摘要:

SUMMARYColour changes in the petals of two varieties of the tropical plant speciesMalvaviscus arboreuswere investigated. The light absorbance of living petals and the absorbance of petal‐extracts were measured. A separation of pigments by means of paper chromatography was attempted. Older stages of living petals show a low absorbance at all wavelengths compared with younger ones, and also a shift of the minimum at 440 nm and the maximum at 520 nm towards higher wavelengths. Petal extracts of different stages also have a different absoiption spectrum; nonnectar producing flowers show a maximum at about 515 nm while nectar producing ones have merely a shoulder at 515 nm which may be due to a loss of red pigments. This loss is clearly demonstrated by paper chromatography and coincides with the beginning of nectar production. Hummingbirds, the main visitors ofMalvaviscus, probably use this colour‐shift for recognizing nectar producing flow

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1971.tb00723.x

年代:1971

数据来源: WILEY

摘要:

SUMMARYIn nitrate reductase preparations from radish cotyledons an endogenous inhibitor of a non competitive nature was found. A method for calculating the amount of inhibitor present was devised. The amount of inhibitor present in one pair of cotyledons decreased with increasing age of the seedlings, in light as well as in darkness. It is suggested that the inhibitor is of a phenolic nature since the inhibition could be reversed by extraction with polyvinylpyrrolidone.

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1971.tb00724.x

年代:1971

数据来源: WILEY

摘要:

SUMMARYSix phenolics were isolated from needles ofLarix leptolepisand identified asp‐coumaric acid, feiulic acid,p‐hydroxybenzoic acid, protocatechuic acid, vanillic acid and syringic acid. Different extraction procedures indicated, however, that these compounds only occurred in the needles in a bound form. The finding of free acids had to be attributed to an artifact in the extraction proced

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1971.tb00725.x

年代:1971

数据来源: WILEY

摘要:

SUMMARYThe present article reports the preliminary results of a pollen‐analytical study of some peat sections with very short sample distances. The resulting diagrams may be an aid to a better understanding of the vegetational developments within the peat bog. The importance of Fungi is also discussed and the curves for fungal spores are compared with the peat stratigraphy and vegetational succession. Attention is also paid to cyclic phenomena observed in the diagrams; an approximately 80‐years' cycle in theAlnuscurve seems to be appar

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1971.tb00726.x

年代:1971

数据来源: WILEY

摘要:

SUMMARYA morphological study was made with respect to the changes during microsporogenesis ofPinus sylvestrisL. from prometaphase I until the tetrad stage. Described and discussed are the breakdown and rebuilding of the nuclear membrane, the mixing of karyoplasm and cytoplasm with the transfer of ribosomal material, the nuclear invaginations, the kinetochore and microtubuli.A decrease of starch in the plastids starts in interphase II. The mitochondria do not change. The “lipid‐complex” appears in telophase II. Many vesicles are present in the cytoplasm during the cell divisions. Ribosomes are observed in all stages, polysomes become visible during interphase II and telophase II. Rough endoplasmic reticulum is absent. The Golgi body produces small and large vesicles and long flat cisternae, similar to smooth endoplasmic reticulum. These Golgi vesicles fuse and form the primary cell wall. The presence of the plasma membrane is postulated as necessary for the synthesis of callose. No difference has been found between the morphological events during callose wall formation and cellulose wall formation. A relation may exist between the callose wall formation and the polysomes and lipid granules and “lipid complex”, but a relation with smooth endoplasmic reticulum is not clear. During diplotene and early tetrad stage the formation of the callose wall proceeds in the

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1971.tb00727.x

年代:1971

数据来源: WILEY

摘要:

SUMMARYAt present 38 species ofRhynchospora, now including alsoDichromena, are known from Suriname, two of which with two varieties. Two new species are described here:Rh. guianensisandRh. sublanata.A key to the Suriname species is presented.For every taxon the distribution and, where known, a brief characteristic of its ecology in Suriname are given.

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1971.tb00728.x

年代:1971

数据来源: WILEY

摘要:

Heukels – van Ooststroom.Flora van Nederland.Zestiende druk bewerkt door Dr. S. J. van Ooststroom. 909 pp., 1038 fig. Wolters‐Noordhoff NV, Groningen 1970. Prijs f 27

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1971.tb00729.x

年代:1971

数据来源: WILEY