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Comparative Effect of Nitrogen Forms on Nitrogen Uptake and Cotton Growth Under Salinity Stress

Dai, Jianlong, Duan, Liusheng, Dong, Hezhong
Journal of plant nutrition 2015 v.38 no.10 pp. 1530-1543
Gossypium hirsutum, ammonium nitrogen, cotton, hydroponics, leaves, nitrate nitrogen, nitrates, nitrogen, nutrient uptake, photosynthesis, root growth, roots, salinity, salt stress, seedlings, sodium, sodium chloride, surface area, viability
The effects of nitrogen (N) forms (ammonium- or nitrate-N) on plant growth under salinity stress [150 mmol sodium chloride (NaCl)] were studied in hydroponically cultured cotton. Net fluxes of sodium (Na ⁺), ammonium (NH ₄⁺), and nitrate (NO ₃⁻) were also determined using the Non-Invasive Micro-Test Technology. Plant growth was impaired under salinity stress, but nitrate-fed plants were less sensitive to salinity than ammonium-fed plants due mainly to superior root growth by the nitrate-fed plants. The root length, root surface area, root volume, and root viability of seedlings treated with NO ₃-N were greater than those treated with NH ₄-N with or without salinity stress. Under salinity stress, the Na ⁺ content of seedlings treated with NO ₃-N was lower than that in seedlings treated with NH ₄-N owing to higher root Na ⁺ efflux. A lower net NO ₃⁻ efflux was observed in roots of nitrate-fed plants relative to the net NH ₄⁺ efflux from roots of ammonium-fed plants. This resulted in much more nitrogen accumulation in different tissues, especially in leaves, thereby enhancing photosynthesis in nitrate-fed plants under salinity stress. Nitrate-N is superior to ammonium-N based on nitrogen uptake and cotton growth under salinity stress.