# Molecular Hydrogen: The Postharvest Use in Fruits, Vegetables and the Floriculture Industry
## 4 Use of H\({}_{2}\) for the Floriculture Industry  
As with fruits and vegetables, hydrogen treatment can be applied to flowers postharvest, therefore such treatments may be of interest to the floriculture industry. A range of flowers and treatments have been studied, as exemplified by the data in Table 2.  
Flowers are relatively easy to treat, once cut. HRW or HNW can simply be added to the feedwater in the vase, or the atmosphere can be gassed if flowers are being kept in a closed container. Donor molecules can also be used with relative safety as long as the flowers are not for human consumption. The global market for cut flowers was approximately USD 34,347 million in 2019 [41], and it has been estimated that it will increase to USD 49,000 million by 2028. It has been reported that \"flowers are vulnerable to large post-harvest losses\" and therefore there \"arises the need for the appropriate post-harvest handling technologies\" [42]. The market for flowers demands that they look good and last for a long period once purchased. There is, therefore, a need for flowers to be maintained in good condition for transport, storage, and in their final place of display. Even in a domestic setting it would be possible for individuals to treat feedwater with donors or treatments which release H\({}_{2}\) into solution, such as those based in magnesium. The question that needs to be asked is: Is there any real benefit in using H\({}_{2}\) treatments? \begin{table}
\begin{tabular}{l l l l} \hline \hline  
[PERSON] et al. [36] found that the use of HRW, at concentrations of 0.5% and 1%, increased the vase life and flower diameter of cut lilies (_Lilium_ spp.). They also found that HRW (50%) had a similar effect in rose (_Rosa hybrid_ L.). The content of leaf malondialdehydedehyde in the leaves of lily decreased, which is a sign of lowered oxidative/nitrosative stress, and this data matched the fact that HRW increased the activity of antioxidant enzymes in both lily and rose. [PERSON] et al. [37] studied the effects of HRW on carnations (_Dianthus carophyllus_), with similar studies being more recently reported [19; 38]. These latter reports used magnesium hydride as a donor or HNW, respectively. In the first of these studies, the use of MgH\({}_{2}\) could be enhanced by the inclusion of citrate to the buffer, prolonging the release of H\({}_{2}\) to the flowers. Under such treatments the flowers had a prolonged shelf life. Hydrogen sulfide (H\({}_{2}\)S), a known signaling molecule in plants [43] (and animals [44]) was shown to increase in the plants, and a H\({}_{2}\)S scavenger, hypotaurine, reversed the effects. Further, it was said that the redox status of the cells was reestablished, and the gene expression of _DcbGal_ and _DcGSTI_, both associated with senescence, was reduced. Overall, the authors concluded that the MgH\({}_{2}\)/citrate mix had a positive effect on the flowers and the mechanism was mediated by H\({}_{2}\)S signaling. In the second study [38], HNW was used, which the authors said prolonged the time that the H\({}_{2}\) was dissolved in the water and therefore gave longer treatment times. It was found that 5% HNW significantly increased the vase life of the flowers. This treatment lowered the activity of nucleases and proteases in the plant tissues, which also showed lower ROS and less oxidative stress. [PERSON] et al. [39] looked at lisianthus (_Eastoma grandiflora_) and concluded that the treatment with H\({}_{2}\) maintained the flowers, with the effects mediated by the maintenance of the cellular redox status. 2,6-dichlorophenol(DCPIP) was used as a possible H\({}_{2}\) inhibitor, although DCPIP is a relatively generic redox acceptor; it is commonly used in redox experiments. The authors comment that upon H\({}_{2}\) treatment, the flower tissues had reduced lipid peroxidation and increased activity of a range of antioxidant enzymes, such as CAT, SOD and APX. Finally, [PERSON] et al. [40] looked at the effects of HRW in relation to the action of NO in lily (_Lilium_ \"Manissa\").