Differential Root Morphology Response to No versus High Phosphorus, in Three Hydroponically Grown Forage Chicory Cultivars

Authors: Zobel, Richard; ALLOUSH, G - VIRGINIA TECH; Belesky, David

Submitted to: Environmental and Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/25/2005
Publication Date: 3/15/2006
Citation: Zobel, R.W., Alloush, G.A., 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(1-2):201-208.

Interpretive Summary: Many soils are low in plant available phosphorus. Some species, for instance chicory, are thought to be phosphorus accumulators and therefore relatively efficient at phosphorus uptake in low phosphorus soils. Forage chicory is becoming more popular as an ingredient in pastures of the mid-Atlantic Appalachian region. This research investigated the morphological differences of roots of three different chicory cultivars grown in high vs no phosphorus hydroponics. The manuscript describes the observations that one cultivar responded to the low phosphorus culture conditions by increasing the length of the smallest diameter roots at the expense of larger roots; while a second cultivar reduced root mass density in response to low phosphorus but did not change overall root morphological characteristics, and the third modified only tap root size in response to low phosphorus. The manuscript concludes that these differences in response provide the potential to select cultivars for specific soil conditions and specific applications.

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 to determine plant mass, mineral composition, and root morphology of three forage chicory cultivars [Grasslands Puna (GP), LaCerta (LC) and Forage Feast (FF)] as a function of P supply. Phosphorus increased chicory growth irrespective of cultivar. Root morphology differed among cultivars irrespective of P supply with FF producing about twice the taproot mass of GP or LC. Total root length and surface area of GP increased, and did not change in LC or FF under - P conditions. Results suggest at least two different plant responses to - P conditions in chicory that seem to be attributes of specific cultivars: a) increase in root length of the 0.28 mm root class (GP); b) decrease in non-taproot mass density with -P and no change in root length or ratios between diameter classes (LC). The change in root length of small diameter class roots, as observed for GP, is typical of the responses to -P described in the literature. The decrease in root density seen with LC is an anatomical response that is not coupled with any observable morphological response. Physiological or anatomical root responses, to environmental perturbations without concomitant morphological changes, precludes the routine use of specific root length as an indicator of environmentally induced changes in root system function.