Senescence studies of festuca pratensis

Abstract

The first part of this investigation deals with an anatomical study of the senescence of Festuca pratensis. Since there were few observable structural changes at the anatomical level the progressing senescence was followed by using chlorophyll loss as a parameter of senescence along the Festuca leaf. As the ageing process was found to occur from the tip to the base of the leaf as if it were excised, the possibility of an 'abscission zone' near the base of the leaf was investigated. Feeding the plants with dyes and radiochemicals showed in older leaves that there was a definite retardation of the entry of these nutrients into the leaf at the ligule region i.e. it appears to act as a controlling mechanism for senescence. In the second part of this study the ligule region was examined closely to try and ascertain whether there were any structural changes in this region as the leaf ages which could account for the retardation of the entry of materials into the leaf. By using sectioning techniques and scanning Electron Microscopy evidence was found for the presence of possible tyloses in the xylem vessels of the ligule region in older leaves. These could indicate a possible mechanism at the ligule which may control or even induce senescence.