Ascophyllum nodosum Extract and Its Organic Fractions Stimulate Rhizobium Root Nodulation and Growth of Medicago sativa (Alfalfa)

Abstract

The effects of the seaweed Ascophyllum nodosum extracts (ANE) on nitrogen (N)–fixing nodules and growth of alfalfa plants were studied under greenhouse conditions. The treatment of alfalfa roots increased the number of total nodules per plant with ANE (69%) and organic sub-fractions methanol (20%) and chloroform (35%) at 1 g L⁻¹ concentration. The number of functional nodules was greater per plant in ANE (36%) and its organic sub-fraction chloroform (105%). Maximum increase in shoot length was observed in ANE-treated plants (42%) and chloroform-treated plants (42%). Root length was longer in the chloroform fraction (15%), whereas the shoot dry-weight accumulation was greater in plants treated with ANE (118%), methanol (85%), and chloroform (85%) than the control. Root dry-weight accumulation increased in plants treated with ANE (118%) and chloroform (69%) compared to the control. Further studies are under way to identify the chemical components in ANE and organic fractions.

Keywords:

• Alfalfa
• Ascophyllum nodosum
• nitrogen fixation
• plant–microbe interaction
• Sinorhizobium meliloti
• symbiosis

Acknowledgments

Research in the BP laboratory is supported by grants from the Atlantic Canada Opportunities Agency, Acadian Seaplants Limited, and Natural Science and Engineering Research Council of Canada. The first author thanks the Deanship of Scientific Research, King Saud University.