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Title: Differential root morphology response to no versus high phosphorus, in three hydroponically grown forage chicory cultivars

Author
item Zobel, Richard
item ALLOUSH, GHIATH - VIRGINIA TECH
item Belesky, David

Submitted to: Environmental and Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/25/2005
Publication Date: 5/18/2006
Citation: Zobel, R.W., Alloush, G., Belesky, D.P. 2006. Differential root morphology response to no versus high phosphorus, in three hydroponically grown forage chicory cultivars. Environmental and Experimental Botany. 57:201-208.

Interpretive Summary: Chicory is a valuable addition to the array of forage plant resources for use in pasture. Chicory also has a remarkable ability to accumulate nutrients and tolerate high nutrient concentrations in the soil. Several cultivars or lines of chicory are available to the forage-livestock producer but no clear understanding exists of how the cultivars respond to phosphorus, a nutrient with important environmental and production influences. Understanding how chicory responds to phosphorus will provide some insight into chicory establishment in existing pasture and the nutrient demands required to maintain chicory in pasture. It will also provide some means of managing sites with excessive amounts of P to help mitigate environmental degradation. We conducted controlled environment experiments to evaluate the development and productivity of chicory in response to phosphorus. Root length and size changed in response to changing phosphorus supply, suggesting that chicory was able to adapt to localized conditions in order to improve phosphorus acquisition. Plants also secreted compounds that influenced the soil immediately adjacent to the root to acquire phosphorus. These abilities were specific to particular genotypes of chicory suggesting that producers and land resource managers should choose chicory cultivars for optimal performance depending on the specific application or need.

Technical Abstract: Forage chicory is a productive forage resource for eastern North America; however, many soils in the region are acidic and deficient in P and might restrict the widespread use of forage chicory. There is no published information on response of forage chicory to P, or P acquisition strategies for morphologically different chicory cultivars. We conducted controlled environment experiments using nutrient culture and soil to determine plant mass, partitioning and mineral composition, characteristics of the rhizosphere and root morphology of three cultivars (Grasslands Puna, Lacerta and Forage Feast) as a function of P supply. Phosphorus increased chicory growth irrespective of cultivar. Root morphology differed among cultivars irrespective of P supply with Forage Feast producing about twice the taproot mass of Puna or Lacerta. Total root length and surface area of Puna increased, did not change in Lacerta, and decreased in Forage Feast under - P conditions. Lateral root branching was significantly greater in - P compared to + P Puna plants, with significantly less branching in Lacerta and Forage Feast. In - P treatments, Lacerta acidified nutrient solution or rhizosphere soil the least compared to Puna or Forage Feast. Results suggest at least three different plant responses to - P conditions in chicory that seem to be attributes of specific cultivars: a) increase in root length of the 0.2 mm root class and decrease of other classes (Puna); b) maintenance of root length at the expense of taproot (Lacerta); and c) 0.2 mm class is unregulated and follows overall change in mass (Forage Feast). The morphology and physiology of cultivars vary and influences cultivar choice for specific applications. Apparently, Puna can function across a range of P supply and could be used in extensively managed pasture as well in situations where P inputs are high.