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To meet demographic demand, global rice production will have to increase by about 2% per year despite losses of land and water supply to industrialisation and urbanisation, and the reduction of availability of farm labour. In Asia, the traditional transplanting of rice is increasingly being replaced by direct seeding that reduces labour costs and saves water. However, yield in direct seeded rice is threatened by weed competition due to the absence of weed suppression through early flooding. Moreover the appearance of "weedy" rice has notably been associated with the use of direct seeding. Weedy rice are plants that appear in and around rice fields and exhibit unwanted wild traits that reduce the quality and the quantity of the harvest. Little is known of the evolutionary origin of weedy rice. The aims of this project were to examine the phylogenetic relationships between weedy rice, cultivars, and wild rice to investigate the origins of weedy rice and to develop molecular diagnostics that would identify weedy rice contamination of seed sources. Using 19 microsatellite markers, individual plants of weedy rice, and cultivars from field samples in Malaysia and the Philippines were genetically characterised together with populations of Oryza niwlra and 0. rlljipogon, rice wild relatives. from different geographical locations in south east Asia, and reference 0. saliva accessions. Genetic differentiation between weedy rice and crop cultivars was evident. Weedy rice populations were more closely related to companion crop cultivars in Malaysia than in the Philippines. In the Philippines, weedy rice appeared to be genetically intermediate between crop cultivars and certain wild rice accessions, suggesting the presence of wild rice genes in their genomes. There are three main hypotheses for weedy rice: the invasion and persistence of preadapted annual wild rice in cultivated fields; the introgression and segregation of genes from annual or perennial wild rice surrounding fields into the sown cultivars; the segregation and expression of weedy traits introgressed during cultivar production. The data presented in this study demonstrated that weedy rice appears to be cultivars with introgressed wild traits. This excludes the first hypothesis. The fact that there is little or no evidence of 0. nivara and 0. rujipogon around the fields in the sampled regions also suggests that the second hypothesis is unlikely unless the source is cryptic. The conclusion of this study therefore has to be that weedy rice plants are "hybrids", carrying cultivar and wild traits. However, the use of 0. nivara in the breeding program of modern varieties to produce lines resistant to diseases may have accidentally introduced genes for unwanted wild traits (e.g. seed shattering, red peri carps, awns) to genomes of cultivars. These traits were subsequently selected against during the development of elite lines, but the release of highly inbred but not completely isogenic lines may allow the segregation and selection of these traits and hence produce weedy rice plants. The distant relationship between the weedy rice and the cultivars in the Philippines, allowed the identification of two genetic regions (one insertion in the microsatellite RM009, and one in the intron 2 of the catalase, CatA, gene) specific to weedy rice. These regions were used to design two PCR based molecular diagnostics that showed nearly 100% correlation between a PCR amplification and the presence of a weedy phenotype. The close genetic relationship between cultivars and the weedy rice samples in Malaysia prevented the identification of such regions.

At the outset of the investigation, it was hoped to elucidate details of meiosis and fertilisation in dioecious and monoecious monocotyledons, with especial reference to the possible presence of sex chromosomes. The chromosomes of the dioecious and monoecious forms examined however, have not lent themselves to such a study, whereas the chromosomes of the hermaphrodite Scilla nonscripta, have proved especially interesting. This plant has therefore latterly been studied almost to the exclusion of others. Scilla nonscripta. The chromosomes during mitosis and meiosis are conceived as always consisting of at least two regularly intertwined spiral chromonemata. An attempt has been made to harmonise this conception, already held by many writers for mitosis, with the appearances observed at meiosis. At fertilisation, the egg nucleus is usually resting and the male nucleus is in a condition corresponding to late prophase. The membrane between the two nuclei breaks down and the reticulum from the male nucleus gradually spreads through the egg nucleus. The fusion of the second male nucleus with the two polar nuclei is similar. In all the divisions of the endosperm nuclei studied, the chromosome complements from the male and polar nucleiremain separate, but a mingling of the two chromosome complements in the nucleus of the embryo begins to occur after the first division. Hydrocharis morsus-ranae. The development of the flower buds has been traced, to find if the reputed lack of seeds in this country is due to any structural peculiarity. In the course of the investigation, however, seeds have been set and the significance of this is discussed. The problem of dioecism and monoecism in the plant has also been investigated. Other Monocotyledons. Five other monocotyledons have been examined, but have contributed little of special interest.

Recent evidence suggests that there may be a relationship between auxins and gibberellins in plant growth. The work described here was undertaken as an attempt to clarify the nature of the interactions between the two hormone systems. The effects of IAA, GA and other growth regulators on the growth of coleoptile, first internode, and first leaf of Avena sativa have been studied using the coleoptile, the first internode, and the first leaf base section tests. IAA and GA have a similar action in inducing elongation of the coleoptile and first internode sections, however, their log. dose-response curves are quite different. The inclusion of the coleoptilar node in the first internode sections has a pronounced effect on the GA response suggesting that GA response is associated with high endogenous growth rate. No synergism is found between IAA and GA. Synergism is observed between NAA and GA but not with 2,4-D and GA. NMSP, PCIB and 2,4,6-T all reduce the GA and IAA responses. First leaf base sections are sensitive to GA but not to IAA, kinetin adenine sulphate, certain amino acids, vitamins and growth factors. The age of seedlings from which sections are cut and the inclusion of part of the first internode have significant effects on the GA response of the first leaf base sections. The results are not in complete agreement with an auxin-mediated mechanism of GA action but suggest that the primary action of IAA and GA are not closely related and that growth factors present in the coleoptilar node and in the first internode may be involved in the growth response to GA of the first internode and of the firstleaf base sections respectively. A preliminary attempt was made to isolate the leaf growth substances in the first internodes. The effects of red and far red light on the growth of first internode sections and of intact seedlings have been investigated. The results have been discussed in the light of our present knowledge of auxin and gibberellin actions on plant growth.