摘要:

SUMMARYCell division in the unicellular coccoid green algaM. geminatahas been studied with transmission electron microscopy. Unlike the division cycle in other coccoid green algae, mitosis occurs not before the cell has expanded until about twice its original volume. Cell expansion involves the escape of part of the protoplast through a break in the cell wall. During mitosis the nuclear envelope remains intact. The spindle is not associated with centrioles, which seem to be absent throughout the cell cycle. The division site at the plasma membrane is marked by a short cortical microtubule which appears before division is initiated. The plasma membrane near the microtubule invaginates to form a coated pit‐like structure. The latter continues to grow inward along with the short microtubule, and in effect constitutes the cleavage furrow. After furrowing, each daughter cell forms a wall layer at the new septum. Cells separate after the old, common wall layer is broken at the level of the septum. A model explaining cytokinetic events, in particular the furrowing mechanism, is presented. It is concluded thatM. geminatamay be considered as a member of a broadly conceived order Chlorococcale

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1987.tb02003.x

年代:1987

数据来源: WILEY

摘要:

SUMMARYImmature embryos of two maize inbred lines (A188 and A632) have been examined during the first three days of in vitro culture using light and electron microscopy. The first day of culture is characterized by an increase in the amount of organelles, changes in vacuolation and in nucleolar morphology. These ultrastructural events take place in both inbred lines and are not influenced by the presence of 2,4D. After one day of culture variation in developmental patterns occurs, which is dependent on genotype and culture conditions. It is found, that in the scutellum of A188 embryos proliferation is activated strongly within two days of culture, followed by the appearance of a broad scutellar meristematic zone. A second meristematic region is observed around the coleorhiza. In A632 embryos only a coleorhizal meristematic zone developed, while in the scutellum proliferation was hardly observed.Therefore we have subdivided the first period of maize embryo culture into two phases. The first phase is called the shock response and takes about one day, while the second phase starts after one day and is called growth response.In concurrent cultures of A188, which were prolonged for several weeks, white compact callus developed accompanied by somatic embryos, while in the A632 cultures non‐embryogenic callus was produce

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1987.tb02004.x

年代:1987

数据来源: WILEY

摘要:

SUMMARYTwelve years after clearance of aPicea abiesstand, the spectrum of water‐soluble phenolic acids in the soil still resembled that of an adjacent, undamaged stand. Ferulic andp‐coumaric acid were the predominant phenolic compounds. Apparently, the spectrum of low molecular phenolics in the soil layers is affected by the original litter material over a long period. The concentrations of water‐soluble acids was highest in the A0‐horizon. A comparison between the sites revealed that concentrations in the clearing were reduced with more than 50% compared to the undamaged stand. The significance of the phenolic acids for plant growth was investigated for two herbaceous woodland (‐clearing) species,Senecio sylvaticusandChamaenerion angustifolium. Both species were tested for their sensitivity to phenolic acids in dependence of nutrient supply under greenhouse conditions. Severe growth reduction occurred at high phenolic acid concentrations (10–3M). Plants that were restricted in growth by a low nutrient supply, were less affected by the intermediate phenolic acid concentrations of 10–5and 10–4M than plants grown at high nutrient supply. The results are discussed in view of vegetation succession on woo

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1987.tb02005.x

年代:1987

数据来源: WILEY

摘要:

SUMMARYThe development of the lower part of the stamen ofGasteria verrucosa(Mill.) H. Duval, the filament, was investigated using interference contrast, transmission and scanning electron microscopy, and was related to the development of the anther.The filament extends during its entire development, in the younger stages mainly in the basal region, in the older stages in the tip. Up to maturity the solidity is gradually improved by the progressive thickening of the tangential epidermal wall and the cuticle from the tip to the base of the filament and the increasing turgidity of the epidermis.The amount of tracheary elements increases up to maturity as does the starch content of the epidermis and the parenchyma. Starting at the pollen mitosis stage, a progressive cytoplasmic degeneration can be observed from the tip to the base and from the central parenchyma to the epidermis. At anther dehiscence the filament tip shrivels and the starch has disappeared from the entire filament. Both the latter phenomenon and the cytoplasmic degeneration may be due to redistribution of substances to other floral parts. The presence of prominent intercellular spaces may be important for the supply of gas to the maturating locule.

