Objective The study was carried out to explore the effects of different concentrations of uniconazole in plug media on the growth and development of different varieties of lettuce seedlings.
Method Five lettuce varieties in southern China were used to study the effects of different concentrations (0-50 mg/L) of uniconazole on seedling growth, leaf shape parameters and soluble solids (TSS) of lettuce.
Result With the increase of uniconazole concentration, the root fresh weight, root dry weight, shoot fresh weight and shoot dry weight of seedlings of various lettuce varieties increased first and then decreased. The root fresh weight and dry weight of bolting-tolerant lettuce and Roman upright lettuce were the highest under 10 mg/L uniconazole treatment, and those of other varieties were the highest under 5 mg/L uniconazole treatment. The total leaf width, maximum functional leaf width and total leaf area of seedlings also reached the maximum under 5 mg/L uniconazole treatment. The total leaf width and total leaf area of butter lettuce seedlings were larger than those of other varieties. The root-shoot ratio of iceberg lettuce, butter lettuce and bolting-tolerant lettuce increased with the increase of uniconazole concentration, while the root-shoot ratio of Hong Kong soft-tail lettuce and Roman upright lettuce increased first and then decreased. In addition, under the treatment of 50 mg/L uniconazole, SPAD values of lettuce seedlings of all varieties increased significantly, while plant height, total leaf area and TSS accumulation were severely inhibited.
Conclusion Strong seedlings of lettuce could be cultivated by the medium with suitable concentration (5 mg/L) of uniconazole. The growth and development of lettuce seedlings would be inhibited by higher concentration of uniconazole.
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