Leaves of Lolium temulentum L. contain both low and high pI acid invertases. Immunoblot analysis of a highly purified preparation of these forms suggested that they both possess a subunit molecular weight of 68 kDa. Protoplasts and their derived vacuoles were isolated from leaf blades and contained sufficient acid invertase activity to account for all the activity found in the soluble fraction of crude homogenates of leaf blades. Alkaline invertase was present in the basal region of leaves and, unlike acid invertase, did not bind to Con A-Sepharose, suggesting that the acid invertase was a glycoprotein and that the alkaline invertase was not. Fructose inhibited both acid and alkaline invertases. The hypothesis is discussed that activity in vivo could be modulated by the concentration of free fructose.

Cell division was examined during leaf initiation in the slow-to-green mutant of Lolium temulentum L. to test the hypothesis that the cell cycle in the leaf primordium is a key regulator of the well characterized reduction in final leaf length in the mutant compared with that of the wild type. The cell doubling time (cdt, by colchicine method) was substantially longer in the youngest leaf primordium (YLP) of the mutant (107 h) than in the wild type (43 h) although the duration of the most rapid cell cycle (cc, by percentage labelled mitoses method) was between 18–20 h in each. As a consequence, the proportion of rapidly proliferating cells was only 20% in the mutant compared with 47% in the wild type. The size of the shoot apical meristem and the plastochron were similar between genotypes which indicates that the shoot meristem was largely buffered from the effects of the mutation. Mitotic cell area was also similar in the YLP of both genotypes. However, as the leaf elongated, mitotic cell area and interphase cell size were significantly larger in the mutant compared with the wild type. This change was coupled with a reduced number of cells per unit length of leaf in the mutant. The data are consistent in showing that the proportion of rapidly proliferating cells in the YLP (but not the rate of cell division) is a key parameter which influences growth of the leaf.

Unifoliated plants of Lolium temulentum L. cv. Ceres, a qualitative long-day grass, were induced to flower by one 24-h long day (LD) or by one 8-h short day (SD) advanced by 12 h in the normal regime, so-called ‘displaced short day’ (DSD). Standard light for SD and DSD was a mixture of fluorescence and incandescence at 400 μmol m−2 s−1 whereas the extension period of the 24-h LD was solely incandescence at 10–15 μmol m−2 s−1. The DSD system was first characterized by the timings of floral induction, stimulus translocation and apical development. Carbohydrates in the blade tissues and in leaf exudate were analysed comparatively in vegetative and induced plants.

Fructans were not detected in the leaf tissues whereas sucrose and starch were found to be present in similar amounts. In SD, their contents exhibited a diurnal fluctuation and were not in large excess. The common change observed during the two inductive treatments was that starch remained at a high level during the LD extension, even though the lighting was unsuitable for photosynthesis, and increased transiently in DSD.

Sucrose was the major sugar contained in the leaf exudate. Its content increased when flowering was induced, but not at the same time in the two systems. In LD, sucrose exudation rose when plants were returned to standard light after the inductive cycle, i.e. after the LD stimulus had left the leaf blade. By contrast, during the DSD, sucrose was transported at the same time as the floral stimulus. Results are discussed together with the methods used to time stimulus translocation and their implications.