Literature Reviews of seed dormancy, the germination of seeds (restricted as closely as possible to the period actually preceding radicle protrusion) and the effects of gamma radiation are included in this thesis. Tritiated water studies of heavily irradiated Sinapis alba seeds showed that these seeds can carry out active metabolism, leading to the formation of tritiated gamma-aminobutyric acid (GABA), alanine, malic acid and citric acid. The compounds which were not labelled by tritiated water in heavily irradiated seeds but which were labelled in non-irradiated seeds were the following: lactic acid, glutamine, sucrose, glutamic acid, aspartic acid and sugar phosphates. Difficulty was experienced in enabling sufficient C-14 substrate to enter the seeds for studying the metabolism of these compounds. The seeds were therefore ground in liquid air prior to the C14-tracer studies. The metabolism of this powder was examined using tritiated water. Over short time intervals this metabolism was similar to that of whole seeds except for the heavy labelling of lipid material which was shown to be ninhydrin positive. At longer time intervals this powder did not develop the complex patterns typical of whole seeds. The metabolites lactic acid, glutamine, sucrose and sugar phosphates were not labelled during 24 hours imbibition in tritiated water, of the Liquid Air Powder (LAP) but were labelled on imbibition of whole seeds. Imbibition of the LAP of both irradiated and non-irradiated seeds with the C-14 substrates gave similar distributions of radioactivity. Aspartate-U-C14 was not rapidly metabolised within 4 hours. In non-irradiated seeds traces of a ninhydrin positive compound (U1) postulated to be succinylarginine were found after 4 hours. Incubation with GABA-1-C14 led to labelled flavonoids within one hour and to labelled alanine and an unknown (U2) within 4 hours. The metabolism of glutamate-U-C14 rapidly led to the formation of GABA at short time intervals and at longer time intervals (4 hours) to labelled GABA, alanine, and two unknowns called “YPN” and U3. In the irradiated seeds labelled lipid was also formed. The unknowns U2 and U3 are postulated to be the same ninhydrin positive compound, possibly a peptide. The transaminases, glutamate-oxaloacetate and glutamate-pyruvate were found to be active in enzyme extractions of dry seeds. Evidence showing a reduction in the activity of transaminases with time of imbibition is also reported. Paper chromatographic analyses of seed metabolism, including a novel method developed for a rapid enzyme assay are included. These results were similar to those obtained using C-14 substrates. In addition conversion of GABA and glutamate to an unknown called UVGB was found. The metabolism of aspartate led to alanine and of alanine, to GABA. The limited metabolism displayed by heavily irradiated seeds immediately after irradiation did not lead to the formation of a seedling for those Sinapis alba seeds which had received a dose of 2.98 Mrep or more. The germination of a very large range of seed species was examined after receiving chronic doses of irradiation. Only parsnip seeds would not germinate after receiving a dose of 0.5 Mrads. Most seeds showed similar responses to that for mustard seeds. One group of irradiated mustard seeds were left in a drawer in the laboratory. These seeds showed complete recovery in both the ability to germinate and in their labelling patterns when imbibed with tritiated water after less than 6 months storage. A similar set of seeds stored over silica gel did not display any recovery. A large experiment was undertaken in which seeds of many species were examined after various periods of storage at fixed or room humidities. Some recovery was observed although not of the same order as that found earlier. Storage at very high humidities led to loss of the ability to germinate. The effects of various solutions were also examined and once again a limited amount of recovery was observed. It is therefore postulated that some other factor, not a fixed relative humidity, was responsible for the dramatic recovery of the first group of mustard seeds. This could be a short period at high relative humidities followed by a longer period at low humidities or possibly some gas in the atmosphere of the laboratory at that time. Plants were grown from the fully recovered mustard seeds. The greater weight and height of these plants compared to those from non-irradiated seeds were shown to be statistically significant.