Abstract Detail

Ecological Section

McKenna, Mary [1], Rodriguez-Rosas, Veronica [2], Diaz-Ruiz, Dawn [3].

Thymol mediates three-way interactions between Thymus, legumes and rhizobia.

Researchers have long known that species in the mint family (Lamiaceae) produce essential oils containing biologically active compounds. We are interested in exploring the potential ecological effects of these secondary compounds in natural plant communities and agroecosystems. Thymol (a principal component of the essential oil of Thymus spp.) is an anti-microbial compound used commercially for its broad-spectrum activity. This study examined the effect of thymol on nodule formation in Medicago sativa (alfalfa) and Vigna unguiculata (cowpea). Experiments were initiated in a greenhouse at the UVA Blandy Experimental Farm in Boyce, VA in summer 2011 and 2012. For alfalfa, we used three treatments: (1) control, (2) addition of 0.3 ng pure thymol (3) addition of thyme essential oil containing 0.3 ng thymol. These concentrations of thymol are biologically realistic (Yamaura et al, 1989). For cowpea, we examined three extra-early maturing varieties of cowpea developed by the IITA in Nigeria with treatments (1) and (2) above as well as (3) growth with thyme seedlings. Inoculated seeds were grown in 50-cell plastic tray inserts filled with a high drainage soil mixture. Trays were placed in a randomized block design, and rotated daily on a greenhouse bench with supplemental lighting (16:8 light L:D cycle) and regular watering as needed. Pots were fertilized weekly with 1/5 Hoagland solution without nitrogen. After three weeks, the thymol treatment significantly increased the number of nodules and seedling root weight in alfalfa. In older alfalfa seedlings (five weeks), the thymol treatment significantly increased shoot weight. In all three varieties of cowpea, significantly more nodules per seedling were observed in treatments with thyme or thymol after five weeks. Two of the three varieties of cowpea also showed significantly larger roots in treatments with thyme and thymol. These results have implications for improving plant nutrition and soil fertility in agroecosystems, particularly for a crop such as cowpea that is critical to food security in rainfed systems such as the Sahel. Further research is also warranted to examine the role of plant secondary compounds in mediating multi-species interactions in natural plant communities, particularly since mints (Lamiaceae) co-occur with legumes (Fabaceae) in many communities worldwide.

Broader Impacts:

1 - Howard University, Biology Department, Washington, DC 20059 USA
2 - University of Puerto Rico, Mayaguez, 00681, PR
3 - University of Central Florida, Orlando , FL, 32816, USA

Keywords:
nitrogen fixation
secondary metabolites
species interactions
plant-microbial interactions.

Presentation Type: Oral Paper:Papers for Sections
Session: 28
Location: Marlborough B/Riverside Hilton
Date: Tuesday, July 30th, 2013
Time: 11:30 AM
Number: 28006
Abstract ID:500
Candidate for Awards:None