Photosynthetic and biochemical characterization of in vitro-derived African violet (Saintpaulia ionantha H. Wendl) plants to ex vitro conditions

Abstract

African violet (Saintpaulia ionantha H. Wendl) is one of the most easily and commonly tissue-cultured ornamental plants. Despite this, there are limited reports on photosynthetic capacity and its impact on the plant quality during acclimatization. Various growth, photosynthetic and biochemical parameters and activities of antioxidant enzymes and dehydrins of micropropagated plants were assessed under three light intensities (35, 70, and 100 μmol m⁻² s⁻¹ photosynthetic photon flux density – PPFD). Fresh and dry plant biomass, plant height, and leaf area were optimal with high irradiance (70–100 μmol m⁻² s⁻¹ PPFD). Chlorophyll and carotenoid contents and net photosynthesis were optimal in plants grown under 70 μmol m⁻² s⁻¹PPFD. Stomatal resistance, malondialdehyde content, and Fv/Fm values were highest at low light irradiance (35 μmol m⁻² s⁻¹ PPFD). The activities of three antioxidant enzymes, superoxide dismutase, catalase, and glutathione peroxidase, increased as light irradiance increased, signaling that high light irradiance was an abiotic stress. The accumulation of 55, 33, and 25 kDa dehydrins was observed with all light treatments although the expression levels were highest at 35 μmol m⁻² s⁻¹ PPFD. Irradiance at 70 μmol m⁻² s⁻¹ PPFD was suitable for the acclimatization of African violet plants. Both low and high irradiance levels (35 and 100 μmol m⁻² s⁻¹ PPFD) induced the accumulation of antioxidants and dehydrins in plants which reveals enhanced stress levels and measures to counter it.