RETRACTED ARTICLE: Effect of root-zone salinity and form of N on photosynthate partitioning in wheat (Triticum aestivum L.)

Carbon-14 pulse labeling technique was used to study the effect of rooting medium salinity and form and availability of N on growth and rhizodeposition of wheat (Triticum aestivum L.). Thirty days old plants grown in continuously aerated Arnon and Hoagland nutrient solution were subjected to ¹⁴C pulse labeling for 24 h and transferred to aqueous rooting medium containing 0, 150, and 300 mM NaCl in all combinations with different forms (calcium nitrate, ammonium sulphate, and ammonium nitrate) and amounts (0.5, 1.0, 1.5, and 2.0 times the standard N concentration (150 ppm) of Arnon and Hoagland plant growth medium). Plant samples immediately after pulse labeling, following 7 days of growth under different rooting medium conditions, and the freeze-dried rooting medium were analyzed for total C and ¹⁴C. Length and fresh/dry weight of root and shoot portions and calculated values of unaccounted ¹⁴C were determined. Presence of NaCl in the rooting medium led to a decrease in root and shoot portions. However, NO₃ ⁻-fed plants showed better growth than NH₄ ⁺-fed plants at all the three salinity levels. Salinity in rooting medium led to higher rhizodeposition and lower loss of ¹⁴C. Relatively higher proportion of ¹⁴C was released as rhizodeposits and retained in root/shoot portions of plants fed with NH₄ ⁺ or NH₄ ⁺+NO₃ ⁻, than those with NO₃ ⁻, while less was respired. The specific activity of the rhizodeposits (kBq ¹⁴C g⁻¹ C) was also higher under saline conditions. The rhizodeposits in NH₄ ⁺-fed plants were more highly labeled as compared to NO₃ ⁻-plants.