Tomato plants often grow in saline environments in Mediterranean countries where salt accumulation in the soil is a major abiotic stress that limits its productivity. However, silicon (Si) supplementation has been reported to improve tolerance against several forms of abiotic stress. The primary aim of our study was to investigate, using comparative physiological and proteomic approaches, salinity stress in chloroplasts of tomato under silicon supplementation. Tomato seedlings (Solanum lycopersicum L.) were grown in nutrient media in the presence or absence of NaCl and supplemented with silicon for 5 days. Salinity stress caused oxidative damage, followed by a decrease in silicon concentrations in the leaves of the tomato plants. However, supplementation with silicon had an overall protective effect against this stress. The major physiological parameters measured in our studies including total chlorophyll and carotenoid content were largely decreased under salinity stress, but were recovered in the presence of silicon. Insufficient levels of net-photosynthesis, transpiration and stomatal conductance were also largely improved by silicon supplementation. Proteomics analysis of chloroplasts analyzed by 2D-BN-PAGE (second-dimensional blue native polyacrylamide-gel electrophoresis) revealed a high sensitivity of multiprotein complex proteins (MCPs) such as photosystems I (PSI) and II (PSII) to the presence of saline. A significant reduction in cytochrome b6/f and the ATP-synthase complex was also alleviated by silicon during salinity stress, while the complex forms of light harvesting complex trimers and monomers (LHCs) were rapidly up-regulated. Our results suggest that silicon plays an important role in moderating damage to chloroplasts and their metabolism in saline environments. We therefore hypothesize that tomato plants have a greater capacity for tolerating saline stress through the improvement of photosynthetic metabolism and chloroplast proteome expression after silicon supplementation.

The current study deals with in vitro propagation, antioxidant property estimation, and assessment of acacetin content in Scrophularia kakudensis Franch. Adventitious shoot induction was achieved from the nodal explant with the highest number of adventitious shoots per explant (17.4) on Murashige and Skoog's (MS) medium fortified with 2.0 mg·L−1 6-benzyladenine (BA) and 0.5 mg L−1 indole-3-acetic acid (IAA). Maximum number of roots per plant (16.5) was noted in half strength MS medium supplemented with 0.5 mg·L−1 IAA. The regenerated plants displayed successful survival ratio (95%) in the greenhouse. The highest content of acacetin, a pharmaceutically important flavonoid, was observed in the shoot extracts (in vitro: 32.83 µg·g−1 FW; in vivo: 30.05 µg·g−1 FW) followed by root extracts. Total phenol and flavonoid contents along with free radical scavenging assays revealed the occurrence of larger amount of antioxidants in shoot extract in comparison with callus and root extracts of S. kakudensis. Thus, the outcome of the present study can be highly beneficial for the germplasm conservation and commercial cultivation of S. kakudensis for therapeutic purposes.

The impact of shifts in the spectral quality of light on morphogenesis, flowering, and photoperiodic gene expression during exposure to light quality of night interruption (NI) was investigated in Dendranthema grandiflorum. The circadian rhythms of plants grown in a closed walk-in growth chamber were interrupted at night for a total of 4 h, using light-emitting diodes with an intensity of 10 μmol·m−2·s−1 PPF. The light quality of the NI was shifted from one wavelength to another after the first 2 h. Light treatments consisting of all possible pairings of blue (B), red (R), far-red (Fr), and white (W) light were tested. Plants in the NI treatment groups exposed to Fr light grew larger than plants in other treatment groups. Of plants in NI treatment groups, those in the NI-WB treatment grew the least. In addition, the impact of shifts in the light quality of NI on leaf expansion was greater in treatment groups exposed to a combination of either B and R or R and W light, regardless of their order of supply. Flowering was observed in the NI-RB, NI-FrR, NI-BFr, NI-FrB, NI-WB, NI-FrW, NI-WFr, NI-WR, and SD (short-day) treatments, and was especially promoted in the NI-BFr and NI-FrB treatments. In a combined shift treatment of B and R or B and W light, the NI concluded with B light (NI-RB and NI-WB) treatment induced flowering. The transcriptional factors phyA, cry1 and FTL (FLOWERING LOCUS T) were positively affected, while phyB and AFT were negatively affected. In conclusion, morphogenesis, flowering, and transcriptional factors were all significantly affected either positively or negatively by shifts in the light quality of NI. The light quality of the first 2 h of NI affected neither morphogenesis nor flowering, while the light quality of the last 2 h of NI significantly affected both morphogenesis and flowering.

Although grafting is broadly used in the production of crops, no information is available about the proteins involved in vascular connections between rootstock and scion. Similarly, proteome changes under the light intensities widely used for grafted seedlings are of practical use. The objective of this study was to determine the proteome of vascular connections using watermelon (Citrullus vulgaris Schrad.) ‘Sambok Honey’ and ‘Speed’ as the scion and bottle gourd (Lagenaria siceraria Stanld.) ‘RS Dongjanggun’ as the rootstock grown under different light intensities (25, 50, 75 and 100 μmol m−2 s−1). Our proteomic analysis revealed 24 and 27 differentially expressed proteins in ‘Sambok Honey’ and ‘Speed’, respectively, under different light intensities. The identified proteins were largely involved in ion binding, amino acid metabolism, transcriptional regulation and defense response. The enhancement of ion-binding, transcriptional regulation, amino acid metabolism, and defense response proteins suggests a strengthening of the connection between the rootstock and scion under high light intensity. Indeed, the accumulation of key enzymes in the biological processes described above appears to play an important role in the vascular connections of grafted seedlings. Moreover, it appears that 100 μmol m−2 s−1 results in better protein expression responses in grafted seedlings.

No abstract