Non-Coordinated Synthesis of RNA's in Pre-Gastrular Embryos of Xenopus Laevis

The rates of syntheses of 18S and 28S rRNA, 5S RNA, capped mRNA and 4S RNA were determined in isolated cells from pre- and post-gastrular embryos of Xenopus laevis. The rate of rRNA synthesis per nucleolated cell Mas about 0.2 pg/hr, or about 5.5 × 10⁴ molecules/hr at the blastula stage, and this value remained constant in later stages. At the blastula stage, about 30 molecules of 5s RNA, 10 molecules of capped mRNA and 900 molecules of 4S RNA were synthesized per molecule of 18S or 28S rRNA. These values were all greatly reduced during the gastrula stage, and at the neurula stage, one molecule each of 5S RNA and capped mRNA and 10 molecules of 4S RNA were synthesized per molecule of 18S or 28S rRNA.     

A Comparison of the Effect of High Temperature on Grain Development in Wheat and Rice

Grain weight at maturity of the wheat cultivar Banks was reducedby about 5% for each 1 °C rise in daily mean post-anthesistemperature in the range from 17.7 to 32.7 °C, using grainweight at 17.7 °C as the base. In contrast, the rice cultivarCalrose had a stable grain weight up to 26.7 °C and abovethat showed a 4.4% drop in weight per 1 °C increase in meanpost-anthesis temperatures up to 35.7 °C, using grain weightat 26.7 °C as the base. In both wheat and rice there wasa reduction in the duration of grain growth with increasingtemperature up to a mean of 26.7 °C. In this range rice,but not wheat, showed a compensating increase in the rate ofdry-matter accumulation. Above 26.7 °C the rate of dry-matteraccumulation fell in both species, although this was more stablein rice than in wheat. In wheat the duration of grain growthcontinued to decrease at temperatures above 26.7 °C, butshowed little change in rice up to 35.7°C, the maximum tested.These data are discussed in relation to the physiological, biochemicaland physical constraints that may act to regulate grain developmentin wheat and rice at high temperature. Triticum aestivum, oryza sativa, grain development, high temperature effects     

The Effect of High Temperature at Different Stages of Ripening on Grain Set, Grain Weight and Grain Dimensions in the Semi-dwarf Wheat 'Banks'

Grain number in the wheat cultivar Banks was reduced by up to11 % with a rise in temperature from 21/16 °C to 30/25 °Cover a 10-d period immediately following first anthesis in general,the upper ‘d’ and ‘c’ florets were moreaffected by high temperature than the basal ‘a’and ‘b’ florets within a spikelet and florets fromthe upper spikelets were more sensitive than those lower onthe ear Grain weight and grain length at maturity were most affectedby a 10 d period of high temperature commencing 7–10 dafter anthesis However, if dry-matter accumulation between thestart of a treatment and grain maturity was used as a base forcomparison, the response was more uniform throughout development,with a peak in sensitivity 25 d after anthesis Although grainposition within an ear did not have a large effect on the responseto temperature, grains from the basal spikelets were more sensitivethan those from the apex, and the upper floret grains of a spikeletwere more sensitive to high temperature than those at the base There is a need to obtain, for a range of cultivars, more comprehensivedata on the effect of the timing and degree of temperature stressfollowing anthesis, for use in interpreting the response torising temperatures late in the development of the crop in thefield Triticum aestivum L, wheat, temperature, grain development     

Scanning Electron Microscopy of the Adoral Ciliary Zone of Entodinium Stein (Ciliophora,Entodiniomorphida)1

The adoral ciliary zone of the rumen ciliates, Entodinium spp., was observed topographically in the SEM. The upper side of the anterior end of the body was indented by the vestibulum, which had cilia arranged on its right wall and ribs along the left wall. The adoral ciliary zone could be divided into at least two arrangements. The outer ciliary zone had many membranelle-like structures, which consisted of cilia arranged radially from the body axis. Each membranelle-like structure consisted of two rows of about eight cilia each lining up in a single file. It was, however, different from a typical membranelle, because its cilia were connected with the vestibular cilia and were arranged not spirally but on a plane. These cilia extended toward the outside because of the projecting cytoplasm from which they originated. In contrast, the cilia of the inner ciliary zone were aggregated to form relatively unsystematic bundles. Since the vestibular opening was slanted on the upper side of the body, the ciliary bundles were thick on the lower side and sparse on the upper side of the body. Neither outer nor inner ciliary zones completely surrounded the vestibular opening. The ciliature started from the left side of the vestibular opening, encircled the lower side of the body, and entered the vestibulum from its right side. The functions of these two types of ciliary arrangements are discussed.