Root Segregation of C3 and C4 Species Using Carbon Isotope Composition

Abstract

Partitioning roots for studying cropping systems containing more than one species is important since root growth interaction could influence system performance. The study objective was to test a method for segregating plant species roots from soil samples taken in a mixed stand of corn (Zea mays L.), a C4, and kura clover (Trifolium ambiguum M. Bieb.), a C3 plant. Soil cores containing both corn and kura clover roots were obtained at three distances from the corn row and at two depths in a Rozetta silt loam soil (moderately well drained, fine‐silty, mixed, superactive, mesic Typic Hapludalf). Root composition of these C4 and C3 species was based on 13C/12C ratios expressed as δ13C. A significant linear relationship (r2 = 0.99) was found between the δ13C and the percentage of corn roots in samples containing known ratios of corn and kura clover roots. This relationship was used to determine corn and kura clover root percentages in field samples. Ratios of 13C/12C effectively segregated corn and kura clover root materials obtained from soil samples and seem to be a powerful tool for partitioning roots of C3 and C4 plants in similar studies.

Use of13C Isotope Discrimination Analysis to Quantify Distribution of Barnyardgrass and Rice Roots in a Four-Year Study of Weed-Suppressive Rice

“…Other 13 C discrimination studies have also shown differential distribution of C 4 and C 3 plant roots with depth or location in field plots (Derner et al 2003;Eleki et al 2005;Polley et al 1992). However, in these studies, the proportion of roots near the soil surface generally was much greater for C 4 plants than for C 3 plants.…”

“…Rice mapping populations studies on d 13 C levels (an expression of 13 C: 12 C isotope ratios) and associated crop productivity traits have indicated quantitative trait loci for d 13 C on five (Xu et al 2009) or on six (Laza et al 2006) of the 12 rice chromosomes. d 13 C analysis has also been used to determine the proportions of C 3 and C 4 plant roots in a number of systems (Derner et al 2003;Eleki et al 2005;Polley et al 1992;Svejcar and Boutton 1985;Svejcar et al 1988), and has been used in programs to improve water use efficiency in rice (Dingkuhn et al 1991;Impa et al 2005;Kondo et al 2004;Scartazza et al 1998).…”

13Carbon Isotope Discrimination in Roots and Shoots of Major Weed Species of Southern U.S. Rice Fields and Its Potential Use for Analysis of Rice–Weed Root Interactions

“…where d 13 C sample is the isotope ratio (in parts per thousand; %) relative to the PDB standard. R sample and R standard are the 13 C/ 12 C molar abundance ratios of the plant sample and the PDB standard (R pd ; 0.0112372), respectively (Eleki et al 2005). Average d 13 C values for C 3 and C 4 plants were reported to be approximately 227% and 213%, respectively (Boutton 1996).…”

“…Equations 10-25 were derived with R pd and other R values expressed on both a molar abundance ratio basis and a mass fraction basis. R pd molar abundance ratio 5 13 C/ 12 C 5 0.0112372 (Eleki et al 2005), and R pd mass fraction ratio 5 (R pd molar abundance ratio)(13/12). Because calculated results were , identical to four decimal places, both models were considered equally acceptable.…”

“…C isotope discrimination analysis, often measured as d 13 C, an expression of the 13 C/ 12 C isotope ratio relative to a fixed standard, has been used previously to determine the proportions of roots of C 3 and C 4 species in a number of field systems (Derner et al 2003;Eleki et al 2005;Gealy and Fischer 2010;Svejcar and Boutton 1985;Svejcar et al 1988). In other applications, 13 C discrimination analysis has been used in rice to improve water use efficiency or transpiration efficiency (Dingkuhn et al 1991;Impa et al 2005;Kondo et al 2004;Scartazza et al 1998;Xu et al 2009) and to explain suppression of a weed species under temporary water stress (Fischer et al 2010).…”