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Item A study on the effects of low temperature pre-sowing treatments and ageing on the germination performance of different tomato seed lots : a thesis presented in partial fulfilment of the requirements for Master of Agricultural Science (Seed Technology) at Massey University,Palmerston North, New Zealand(Massey University, 1989) Ranganarasimhiah, RamamurthyAlthough the total germination capacities were not significantly different, ten different tomato seed lots differed in their vigour. LTPST caused significant improvement in germination rate both in high and low vigour seed lots of different cultivars of tomato seeds tested without altering their germination potential. The degree of improvement in germination rate was positively related to the initial germination rate of the seed lots and it was even possible to predict the effectiveness of the treatment based on the initial T5O of untreated seeds. Despite the treatment always causing a significant improvement in germination rate, the improvement in uniformity was lot-dependent and the treatment had little or no effect on initial seedling growth. Increased SMC and temperature caused rapid loss of viability and germination rate during storage. The effectiveness of LTPST treatment before ageing differed with seed lot and subsequent ageing conditions used. The application of the LTPST after ageing restored the germination rate to that of unaged untreated seed but as expected had no effect on loss of viability. The survival pattern of tomato seeds under rapid ageing followed a normal distribution and parameters of survival curves were in agreement with the norms of the general viability model for orthodox seeds. On the basis of these results of LTPST on aged seeds, it is argued that factors affecting loss of seed vigour may be different from those causing loss of seed viability during storage.Item The effect of temperature on growth and development of peas : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Horticulture at Massey University(Massey University, 1983) Ragan, PaulThe influence of temperature on the growth and development of the garden pea was studied at Massey University during 1978-79. Cultivars with single and multiple (double and triple) podding characteristics were grown in a greenhouse experiment with high, medium and low temperature treatments, a field experiment with four successive sowings and a climate room with alternating high and low temperature treatments between vegetative and reproductive growth phases. Plant response to temperature was examined using growth analysis and component analysis techniques. High temperature produced a smaller plant with shortened internodes and a delay in pod set. Net assimilation rate was closely linked with final fresh weight yield and harvest index. There was a direct relationship of net assimilation rate and growth duration to yield when net assimilation rate was not limiting; fresh weight yield increased in direct relation to the number of yield components. High temperature effects complicated by flower and pod abortion indicated that the behavior of yield components must be considered along with harvest index as a selection criterion for earliness and high yield in peas. In all cultivars, the number of yield components decreased as temperature increased, particularly the number of pods per node when high temperature occurred during the vegetative phase. High frequency podding cultivars exhibited the highest instability. Net assimilation rate and competition for assimilates between yield components (sinks) determined the number of yield components that were retained. No one component was identified as the main source of variation in pea yield. Positive interactions between components of yield were identified with yield increases when net assimilation rate was nonlimiting and yield decreases when net assimilation rate was limiting. Negative interactions were associated with yield stability. A balance of negative and positive interactions between components of yield combined with a nonlimiting net assimilation rate (assimilate supply) is needed in high yielding pea cultivars.Item The effects of temperature and irrigation on the establishment and growth of lucerne (Medicago sativa L.) on Manawatu sand country : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Plant Science at Massey University(Massey University, 1973) Brown, Noel SamuelThis research was undertaken to study the establishment of lucerne on one of the drier soils of the Manawatu sand country. Lucerne has often been difficult to establish on these soils, yet once established grows well, possibly due to the large supply of water that is to be found in the water table a metre or so below the surface. Difficulty in establishing lucerne has often been attributed to shifting of the unconsolidated cultivated sand surface by wind, and also to the low moisture holding capacity of the soil. Lucerne stands are usually sown in the spring, but the available soil moisture may be quickly evaporated by the strong prevailing westerly wind at this time and wind erosion may occur, often burying plants with sand and leaving other young plants with their root systems exposed. Another possible reason for poor establishment of lucerne could be the high surface temperatures often experienced on the bare surface. The aim of the field study was to examine the effects of soil temperature, soil moisture and wind erosion on lucerne establishment. Subsequently, glasshouse experiments were conducted to investigate the effects of temperature variations in the soil and on the surface on the growth and survival of lucerne seedlings. [From Introduction]