Growth Stimulation Activity of Alginate-Derived Oligosaccharides with Different Molecular Weights and Mannuronate/Guluronate Ratio on Hordeum vulgare L

The differentiated components of alginate-derived oligosaccharides (AOS) lead to different activities on plant. Optimizing AOS use efficiency is, therefore, of major importance for the implementation of precision agriculture. Effects of AOS on biophysical characteristics and growth and development of barley (Hordeum vulgare L.) have been investigated. The experiments were conducted by soaking the seeds in AOS solutions with different molecular weights and Mannuronate/Guluronate ratio. The results showed that depending on their components, AOS stimulated the growth of seedlings and roots differently. AOS with low MW (500–3000 Da) and higher M/G ratio (> 1) had better promotion on the plant. The promoting effects on seedlings and roots were not an exact match. Our results suggested that the promotion effects of AOS on seedlings might be caused by the stimulation on photosynthesis and the roots growth were promoted probably due to the enhanced absorption activity. In gene level, we demonstrated that AOS induced the expression of development-related genes including auxin response factor and mitogen-activated protein kinase, thereby promoting the growth. Our research may provide a basis for more targeted and precise use of AOS in agriculture.