摘要:

A survey of haploid chromosome numbers of 18 North American taxa ofOxalissectionIonoxaliswas initiated to determine the relationship between ploidal level, geographic distribution, and the occurrence of tristyly and distyly. Although chromosome numbers in the section are variable, the majority of tristylous populations are diploid. Among the distylous taxa a greater diversity of ploidal levels exists, with the higher chromosome numbers predominating. In sectionIonoxalisthe majority of the tristylous taxa are geographically restricted endemics of southern Mexico, while the distylous taxa have more extensive distributions ranging to the north. The association of diploidy and geographic endemism in the majority of the tristylous taxa suggests that these species are relictual. A few widespread tristylous taxa are polyploid, and often somewhat weedy. The probable derivation of widespread polyploid species from the restricted diploid endemics of southern Mexico appears to have been accompanied by the evolution of distyly from tristyly. The frequent association of polyploidy and distyly in sectionIonoxalishas apparently resulted from the concurrence of two evolutionary trends: increase in ploidal level and the derivation of distyly from tristyly.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1976.tb11791.x

出版商:Wiley    

年代:1976

数据来源: WILEY

摘要:

Umbelliferone decreases the elongation rate and initiates a swelling response in cucumber roots. Associated with these growth effects are increases in peroxidase activity in water soluble, salt soluble, and wall bound fractions. The effect on elongation is reversible and is separated in time from the swelling response. Increased peroxidase levels appear after the elongation rate has been reduced but coincident with the swelling response. It is suggested that umbelliferone effects axial elongation and radial expansion through different mechanisms.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1976.tb11792.x

出版商:Wiley    

年代:1976

数据来源: WILEY

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1976.tb11793.x

出版商:Wiley    

年代:1976

数据来源: WILEY

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1976.tb11778.x

出版商:Wiley    

年代:1976

数据来源: WILEY