LE3 .A278 2011

2011

Kristie, David

Acadia University

Bachelor of Science

Honours

Biology

Biology

Extracts derived from various species of brown algae are known to benefit plant performance. Despite numerous studies on the effects of these products, the bioactive compounds responsible remain unknown. Objectives of this study were to attempt to isolate the compounds that are responsible for the high levels of rooting and gibberellin-like (GA-like) activity present within three seaweed extracts (SWEs), Acadian Marine Plant Extract Fertilizer (ASL), Kelpgrow Liquid Seaweed Extract (Kelpgrow) and Kelpak Liquid Seaweed Bioregulator (Kelpak). We also examined whether laminarin, a storage polysaccharide found in brown algae, could induce rooting or GA-like effects similar to that of the SWEs. Fractions of the SWEs less than and greater than 13,000 MW were obtained by dialysis and tested using the Mung Bean Adventitious Rooting Bioassay (MBARB) and the Lettuce Hypocotyl Bioassay (LHB). All three SWEs were able to elicit a significant rooting response; Kelpak elicited a rooting response characteristic of auxins as the majority of its rooting activity is found in its LMW (<13,000 MW) fraction and the roots generated resemble those induced by auxins. The root initiating activity of both ASL and Kelpgrow appeared to be split between molecules greater than 13,000 MW and smaller than 1,000 MW. However, root morphology suggested that the LMW compounds are not auxins. Commercial laminarin elicited a rooting response at concentrations found in SWEs. This activity was eliminated by digestion with laminarinase. However, partially purified laminarin extracted from the SWEs by the McKinnon lab at NRC-IMB did not elicit a rooting response. The three SWEs were also able to elicit a significant GA-like response; however, the GA-like activity of dialyzed fractions was found to be highly variable. As a result, the size of the molecules responsible for the GA-like effects of SWEs remains unclear. Commercial laminarin had no effect in the LHB. Overall, this study suggests that laminarin could be responsible for the rooting activity of ASL and Kelpgrow SWEs, but more research is needed to determine its role.

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https://scholar.acadiau.ca/islandora/object/theses:798