摘要:

AbstractThe transition from resting to mitotically active potato tissue (excised disks) is accompanied by and virtually dependent on transcription, translation and increased metabolic activity. Thus enhanced RNA‐ and protein‐syntheses are well known features of potato tuber slices, allowing the cells to raise the level of several metabolic pathways (i.e., starch breakdown, pentose phosphate shunt, glycolysis, respiration and others) and ultimately leading to mitotic activity. Mitosis can be totally, yet reversibly suppressed by incubation of the tissue fragments in Tris (hydroxymethyl)‐aminomethane buffer. Neither total respiration nor its sensitivity to several inhibitors is affected during blockage of mitosis. Fluctuations in the levels of glucose‐6‐phosphate, fructose‐6‐phosphatc, phospho‐enolpyruvate and pyruvate are exactly the same in Tris‐inhibited as in non‐inhibited cells. Thus the Tris ion is not modifying glucose catabolism. The same is true for the time‐course of activity of hexokinase, glucose‐6‐phosphate‐ and 6‐phosphogluconate dehydrogenase, glucosephosphate isomerase, triosephosphate isomerase, enolase, phosphoglyceromutase and “malic enzyme”. Although the rapid decrease in activity of phosphoglucomutase, aldolase, pyruvate kinase and glutamic‐pyruvic transaminase after slicing (characteristic for non‐inhibited cells) does not occur in Tris‐treated tissue, these small differences are not thought to be causative in inhibition of mitosis.The results indicate, that nucleic acid metabolism is

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1971.tb06704.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

AbstractThe germination of lily pollen (Lilium longiflorumcv. Ace) was impaired by freeze‐drying. This loss of viability was associated with a modified pattern of respiration and an increased leakage of soluble carbohydrates, phosphate, and ninhydrin‐positive material into the culture medium. 2,4‐Dinitro‐phenol, (DNP), an uncoupler of oxidative phosphorylation showed a decreased ability to stimulate O2uptake in freeze‐dried pollen. The altered viability, respiration, and permeability resulted from drying under vacuum and not the initial freezing of the pollen. Mature lily pollen contained approximately 0.3 “Ai phosphate, of which 15 % was inorganic phosphate and about 50 %>was acid soluble organic phosphate of unkno

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1971.tb06705.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

AbstractSignificant changes in nucleic acids are associated with both maturation and senescence ofHedera helixleaf tissues. DNA content was unaffected by senescence, and there were no quantitative differences between juvenile and transitional forms. The adult tissue, however, contained less DNA than the other forms. The total RNA content was reduced by senescence in juvenile and transitional tissue but not in adult. Maturation, on the other hand, progressively decreased the total RNA content. Similar changes in sRNA and rRNA indicate that maturation involves quantitative changes in these fractions. Quantitative differences in the nucleotide analyses suggest that different sRNA and rRNA species are responsible for the biological processes associated with maturation.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1971.tb06706.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

AbstractThe discrimination between strontium and calcium is not only conditioned by the Sr/Ca ratio of the nutrient solution but also by the total dose (Ca + Sr) of the medium. The variation of the observed ratio in relation to the total dose is closely related with the Sr/Ca ratio of the solution. Sr is preferentially fixed by the roots when the Sr/Ca ratio of the solution is low; such a result is observed in the shoots for higher ratios. For all the treatments, the OR of the leaves is lower than unity (discrimination against strontium). When the stable strontium concentration of the solution is not detectable, an increase in the calcium concentration reduces the radiostrontium retention by the roots.

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1971.tb06707.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

AbstractLycopenc biosynthesis of parenchyma chromoplasts was studied in detached tomato fruits,Lycopersicum esculentumMill, cv. Waltham Forcing, and found to be phytochrome mediated. A few minutes of red light during the day enhanced lycopene formation. Far‐red irradiation did not enhance lyco‐pene biosynthesis. Far‐red following red nullified the promotive effect of red light. Lycopene content increased two‐fold in the presence of abscisic acid. Ripening of tomatoes was inhibited when gibberellin, kinetin and ascorbic acid were applied to green tomatoes. Gibberellin (A3) was more inhibitory to lycopene synthesis than

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1971.tb06708.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

AbstractDNA synthesis was measured during a 30 hour period in stem segments containing a wound — either sterile or inoculated withAgrobacterium tumefaciens— and in control stems ofVicia faba.An identical series of experiments was conducted both on upper, still growing internodes and on lower, mature ones. The incorporation of3H‐thymidine was determined from extracted DNA with a liquid scintillation spectrometer. The results from the two internodes were fairly similar. DNA synthesis was not significantly different in the two types of wounds. It rose above control level at about 10 hours after wounding and reached its peak at about 19 hours. Roughly, this pattern of DNA synthesis seems to correspond to the minimum conditioning and transformation time as found in other plants. However, the decisive factor need not be DNA synthesis, but could be some other process coinciding wi

