Invertase Activity, Carbohydrate Metabolism and Cell Expansion in the Stem of Phaseolus vulgaris L.

In the stem of Phaseolus vulgaris L. the specific activity ofacid invertase was highest in the most rapidly elongating internode.Activity of the enzyme was very low in internodes which hadcompleted their elongation, in young internodes before the onsetof rapid elongation, and in the apical bud. From shortly afterits emergence from the apical bud the elongation of internode3 was attributable mainly to cell expansion. Total and specificactivities of acid invertase in this internode rose to a maximumat the time of most rapid elongation and then declined. Transferof plants to complete darkness, or treatment of plants withgibberellic acid (GA₃), increased the rate of internode elongationand final internode length by stimulating cell expansion. Bothtreatments rapidly increased the total and specific activitiesof acid invertase in the responding internodes; peak activitiesof the enzyme occurred at the time of most rapid cell expansion. In light-grown plants, including those treated with GA₃, rapidcell and internode elongation and high specific activities ofacid invertase were associated with high concentrations of hexosesugar and low concentrations of sucrose. As cell growth ratesand invertase activities declined, the concentration of hexosefell and that of sucrose rose. In plants transferred to darkness,stimulated cell elongation was accompanied by a rapid decreasein hexose concentration and the disappearance of sucrose, indicatingrapid utilization of hexose. No sucrose was detected in theapical tissues of light-grown plants. The results are discussed in relation to the role of acid invertasein the provision of carbon substrates for cell growth. Key words: Cell expansion, Acid invertase, Hexose, Sucrose, Phaseolus     

Production of benthic macroinvertebrate communities along a southern Appalachian river continuum

1. Annual production was estimated for macroinvertebrate communities of principle habitats along a first- to seventh-order river continuum in the southern Appalachian Mountains (U.S.A.). Annual production was relatively low in depositional habitats, pebble/gravel substrata, and on cobble devoid of plant biomass (mosses and hydrophytes). Production was greater in bedrock habitats and greatest on hydrophyte-covered cobble, with estimates reaching 364 g AFDM (ash-free dry mass)m^–2 yr^–1 in a sixth-order river reach. Annual production in depositional habitats was correlated to standing crops of benthic organic material (BOM) in low-order stream reaches but not in higher-order reaches, indicating differences in BOM availability with stream size. In cobble, pebble/gravel and bedrock habitats production was significantly correlated to standing crops of aquatic plants, which can stabilize substrata and enhance access of collector-filtering invertebrates to entrained food resources. 2. By accounting for proportional availability of habitats along the continuum, estimates of total production ranged from 5 to 154 g AFDM m^–2 yr^–1, and increased significantly with stream size. Annual production estimated for sixth- and seventh-order reaches of the continuum were amongst the highest reported thus far for lotic systems. Organization of the benthic community along the continuum, based on production estimates for individual functional feeding-groups, generally supported predictions of the River Continuum Concept (RCC): shredder contributions were greatest in low-order reaches and declined downstream; scraper percentages were greatest in the middle of the continuum; collector-filterer contributions increased with increasing stream size. Longitudinal trends for collector-gatherers and predators did not support RCC predictions; these groups appeared to be influenced by localized changes in habitat availability and occurrence of vertebrate predators along the continuum.     

Analysis of segment number and enzyme variation in a centipede reveals a cryptic species, Geophilus easoni sp. nov., and raises questions about speciation

Geophilomorph centipedes provide an unusual opportunity to examine patterns of variation in segment number within extant species. (Most other arthropod species are invariant in this respect.) Recent work on several geophilomorph species has revealed latitudinal clines in segment number, but has generally not called into question the identities of the species themselves. However, analysis of a unique pattern of variation in British populations of Geophilus carpophagus Leach, coupled with other morphological and enzyme data, reveals a cryptic species, Geophilus easoni sp. nov. This species has not yet been detected on the European mainland. Four distinct hypotheses are advanced regarding the speciation event through which G. easoni arose and the phylogeographic processes that resulted in the present distributions of the two species in Britain. Further study will be necessary to test these hypotheses. In any event, G. carpophagus and G. easoni provide something that has until now been absent: a case study of the genetic differences between closely-related geophilomorph species.     

Encystment and Excystment of the Heterotrichous Ciliate Blepharisma stoltei Isquith*

SYNOPSIS. The structure and cytochemistry of encystment and excystment of Blepharisma stoltei Isquith are described. The encystment process may be subdivided into 4 stages: (i) in the precystic stage the buccal apparatus overlaps about the posterior, (ii) in early encystment, the buccal apparatus is resorbed and an ectocyst is secreted, (iii) an interwall space, endocyst, and plug are secreted during late encystment, and (iv) the resting cyst stage typically has disc-like structures on the ectocyst, and a vacuole in the macronucleus. In excystment, 6 distinct stages may be defined: (i) partial kineties are formed in early excystment, (ii) permanent kineties give rise to anlagen of the buccal apparatus during stomatogenesis, (iii) the organism elongates and reforms the vegetative shape in late excystment, (iv) some cysts then divide, (v) the redeveloped organism is liberated thru the plug pore, and (vi) the postcystic stage resembles the vegetative form except for its size and lack of pigmentation. Cortical structures, extracellular membranes, and the macronuclear membrane are composed of protein-lipids. Unbound protein and RNA are found in the cytoplasm thruout the cystic cycle. DNA is present only in the nuclei. Polysaccharides, 1st found in the cytoplasm, are shifted to the plug in encystment. The plug material disappears during excystment, while PAS positive granules appear in the cytoplasm.     

