Precursors of volatile components in tomato fruit—I. : Compositional Changes during development

The composition of tomato fruit at nine different stages of maturity was studied. The dry matter content decreased gradually, whereas the alcohol-soluble material and non-protein nitrogen increased with ripening. Total nitrogen decreased up to the large green stage and then increased during ripening. Starch accumulated until nearly the large green stage and then diminished rapidly. Of the two components of starch, amylose decreased much faster than amylopectin, and the ratios of amylopectin and amylose thus increased during ripening. Among the amino acids, glutamic acid was present in an exceptionally high concentration, and its concentration doubled during ripening. A concomitant decrease in the concentration of several other amino acids was noted. The possibility of amino acids serving as precursors for the synthesis of volatile aroma components in tomato is discussed.     

Ultrastructural changes in wheat embryos during a “presowing drought hardening” treatment

Summary Changes in the ultrastructure of the shoot apex of wheat embryos were studied during a reputed drought hardening treatment consisting of 48 hours of hydration followed by dehydration to air dry weight and during a subsequent second hydration for 48 hours. In the initial dry state lipid droplets are closely packed against the cell walls and the mitochondria and plastids have little internal structure. During the first hydration the lipid droplets are reduced in number and disperse while the mitochondria and plastids assume a normal appearance. The nucleus does not change appreciably. Under the conditions used in this work dehydration to air dry weight is not lethal to the embryos although notable changes in cellular structure occur: 1. Massive condensation of the normally loosely organized chromatin, 2. some loss of internal mitochondrial structure, 3. specific association of short elements of rough ER with vacuoles and lipid droplets, and 4. formation of fibrillar elements in the cytoplasm. In some respects then, embryos dehydrated after a 48 hour soaking have a very different structure to that of embryos that have dried during maturation of the seed. Since these changes are, in the case of viable embryos, reversible upon rehydration they cannot be linked, as such, to any long term drought hardening effect of the treatment. It is suggested that some changes, particularly the condensation of chromatin, may indicate a protective response to water stress. The kind of information needed to sustain this suggestion is discussed.This project is supported by grants from the Rural Credits Development Fund and the Australian Research Grants Committee.     

DMA polymorphisms in adhesion molecule genes — a new risk factor for early atherosclerosis

To contribute to the analysis of the genetic background of atherosclerosis, especially endothelial dysfunction, we searched for DNA polymorphisms in the genes encoding E-, P-, and L-selectin, and ICAM-I and VCAM-I. We detected 17 mutations by single-strand conformation polymorphisms analysis and direct sequencing. Five of them resulted in an amino acid substitution. In E-selectin, exchanges from serine to arginine (position 128), from leucine to phenylalanine (position 554), and a DNA mutation from guanine to thymine (position 98) present significantly different allele frequencies in young patients with angiographically established, severe atherosclerosis, compared with an unselected population. Results suggest that these polymorphisms are associated with a higher risk for early severe atherosclerosis.     

Populational analysis of thermal responses—I. Changes in the heat resistance of muscle tissue and contractile muscle models of Salamandra salamandra larvae

• 1.1.|Study has been made of the heat resistance of m. rectus superficialis and their contractile models of larvae of 12 families of Salamandra salamandra kept at three different temperatures: 14, 21 (optimal) and 27°C. The heat resistance of the organism has been studied only in larvae kept at 21°C.
• 2.2.|An inverse linear relation has been found between the level of the average heat resistance of muscles for offspring, of the same family, under optimal conditions and its increase caused by a change in environmental temperature. A similar relationship was observed in contractile muscle models. This implies that a population responds to a change in environmental temperature as a function al system.
• 3.3.|The analysis of individual differences in the pattern of response of muscles, and their contractile models, to changes in environmental temperature allows the systemal and individual components to be isolated. The extent of co-ordination in responses of different individuals of the population can be evaluated from the proportion of the systemal component. The value of this component varies from 0.60 to 0.90.
• 4.4.|Selective advantage during thermal selection belongs to individuals with lower heat resistance of muscles.

