Influence of Temperature Regimes on Germination of Cotton (Gossypium hirsutum l.) Varieties

The laboratory experiment was performed at the Seed Testing Laboratory, Department of Agronomy, Faculty of Crop Production, Sindh Agriculture University Tandojam.The experiment was replicated randomized complete design conducted during 2013. Cotton varieties Hari dost, Shahbaz and Sindh-1 were used. Seeds of cotton varieties are placed in a Petri dish having 13.5cm diameters (15 seeds in each Petri dish) on a double layer of Whatman filter paper and kept in seed germinator (Model-PL3) at various temperature regimes. The seeds were moistened whenever necessary. The seed germination % was recorded after 48 hours. The shoot, root length, including fresh and dry weights as well as root shoot ratio was further recorded after 12 days.The results for cotton varieties showed that maximum seed germination (79.78 %), root length (10.75 cm), shoot length (23.09 cm), root fresh weight (887.40 mg), shoot fresh weight (6434 mg), root dry weight (66.34 mg), shoot dry weight (482.2 mg), root shoot ratio (0.464) were observed in variety Sindh-1. However, the variety Shahbaz ranked second with seed germination (73.81 %), root length (6.99 cm), shoot length (15.81 cm), root fresh weight (618.6 mg), shoot fresh weight (4788 mg), root dry weight (48.27 mg), shoot dry weight (345.9 mg), root shoot ratio (0.432) were observed. On the other hand Hari dost had minimum (67.01 %) seed germination, root length (6.75 cm), shoot length (15.09 cm), root fresh weight (610.9 mg), shoot fresh weight (4650 mg), root dry weight (46.64 mg), shoot dry weight (342.0 mg), root shoot ratio (0.443) were observed. The 35oC temperature recorded maximum seed germination (79.73 %), shoot length (21.10 cm), root length (9.85 cm), shoot fresh weight (5858 mg), root fresh weight (765.4 mg), shoot dry weight (436.7 mg), root dry weight (58.25 mg) and root shoot ratio (0.447), whereas the 25oC temperature recorded maximum seed germination (76.83 %), shoot length (20.82 cm), root length (9.56 cm), shoot fresh weight (5543 mg), root fresh weight (756.5 mg), shoot dry weight (422.9 mg), root dry weight (56.96 mg) and root shoot ratio (0.459) were observed. However, the lowest seed germination (64.04 %), shoot length (12.07 cm), root length (5.08 cm), shoot fresh weight (4472 mg), root fresh weight (595.0 mg), shoot dry weight (310.5 mg), root dry weight (46.03 mg) and root shoot ratio (0.414) was recorded at 15oC temperature regimes. Keywords: Cotton, Temperature, Germination, Varieties