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1987.tb02006.x

年代:1987

数据来源: WILEY

摘要:

SUMMARYConditions for the formation of a long first internode (mesocotyl shoot) of maize (Zea maysL.) formed in a relatively short period of time were analyzed. If an inert substrate was used, the growth of such a shoot is mainly determined by the uptake of water. Effect was examined of acidified water (a substitute for acid rain) on morphology and anatomy of first internodes and of roots of young seedlings produced by deeply sown maize grains in an inert substrate under conditions mentioned above.Light microscopical investigations of transverse sections of first internodes and roots revealed more tracheary elements mainly consisting of a greater number of tracheids, in the mesocotyl of those seedlings cultivated with acidified water. The effect was more distinct if a combination of sulphuric and nitric acid was applied and less distinct if nitric acid, sulphuric acid or hydrochloric acid were applied. Radial endodermis cell walls (cross walls were not measured) in the mesocotyl were up to twice as thick in plants treated with acidified water than in plants of the control with tap water. Possible water stress symptoms caused by the supplied acidified water are discussed.

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1987.tb02007.x

年代:1987

数据来源: WILEY

摘要:

SUMMARYThe contents of K+, Mg2+, Na+, Ca2+, Rb+, Mn2+, Cu2+, Al3+, P, Br–, and Cl–were measured in tomato fruits, which were picked from the plant at various stages of development, starting from the day of anthesis. Determinations were also carried out of transpiration rate, increase in fruit water, and dry and combustable fruit materials.Measurements of the ion contents in the fruit, and the import characteristics of Ca2+indicated that the ratio of CO2production and photosynthetic CO2fixation rates did not appreciably change during the entire period of fruit growth. The overall efficiency of conversion of imported to fruit dry matter was assumed to be about 100%.The high initial ion concentrations in the fruit have been attributed to an initially high rate of water and solutes supply by the xylem. The varying fractional contribution of the xylem to ion and water import results in varying import rates of solutes in the fruit. The maximal percentage of phloem delivery during the period of highest growth rate could be estimated as 99, 98, 94, 0, 99, 78, 93, 94, 98, 97 and 97% for K+, Mg2+, Na+, Ca2+, Rb+, Mn2+, Cu2+, Al3+, P, Br–, and Cl–respectively.The average fractional phloem contribution to the import of dry matter and water could be determined as 98 and 84% respectively. The amounts of Ca2+, imported during the early stages of fruit development, were shown to be important with respect to the avoidance of the occurrence of blossom‐end rot during the period of highest growth rate of

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1987.tb02008.x

年代:1987

数据来源: WILEY

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1987.tb02009.x

年代:1987

数据来源: WILEY

摘要:

M. K. Hecht, B. Wallace&G. T. Prance(Eds.):Evolutionary Biology, Vol. 20. Plenum Press, New York and London, 1986. XV + 472 pp., ill. Cloth $ 59.50 ISBN 0‐306‐422

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1987.tb02010.x

年代:1987

数据来源: WILEY

摘要:

Klingmüller, W. (Ed.):Azospirillum III. Genetics, physiology, ecology. Proceedings of the Third Bayreuth Azospirillum Workshop. Springer Verlag, Berlin, Heidelberg, New York, Tokyo, 1985. XIV + 263 pp., 102 figs. Hard cover DM 78,– ISBN 3‐540‐

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1987.tb02012.x

年代:1987

数据来源: WILEY

摘要:

J. L. Harper, B. R. Rosenand J. White(Eds.):The growth and form of modular organisms. Proceedings of a Royal Society discussion meeting held on 27 and 28 June 1985. The Royal Society, London, 1986. 250 pp., ill. Hard cover. £43.00 UK, £46.00 overseas. ISBN 0‐85403‐281‐9. (Phil. Trans. R. Soc. Lond. B. 313, No. 1159. 1–

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1987.tb02013.x

年代:1987

数据来源: WILEY