Abstract
Effects of temperature, storage time and their combination on germination of aspen (Populus tomentosa) seeds were investigated. Aspen seeds were germinated at 5 to 30°C at 5°C intervals after storage for a period of time under 28°C and 75% relative humidity. The effect of temperature on aspen seed germination could not be effectively described by the thermal time (TT) model, which underestimated the germination rate at 5°C and poorly predicted the time courses of germination at 10, 20, 25 and 30°C. A modified TT model (MTT) which assumed a two-phased linear relationship between germination rate and temperature was more accurate in predicting the germination rate and percentage and had a higher likelihood of being correct than the TT model. The maximum lifetime threshold (MLT) model accurately described the effect of storage time on seed germination across all the germination temperatures. An aging thermal time (ATT) model combining both the TT and MLT models was developed to describe the effect of both temperature and storage time on seed germination. When the ATT model was applied to germination data across all the temperatures and storage times, it produced a relatively poor fit. Adjusting the ATT model to separately fit germination data at low and high temperatures in the suboptimal range increased the models accuracy for predicting seed germination. Both the MLT and ATT models indicate that germination of aspen seeds have distinct physiological responses to temperature within a suboptimal range.
Highlights
Populus tomentosa is a native Populus species which distributed mainly in the middle and lower reaches of Yellow River in the north of China [1]
Based upon the thermal time (TT) and maximum lifetime threshold (MLT) model, we further developed a model that could describe the effect of combined factors of both temperature and storage time on seed germination
Effect of Temperature on Seed Germination In control seeds, representative germination rates for 10, 30, 50 and 70% of germination were plotted against germination temperature to show the trend of change in germination rates with temperature (Figures 1A and C)
Summary
Populus tomentosa is a native Populus species which distributed mainly in the middle and lower reaches of Yellow River in the north of China [1]. Many studies have indicated that the successful regeneration of aspen seeds is extremely dependent on bare and moist soil conditions created by flood events in the riparian woodland ecosystem. Human activity, such as river regulation and water reclamation projects, further destroy this ecosystem and decrease the probability of seed germination [4,8,9,10]. An optimal condition for seed germination is only sustained for a short period of time due to the limitation of temperature, moisture, and other environmental factors. The time to germination might be one of the key factors determining the successful regeneration of aspen seeds
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