Scutellar Amylase Activity in Naturally Aged and Accelerated Aged Wheat Seeds

Scutellum extracts of dry unaged and differentially aged wheatseeds showed appreciable and ß amylase activities,these being higher in unaged and lower in aged seeds. This indicatesthat scutellar amylase may remain long-lived in seeds. Duringgermination of both unaged and aged seeds an increase in scutellaramylase (particularly ß) occurs. Initiation of thisgermination associated increase in amylase activity, however,was found to occur relatively late during imbibition. Further,while scutellar amylase increased considerably during imbibitionin unaged seeds, in differentially aged seeds the increase wassmall. This also contributes to the reduced scutellar amylaseactivities in aged seeds. Triticum aestivum L., wheat, naturally aged, accelerated aged, unaged, germination, scutellar and ß amylase     

Genetic heterogeneity among the founders of laboratory populations of Drosophila IV. Scutellar chaetae in different environments

The incidence of flies with more than four seutellar chaetae (additional chaetae) has been followed for up to 3 years in 4 lines at 15°C, 20°C, 25°C and 27.5°C derived from each of 3 strains, initially set up from single inseminated females of Drosophila melanogaster, collected in the wild single the same locality at the same time. Within each set of temperature lines, the incidence of additional chaetae was highest in one strain, intermediate in another strain, and lowest in the third. This shows that the differences between lines can be at least partly attributed to differences between the founder females of the three strains, although some divergence occurred between lines within strains in some cases. With respect to quantitative traits, the results indicate that in situations where new habitats are occupied by a small number of colonists, the nature of the founder female is possibly of greater importance than the different environments of the new habitats.Some of this work was supported by the Australian Research Grants Committee.     

Effects of Ageing on Amylase Activity and Scutellar Cell Structure during Imbibition in Wheat Seed

In wheat seed the scutellum plays an important role in the hydrolysisof stored substrate during germination. This layer is activatedfirst, whilst the aleurone becomes activated later. A good correlationexists between the initiation of visible germination and theappearance of enzyme activity in the scutellum. Enzyme activityin the aleurone becomes apparent only when the germinating seedlingreaches the rapid growth phase. Electron microscopic observationsshow that during the later stages of germination the scutellarcells develop finger like projections. These may serve to absorbendospermic reserves hydrolysed by aleurone amylase. The scutellumof aged non-germinating seeds showed no amylase activity andno finger like projections were produced even after prolongedimbibition.Copyright 1993, 1999 Academic Press Wheat (Triticum aestivum L.), deteriorated, germination, scutellum, scanning electron microscopy, aleurone     

Localization of ATPase Activity on the Plasmalemma of Scutellar Epithelial Cells of Germinating Barley (Hordeum vulgare L.)

Chaffey, N. J. and Harris, N. 1985. Localization of ATPase activityon the plasmalemma of scutellar epithelial cells of germinatingbarley (Hordeum vulgare L.).—J. exp. Bot 36: 1612–1619. ATPase activity has been localized at an ultrastructural levelin the absorptive region of the scutella of germinating barley(Hordeum vulgare L.). The enzyme is localized on the plasmalemmaof the epithelial cells. Using the Gomori reaction the depositionof reaction product on the plasmalemma, which is dependent uponthe presence of supplied ATP, was precluded or reduced by theinhibitors orthovanadate, mercuric chloride and DCCD, whilstß-glycerophosphate would not act as an alternativesubstrate. The mitochondria demonstrated phosphatase activitywith both ATP and ß-glycerophosphate as substrate.The results are discussed in relation to the active uptake ofmetabolites by the scutellum during germination and the structuralmodification of the plasmalemma of the epithelial cells to formplasmatubules. Key words: ATPase, Hordeum vulgare L., localization (ultrastructural)     

Studies on the Scutellar Bristles of DROSOPHILA MELANOGASTER. II. Long-Term Selection for High Bristle Number in the Oregon Rc Strain and Correlated Responses in Abdominal Chaetae

Results are presented of 135 generations of selection for high scutellar bristle number in two lines M and M3 derived from the same original mating of one female with 5 bristles by one male with 4 bristles, the latter being the wild-type canalised phenotype. Results are also given of two relaxed lines per line and of a reselection line M2 derived from the first relaxed line of line M which had regressed almost to base population level. The effect of introducing the sc(1) allele into the M and M3 selected backgrounds was studied at generations 39-44. At the end of selection the effect of an extra dose of sc(+) was also studied in males of all selected backgrounds. The correlated responses in abdominal bristles were followed in all lines.-Considering their common origin, the selection lines differed markedly in pattern of scutellar response and in most other aspects observed, namely correlated responses in abdominals and p.c. scutellars, sex differences, and behaviour on relaxation. Selection limits for scutellar bristles in lines M and M2 were equal to or greater than the most extreme reported in the literature.-The probit span of the canalised 4 bristle class decreased in each selection line as the mean scutellar bristle number increased, and increased again in the relaxed lines as the mean bristle number decreased. In the context of an hypothesis that canalisation at 4 bristle is due to regulation of the scute locus, this result is now interpreted as being due mainly to selection for poor regulators of sc(+), in contrast to a previous interpretation that only the minor gene background was altered by selection, the canalisation (regulation) genotype not being affected.-Introducing the sc(1) allele into the selected backgrounds M and M3 showed a reduced effect on sc(1) flies compared with sc(+) flies, and an interaction of sc(1) and sc(+) with selected background. sc(1) flies had about the same number of bristles in both backgrounds though the mean of sc(+) flies in line M was about 3sigma higher than in line M3. Dominance of sc(+) to sc(1) was reduced slightly in M3. However, the effect of an extra dose of sc(+) at the end of selection was about the same as in unselected in all lines, so the first or dominance level of regulation of the scute locus was not significantly affected by selection, though the second or canalisation level of regulation was.-A large positive correlated response in abdominal bristles occurred in all lines. The response in line M was about twice that in M2 and M3 and was in fact as large as can be obtained from direct selection on abdominals. In line M some genes may have been selected with a proportionately greater effect on abdominals than on scutellars. This is supported by the further observation in line M that the abdominal scores of flies with particular scutellar bristles scores increased as the scutellar mean increased. An attempt was made to apply to these results Rendel's (1962) model of competition between scutellars and abdominals for common bristle-making resources. This could not be done satisfactorily mainly because the assumptions in the model about the similarity of effects in scute and wild-type flies were not met in the present material.