Nitrate and ammonium uptake by wheat seedlings as affected by salinity and light

Nitrate (NO₃ ^-) and ammonium (NH4⁺) are the two main forms of nitrogen (N) taken up by plants. Several environmental factors affect the uptake of N. This work was undertaken to study the induction of NO₃ ^-and NH₄+ transport systems in wheat (Triticum aestivum L.) roots as affected by salinity and light. Wheat seedlings were germinated in sterilized vermiculite and plants were grown in a growth chamber under controlled conditions for eight days with a nutrient solution without N, and with or without sodium chloride (NaCl). Uptake rates of NO₃-, NH₄+, or NH4+ + NO₃- were calculated by measuring the disappearance of N from the solutions. The NO₃- uptake developed with time, either through induction or activation. Salinity pretreatments increased net uptake rates of NO₃- and NH₄ ⁺, suggesting that plants were in a higher N-deficient status when grown in saline conditions. Light decreased initial NO₃- uptake but had little effect on initial NH₄ ⁺ uptake.