Effect of Glomus fasciculatum On Nutrient Uptake and Growth of a Medicinal Plant, Coleus forskohlii

Aims: Coleus forskohlii Briq. (syn. Coleus barbatus Benth.) belonging to the family Lamiaceae is a well known plant throughout the country and known as ‘pashanbhedi’ in Sanskrit and ‘pathatchur’ in Hindi is one of the most potential medicinal plants of the future, as its pharmacoproperties have been discovered only recently. Its tuberous roots are found to be rich source of forskolin which is being used as a remedy for hypertension, glaucoma, asthma, congestive heart failures and certain types of cancers and also being use as vegetables. In addition, forskolin is reported to have used in the preparation of medicines for controlling body weight, preventing hair greying and restoring normal colour of grey hairs. Its foliage is also employed in treating intestinal disorders and used as a condiment since a long time. Keeping the above views in mind, the present investigation was undertaken to study the influence of an arbuscular mycorrhizal (AM) fungus, G. fasciculatum on phosphorus uptake and growth of Coleus forskohlii.

Study Design: Various tests or experiments were done in this study. Total leaf tissue phosphorus content was determined following the Microkjeldhal method of Jackson (1973) and chlorophyll estimation was done following the method of Mahadevan and Sridhar (1982) .Root colonization of C. forskohlii by G. fasciculatum was observed by the ‘Rapid clearing and staining technique’ (Phillips & Hayman, 1970). Forskolin content in C. forskohlii tubers was estimated by High performance liquid chromatography (HPLC).

Place and Duration of Study: Sample: The experiment was carried out in the Department of Botany, Burdwan University. A soil culture of Glomus fasciculatum was propagated as endomycorrhizal species in Zea mays as suitable host in pot culture using sterile sand and soil (pH 5.6; organic carbon 0.6%, P content 45 ppm) in 1:1 ratio. 400 gm of rhizosphere soil with AM-inoculated root fragments of Zea mays was introduced in the dry, loamy, fine-textured soil (pH 5.8; organic carbon 0.6%, P content 45 ppm, total nitrogen 0.03%) of pot culture (2.0 kg of soil per pot) at a depth of 2 inches below the Coleus cutting (12-16 cm long comprising 3-4 pairs of leaves) being planted, between June 2011 and July 2012.

Results: Responses of an arbuscular mycorrhizal (AM) fungus, Glomus fasciculatum on phosphorus uptake by the plant at different developmental phases have been studied. The result indicates that symbiotic association of mycorrhizal fungus amounts to greater uptake of phosphorus and increased chlorophyll content in AM treated plants than in non mycorrhizal plants which gradually happened to be maintained throughout their developmental stages. Different growth parameters like plant height, root length, no. of roots, no. of leaves, no. of branches, fresh weight of shoot, roots, tubers and forskolin content were significantly higher in AM treated plants than in respective controls.

Conclusion: The better growth of mycorrhizal plants was attributed to improved nutrient uptake, especially phosphorus. The result suggested that G. fasciculatum is one of the most potentially effective bio-fertilizer of Coleus forskohlii.