Abstract
The aim of the present study was to evaluate the effect of short-term high or low temperature treatments applied during seed imbibition on plant tolerance to chilling. Chilling tolerance was also investigated on seedlings obtained from dry seeds stored at low temperatures. Sunflower seeds (Helianthus annuus L. ‘Wielkopolski’) were stored at 5°C or 25°C and then subjected to low (2.5°C and 5°C) or high (35°C and 45°C) temperatures for two hours during imbibition. They were subsequently exposed to chilling (2.5°C) for three weeks. Afterwards, the seeds were transferred to 25°C for chilling injury evaluation or sown in pots and grown in the field for further growth investigation.
The obtained results indicate that the sunflower seedlings, obtained from dry seeds stored at 25°C, were chilling sensitive to an exposure of 2.5°C for three weeks, which was manifested by slow root elongation, external root discoloration and a long Mean Emergence Time (MET). The storage of dry seeds at 5°C reduced seedling injuries exhibited by external root discoloration and increased chlorophyll content in leaves. Short-term (two-hour) low (2.5 and 5°C) or high (35 and 40°C) temperature treatments applied to the moistened seeds alleviated chilling effects, stimulating root elongation, limiting external root discoloration and shortening MET, accelerating plant flowering and seed maturation time, increasing the diameter and weight of the anthocarp as well as seed yield and chlorophyll content.
The positive response of these methods in respect to an increase in sunflower plant tolerance to chilling indicates a possibility of their application in practice.