Mycorrhiza and Carbohydrate Relations in Sorghum and Shortleaf Pine (Pinus echinata Mill.).

Mycorrhizal fungi dwell in the soil and infect plant roots seeking sugar and other metabolites they cannot produce. Plant roots would allow such infection to occur since they also obtain mineral nutrients and water which the fungal hyphae can abstract from the larger soil volume. Therefore the symbiosis is mutually beneficial to the host plant and the symbiont. Although this part of the association has been studied extensively, researchers are not certain as to which metabolite(s) is responsible for initiating the symbiosis. The objectives of the study are: (i) to develop staining techniques to identify mycorrhizal fungi in sorghum roots; (ii) to identify the metabolites (carbohydrate, amino acid and/or organic acid) in sorghum and shortleaf pine (Pinus echinata, Mill.) roots that could be responsible for the symbiosis. Approximately 50 g of a mix culture mycorrhizal fungi was used to inoculate the growth medium. Five sorghum seeds or pine acorns were planted in each inoculated and non-inoculated pot/cells and allowed to grow. Plants were grown in a greenhouse using a soil and peat mixture containing a 10-10-10 fertilizer. After two weeks of growth, a 25 ppm B solution was applied to the foliage weekly to both inoculated and non-inoculated plants. After two months of growth, plants were gently removed from containers and washed with water to remove adhering soil particles. Lateral roots were excised from each plant and placed in petri dishes containing 2% acetic acid. The presence of root infection were determined using an ink staining technique that preferentially stained the fungus in sorghum in mycorrhizal roots.