POSSIBILITY OF PREDICTING SOLUTE UPTAKE AND PLANT-GROWTH RESPONSE FROM INDEPENDENTLY MEASURED SOIL AND PLANT CHARACTERISTICS .6. GROWTH AND UPTAKE OF RAPE IN SOLUTIONS OF CONSTANT NITRATE CONCENTRATION

The growth and nitrogen uptake response of rape plants to nitrate concentration at the root surface were studied in solution culture in a controlled environment cabinet over a period of 24 days. NO3- was supplied at the rates of 10-5M, 5×10-5M, 10-4M, 10-3M and 10-2M in solution and was maintained near these levels. With increasing mean N concentration in the tissues, the relative growth rate and leaf area ratio increased and unit leaf rate decreased slightly. Values of all three growth parameters decreased with plant age. The shoot: root dry weight ratios and their N content ratios increased with increasing mean per cent N in the plant. The length or surface area per unit dry weight of roots was correlated negatively with per cent N and positively with age. The maximum mean inflow of nitrate to rape roots decreased sharply with age. The concentration at which half maximal mean inflow was attained was 3.44×10-5M NO3-. © 1979 Martinus Nijhoff Publishers.