THE PRODUCTION OF AFRICAN MARIGOLD (TAGETES ERECTA L.) BY THE NUTRIENT FILM TECHNIQUE. THE INFLUENCE OF SOLUTION CONDUCTIVITY ON GROWTH AND CAROTENOID LEVELS

The plants were tolerant to a wide variation in nutrient solution concentration; vegetative growth and flower production were unaffected by increasing the solution electrical conductivity (Ec) from 1.5 to 3.0 mS cm^-1. A further increase in solution Ec to 6.0 mS cm^-1, decreased total plant dry matter (64%) and flower yield (81%) compared to the control. The reduction in flower yield resulted both from a reduction in flower number (67%) and flower weight (41%). At 6.0 mS cm^-1, plants flowered 10 days earlier than the control.

The concentration of carotenoids in the flowers was studied over the harvest period of the experiment and at three stages of flower development. During the first three weeks, the level of carotenoids increased to a maximum and then remained constant throughout the harvest period. It was also found that the concentration decreased with the age of the flower. In both cases, the concentration of carotenoids was maximum at 3.0 mS cm^-1. The total carotenoid yield was greatly decreased at 6.0 mS cm^-1, due to the reduction in flower number and weight.

Download Adobe Acrobat Reader (free software to read PDF files)