     

The weed seed bank of soils in a landscape segment in southern Bavaria — I. Seed content, species composition and spatial variability

The purpose of the present investigation was to examine the composition and the spatial variability of the arable soil seed bank in one large, coherent landscape segment, where the cultivation practice of neighboring farms and the gradients in soil properties determine the distribution of the weed seeds in soil. To this end, a 50×50 m grid of 338 reference points was fixed throughout a 143 ha area in southern Bavaria. The seed bank contained a median density of 4950 seeds per m² able to germinate. These values showed remarkable variation throughout the investigated area. Thus, 27% of the sampling area contained less than 2500 seeds per m², another 23% were below 5000 seeds per m² and 19% ranged among 5000 and 10 000 germinating seeds per m². Among the remaining sites, 22% showed seed densities between 10 000 and 20 000 and 9% more than 20 000 seeds per m². To visualize the spatial distribution of the weed seed bank over the whole study area, the interpolation method kriging was used. For this purpose the spatial continuity must be described by means of a semivariogram analysis. The goodness of the interpolation results depends on the fit of the semivariogram model which shows the spatial dependency. Two important characteristic parameters of this model are the nugget and the range. The nugget expresses the sampling error and the local variability up to the 50 m sampling distance, which cannot be detected by the semivariogram. Therefore the interpolation cannot describe the seed bank variation on a scale below this threshold. In our investigations the nugget comprises about one third of the total variance. The estimation error increases towards the border of the investigated area. In general, this is due to missing sampling points at the field edges. The range observed in the present investigations was 340 m. Beyond this no more spatial variability exists and the measurements are independent of each other. The species occurring in more than five of the investigated samples were ordinated by Detrended Correspondence Analysis and classified by k-means cluster analysis of the ordination axes. Five weed communities were recognized from this analysis which distinctly differed in their relation to the soil type and to the preceding management.     

Anhydrobiosis in nematodes—I. The role of glycerol myo-inositol and trehalose during desiccation

• 1.1. The concentrations of free glycerol, inositol and trehalose in five species of nematodes were determined. Analyses of total inositol content were also made.
• 2.2. Significant differences in free and bound sugar levels were found between the two good anhydrobiotes Anguina tritici and Ditylenchus dipsaci and the three poor survivors Pangrellus redivivus, D. myceliophagous and Turbatrix aceti.
• 3.3. Highest trehalose contents were found in desiccated A. tritici and D. dipsaci, but glycerol levels were low.
• 4.4. P. redivivus and T. aceti contained high concentrations of free glycerol.
• 5.5. Desiccated A. tritici larvae contained more free and bound inositol than all other species studied, but desiccated D. dipsaci larvae had higher levels of bound inositol than P. redivivus, D. myceliophagous and T. aceti.
• 6.6. Dramatic reductions in inositol and trehalose contents were found in revived A. tritici larvae and freshly extracted D. dipsaci larvae. This was accompanied by an increase in glycerol content.
• 7.7. The results are discussed in relation to the possible biochemical adaptations employed by anhydrobiotes during desiccation.

     

Studies on the haemolymph proteins of the blowfly Phormia regina—I. Changes in ontogenetic patterns

Detailed analyses of the haemolymph during development of blowfly Phormia regina have demonstrated a 12-fold increase in haemolymph volume during the 2nd to 5th day of larval life. Within the same period the total concentration of proteins increases about 24-fold, and reaches a maximum value of about 20 per cent (w/v) shortly before pupation. During metamorphosis both haemolymph volume and haemolymph protein concentration fall distinctly, the most rapid decline occurring during the time of transformation from larva to white pupa and at adult emergence. In the newly emerged flies the total protein concentration amounts to 3·5 per cent (w/v) which is only about one-sixth of that in the mature larva. Acrylamide gel electrophoresis indicates the presence of at least 19 protein bands in haemolymph. Characteristic changes in the ontogenetic patterns have been observed during development, including the appearance of new protein fractions and the disappearance of others in both pupal and adult stages. Furthermore, the distinct difference in the electrophoretic patterns between haemolymph and moulting fluid is indicative of the different origin of the respective protein components.     

