Postharvest Physiology of Ornamentals: Processes and Their Regulation

The ornamentals industry is a very important agricultural sector. More than 90 countries are active in the floriculture world, with the global ornamental trade volume of cut flowers/foliage and potted plants currently reaching more than $130 billion USD per year. The postharvest quality of these ornamental products is mainly dependent on their visual value, where the consumer expects an attractive appearance for at least 7 days of vase life for cut flower/foliage bouquets, and at least 3 weeks for flowering/green potted plants under indoor conditions. To improve this ornamental industry and meet future postharvest quality requirements, there is a need for further research to get a better understanding of the mechanisms underlying the various physiological processes operating after harvest in these ornamental products. This research can lead to the development of new strategies for quality control of ornamental products during storage, transport, and vase/shelf life.

We have encouraged studies reflecting the latest scientific research findings dealing with various aspects of the postharvest physiology of cut ornamentals and green foliage, focusing on the following main topics: (1) The role and use of various plant hormones, sucrose, and other chemicals for postharvest handling and quality maintenance; (2) Adopting environmental friendly and sustainable strategies for improving the keeping quality and extending storage duration; (3) Links between biological processes and physiological functions after harvest.

The Special Issue comprises nine papers by authors from eight countries in Asia, Europe, and North and South America. They represent a wide range of aspects related to senescence processes, prolonged storage, quality maintenance, floral scent, and the use of plant growth regulators (PGRs) and various chemicals. The various ornamental systems included cut flowers of Lilium, Peony, Lisianthus, Orchids, Chrysanthemum, and Freesia, as well as cut foliage of Polygonatum multiflorum ‘Variegatum’, Phalaenopsis plantlets, and Chrysanthemum cuttings.

Senescence processes after harvest were investigated in cut flowers of Lilum [1], Peony [2,3,4], Lisianthus [5], and Mokara orchids [6], as well as in cut foliage of Polygonatum multiflorum ‘Variegatum’ [7]. Several authors studied the effects of various PGRs such as salicylic acid, gibberellin (GA₃) [1], ethylene [6] or 5-Aminolevulinic Acid (ALA) [7] on different senescence parameters in cut flowers of Lilium, Mokara orchid and cut foliage of Polygonatum multiflorum. These PGR treatments reduced the senescence and consequently improved the quality and extended the longevity of these ornamental systems, except for ethylene. Since ethylene is well-known as a senescence accelerator, its activity and biosynthesis inhibitors were found to reduce the senescence processes studied in cut flowers of the Mokara orchids [6].

Among the various chemicals used for quality maintenance, the use of nanosilver (NS) formulation should be emphasized as a relatively new compound for future use. Indeed, NS successfully reduced senescence and improved the quality of cut flowers of various Peony cultivars [2,4] and Lisianthus [5]. Silver is a well-known antibacterial agent that has been used for decades to prolong the vase life of flowers. However, all silver-containing compounds used thus far are toxic to the environment. Therefore, since NS is easy to prepare and shows relatively little environmental toxicity, it has become a common substance in postharvest treatments of cut plant material.

Several papers dealt with cut flowers of Peony [2,3,4], which are considered to be at the top of the list of the 20 most important cut flowers; however, their use is somewhat limited, as cut peonies are usually available only in local markets and for a short harvest time of 3–4 weeks. Therefore, their preservation for a longer time is very important. Treatments for the prolonged cold storage of cut Peony flowers were assessed [2,3], and it was determined that these treatments allowed them to be in storage for 16 weeks at −6 °C [3]. All these treatments successfully improved the keeping quality of these important cut flowers after transport.

Floral scent during vase life is an important quality for the marketing of ornamental plants; however, it is usually reduced after cold storage. Analysis of volatile organic compounds (VOCs) present in three fragrant cut flowers of high economic importance—Chrysanthemum, Lilium, and Freesia—confirmed that the concentration and abundance of these VOCs are not directly related to the human perception of floral scent [8]. This research can further contribute to satisfying consumer demands, by assessing the floral scent throughout the cold storage and vase life periods.

Finally, a model used in the agro-food sector to estimate the required properties of custom-made Equilibrium Modified Atmosphere Packaging (EMAP) has been validated for the first time for its applicability to floriculture products [9]. The model was applied to Phalaenopsis plantlets and Chrysanthemum cuttings, which represent the propagation material of two of the most important floriculture products, sold as cut flowers or potted plants. The successful model can be further used to estimate the dynamic oxygen consumption rate profile during the storage and transport of various products.

Taken together, this set of original papers represents an essential contribution to our understanding of the processes controlling the quality of ornamental products after harvest, whilst suggesting environmentally friendly solutions for extending their attractive appearance.