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1971.tb06709.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

AbstractThe RNA‐synthesizing activity of the tissue, template activity of the chromatin, histones and other parameters were analyzed for young leaves, senescent leaves and the pith tissue of tobacco. The amount, of RNA, DNA and the extent of incorporation of32P into RNA was much lower in old leaves and the pith tissue than in young leaves. Furthermore, the32P sucrose density gradient patterns of RNA from the three tissues were very different. In old leaves, the label was found mostly in low molecular weight RNA region, presumably as a result of degradation of RNA by soluble and chromatin‐associated ribonucleases which were higher in old leaves. — In addition to significant differences in the composition of chromatin, large differences in the ratios of FI: FII: FIII: : histone fractions from the three tissues were noted and the fully differentiated old leaves and the pith tissue had proportionately more FIIand FIIIhistones than the less differentiated young leaves. The FIIIhistone of tobacco differed from that of pea and calf thymus in having lys/arg = 1.2. — Although some correlation between RNA‐synthesizing activity of the tissue, template activity of chromatin and the histone composition was noted for the pith tissue and the young leaves, the situation with old leaves was more complicated, probably due to the occurrence of chromatin‐associated deoxyribonuclease and involvement of other factors which may also effect RN

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1971.tb06710.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

AbstractA methanol extract of leaves of oat seedlings grown in sand cultures in the dark contained a compound which inhibited the growth ofOphiobolus graminis.The inhibitory factor was isolated and proved to be present in the plant as methoxyhydroquinone glucoside. The glucoside was readily hydrolysed to the corresponding aglucone. The methoxyhydroquinone, or possibly its oxydation product, methoxy‐P‐benzoquinone, was inhibitory to bothOphiobolus graminisvar.graminisandOphiobolus graminisvar.avenae, whereasFusarmm oxysporumvar.lycopcrsiciwas not affected. Synthetic methoxyhydroquinone at 80 mg/l gave a 100% inhibition ofOphiobolus graminisvar.graminis.After being exposed to 80 mg/l of the inhibitor for 24 h the mycelium was unable to initiate growth when transferred to a fresh nutrient solution. Only extracts from young leaves showed inhibitory activity, extracts from mature leaves giving no inhibition. The hydroquinone, or its glucoside, was not detected in roots of young seedlings, where avenacin was the only antifungal compound pres

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1971.tb06711.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

AbstractOlive trees must be exposed to a period of winter chilling temperatures in order to form inflorescences the following spring. The effects of diurnally fluctuating and constant temperatures on flower induction and sex expression in the olive were compared under controlled environment conditions. The effect on flowering of diurnally fluctuating temperatures depends upon the length of time at the higher temperatures. While daily exposure to the high temperatures (21° to 26°C) for a short period (four hours) intensified the effectiveness of the low temperatures (7° to 12.5°C), when the high temperature duration was 12 hours it counteracted the low temperature action. Possibly, daily low temperatures act to stimulate reactions leading to floral hormone synthesis, while daily short exposures to high temperatures act to maintain metabolic activity, promote energy‐yielding reactions, and possibly stimulate cell‐division activity. In the olive, an intermediate constant temperature (12.5°C) favors both types of reactions and induces flowering; however, in this case, the pistils fail to develop. The olive has very specific temperature requirements for flowering and neither the mean temperature nor the accumulated number of hours below a given value,e.g.7°C, adequately characterizes these req

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1971.tb06712.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY

摘要:

AbstractUsing auxin‐responsive diploid strains ofSaccharomyces cerevisiaeandS. ellipsoideus, we studied the role of cell wall‐degrading enzymes in the auxin‐induced cell expansion. Highly purified fungal β‐l,3‐glucanase added to cell suspension caused cell expansion in these strains. The cell expansion induced by auxin was inhibited by the addition of õ‐glucono‐lactone, which inhibited the activity of a crude β‐l,3‐gluca‐nase preparation from yeast in a competitive manner. Laminarinase activity was significantly higher in the extract from auxin‐treated yeast cells than in the extract of cells not treated with auxin. These results support the idea that auxin induces expansion of yeast cells of certain strains through enhancement of the activity of wall polysacc

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1971.tb06713.x

出版商:Blackwell Publishing Ltd    

年代:1971

数据来源: WILEY