Circadian Adrenocortical Periodicity Changes in Adult Rats Stimulated During Early Development—I. Effect of Prednisolone

The aim of this study was to test the feasibility of manipulating the adrenocortical circadian rhythm in adult rats by early postnatal prednisolone treatment. Prednisolone, when injected at 7-9 or 17-19 days after birth, produced a permanent suppression of the circadian rhythm of the basal levels of plasma 11-OH-corticosteroids and the rhythm of its responsiveness to stress. The administration of prednisolone at age of 2-4 or 12-14 days did not affect the circadian adrenocortical patterns in adults. Evidence was obtained for the existence of two critical periods during early development. Stimulation with prednisolone during these periods caused a profound modification of circadian periodicity in the performance of the pituitary-adrenocortical system. This modification was not related to changes in adrenal cortex ACTH responsiveness and also to altered stress reactivity of the pituitary-adrenocortical system. It was the presumable consequence of a blockage of a regulatory central mechanism initiating circadian variations in the pituitary-adrenocortical function. The existence of two distinct critical periods suggests that some prednisolone-sensitive links of this central pacemaker mechanism mature asynchronously during early postnatal life.     

Recent advances in systemic acquired resistance research — a review

Little is known about the signal transduction events that lead to the establishment of the broad-spectrum, inducible plant immunity called systemic acquired resistance (SAR). Salicylic acid (SA) accumulation has been shown to be essential for the expression of SAR and plays a key role in SAR signaling. Hydrogen peroxide has been proposed to serve as a second messenger of SA. However, our results do not support such a role in the establishment of SAR. Further elucidation of SAR signal transduction has been facilitated by the identification and characterization of mutants. The lesions simulating disease (lsd) resistance response mutant class exhibits spontaneous lesions similar to those that occur during the hypersensitive response. Interestingly, some lsd mutants lose their lesioned phenotype when SA accumulation is prevented by expression of the nahG gene (encoding salicylate hydroxylase), thereby providing evidence for a feedback loop in SAR signal transduction. Characterization of a mutant non-responsive to SAR activator treatments has provided additional evidence for common signaling components between SAR and gene-for-gene resistance.     

“Self-tanning”—a new and important source of stoichiometric error in cytophotometric determination of nuclear DNA content in plants

A Feulgen-densitometric comparison of nuclear DNA contents (C-values) was performed in various plant species (a fern, four gymnosperms, 16 woody and herbaceous angiosperms) after two types of fixation, additive (neutral formaldehyde) and non-additive (methanol-acetic acid, 3:1, MAA). Nuclei from tissues containing a significant amount of polyphenols (of the hydrolysable and non-hydrolysable tannin type) always showed reduced stainability and distorted spectral absorbance curves after MAA-fixation, while after formaldehyde-fixation no evidence for distorted staining was found. No fixation-dependent differences in Feulgen-DNA contents were stated in nuclei from tissues having no polyphenols. Distorted Feulgen-staining is a consequence of cellular self-tanning during fixation. Tanning is impaired by formaldehyde which binds to tannins and inactivates them. The rationale for using formaldehyde as a fixative in Feulgen-cytophotometry can be mainly seen in its capability of eliminating the self-tanning error. Standardization in plant DNA cytophotometry, and recent reports on unorthodox nuclear DNA variation in conifers are critically discussed.The author dedicates this paper, with emotions of respect and gratitude, to emer. O. Prof. DrElisabeth Tschermak-Woess on the occasion of the 70th anniversary of her birthday. She guided his Ph.D. Thesis in the years 1968 to 1972.