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Dry Matter Production, Yield, and Allocation of Carbon-14 Assimilates by Wheat as Affected by Nitrogen Source and Salinity

Dep. of Plant Nutrition and Soil Fertility, Ctr. de Edafología y Biología Aplicada del Segura (CEBAS), Consejo Superior de Investigaciones Científicas (CSIC), Apdo. 4195, 30080 Murcia, Spain

S. H. Lips

Desert Agrobiology Training and Res. Ctr. (J. Blaustein Inst. for Desert Res.) and Biology Dep. (Fac. of Natural Sciences), Ben-Gurion Univ., Sede Boqer, Israel

^* Corresponding author.

Wheat (Triticum aestivum L.) growth is affected by both salinity and the type of N fed to the plants. The objective of this research was to determine the effect of salinity applied at different stages of the life cycle of wheat plants supplied with either NH₄ or NO₃ on growth, yield, and translocation of photosynthates. Plants were grown in sand culture irrigated with nutrient solution until maturity. The nutrient solution contained 4 mM N, either as (NH₄)₂SO₄ or Ca(NO₃)₂. Salinity (60 mM NaCl) was applied to the nutrient solution at 19, 70, and 92 d after sowing. Some of the plants received ¹⁴CO₂ pulses 100 d after sowing, and ¹⁴C distribution in each plant part was determined 24 h later. Dry biomass production and grain yield were reduced when salinity was applied 19 d after sowing (beginning of the vegetative stage), whereas no effect of NaCl was observed when salinity was applied later. Ammonium-fed plants always produced more tillers and spikes than NO³-fed plants. Total grain yield was similar with plants growing in either N form. Nitrate-treated plants produced fewer, but heavier, spikes due to a larger number of grains per spike than NH⁴-fed plants. Ammonium-fed plants showed a preferential allocation of ¹⁴C-assimilates to young developing tillers. Nitrate-fed plants, under similar conditions, allocated assimilates preferentially to grain. Salinity enhanced translocation of assimilates to the spikes when plants were grown with NO₃.

Received for publication June 30, 1992.