Growth, photosynthesis and protein content in cucumber plants as affected by supplied nitrogen form

Cucumber plants were grown hydroponically in three different nutrient solutions to determine the effect of NO3 ‐/NH4 + ratio on several parameters. Top and root growth, CO2 fixation, and ion content (K+, Ca+2, NO3 ‐) were always lower when urea and ammonium nitrate were the major N source as compared with a Hoagland solution in which nitrate was the major N source. No significant differences were found in total N and protein content among the three nutrient solution treatments.