Photosynthesis in Ranunculus asiaticus L.: characterization in two Mediterranean hybrids under fluorescent white light

Ranunculus asiaticus L. is a quantitative long-day species, originating from Mediterranean area, grown in cold greenhouse for cut flowers and potted plants. Flowering in ranunculus is a complex process, strongly steered by the temperature and the photoperiod. Vernalization of rehydrated tuberous roots, used as propagation material, anticipates sprouting and leaf rosette formation and flowering. It is known that the time for flowering and the sensitivity to cold treatment vary in the numerous commercial hybrids, while no information seems to be available on the influence of vernalization on the photosynthetic process. The aim of the experiment was to investigate the influence of two hybrids, MDR (medium earliness) and MBO (early flowering), and two preparation treatments of tuberous roots, only rehydration (Control, C) and rehydration plus vernalisation (V), on photosynthesis and photochemistry and photosynthetic pigments content in plants grown in pot in growth chamber, under controlled environment. In control plants, photosynthesis was higher in MDR-C than in MBO-C, while the maximal PSII photochemical efficiency (Fv/Fm) slightly decreased in the first hybrid. MBO-C developed more leaves and a consequent higher plant leaf area. Compared to only rehydration, vernalization of rehydrated tuberous roots increased the number of leaves and the plant leaf area in both the hybrids. The preparation treatment did not affect photosynthetic rate while it decreased the maximal PSII photochemical efficiency (Fv/Fm) in both the hybrids. A significant interaction was found between the hybrid and the preparation treatment in the content of photosynthetic pigments, which decreased in plants from vernalized tuberous roots compared to those from only rehydrated roots in MDR, while increased with vernalization in MBO.