Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 15, 2003
Publication Date: January 1, 2005
Citation: Brauer, D.K., Staley, T.E. 2005. Early developmental responses of white clover roothairs to calcium protons and aluminum in solution and soil cultures. Crop Science. 45:1216-1222. Interpretive Summary: Acidic soils are common throughout the world and low soil pH can limit the productivity of forage legumes by decreasing the extent by which these plants associated with symbiotic rhizobia bacteria to supply the plant's nitrogen needs. Although acidic soil conditions are known to affect various plant processes, there is little documentation as to the effect of acidic soil conditions on the growth of root hairs, a structure that is involved in early steps in the establishment of legume-rhizobia symbiosis. Experiments conducted with white clover growing in both soils and hydroponic solutions indicated that the growth of root hairs were not as sensitive to acidic soil conditions as the establishment of nodules. This information is of interest to plant physiologists and breeders, microbiologists working with rhizobia, and agronomists who are trying to further understand the physiological processes related to poor nodulation of forage legumes in acidic soils.
Technical Abstract: Acidic soils tend to limit the nodulation of forage legumes and root hairs are important for Rhizobia binding and the initiation of nodule formation. This study examined the effects of Ca, pH and Al on the growth and development of root hairs in nutrient solutions and soils with white clover (Trifolium repens L., cultivar Huia) seedlings. The production of root hairs by one to two day-old seedlings was not affected by increases in solution Al up to 0.024 mM in nutrient solution experiments, but show a pronounced optimum at a calculated root surface pH of 3.8. Root hairs growth and production was also assessed in Gilpin series silt loam from New, WV amended with various levels of lime with white clover seedlings 2 to 10 days after planting. Soils ranged in pH from 4.6 to 5.3 and soil exchangeable Al from 1 to 2.4 Cmol per kg soil. No significant differences in root hair growth and development as a function of soil pH and/or soil available Al were observed. These results are in contrast with previous results conducted under similar experimental conditions that demonstrated an effect of soil pH/soil available Al on root growth and nodulation. When results from this and the previous report are considered together, the combined result suggest that root growth and nodulation were more sensitive to acidic soil constraint than root hair growth.