摘要:

SUMMARYThe anatomy of the mature wood of three species of the South American genus of woody climbersDicranostylesBth. is described and compared with that of the secondary wood of other genera of theConvolvulaceae. The stems are characterized by the occurrence of concentric rings of included phloem tissue. In most characters the three species are quite similar, except for the absence of rays over two cells wide inD. guianensis. Instead of these, aggregate rays occur at intervals between consecutive rings of included phloem.D. mildbraedianapossesses fibre tracheids with next to the normal large bordered pits numerous very large irregular slits giving the impression of a helical sculpturing of the walls. From a comparison with other Convolvulaceous genera likeBonamia, Ipomoea, Maripa, Neuropeltis, andPrevostea1it appears that nearest toDicranostylesin general appearance as well as in anatomical structure is the genusMaripa. The resemblance toIpomoeaseems only superficial. The relation between anatomical conformities of genera and their position in the various systems of subdivision of the family is discussed.

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1969.tb00582.x

年代:1969

数据来源: WILEY

摘要:

SUMMARYThe symbiosis of endotrophic fungi withCalluna, EricaandVacciniumspecies was studied in artificially infected seedlings and cuttings. The fungi investigated are not species‐specific,e.g., a fungus isolated from the EuropeanVaccinium oxycoccuscan serve the North AmericanV. macrocarponas a symbiont. When added to sterile cuttings the fungus stimulates root formation, and both with seedlings and cuttings it enhances growth.These symbiotic fungi have cellulase and pectinase.The process of penetration into the epidermis has been studied electron microscopically. The protoplast of an invaded epidermal cell is not killed by the fungus which eventually is digested by the living plant cell. The fungus cannot invade the subepidermal cells, probably because the secondary cell wall of the latter consists of, or contains, multiple layers of suberin. However, break‐down products of the digested mycelium may not be prevented by the suberin layer from being assimilated, as radioactive serine was found to be taken up when applied ca. 1 cm from the tip of the r

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1969.tb00583.x

年代:1969

数据来源: WILEY

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1969.tb00584.x

年代:1969

数据来源: WILEY

摘要:

SUMMARYChloroplasts lost their starch‐synthesizing enzymes (phosphorylase, ADPGα‐glucan glucosyltransferase) during a period of darkness. Enzyme activities returned in the light, but this process could be reversibly inhibited with actinomycin D or chloramphenicol. It is concluded that the enzymes are produced in the chloroplast and that starch production is dependent on the functioning of the protein synthesis as directed by the nucleic acids in the chloroplast. The localization and extension of DNA areas in chloroplasts and chloroamyloplasts showed a relationship to the number and size of the starch granules produced. In many cases there was a close contact between DNA areas and starch granules.DNA and RNA were found in a variety of plastids, in agreement with the expectation expressed by various authors.It is likely that all plastids contain their own mechanism for nucleic acid‐controlled protein synthesis, and that the starch‐synthesizing enzymes are always among the proteins thus

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1969.tb00585.x

年代:1969

数据来源: WILEY

摘要:

SUMMARYJoseph Gaertner (1732–1791) was the first to develop a carpological taxonomy in his bookDe fructibus et seminibus plantarum(1788–1791). The scope and background of this work are discussed; its history is sketched on the basis of the Banks correspondence at the British Museum; the main sources of material are listed. A brief outline of Gaertner's life is given, also mainly based on letters from him and his contemporaries to Joseph Ba

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1969.tb00586.x

年代:1969

数据来源: WILEY

摘要:

SUMMARYBleeding inflorescence stalk tips of 10–15 cm length, still attached to the plant, were cooled in melting ice. The result was a considerable prolongation of the exudation period. Apparently the wound‐sealing process was strongly retarded. Although the rate of bleeding seemed slightly lower, the dry‐matter content of the exudate was 10–20% higher at 0 °C than at 20–25 °C.When excised inflorescence tops were cooled as a whole, exudation gradually declined and stopped within 45 minutes. It recommenced within a few minutes when brought to room temperature.It is concluded that both the sugar secretion and sugar uptake by cells surrounding the intact sieve‐tubes stops at a low temperature. The secretion process is assumed to be the driving force of the exudation. As the bleeding continues at low temperatures, its driving force will be localized mainly outside the cooled

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1969.tb00587.x

年代:1969

数据来源: WILEY

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1969.tb00588.x

年代:1969

数据来源: WILEY