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Rice is the leading staple for half the world’s population. Climate change, expanding populations and loss of agricultural land are projected to reduce rice yields by upwards of 30%. Significantly, rice yields decline by 10% for every 1°C increase in temperature. Temperatures ≥ 32°C can cause failure in male reproductive development and eliminate yields in some cultivars. This dissertation determined the developmental features and mechanisms associated with failure in male reproduction at temperatures of 32 °C and 36 °C in temperature tolerant and sensitive cultivars of O. sativa and O. glaberrima. Temperatures of 32 °C impaired anther dehiscence in the temperature sensitive cultivar of O. sativa by preventing septum cell wall degradation, which is essential for pollen dispersal. Temperatures of 36 °C induced abortion in pollen development either during meiosis primarily in O. sativa or at the uninucleate stage in O. glaberrima. Abortion during meiosis was associated with autophagic programmed cell death, whereas failure at the uninucleate stage of pollen development was associated with features of necrosis such as cytoplasmic shrinkage and cell wall collapse. Increased hydrogen peroxide production was detected in aborting meiocytes and uninucleate microspores at 36 °C, indicating that this reactive oxygen species may contribute to the failure of male reproductive development in rice during high temperature stress. Identification of the timing of failure in male reproductive development, and the cellular features associated with these processes in rice, form the basis for the identification of molecular mechanisms that control yield responses to high temperature stress.

A knowledge of the basic atmospheric parameters and their variability is required both for climatological purposes and theoretical studies. Meteorologists generally use constant pressure maps at a number of levels to study the broad scale structure of the atmosphere. Vertical cross sections are then used to provide a finer structure and also to permit a vertical integration of the various constant pressure levels. Research meteorologists at McGill have analysed hemispheric weather maps and meridional cross sections along 80oW on a daily basis for a three year period to determine major parameters in the general circulation. This study attempts to provide a useful contribution with respect to mean monthly and seasonal cross section parameters. [...]

p. 2 (Abstract) missing from manuscript. / [...] None of the above approaches considered the heat capacity of the stone which for large hail can be quite high, and may aid in keeping the particle temperature below 0 C. It is one purpose of this thesis to investigate this effect. [...]

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