Regulation of Root-zone Temperature by Root-zone Environmental Control System affects Growth and Flowering of Verbena × hybrida and Pelargonium × hortorum

To reveal whether the growth of potted flowers is regulated by the root-zone temperature, the effect of root-zone temperatures on the growth of potted flowers such as Verbena × hybrida and Pelargonium × hortorum was investigated using a root-zone environmental control system (RECS). When Verbena × hybrida plants were grown under 15, 20, and 25°C root-zone temperatures (RZT), the growth of the top was markedly promoted at 25°C RZT, and dry weight of the whole plant at 25°C RZT increased ca. 1.5 times compared to that of 15°C RZT. In addition, the potted flowers of Pelargonium hortorum were grown with non-heating, 13°C heating, and 18°C heating of root-zones with an 8°C minimal air temperature during the winter season. The growth of the top, flowering rate, and number of florets increased with 18°C heating, and the dry weight of the whole plant increased ca. 2 times compared to that of non-heating. In conclusion, it was revealed that the growth of potted flowers could be controlled by RZT using RECS.