Systematics of Euplotes (Ciliophora, Hypotrichida); Toward Union of the Old and the New

SYNOPSIS. Prior to the general use of methods revealing the silverline system, members of the genus Euplotes were separated on the basis of body shape, sculpturing and arrangement of cirri. Since 1954, species have been separated on the basis of number of dorsolateral cilium rows, dorsal silverline system, number of fronto-ventral cirri, and form of the macronucleus. This paper describes E. charon Müller, 1773, E. quinquecarinatus Gelei, 1950, E. alatus Kahl, 1932, and E. bisulcatus Kahl, 1932, 4 species that are difficult to separate solely on the basis of the latter set of characters. By discussion of characters elucidated by a nigrosin-HgCl₂-formalin method, it is suggested that the following can form a basis for identification of members of this genus: 1) cortical sculpturing, 2) arrangement of all ciliary organelles, including dorsal and endoral cilia, and 3) details of the silverline system. Existing methods are indicated, some far more simple than silver methods, with which these characters can be elucidated.     

THE STIMULATORY PROPERTIES OF SOME ORGANIC SUBSTANCES ON CYSTS OF THE BEET EELWORM, HETERODERA SCHACHTII SCHMIDT

Techniques for determining the influence of various substances on the rate of larval emergence from cysts of the beet eelworm are described. There is no significant difference between the rates of larval emergence in glutamic acid, galactinol, inositol and water; the rate of larval emergence in beet diffusate, on the other hand, was significantly higher. Studies of larval emergence in carbohydrates suggest that the cyst population used in the experiments was heterogeneous, consisting of two types of cyst which have different reactions to stimulation at different concentrations. The significance of root exudates in relation to beet eelworm is discussed.     

Flowering phenology and reproductive biology of Drosera anglica (Droseraceae)

Prompted by the sparse knowledge of the reproductive biology of carnivorous plants, compared with studies of their trapping habits, we investigated the flowering phenology and pollination biology of Drosera anglica Huds. in two fens in mid-western Canada. Seed set and germination were used to compare the effectiveness of a series of pollination treatments, including single insect visits to virgin flowers. Flowers opened during mid-morning but closed by early afternoon, and exhibited pseudo-cleistogamic behaviour in cool, overcast weather. D. anglica was found to be self-compatible, and able to self-pollinate and self-fertilize. Geitonogamy was an uncommon mode of self-reproduction because plants typically possessed a lone inflorescence upon which a single, short-lived flower opened, a few days before the next bud reached anthesis. Insect visits to the fragrance-lacking, nectarless flowers, chiefly by flies (Diptera: Syrphidae), were infrequent (one visit per 1 h 40 min of observation), and the low frequency of seed set and low numbers of seeds per fruit in pollination treatments involving insects, suggest the species does not rely on insects to effect pollination. Self-pollination, with or without the aid of a vector (insects, wind) was as effective as natural pollination; ultimately, autogamy is chiefly responsible for natural seed set. Thus, the species exhibits characteristics of facultative autogamy.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 147 , 417–426.     

FIRST RECORD OF THE INDO‐PACIFIC REEF CORAL GENUS ISOPORA IN THE CARIBBEAN REGION: TWO NEW SPECIES FROM THE NEOGENE OF CURAÇAO,NETHERLANDS ANTILLES

Abstract: The coral genus Isopora, a sister group of the modern dominant Acropora until now only known from the Pliocene to Recent of the Indo‐Pacific, is recorded in the Caribbean for the first time. Two new species, Isopora ginsburgi and Isopora curacaoensis, are described from the Neogene Seroe Domi Formation of Curaçao, Netherlands Antilles. Study of large collections made systematically through the sequence indicates that Isopora first occurred in the Caribbean during the Mio–Pliocene, at approximately the same time as the origination of many modern Caribbean reef coral dominants including Acropora cervicornis. It last occurred in the region during the late Pliocene as part of a pulse of extinction, in which several genera that live today in the Indo‐Pacific became extinct in the Caribbean. Throughout its Caribbean duration, Isopora co‐occurred with the two abundant modern Caribbean species of Acropora, A. cervicornis and A. palmata. Comparisons with Neogene collections made elsewhere in the Caribbean indicate that Isopora was restricted in distribution to the southern Caribbean. Isopora species are viviparous, while Acropora are oviparous, and this difference in reproductive strategy may have played a role in the extinction of Isopora in the Caribbean. The occurrences of Isopora reported in this study are the oldest records to date of Isopora worldwide, and are important for understanding the biogeographic separation between reef coral faunas in the Caribbean and Indo‐Pacific regions.