PHYSIOLOGICAL CHARACTERIZATION ON SEED AGING OF SIX NATIVE SHRUB SPECIES

Vegetation reclamation in oil-sands requires a consistent and adequate supply of seeds of native shrubs. However, annual seed production is erratic and seeds are usually short lived and insufficient for the reclamation projects. Seeds of six native shrub species including: Prunus virginiana, Prunus pensylvanica, Arctostaphylos uva-ursi, Shepherdia canadensis, Cornus sericea, and Viburnum edule were used to analyze physiological changes during storage and artificial aging processes. The shrub seeds were studied for one year during storage under eight different combinations of temperature (-20, 4, 22.5 °C), atmosphere (Air / N2) and relative humidity (RH; 7-8 % / 3-4 %). No significant differences were detected among the storage parameters after one year; however, sub-zero and N2 environments showed a potential in maintaining a higher seed vigour during storage. In the artificial aging experiment, seeds were subjected to 45 oC, 60 % RH for 5-25 d. For most shrub species, the seed viability decreased significantly after 10-15 d artificial aging and was down to 0 % after 20 d. The germination percentage declined already after 5 d; therefore, there was a delay in detecting viability loss using the tetrazolium test. Non-aged seeds and aged seeds of most collections showed significantly different seedling lengths, which indicated a negative effect of accelerated aging process on the seedling growth. The electrolyte conductivity, as well as seed dehydrin protein expression, is strongly correlated with the seed vigour, which can be used as seed quality assessment methods in seed longevity predicting. A loss of membrane integrity occurred during the accelerated seed aging processes, as indicated by an increased electrolyte conductivity that was negatively correlated with the seed viability and germination. During artificial aging process, heat stress of Prunus virginiana induced expression of dehydrins with a molecular mass of 27 kDa, which reached a detectable level after 5 d. The storage protocol developed in this study would benefit the adequate supply of viable shrub seeds for reclamation. With species-specific parameters taken into consideration, the artificial aging technique to predict seed longevity can be further expanded to other non-crop species used in reclamation of lands after oil extraction