Background: Cut flower longevity is often limited by adverse water relations or oxidative stress. The potential of single- and multi-walled carbon nanotubes (SWCNTs and MWCNTs, respectively) on prolonging vase life was addressed. Dose–response curves were obtained by applying five concentrations (0–80 mg L⁻¹) of SWCNTs or MWCNTs either once as a foliar spray or continuously in the holding solution of three carnation cultivars. Next, the optimal concentration of either SWCNTs or MWCNTs was employed to evaluate several parameters critical for vase life. Results: Foliar spray application exerted minor effects on water relations, flower opening and keeping quality. By contrast, including CNTs in the holding solution sustained a positive water balance for a longer period, improved flower opening and prolonged vase life. These effects were similar between SWCNTs and MWCNTs, and were concentration-dependent. The optimal concentration for vase life was higher for MWCNTs as compared to SWCNTs, and for two cultivars as compared to the third one. At optimal concentration, SWCNTs or MWCNTs in the holding solution generally maintained turgidity, and alleviated chlorophyll degradation, electrolyte leakage and lipid peroxidation. These effects were related to increased activation of enzymatic (ascorbate peroxidase, catalase, peroxidase and superoxide dismutase) and non-enzymatic (carotenoids, polyphenols, and flavonoids) antioxidants. Conclusion: CNTs in the holding solution were very effective in stimulating vase life through improved water relations and enhanced antioxidant machinery stimulation. Graphical

In this study, the joint effects of developmental stage and soil water availability on biomass accumulation, harvest index, as well as essential oil content, yield and composition were investigated in Thymus armeniacus. For comparison purposes, Thymus kotschyanus was also considered. Plants were irrigated to either 75 or 50% of field capacity, and were sampled at 50 or 100% blooming. In both species, water deficit exerted limited effect on the time required to initiate or complete flowering. In most critical aspects of yield (harvestable organs dry weight, essential oil yield), T. armeniacus was found to be superior than T. kotschyanus. In these traits, however, T. armeniacus underwent a more drastic water deficit-induced decrease. Across treatments, metabolite levels fairly correlated to transcript accumulation profiles of terpene synthases and cytochrome P450 genes. Indices affiliated with reactive oxygen species were inter-correlated with the activity of five major antioxidant enzymes, while the same was noted between leaf water status and pigment content. Taken together, these results indicate that when water availability can be achieved, higher yields will be obtained by cultivation of T. armeniacus. Under water deficit conditions, instead, the more drought tolerant T. kotschyanus stands out as the primary choice.

In this study, the optimal concentration of sodium hydrosulfide (NaSH), salicylic acid (SA), and titanium dioxide nanoparticles (TiO₂NPs), and their relative effectiveness on alleviating the adverse effects of water deficit on ornamental quality, were investigated in periwinkle. Plants were cultivated under three water deficit levels (80, 50, and 20% available water content) and received two foliar applications of TiO₂NPs (0, 0.5 and 1 mM), NaSH (0.5 and 1 mM), or SA (1 and 2 mM). Water deficit deteriorated ornamental quality, amplified the risk of buckling (lower stem strength) and suppressed longevity. It decreased both light interception (leaf area) and carbon assimilation. Besides impaired hydration status, water-stressed plants underwent oxidative damage as indicated by reduced chlorophyll content, elevated membrane degradation, and lipid peroxidation. Spray treatments improved all traits, besides stem strength and proline content. Additionally, they enhanced carotenoid content and the activities of catalase and peroxidase. Their relative effectiveness (TiO₂NPs > NaSH > SA) and optimal concentration (i.e., 0.5 mM (TiO₂NPs, NaSH), and 1 mM (SA)) was independent of water deficit level. In conclusion, this study provides practices for improved ornamental quality and longevity independently of water availability, with their positive effect being stronger under irregular or limited water supply.

Nano-selenium (nano-Se) is an eco-friendly and inexpensive compound. The potential of including it in the holding solution to stimulate vase life was investigated by conducting two experiments. In the first one, dose-response curves were generated by applying different nano-Se concentrations (0–1 and 0–1.5 µM for rose and carnation, respectively) in the holding solution of three cultivars per species. Nano-Se in the holding solution improved vase life in all cases, besides one carnation cultivar. The optimal concentration was considerably higher in carnation as compared to rose (1–1.5 and 0.25–0.75 µM, respectively), and was cultivar dependent. Nano-Se improved cut flower water balance by enhancing water absorption more than transpiration. In the second experiment, the optimal holding solution nano-Se concentration was employed to evaluate the underlying processes in the two cultivars per species, where vase life was mostly increased. Physiological and biochemical characteristics were assessed in both leaf and petal tissues. Nano-Se ameliorated chlorophyll degradation, electrolyte leakage and lipid peroxidation owing to up-regulation of both enzymatic and non-enzymatic antioxidants. In conclusion, the nano-Se-induced vase life extension was associated with both upgraded antioxidant status and improved water relations, setting it as a low-cost and environmentally-safe agent of prolonging floral longevity.