Growth and flowering of gerbera plants grown on temperature-regulated rockwool medium in relation to photosynthesis and water potentials

The effects of regulation of medium temperature at 19-23°C on the growth and flowering of Gerbera hybrida Hort. 'Nini' were investigated in relation to leaf water potential, photosynthesis and dry matter distribution. The number of inflorescences developed per crown was 1.8-2.0 and was almost constant in all temperature regimes throughout the experiment. The increase in the number of inflorescences caused by regulation of medium temperature was attributed to an increase in the number of newly formed crowns, which was observed in plants grown on cooled medium in summer and/or heated medium in winter. The water stress during the daytime was reduced by the cooling of the medium in summer and consequent high stomatal conductance resulted in an increased photosynthetic rate, which presumably facilitated the accumulation of dry matter in the crown. On the other hand, heating of the medium inhibited the accumulation of dry matter in roots. The combination of medium cooling in summer and heating in winter did not have any additive effects on cut flower yield.