Abstract
Presowing treatements to seed are reasonable for elevating the seedling production efficiency. This experiment was carried out to determine the effects of $GA_3$ [0 (water) : 0.01 mM] and light qulaity (red : white) simultaneously treated before sowing on seedling emergence and growth of tobacco (Nicotiana tabacum L.) cv NC 82 and Burley 21. Red or white light was illuminated 12 hours a day while seeds of the cultivars were imbibed with either water or $GA_3$ 0.01 mM for 3 days. Seedling emergence was measured up to 20 days after sowing but morphological characters and dry weights were done 40 days. The seedling emergence rate of cv NC 82 was more affected by light quality and $GA_3$ pretreatments than that of cv Burley 21. Light quality more influenced the rate than $GA_3$ while red light or water imbibition enhanced the rates of the two cultivars compared to the other treatement. Although mean plant height and leaf number per seedling were nearly equal between the treatements, red light declined leaf area per seedling of cv Burley 21 of which seeds were imbibed in water but white light decreased the areas of both cultiars of which seeds were soaked in $GA_3$solution. Shoot dry weight was greater in cv NC 82 but less in cv Burley 21 pretreated with red light, and root dry weight showed the reverse result in white light, meaning that presowing light and $GA_3$ treatments could be changed the seedling development and growth of tobacco.
