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151.
152.
Robert W. Read 《Biotechnic & histochemistry》1964,39(2):99-106
This technique is very useful where pollen is readily available and when roots or microspore mother cells are difficult to obtain or to process. It provides a relatively uniform means of studying chromosomes in a great number of species. Pollen is collected from buds at anthesis or the day before and sown on a medium containing H3BO3, 100 ppm; colchicine, 0.04%; lactose, 12%; gelatin, 5%; egg albumen, 1 drop in 10 ml. The gametic chromosome complement is studied at mitosis of the generative cell in the pollen tube. In species which have sufficiently large chromosomes it is possible to construct idiograms for comparative studies. All palm species here reported have a haploid complement of n = 18, and the chromosomes range in length from 0.5-3.5 μ. 相似文献
153.
Robert B. Spies 《Journal of morphology》1975,147(2):187-207
The functional anatomy of the head of Flabelliderma commensalis is described and compared to other flabelligerid polychaetes. Prostomial parts include the dorsal lip, the palps, two pairs of nuchal organs, four eyes and the prostomial lobe and ridge. The eyes are inverse pigment cup types with the medial portions of the sensory cells expanded to form a clear lens-like body. Peristomial parts include the median and ventral lips, the branchial membrane and the branchiae. The derivation of the nephridiopore is unknown. The spiraled branchiae of Coppingeria and the gill books of Diplocirrus are newly described variations in branchial structure. The head is retractable in some species and the anterior setigers are modified to form a protective setal cage. Two methods are employed for feeding: one for host fecal pellets and the other for detrital materials. Chemoreception, respiration, feeding and cleaning rely on a complex pattern of ciliary currents. 相似文献
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155.
Stanislaw Kowalczyk Anna Jakubowska Elbieta Zieliska Robert S. Bandurski 《Physiologia plantarum》2003,119(2):165-174
1- O -(indole-3-acetyl)- β - d -glucose: myo -inositol indoleacetyl transferase (IA- myo -inositol synthase) is an important enzyme in IAA metabolism. This enzyme catalyses the transfer of the indole acetyl (IA) moiety from 1- O -(indole-3-acetyl)- β - d -glucose to myo -inositol to form IA- myo- inositol and glucose. IA- myo -inositol synthase was purified to an electrophoretically homogenous state from maize liquid endosperm by fractionation with ammonium sulphate, anion-exchange, adsorption on hydroxylapatite, affinity chromatography on ConA-Sepharose, preparative PAGE and isoelectric focusing. We thus obtained two enzyme preparations which differ in their R f on 8% polyacrylamide gel. The preparation of R f 0.36 contained a single 56.4 kDa polypeptide, whereas the preparation of R f 0.39 consisted of two polypeptides of 56.4 and 53.5 kDa. Both purified preparations of IAInos synthase also exhibited the activity of an IAInos hydrolase, showing that the dual activity was associated with a single protein. Results of gel filtration and analytical SDS-PAGE suggest that the native enzyme exists as both a monomeric (65 kDa) and homo- or heterodimeric form (110–130 kDa). Analysis of peptide maps and amino acid sequences of two 21 amino-acid peptides showed that polypeptides of 56.4 and 53.5 kDa have the same primary structure and that the 3 kDa difference in molecular mass is probably caused by different glycosylation levels. Comparison of this partial and internal amino acid sequence with sequences of other plant acyltransferases indicated similarity to several proteins which belonged to the serine carboxypeptidase-like (SCPL) acyltransferase family. 相似文献
156.
157.
158.
Ian D. Hodkinson Jeremy M. Bird Jane K. Hill Robert Baxter . 《Ecological Entomology》2001,26(4):376-387
1. Salix lapponum host plants at an upper altitudinal site differed significantly in size, structural density, phenology, growth performance, and spatial isolation from those growing at a lower site. 2. Plant differences were paralleled by significant differences in psyllid population density and phenology parameters, with psyllid population density, percentage of catkins occupied, and phenological development relatively lower or retarded at the upper site. Population densities at the upper site, nevertheless, remained high. 3. Plant measurements were good predictors of insect density, often explaining up to 73% of the variance in abundance among plants at a given site. 4. Sets of four plant characters identified by best subsets regression were better predictors of psyllid density and development than single factors, although differences were often not great and the combinations of characters selected by multiple regression sometimes differed from the best single predictors. 5. Best single predictors of psyllid density on catkins were measurements of plant size, particularly height, length, and basal stem diameter. Shoot density and catkin phenology were occasionally important but plant isolation and prior growth performance were less important. 6. By contrast with density, age structure of the psyllid population was predicted best from plant phenological measurements, notably catkin phenology. 相似文献
159.
160.
Robert S. Boyd 《American journal of botany》1988,75(10):1540-1548
The microdistribution of a beach plant, Cakile maritima, was examined relative to patches of an introduced beachgrass, Ammophila arenaria. Sampling was done with belt transects oriented parallel to the beachfront to minimize the influence of physical factors along the land/sea gradient. No Cakile individuals were found within Ammophila patches, and a 3–4 m wide zone of decreased abundance occurred outside of patch borders. I hypothesized that this microdistribution was due to foraging behavior of deer mice, Peromyscus maniculatus, which nest in Ammophila patches and forage outward from them. Manipulative experiments using fruits and seedlings of Cakile confirmed that herbivory was higher inside patches and in border areas. Seedlings protected from herbivory by wire cages survived and grew equally well both inside and outside of Ammophila patches, demonstrating that differences in other habitat factors were not of major importance in determining Cakile microdistribution. Herbivory by mice was concluded to be of primary importance in determining the microdistribution of Cakile relative to Ammophila. Rodent herbivory may influence microdistributions of beach plants along the land/sea gradient, and may also be partly responsible for decreased plant species richness often observed in Ammophila-dominated areas on the West Coast. 相似文献