EFFECT OF TEMPERATURE ON PLANT DEVELOPMENT AND INFLORESCENCE STRUCTURE OF SALVIA ROEMERIANA

Salvia roemeriana, a species native of North America, is a new ornamental crop suitable for pot plant production and bedding decoration. Blooming is showy in late spring and may occur in early autumn again. From a rosette of leaves an apical and some lateral inflorescences develop carrying flowers usually up to 3 cm long. A trial was carried in a controlled environment to evaluate the effect of temperature on plant development and inflorescence structure. Seed propagated plants at 1- or 8-node stage were grown at 6°C, 12°C, 18°C or 24°C (±1,2°C each) for 4 months with a photoperiod of 12 h and a light intensity of 65 μmol m^-2 s^-1 (PPFD). Part of the plants at 6°C were shifted at 24°C after 6 weeks of cold treatment.
Increase of temperature resulted in a linear increase of the node number developed per month. Plants grown at 12°C or constantly at 6° C were not flowered yet at the end of the trial. Temperature did not affect the final number of nodes below inflorescence, so the 6°C period before growth at 24°C resulted only in a delay of flowering time. At 24°C (with or without 6°C pre-treatment) the number of both flowers and verticillasters was lower than at 18°C, with a higher effect on lateral inflorescence and on 1-node plants. In most cases flowers resulted cleistogamic-type on plants grown at 24°C or 6/24°C and on lateral inflorescences.
On the base of these results, S. roemeriana should be grown at temperature of 18°C to obtain in about 80 days plants from seed with high display of flowering structures.