EFFECTS OF SUPPLEMENTAL LIGHTING AND ROOT-ZONE TEMPERATURE ON GROWTH OF CHRYSANTHEMUMS IN NUTRIENT FILM

Abstract

Winter (8 Nov. – 16 Jan) and spring (28 Feb. – 8 May) crops of Chrysanthemum morifolium ’Polaris’ were grown in nutrient film culture in greenhouses. Supplemental high pressure sodium lighting (80 μmol s−1 m−2) was provided to half the plants in each crop during the first 21 d of growth while root zone temperature (RZT) was maintained at either 12, 20 or 28 °C for the duration of the production period. Root and shoot dry weights and leaf area were increased by supplemental lighting when measured at the end of the vegetative growth stage (14 long days). At maturity, flower and vegetative dry weight, stem length, leaf area and flower number were increased by early supplemental lighting. For stem length and flower dry weight the beneficial effects were greater for the winter crop. Leaf area and root dry weight were reduced at 12 °C RZT, particularly under supplemental lighting. Flower buds were formed more rapidly on plants grown under supplemental lighting and for those grown at 20 or 28 °C RZT. Increasing RZT from 12 to 20 °C was generally more beneficial than an increase from 20 to 28 °C for both vegetative and flower traits.Key words: Chrysanthemum morifolium, irradiance, solution culture, hydrophonics, cut flowers