The morphology and nitrogenase activity (ARA) of Gloeotrichia pisum Thur. growing on deepwater rice were studied in situ at Sonargaon, Bangladesh, and compared with results from laboratory studies. The alga showed obvious similarities and dissimilarities. Hairs, gas vacuoles and akinetes, which were found in the field, were not found In the laboratory, even though the influences of quantity and quality of light flux and nutrient deficiency were tested. The response of nitrogenase to changes in light flux was rapid. A reduction in flux brought about similar results in the field and In the laboratory. Diel changes in nitrogenaee activity showed a maximum at mid-day In the presence of maximum light flux, but considerable activity (3.7% of dally total) took place at night. The activity In a medium free of combined carbon by bacteria free G. pisum indicates that the rate and duration of nitrogenase activity in the dark depend on the preceding light conditions. In batch culture, higher nitrogenase activity was observed when dark-grown alga was reilluminated, than the maximum activity ever found under continuous Illumination. The variation of nitrogenase activity in batch culture was studied in relation to the growth characteristics and developmental stages of the alga. Maximum activity (1.4 nmol C(_2)H(_4) µg ch1 a(^-1) min(^-1)), was observed after about one day of growth under continuous light. During this period, juvenile filaments were abundant (hence maximum heterocyst frequency), cyanophycin granules lacking and cultures had the lowest ch1 a : d. wt ratio. Heterocyst differentiation occurred between 14 and 24 h of growth and cell division was observed only after heterocyst differentiation. It appears that the juvenile filament is the most active nitrogen fixer during the life cycle of the alga. Reasons for low nitrogenase activity of about 0.352 nmol C(_2)H(_4) µg ch1 a(^-1) min (^-1) in the field have been discussed. It is estimated from diel changes in N(_2)-fixing activity and based on ARA of 77.4 nmol C(_2)H(_4) tiller(^-) min(^-1) and(^2) using some approximations, that G. pisum contributed about 4 kg N ha(^-1) season" in deepwater rice fields at Sonargaon in 1983.A brief morphological study was also Included. In the field, rapid colonization was observed on freshly submerged rice culms. Colonies contained Intersheath spaces on their periphery and exhibited zonation of filaments. In the larger ones. The mechanism of the formation of a radiating colony in the laboratory has been described and discussed. Differentiation of a hormogonium into a filament was studied in batch culture. The basal youngest cell differentiated into a heterocyst, whilst the rest of cells divided repeatedly, forming several groups of cells in a row. Subsequently most of these groups of cells were liberated successively as hormogonia.

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The nutrient elements needed for the optimum growth and yield of pear trees is vitally important to the pear growers. The knowledge of the amounts and kinds of fertilizer to apply to obtain this growth could increase the production and cut the costs for these growers. Field experiments have been made on the nutritional elements needed for pears, but the results were affected by many variants, such as the availability of the elements and rainfall. The growing of fruit trees in sand with controlled nutrient solutions added had been used to obtain data not possible to obtain under field conditions. Since other factors affect the absorption of the nutrient elements in the field experiments, an experiment for the application of varied nutrient solutions on one year old Anjou pear trees, grown in sand culture, was undertaken. The purpose was to try to determine the influence that the concentration and the ratio of nitrogen and phosphorus in the nutrient solutions would have on the amount of nitrogen and phosphorus which the pear trees would absorb into the leaves. One year old pear trees were grown in a sand culture in a greenhouse through one growth period. The experiment was set up as a factrial with three levels each of nitrogen and phosphorus. The solutions were applied through an automatic system which irrigated the trees every hour. The solutions were checked daily and were changed once every week. The trees were harvested and the leaves were analyzed for nitrogen and phosphorus. The results indicated that the supply of nitrogen was adequate at all levels to support normal development of the leaves of the trees. The supply of nitrogen in the nutrient solution did not cause the percent of nitrogen in the leaves to vary by a statistically significant amount. The analysis of the variations of the percent of phosphorus in the leaves showed significant differences between treatments. The main effect of the phosphorus in the nutrient solution was to increase the phosphorus content of the leaves as the supply of phosphorus was increased. The main effect of phosphorus on nitrogen was negative at all levels. This effect was noticeable at the highest phosphorus level, but it was not statistically significant. The ability of the Anjou pear tree, to absorb both nitrogen and phosphorus from a nutrient solution with very low levels of each of the elements, implies that heavy fertilization with either of these elements may not be necessary for normal, vigorous growth; this is especially true in the case of phosphorus. / Graduation date: 1960

Typescript. / Thesis (Ph. D.)--University of Hawaii, 1966. / Bibliography: leaves 109-117. / viii, 117 l mounted illus. (part col.), tables

Typescript. / Bibliography: leaves 127-137. / xv, 137 l graphs, tables

The chemistry of the tantalum dinitrogen complex ([NPN]Ta)₂‚‚(μ-H)₂‚‚(μ-η¹:η²-N₂‚‚)Ta-[NPN], 1, (where [NPN] represents the acyclic tridentate ligand [(PhNSiMe₂‚‚CH₂‚‚)₂‚‚-PPh]²‚‚-), with primary alkenes, group IV and V metallocene complexes, and GaCp* is explored. The reaction of 1 with 1-pentene and 1-hexene occurs via olefin-insertion into the metal-hydride bond to give two new complexes, ([NPN]Ta(CH₂)₄CH₃)₂‚‚(μ-η¹:η¹-N₂‚‚), 10, and ([NPN]Ta(CH₂‚‚)₅CH₃)₂‚‚(μ-η¹:η¹-N₂‚‚), 11, which were characterized using NMR spectroscopy. The solid-state structure of 11 was established and revealed that N₂ has been transformed into a bridging end-on mode. In contrast to its G symmetry in solution, the solid-state structure of 11 is C, symmetric; a VT-NMR study was performed and showed that 11 exists as an equilibrium between two isomers in solution: a C, symmetric isomer 11A,which is the predominant isomer at room temperature, and a C, symmetric isomer 11B,which is the minor isomer. The reactivity of 1 with group IV and V metallocenes was investigated. The reaction of 1 with Cp₂‚‚Hf(PMe₃)(η²-Me₃SiCCSiMe₃) produces [N(μ-P=N)N]Ta(μ-H)₂(μ-N(Hf-Cp₂‚‚))Ta[NPN], 14, in which N₂ is cleaved and new Hf-N and P=N bonds have formed. The reaction of 1 with group V metallocene hydrides Cp₂‚‚MH₃ (M Nb, Ta) was also attempted however these complexes do not react with 1. The reaction of 1 with GaCp* produces a new complex, [NPN]Ta(μ-N(GaCp*))Ta(=NPμ)[NPIA,-N], 18, which was characterized using NMR spectroscopy. Complex 18 decomposes over several days in solution, and one product of decomposition that was isolated was [(PhNH)(NPμ-N)Ta]₂‚‚, 19. The solid-state structure of 19 showed that the [NPN] ligand was cleaved at the N-Si bond, similar to that observed for the reaction of 1 with 9-BBN and HB(C₆H₅)₂‚‚. A mechanism for the formation of complexes 18 and 19 is proposed.

Bibliography: leaves 151-177. / xxiii, 177 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Science, 1993