the polluted El Gato stream only L. hoffmeisteri and L. claparedeianus were found.     

On species of genus Lepadella (Eurotatoria:Monogononta:Colurellidae) from North-Eastern India,with remarks on Indian taxa

Ten species of Lepadella Bory de St. Vincent, 1826, including one new species and one new form, are documented from North-Eastern India. Two of these species are new records from this country and six are new reports from N.E. region. Comments are also made on the status and distribution of various Indian taxa.     

Recruitment of lysozyme as a major enzyme in the mouse gut: Duplication,divergence, and regulatory evolution

Summary Two major types of lysozymec (M and P) occur in the mouse genus,Mus, and have been purified from an inbred laboratory strain (C58/J) ofM. domesticus. They differ in physical, catalytic, and antigenic properties as well as by amino acid replacements at 6 of 49 positions in the amino-terminal sequence. Comparisons with four other mammalian lysozymesc of known sequence suggest that M and P are related by a gene duplication that took place before the divergence of the rat and mouse lineages. M lysozyme is present in most tissues; achieves its highest concentration in the kidney, lung, and spleen; and corresponds to the lysozyme partially sequenced before from another strain ofM. domesticus. InM. domesticus and several related species, P lysozyme was detected chiefly in the small intestine, where it is probably produced mainly by Paneth cells. A survey of M and P levels in 22 species of muroid rodents (fromMus and six other genera) of known phylogenetic relationships suggests that a mutation that derepressed the P enzyme arose about 4 million years ago in the ancestor of the housemouse group of species. Additional regulatory shifts affecting M and P levels have taken place along lineages leading to other muroid species. Our survey of 187 individuals of wild house mice and their closest allies reveals a correlation between latitude of origin and level of intestinal lysozyme.     

Meloidogyne californiensis n. sp. (Nemata: Meloidogyninae), Parasitic On Bulrush,Scirpus robustus Pursh

Meloidogyne californiensis n. sp. is described and illustrated from bulrush Scirpus robustus in California. LM and SEM studies revealed that this species differs from other known species in the genus Meloidogyne especially by the prominent posterior cuticular protuberances in the female, the distinct shape of the perineal pattern which is marked by one prominent stria in the perineum, indistinct lateral lines, many broken discontinuous striae on both sides of the arch, and the excretory pore being located posterior to stylet base. Second-stage juveniles 448-628 μm long, stylet length 11-13 μm, styler delicate, with small knobs sloping posteriorly, cephalic region with 2 or 3 annuli, and inflated rectum. Males vary greatly in size (712-1,952 μm), stylet length 18-28 μm (mean 22 μm), cephalic region slightly set off the body with two or three annuli, spear heavy with massive rounded knobs, lateral field marked by four areolated incisures as seen by SEM.