Raj_Final_Thesis.pdf (1.54 MB)
Aspects of the biology of Papaver bracteatum lind, a new crop for Tasmania
thesisposted on 2023-05-26, 05:13 authored by Madam, PRK
Papaver bracteatum L, a species that accumulates high concentrations of the pharmacologically important alkaloid thebaine in its fruit capsules, has been identified as a potential new perennial crop in Tasmania, Australia. Previous attempts to establish the crop from seed in Tasmania have met with limited success, with slow and irregular emergence reported under field conditions and low flowering percentages in the year of planting. The recent availability of improved germplasm and advances in agronomic techniques associated with crop establishment has provided the impetus for a re-evaluation of P. bracteatum as a new horticultural crop. This project focussed on understanding aspects of the biology of P. bracteatum needed for the development of production strategies for the successful commercialisation of this crop in Tasmania, Australia. Papaver bracteatum seeds displayed no physiological dormancy and germinated in both light and dark conditions. The optimum temperature range for the germination was found to be between 18¬¨‚à´ and 25¬¨‚à´C, with lower and upper cardinal temperatures of 5¬¨‚à´C and 35¬¨‚à´C respectively. During storage, a decrease in germination viability of between 0.2% and 0.1% per week was recorded over a period of 100 weeks under 20vÄv¿C and ambient humidity conditions. Germination was found to be sensitive to water stress, with germination inhibited at water potentials of -0.1 and -0.3 MPa. It was concluded that sensitivity to water deficits may explain poor field emergence. Grading of seed-lots to retain the larger sized and denser seed fraction improved germination percentage and seedling vigour. During seed production, harvesting after the 70 DAFB resulted in the highest seed quality. Seedlings required an extended period of juvenile growth before they became competent to flower. Plants were capable of initiating flowering 20 weeks after planting when grown under glasshouse conditions and approximately 30 weeks after planting when grown under shade house conditions. The transition from juvenile to mature stages was found to correspond to a fully expanded leaf number of approximately 17. Leaf morphological characteristics used as phase change indicators in other species were shown not to be applicable in P. bracteatum. Trichome distribution and density, leaf size and plant height, which was a measure of leaf erectness and leaf length, varied considerably with growing conditions and did not provide a consistent value at the phase change that could be used as an indicator. Papaver bracteatum was shown to require a period of vernalisation to induce flowering. Results suggested that less than 4 weeks exposure to vernalising night temperatures can induce flowering that and adequate vernalisation may occur within a night temperature band of at least 5¬¨‚à´ to 10vÄv¿C. Observations also led to the conclusion that, unlike the annual opium poppy species P. somniferum, P. bracteatum does not have a daylength sensitive flowering response. Application of gibberellic acid to plants grown under marginally inductive conditions induced more rapid and more even flowering within the plant population. Knowledge of the flowering response in P. bracteatum was used to develop recommendations for planting time and production environment to ensure flowering and therefore high capsule yields in the season that the crop is planted.
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