Structure/function relationships in the graminaceous leaf

Abstract

Aspects of the structure/function relationships in leaves of Lolium temulentum L. were examined during their growth, ageing and senescence. The first part of the thesis deals with the blade and sheath and demonstrates the presence of interactions within leaves (between blade and sheath) and between leaves during their extension growth. ' A short biddhemical study of aspects; of blade and sheath ageing and. senescence of attached 4th leaves examined changes in fresh and dry weight, total chlorophyll, soluble protein, and nucleic acids (both quantitative and qualitative by polyacrylamide gel electrophoresis). The overall patterns of change were similar to those previously described for artificially' induced grass leaf senescence but differences were found between the two organs. It was concluded that the blade was not a good model for sheath or leaf senescence. A study of the vasculature of the leaf - with particular reference to metabolite trans port during ageing and senescence - revealed the presence of tyloses in the protoxylem vessels/lacunae at the blade/sheath junction of senescing leaves. The second part of the thesis deals with the membranous ligules of L. temulentum, L. perenne L., L. multiflorum Lam., L. x hybridum Hausskn., and Festuca pratensis Huds. The structure and ultrastructure of all appeared to be the same and had the appearance of a glandular organ. Using a number of cytochemical procedures in L. temulentum, catalase, cytochrome c oxidase and succinate dehydrogenase activities were identified, along with the apparent secretion of a glycoprotein- like material by the cells of the adaxial epidermis. Aspects of the endomembrane system of cells of the latter tissue and initiation and early development of the ligule of L. temulentum were also studied. The structure/function relationships within these ligules are discussed in terms of a possible function of the membranous grass ligule. Aspects of ligule and root cap biology in L. temulentum were compared.