Jianhua Zhang

Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Panicum virgatum and Agropyron psammophilum are the two dominant sand-binding grasses on the sand dunes along Lake Erie at Port Burwell Provincial Park. In this thesis, results on some aspects of seed and seedling ecology are presented.;Seeds of P. virgatum possess innate dormancy. Pretreatment for two weeks at constant or alternating temperatures ranging from 5 to 15{dollar}\sp\circ{dollar}C under either dark or light/dark conditions significantly improved seed germination. Injury to the seed embryo also significantly increased seed germination. After ripening of seeds in dry storage at room temperature did not alter their germinability significantly during the first 26 weeks. Seeds of A. psammophilum did not exhibit any seed dormancy.;Seed size of P. virgatum and A. psammophilum showed considerable variability. Seed size had significant effect on seedling size at early stages of development in both species. This effect disappeared with time in P. virgatum. However, the seedling size fluctuated in A. psammophilum because the relative growth rate had a negative correlation with seed size for young seedlings but a positive correlation with seed size for older seedlings.;Greenhouse experiments indicated that seedling size was mainly dependent on weight of the endosperm rather than the embryo size in both species. Removal of a part of the endosperm resulted in seedlings of smaller sizes with more proportion of dry matter allocated to the root and less to the leaf of resulting seedlings in comparison with the control.;The maximum depth of emergence of P. virgatum and A. psammophilum seedlings was 11 and 7 cm in the field and 16 and 8 cm in a greenhouse, respectively. Sand burial stimulated the growth in height of P. virgatum seedlings. In A. psammophilum burial of seedlings resulted in an increase in height, number of green leaves and tillers, and dry weight. Seedlings of P. virgatum that emerged from shallow burial depths had fewer surviving individuals. In contrast, seedlings emerging from deep burial depths had more individuals surviving than random expectation. Seedlings emerging from shallow depths could withstand greater post-emergence sand burial than those emerging from deep sand burial.



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