No description available.

In greenhouse and controlled environment experiments, the influences of temperature, P nutrition-, and foliar sprays of 3 growth retarding chemicals on the growth, yield and mineral composition of Pisum sativum L. cv. Dark Skin Perfection were investigated. The utilization of P under 4 air and soil temperature regimes within the physiological range was also studied. The dwarfing effect of high temperature was related to that due to relatively high concentrations of growth retarding chemicals. Banded P fertilizer, applied at rates of up to 352 lb. per acre, increased plant growth, pea yield and the uptake of N, P, K, Ca and Mg. P increased the total contents of all 5 minerals in all 3 tissues (vine, pod and pea seed), but had multiple effects on mineral concentrations. Efficiency of P in producing pea yield increase was maximum at the 44 lb. per acre rate. The high air temperature of 30° decreased growth, pea yield, and total mineral uptake, compared with a temperature of 21°. The high soil temperature of 18° increased these 3 groups of variables, as compared with a temperature of 10°. Increases in mineral concentration at the high air temperature were largely due to "concentration effects'' resulting from smaller plants. Increases due to the high soil temperature were absolute because they occurred even in bigger plants. Increase in mineral uptake at the high soil temperature was not due to increased root growth, but was a result of increased metabolic activity. The effect of soil temperature on total absorption was greater than on translocation into the pea seed. (2-chloroethyl) trimethylammonium chloride (Cycocel) at 1 ppm was the most effective in terms of growth and yield stimulation. 2,4-dichlorobenzyl tributylphosphonium chloride (Phosfon) at 100 ppm was the most effective with respect to growth retardation, but markedly decreased pea yield. N-N-dimethylamino succinamic acid (B-Nine) at concentrations of 1 and 100 ppm was ineffective in altering growth pattern. Effects of the growth retarding chemicals on mineral uptake largely reflected plant size differences, and were not absolute effects. Cycocel and Phosfon at low concentrations are promising for use in arresting excessive vegetative growth and its attendant problems, and in increasing pea yield without deformative effects. The effects of relatively high concentrations of Cycocel and Phosfon were similar to those of high temperatures with respect to plant dwarfing, changes in mineral composition and alteration in the levels of Glucose, G-l-P, G-6-P, F-6-P, Fl,6-P, ADP and ATP. It appears that high concentrations of growth retarding chemicals and high temperatures depress plant growth by reducing the utilization of ATP in the phosphorylation of sugars, in the glycolytic sequence. The nearest-optimal air and soil temperature regime for plant growth and mineral uptake was the 21/13/18° day/night/soil. For uniformity in the nomenclature of plant growth regulators, it is suggested that growth retarding chemicals be called "RETARDINS". / Land and Food Systems, Faculty of / Graduate

Pea plants (Pisum sativum cv. Dark Skin Perfection) were grown in a controlled-environment at 25°C day and 15°C night temperature and were then transferred to various high temperature environments. These environments were 32°, 35° and 38°C day temperature with 22°, 25° and 28°C night temperatures respectively. Sample plants were taken at three weeks after planting before transfer to high temperature; and after 1, 10, 100, 1000 minutes and 6 days of exposure to high temperature. The sample plants were analysed for total, organic, inorganic and lipid phosphorus. Growth measurements were also taken. There were no significant changes in the concentrations of organic, lipid and total phosphorus and of inorganic phosphorus except at 6 days exposure to high temperature at which time there was a marked increase in the concentration of inorganic phosphorus. Transfer of plants from the cooler environment to the warmer environments, generally resulted in shorter internode lengths and overall shorter plant height. / Land and Food Systems, Faculty of / Graduate

Bibliography: leaves 86-90 / Microfiche. / viii, 90 leaves, bound ill., maps 29 cm

No description available.

No description available.

No description available.

Phosphorus and phytoplankton dynamics in freshwater are usually thought to be tightly coupled and interdependent, yet orthophosphate uptake in situ has been observed to be mediated largely by particles of bacterial size. The purpose of this thesis is to examine the general hypothesis that freshwater bacterioplankton are markedly superior competitors for phosphorus, relative to the phytoplankton. Using isolates of three species of pelagic bacteria, and two of algae, it was shown that the bacteria possess much higher affinity orthophosphate uptake kinetics than the algae. In a Monte Carlo simulation study, the accuracy and precision of these Michaelis-Menten parameter estimates were found to depend strongly upon the experimental design matrix. Bacterial superiority in uptake was also reflected in terms of growth, in chemostat competition experiments, which also showed algal and bacterial uptake of orthophosphate to be well correlated with their relative long-term phosphorus assimilation. In parallel experiments in situ, bacterioplankton were found invariably to be responsible for more than 97% of the orthophosphate uptake. In contrast, excreted organic phosphorus was utilised almost exclusively by the phytoplankton. There is little evidence as yet that excretion and reuptake of phosphorus is important in redistributing phosphorus among the plankton.

No description available.

No description available.