Growth, quality, and physiological characteristics of gerbera (Gerbera jamesonii L.) cut flowers in response to different NO3 -:NH4 + ratios

We investigated the effects of different NO3 (-):NH4 (+) ratios in nutrient solution on the yield and growth of gerbera (Gerbera jamesonii) cut flowers in soilless culture. Two cultivars of gerbera (red 'Stanza' and yellow 'Double Dutch') were supplemented with four different NO3 (-):NH4 (+) ratios (100:0, 80:20, 60:40, and 40:60). Replacing 20% nitrate in the nutrient solution with ammonium resulted in the higher number of leaves per plant, highest fresh and dry weights of roots and shoots, greatest number of flowers, highest flower stalk diameter and flower disk diameter, longest vase life, highest fresh and dry weight of inflorescences, and highest relative water contents in petals compared with the control. Decreasing the NO3 (-):NH4 (+) ratio to 60:40 caused a considerable reduction in plant growth and biomass. The chlorophyll and carotenoid contents, as well as catalase (CAT) and peroxidase (POX) activity, increased with increasing proportion of ammonium-to-nitrate in the nutrient solution. The results suggest that a NO3 (-):NH4 (+) ratio of 80:20 should be used for gerbera cut flower production to achieve the highest growth and quality.