Photosynthesis, biomass partitioning and peroxisomicine A1 production of Karwinskia species in response to nitrogen supply

Species of the genus Karwinskia are medicinal woody plants producing secondary metabolites (anthracenones, peroxisomicine A1) with antitumour effects. We investigated the photosynthetic and growth characteristics of Karwinskia parvifolia Zucc. and Karwinskia humboldtiana Rose plants grown at two rates of nitrogen supply. There were significant differences in growth, CO2 exchange (photosynthesis, respiration), chlorophyll and nitrogen concentration between plants grown at high nitrogen supply (HN) and low nitrogen supply (LN). At HN, the plants of both species grew faster than those cultivated at LN. Rates of photosynthesis, leaf respiration and root respiration, quantum yield, the concentration of chlorophylls (a, b, a+b), specific leaf area, leaf mass ratio and peroxisomicine A1 concentration were higher in plants grown at HN. The species‐specific difference in the daily carbon budget was mainly due to variation in rates of carbon fixation. K. parvifolia responded more strongly to the nitrogen treatment than K. humboldtiana, in terms of growth, as well as with respect to photosynthesis and peroxisomicine A1 concentration.