Moving lamps increase leaf photosynthetic capacity but not the growth of potted gerbera

To investigate the responses of leaf photosynthesis and plant growth to a moving lighting system, potted gerberas (Gerbera jamesonii H. Bolus ex J.D. Hook “Festival”) were grown under supplemental lighting in a greenhouse with either a stationary or a moving lighting system positioned above the benches. The stationary system consisted of a fixed high pressure sodium (HPS) lighting system, while the moving lighting system consisted of a moving HPS fixture attached to a cable system to move the light fixture back and forth over the crop. In both cases, the supplemental lighting was applied from 6:00 to 24:00 h with the same supplemental daily light integral (4.9 mol m⁻² day⁻¹). Moving lamps significantly increased leaf photosynthetic capacity as represented by light saturated net CO₂ exchange rate (NCER) (A_sat), light- and CO₂-saturated rate of NCER (A_max), maximum rate of Rubisco carboxylation (V_cmax), maximum rate of electron transport (J_max) and rate of triose phosphate utilization. However, in situ leaf NCER and stomatal conductance, leaf chlorophyll content index, leaf area, leaf thickness, fresh weight of plants were significantly lower under moving lighting than under stationary lighting. It is suggested that the reduced growth of plants under moving lighting might be due to (1) the overall lower light use efficiency of leaves under moving lighting than those under stationary lighting; (2) the slower response time of the photosynthetic system compared to the rate of change in light intensity under moving lighting.