Nitrogen supply through transpiration mass flow can limit nitrogen nutrition of plants
Plhak, F. (Masarykova Univ., Brno (Czech Republic). Prirodovedecka Fakulta)
Pea (Pisum sativum), sunflower (Helianthus annuus) and maize (Zea mays) plants were cultivated for 10 days in hydroponics at 1mM and 7mM nitrate or ammonium concentrations at regulated pH 6 and ambient CO2 level. Plant growth, concentration of total N and both ions in plant tissues, uptake of water and both N ions were evaluated, N uptake related to transpiration mass flow and to diffusion supply was calculated. Pea and sunflower preferred nitrate nutrition while maize plants used both N ions. The concentration of total N as well as of both N ions in plant tissues increased with N level with some exceptions. The uptake of both N ions related to transpiration mass flow was dependent on transpiration rate and N ion concentration. At a 7mM N concentration N uptake in pea plants was totally supplied by transpiration mass flow, in sunflower plants the ratio of N supply related to transpiration mass flow amounted to 50 % and in maize plants N supply through diffusion prevailed, amounting to 70-80 %. These results explicate N starvation at low N supply that can intensify at elevated CO2 causing decreased stomatal diffusion.
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