Seaweed extracts are known to have a stimulatory effect on the growth and development of plants. This study investigated the effect of applying a commercial seaweed concentrate (kelpak) on rhizobia growth (Bradyrhizobium strain CB756 and Bradyrhizobium japonicum strain CB 1809) and nitrogen fixation in cowpea ( Vigna ungulata L. Walp.) and soybean (Glycine ma.x L. Merr.) plants. Two concentrations of Kelpak (1:100 v/v and 1:500 v/v seaweed concentrate dilutions) were applied to pots with seeds or seedlings at sowing and after every 14 days (1:l00A; 1:500A), at sowing and after every 7 days (1:100B; 1:500B) or after germination and after every 14 days (1: l00C; 1:500C). From the first experiment, cowpea plants in the various treatments showed no change in shoot biomass. The root biomass was significantly inhibited in treatment 1:100B relative to the control. The nodule dry matter of cowpea was reduced in 1:100A, 1:100B and 1:100C Kelpak concentrations compared to control, with a significant increase only in 1:100B Kelpak concentration. As a result, cowpea plants showed the highest total biomass in 1:500B treatment. Although shoot N in cowpea plants remained unchanged under the various kelpak treatments, root N was significantly reduced. Soybean plants showed a significant decrease in shoot and root biomass compared to the control. Nodule dry matter was lowest for soybean plants in Kelpak treatments 1:500B, 1:100B and 1:100C. As a result, there was a decrease in soybean total growth in treatment 1:500B compared to the control. Total N in shoots and roots was highest in soybean plants growing in 1:500A relative to the control. Culturing cells of Bradyrhizobium strain CB756 with Kelpak showed a significant increase in growth at 1:100 and 1:500 dilutions compared to the control. However, over the 93 h period with sterile Kelpak culture there was an inhibition in growth of strain CB756 relative to the control. Beyond the 93 h there was a significant increase in growth of Bradyrhizobium japonicum strain CB 1809 in all Kelpak treatments. The 1:100 concentration showed the highest bacterial growth compared to the control and the other treatments. These data suggests the presence of an active molecule in Kelpak that stimulates rhizobial growth and its symbiotic interaction with legumes.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uct/oai:localhost:11427/25864 |
| Date | 17 February 2017 |
| Creators | Leitao, Daniela |
| Contributors | Dakora, Felix D |
| Publisher | University of Cape Town, Faculty of Science, Department of Biological Sciences |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Bachelor Thesis, Honours, BSc (Hons) |
| Format | application/pdf |
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