Effects of Carbon Dioxide and Photosynthetic Photon Flux on Mineral Content in Chrysanthemum Allowing for Growth as a Covariate

The effect of CO2 concentration (330 and 675 mu L.L-1) and photosynthetic photon flux (PPF) (mean daily peaks of 550-1400 mu mol.m(-2)s(-1)) on total mineral contents in shoots was studied in chrysanthemum [Dendranthema x grandiflorum (Ramat) Kitam 'Fiesta'] during three times of the year. Growth (as measured by shoot dry weight) and shoot mineral contents (weight of nutrient per shoot) of hydroponically grown plants were analyzed after 5 weeks. There was a positive synergistic interaction of CO2 concentration and PPF on growth with the greatest growth at high PPF (1400 mmol.m(-2).s(-1)) with high CO2 (675 mu L.L-1). When growth was not used as a covariate in the statistical model, both CO2 concentration and PPF significantly affected the content of all eight nutrients. However, after growth was included as a covariate in the model, nutrients were classified into three categories based on whether CO2 concentration and PPF level were needed in addition to growth to predict shoot nutrient content. Neither CO2 concentration nor PPF level was needed for Mg, Fe, and Mn contents, whereas PPF level was needed for N, P, K, and Ca contents, and both CO2 concentration and PPF level were required for B content.