Effect of photosynthetic photon flux density on growth, photosynthetic competence and antioxidant enzymes activity during ex vitro acclimatization of Dieffenbachia cultivars

The effects of 35, 70 and 100 µmol m−2 s−1 photosynthetic photon flux density (PPFD) were investigated on ex vitro acclimatization of micropropagated Dieffenbachia plants. Various growth characteristics, photosynthetic parameters and activities of antioxidant enzymes and dehydrins (DHN) were investigated. Fresh and dry plant biomass, plant height and root length were highest under the highest PPFD (100 µmol m−2 s−1), but this treatment was responsible for a reduction in the number of leaves. Chlorophyll and carotenoid contents and net photosynthesis were also optimal in plants grown under the highest irradiance. Stomatal resistance, transpiration rate and Fv/Fm values decreased with the incremental light irradiance. Activities of the antioxidant enzymes superoxide dismutase, catalase and glutathione peroxidase were higher in the plants treated with 70 and 100 µmol m−2 s−1 PPFD. Accumulation of 55 kDa, 40 and 22 kDa DHN was observed in all light treatments. These results depict that lower PPFD (35 µmol m−2 s−1) was suitable for acclimatization of Dieffenbachia plants. High PPFD (>70 µmol m−2 s−1) induced accumulation of antioxidants and accumulation of DHN in the plants which reveals enhanced stress levels

In vitro

Ludwigia palustris (L.) Ell. is an aquatic perennial herb present in several regions of Italy, which is one of its native countries. In this research, micropropagation and encapsulation protocols were established from axillary buds of L. palustris. Shoots proliferated on half-strength Murashige and Skoog medium without growth regulators. Different culture vessels were tested. Shoots in GROWTEK bioreactor showed the highest fresh and dry weight and total length while the plantlets grown in the RITA bioreactor showed the highest shoot number per explant. Encapsulation of L. palustris microcuttings with sodium alginate formed small and whitish beads which were stored for 14 or 28 days at 7° or 25°C. Storage for 14 days at both temperatures gave the best results but prolonged storage at 25°C decreased the shoot viability to 73%. After 4 weeks of recovery, all the plantlets showed the typical features of the species. Even though the latest Italian IUCN Red List does not mention L. palustris, conservation measures are proposed at local level because this species locally remains vulnerable mainly due to the loss of adequate habitats.Our protocol could be one of the methods for ex situ conservation of L. palustris particularly because its seed storage behavior is uncertai