An Ultrastructural Investigation of 180°-Rotated Ciliary Meridians in Tetrahymena pyriformis*

SYNOPSIS. An ultrastructural investigation has been carried out on 180°-rotated ciliary meridians (inverted meridians) in Tetrahymena pyriformis temperature-sensitive mutant (mol^b/mol^b), syngen 1, strain B. The longitudinal, transverse and postciliary microtubular bands, the kinetodesmal fiber, and the parasomal sac, are shown to be disposed at a 180° angle to their normal positions or orientations. Other abnormalities are as folows: the first 2 basal bodies of the inverted meridian fail to organize into “couplets” and the inverted meridian intrudes into the anterior pole region; an extra longitudinal microtubular band is found in one of the cell lines.     

Control of pearl millet downy mildew by seed treatment with metalaxyl*

Three formulations of the systemic fungicide metalaxyl were tested in various seed treatments for the control of pearl millet downy mildew in three field experiments with downy mildew-susceptible pearl millet hybrid NHB-3. Uniform, high levels of sporangial inoculum of the causal fungus, Sclerospora graminicola, were provided throughout the growth of the test crops from inoculated infector rows of NHB-3, planted earlier between the test plots. Significant reductions in downy mildew were obtained with all fungicide treatments. Best control was obtained when seed was soaked in a 0.5% aqueous solution of a liquid formulation (mean infection index of 9.8% compared with 94.8% in the untreated check). The degree of control with the wettable powder formulations was directly related to fungicide dosage, and there were no significant effects of application method. Simple dusting of seed at 2 g a.i./kg, a rapid and simple operation requiring small quantities of fungicide and no special application equipment, gave a high level of control (infection index of 12.6% compared with 78.9% in the untreated check). In two experiments grain yields from all the treated plots were significantly greater than from the untreated plots (means of 1234 and 1534 kg/ha for treated plots compared with 485 and 743 kg/ha, respectively), and in the third, the treatment with the least downy mildew gave significantly more grain than the untreated check (1228 compared with 727 kg/ha).     

Morphological studies of Asian rice and its related wild species and the recognition of a new Australian taxon

In order to clarify the taxonomy and the interrelationships among Asiatic cultivated rice, Oryza sativa , and its related wild species ( O. rufipogon, O. nivara and O . barthii ), 41 morphological characters were examined. Numerical taxonomic methods were used to analyse the data and to illustrate species relationships.
Distinctive differences among the materials studied suggest the retention of O. rufipogoon, O. nivara and O . sativa as three distinct species. The origin of O. sativa from O. nivara through domestication is discussed. An annual wild taxon from Australia, which had been classified as a form of O. nivara , is shown to be distinct from typical O. nivnra and is raised to specific rank. This species has been named O. meridionalis Ng.     

Determination of the Pattern of Winter Dormancy in Lateral Buds of Apples

Controlled environmental conditions and decapitation treatmentswere used to distinguish and determine the relative importanceof environmentally-imposed dormancy, correlative inhibitionand rest on the imposition of winter dormancy of lateral budson detached shoots and potted seedlings of apples. It is establishedthat the winter dormancy of lateral buds follows a pattern similarto that previously proposed for buds in general. The minimum procedure for the assessment of dormancy in lateralbuds is discussed. Malus sylvestris L, apple, bud dormancy, winter dormancy     

Axial and Transnodal Movement of 14C, 22Na, and 36Cl in Nitella translucens

The time courses of axial movement in Nitella translucens ofa number of ¹⁴C-labelled compounds and of ³⁶C1 and ²²Na havebeen determined together with simultaneous microscopical observationsof the rates of visible protoplasmic streaming. In general,the translocation profiles suggest the irreversible absorptionof tracer though there are examples of reversible absorption.The coupling between visible streaming and the front of theaxial transport is weak. Light, DCMU (dichlorophenyldimethylurea),and temperature affect the translocation but visible streamingis affected only by temperature and the passage of an actionpotential. There is evidence, from a number of compounds, ofa faster-thari-streaming translocation of small amounts of tracerin the form of ‘pulses’ which are completely detachedfrom the main body of tracer. Either vesicles or microperistalticpackets are thought to account for this rapid moiety. Observations of transnodal transfer suggest that an active mechanismis involved in the transference of carbonate, urea, acetate,and chloride. The influxes of the various compounds have been calculated andshown to be in good agreement with existing published values.Action potentials reduce the influx of carbonate, chloride,and possibly acetate, as do lack of light and DCMU. It is suggestedthat the influx of these anions is coupled with the active anionpump and with loading sites on the plasma membrane which becomeinoperative during and immediately following an action potential.     

Proleptusmackenzieisp.n. (Nematoda, Spirurida) from Raja fyllae in the Barents Sea

Previous work on species of Proleptus Dujardin, 1845 and related genera is briefly reviewed. Proleptus mackenziei sp.n. is described and figured. P. mackenziei is close to P. obtusus, P. acutus and P. malayi but differs from them in the host, position of the vulva which is 2/5/ of the body length from the anus and in the detailed arrangements of the papillae on the male tail.