Mg and K effects on cation uptake and dry matter accumulation in tall fescue (Festuca arundinacea)

Abstract

HiMag tall fescue (Lolium arundinaceum (Schreb.) S.J. Darbyshire = Festuca arundinacea Schreb) was selected for high Mg concentration in the herbage to reduce grass tetany risk to ruminants; however, the mechanism of increased Mg uptake into shoots is unknown. The objective was to determine cation concentrations of roots, crowns, and leaves in plants of cv. HiMag and its parents, cv. Kentucky 31 and cv. Missouri 96, grown in nutrient solution for 42 days, and determine if cation ratios in roots, crowns, and leaves are different, indicating a difference due to translocation. Treatments were "basal" (1.5 mM K and 0.5 mM Mg), "K" (3.2 mM K), "Mg" (1 mM Mg), and "K+Mg" (3.2 mM K and 1 mM Mg). For HiMag, Mg was lower in roots (Trial 2 only), not different in crowns, and greater in leaves than Kentucky 31 and Missouri 96. Doubling the K and Mg of the nutrient solution from basal levels resulted in a 44% reduction of root Mg in Kentucky 31 and Missouri 96, compared to a 17% reduction in root Mg for HiMag. The K inflow rate in HiMag for the basal treatment was lower than that in Kentucky 31 and Missouri 96. These results provide evidence for a process that limits K uptake and an active Mg translocation mechanism in tall fescue. HiMag was apparently selected for traits that promote translocation of Mg from roots to shoots.

Ion Uptake in Tall Fescue as Affected by Carbonate, Chloride, and Sulfate Salinity

“…Although Ca content could affect other nutrients in the shoots, it did not translate into detectable differences between two cultivars in this study. Cultivar differences in Ca and Mg uptake also were reported previously [25] – [26] . Gao et al [6] reported that ‘Tar Heel II’ and ‘Wolfpack’ were not differentiated in physiological responses to NaCl, Na 2 SO 4 , Na 2 CO 3 , and CaCl 2 at a wide range of concentrations.…”

“…When tall fescue is used as a forage crop, a high Mg content in the shoot tissues is required to avoid grass tetany. An index of K/(Ca+Mg) in terms of molar concentration is commonly used for the assessment of the sufficiency level of Mg, and a ratio of <2.2 is considered sufficient [25] . In the present study, the index was 2.27 to 2.32, 2.29 to 2.68, and 2.28 to 2.51 for NaCl, Na 2 SO 4 and Na 2 CO 3 treatments at different concentration levels, respectively.…”

Experimental determination of magnesium isotope fractionation during higher plant growth

“…In all experiments, most of the Mg has been transferred in the shoots (leaf + stem) (91% and 92% for the rye grass and 78% and 85% for clover, see Fig. 2B), as is often the case for these species (Scott and Robson, 1990;Belastegui-Macadam et al, 2007), as well as for tall fescue (Shewmaker et al, 2008) and wheat (Scott and Robson, 1991). We have also estimated that seeds represent a maximum contribution of 0.1% of the bulk plant Mg (not shown here).…”

THE INFLUENCE OF ORGANIC MATTER ON YIELD AND QUALITY OF WINTER WHEAT Triticum aestivum ssp. vulgare (L.) CULTIVATED ON SOILS CONTAMINATED WITH HEAVY METALS

“…Just as in case of calcium, there was in grain smaller contents of magnesium, which was apparently translocated from roots to above ground part of winter wheat. Straw magnesium concentrations in this study ranged from 0.53 to 3.55 g·kg −1 compared with 2.40-3.12 g·kg −1 in a companion field study [23]. Notation: see Table 1 Content of sodium in grain of winter wheat was the smallest in variant with farmyard manure whereas the highest in variant with brown coal on both contaminated soil and without heavy metals (Table 4).…”