BIOMASS AND DYNAMICS OF GROWTH OF ULVA SPECIES IN PALMONES RIVER ESTUARY1

During the last decade, the Palmones River estuary has undergone severe eutrophication followed by a green tide episode; two species of Ulva, rotundata Blid. and Ulva curvata (Kütz.) De Toni, were the main macroalgae responsible for this bloom. From November 1993 to December 1994, we followed the biomass, the growth dynamics, and tissue elemental composition (C:N:P)of Ulva species, as well as some physicochemical variables in the estuary. Maximum biomass (up to 375 g dry wt·m^?2 in some spots, corresponding to a thallus area index of nearly 17 m²Ulva·m^?2 sediment) were observed in June and December. However, the biomass varied among the sampling stations. Water nitrate, ammonia, and phosphate showed high concentrations throughout the year, with extremely high transient pulses, sustaining the high growth rates observed. Growth rates were estimated directly in the field. The rates were generally higher in Ulva discs maintained in net cages than those estimated by changes in biomass standing stock between two consecutive samplings. The difference between both estimates was used to quantify the importance of the processes causing loss of biomass, which were attributable to grazing, exported biomass, and thallus decomposition under anaerobic conditions resulting from extreme self-shading. Maximum chlorophyll content was found in winter, whereas the minimum was in spring. Atomic N:P ratios were generally higher in the algae than in the water. However, the absolute concentrations of tissue N and P were always higher than the critical levels for maximum growth, which suggests that growth was not limited by inorganic N or P availability. The results suggested that the increase in nutrient loading in the river may have triggered the massive development of green algae and that light limitation and temperature stress in summer seem to be the main factors controlling the abundance of Ulva in the estuary. In addition to light availability and thermal stress, the different loss processes may have a decisive role in the dynamics of Ulva biomass.     

Elemental signatures of human diets from the Georgia Bight

Multielement analysis was performed on bone samples extracted from the femora of 39 adults from three mortuary sites (Johns Mound, Santa Catalina de Guale, and Santa Catalina de Guale de Santa Meria) and time periods (late preagricultural, early contact, and late contact) in the Georgia Bight. This study was used to investigate whether elemental analysis would support or contradict other lines of data regarding diets and dietary change previously generated for the region. The data are in agreement with an earlier interpretation, based on stable isotopes, that dietary maize increases through time but fails to support the idea that marine resources decreased in importance. Rather, it appears that the wild plant food component of the diets decreases as maize increases in importance; throughout the sequence, marine resources comprise a significant portion of the diets. © 1995 Wiley-Liss, Inc.     

Velvetleaf,Abutilon theophrasti (malvaceae), history and economic impact in the United States

Velvetleaf,Abutilon theophrasti, a native of China, was originally introduced into the New World before 1750 as a potential fiber crop for the American colonies. Initial introductions may have come from England because of similar interests in the development of fiber crops. Commercial fiber production from velvetleaf was attempted by U.S. farmers for more than a century. The latest known attempts were made in the latter part of the 19th century in Illinois and New York. Velvetleaf never competed well with hemp, at least partly due to a lack of proper machinery for fiber processing. These early experimental plantings were apparently the source of velvetleaf as a weed in row crops. One velvetleaf plant is capable of producing as many as 8,000 seeds, and viability may extend beyond 50 yr. The plant is well adapted to our upper Midwest where maize (Zea mays) and soybeans (Glycine max) are the major row crops. The reservoir of velvetleaf seed in the soil is increasing. The current annual economic loss due to velvetleaf in maize and soybeans is estimated to be approximately $343 million per year.     

Ultrastructural and histochemical studies on guard cells

Serial thick sections of guard cells from Vicia faba L., Nicotiana tabacum L., Allium cepa L., Zea mays L. and Beta vulgaris L. were obtained systematically (600–800 nm) and viewed with the transmission electron microscope in an effort to demonstrate the presence or absence of a symplastic transport pathway within the stomatal complex. Eight to ten stomata from each species were examined, and no continuous plasmodesmata were found connecting guard cells to sister guard cells or to adjacent epidermal or subsidiary cells. Continuous plasmodesmata were observed in immature guard cells, but were sealed (truncated) during the development of the mature cell wall. Histochemical stains, phosphotungstic acid and silver methenamine, were used to demonstrate differentiation within the mature guard-cell wall. The structural differentiation of the stomatal apoplastic region is discussed in relation to fanctional specialization. Plasma-membrane elaborations or plasmalemmasomes were identified in the guard cells of Zea, and it is suggested that these structures may function in ion transport.Abbreviations PTA-HCl phosphotungstic acid and hydrochloric acid - SM silver methenamine - UA-LC uranyl acetate and lead citrate     

Influence of Sulfur Nutrition on Developmental Patterns of Some Major Pea Seed Proteins and Their mRNAs

In addition to the marked reduction in legumin synthesis and legumin mRNA levels reported earlier (Chandler, Higgins, Randall, Spencer 1983 Plant Physiol 71: 47-54), pulse labeling of S-deficient Pisum sativum L. seeds showed that a high relative level of total vicilin (vicilin plus convicilin) synthesis was maintained throughout the entire phase of protein accumulation, whereas in nondeficient seeds vicilin synthesis is largely confined to the first half of this phase. Fractionation of pulse-labeled proteins on Na-dodecylsulfate-polyacrylamide gels showed that the synthesis of the M_r 50,000 family of vicilin polypeptides was increased and greatly extended in S-deficient seeds whereas that of convicilin was slightly reduced. Other changes apparent from pulse-labeling experiments include a depression, to different degrees, in the synthesis of three major albumin polypeptides.

The level of the mRNAs for seven major seed proteins was followed throughout development of control and sulfur-deficient seeds. In all cases, the changes in each mRNA closely reflected the pattern of synthesis of its corresponding polypeptide seen by pulse labeling. S-deficient seeds showed an elevated level of M_r 50,000 vicilin mRNA which remained high throughout seed formation, whereas legumin mRNA levels were greatly reduced at all stages of development.

When S-deficient plants were given an adequate supply of sulfate midway through seed development, there was a shift toward the protein synthesis profile characteristic of healthy plants. The synthesis of legumin and two albumins rapidly increased and the synthesis of M_r 50,000 vicilin declined more slowly. Similar responses were seen in detached, S-deficient seeds supplied directly with adequate sulfate.

     

Partial deletion of 4p16 band in a ring chromosome and wolf syndrome

Summary A new case of ring chromosome 4 in a 2-day-old female child with multiple malformations is described. By means of the GTG-banding technique, a karyotype 46,XX,r(4), (p16q35) was determined. The characteristics of the child's karyotype and the relationship with the structure of the chromosome, especially the location of the deletion that produces the syndrome, are compared with previous reports.