ReviewAdvances in application of small molecule compounds for extending the shelf life of perishable horticultural products: A review
Graphical abstract
Introduction
In recent times, customers pay more attention to the nutritional value and original quality of harvested horticultural products. Eating quality or ornamental value of horticultural products is largely dependent on preservation technology. Therefore, the application of new techniques to improve the postharvest quality of fresh-cut flowers, vegetables and fruits is urgently needed. Browning and other discolorations, tissue softening, surface dehydration, development of off-odours, water loss, as well as microbial spoilage are some of the common symptoms associated with deteriorating horticultural products (Rojas-Graü et al., 2009).
Many different kinds of molecules transmit information between the cells of multicellular organisms. These molecules are produced by signaling cells and subsequently bind to receptors in target cells, acts as ligands and chemical signals that travel to the target cells to coordinate responses (Jablonka, 1994). Over the past decade, the role of signaling molecules, such as nitric oxide (NO), hydrogen peroxide (H2O2), carbon monoxide (CO), hydrogen sulfide (H2S) and hydrogen gas (H2), have been extensively studied for their wide biological applications. A large number of papers on CO and H2S were published during the last century, but these studies were related mostly to toxicological and environmental concerns (Wang, 2014). Gradually, it is also becoming clear that signaling molecule could regulate a variety of biological processes both in animals and plants. They are involved in numerous mammalian physiological processes, including the maintenance of blood pressure, relaxation of smooth muscle, inhibition of platelet aggregation and contraction of gastrointestines (Kovacic and Somanathan, 2011). In plants, those small molecules compounds have been linked to a range of physiological and developmental processes including endogenous ethylene biosynthesis, seed germination, root growth, stomatal closure, fruits and flower senescence. In addition, small molecule compounds are also involved in plants response to multiple environmental stresses, such as salinity, drought, heat stress and metal stress (Wang and Liao, 2016). The role of various signaling factors in plants responses to abiotic stresses is well studied through investigating their involvement in the regulation of the physiological processes. In recent years, it was shown that treatments with some low molecular mass compounds can extend the postharvest life of horticultural crops by regulating a variety of growth and developmental processes and through improving the resistance to abiotic and biotic stressful impacts (Guo et al., 2015).
Ripening of horticultural products is a complex and genetically programmed process that results in numerous physiological, biochemical, and structural changes. As influenced by endogenous and environmental factors, these changes are the result of the coordinated activation of multiple transcription regulatory and biochemical pathways. Flowers, fruits and vegetables are classified as climacteric or non-climacteric according to their ripening pattern, presence of a burst in respiration, and ethylene production during postharvest. In climacteric produce, ripening process is associated with increasing ethylene production and respiration. Small molecule compounds inhibit ethylene signal transduction pathway, thus, resulting in decreasing ethylene biosynthesis. However, in non-climacteric produce, ethylene plays a secondary role and signals that trigger most of the ripening pathways are unknown (Ghidelli and Perez-Gago, 2016). Thus, small molecule compounds may be beneficial in activation or inhibition of certain metabolic pathways during postharvest life of horticultural products.
The innovative use of molecules is indispensable for maintaining freshness and safety of fresh-cut flowers, fruits and vegetables and its significance in the horticulture industry cannot be over-emphasized. A few studies have demonstrated the effectiveness of these compounds when applied to different horticultural commodities (Soegiarto and Wills, 2004). But the postharvest life of cut flowers, fruits and vegetables is still being largely explored to better keep fresh by enhancing the nutritional value and original sensory quality. This review discusses the recent advances in the innovative use of small molecule compounds to maintain freshness and prolong postharvest life of horticultural products. An overview of studies on small molecule compounds crosstalk and the regulation of the expression of genes associated with senescence during postharvest life of horticultural products is also discussed.
Section snippets
Nitric oxide (NO)
NO, a highly reactive signaling molecule, has been linked to a range of physiological and developmental processes including endogenous ethylene biosynthesis, chlorophyll production, root growth, fluid loss, and in fruits and flower development (Qiao and Fan, 2008). Postharvest application of NO has been shown to effectively extend postharvest life of a range of flowers, fruits and vegetables by inhibiting the emission of ethylene (Liao et al., 2013).
It has also been shown that NO extends vase
Interaction between ethylene and gaseous compounds
Ethylene, as a pleiotropic plant hormone, has been known to initiate a variety of maturity processes and senescence. Ethylene is the naturally occurring plant gas and it causes premature senescence of both leaves and flowers. The pathway of endogenous ethylene production in plants has been adequately elucidated. Ethylene biosynthesis starts with DL-methionine, from which S-adenosyl-methionine (SAM) is synthesized by the action of SAM synthase. SAM is converted to 1-aminocyclopropane
Gaseous compounds regulating gene expression during postharvest freshness of horticultural products
The expression of most of genes has been found to be up-regulated during the senescence of horticultural products while some genes were also found to be down-regulated indicating that there exists a complex interplay between the expression patterns of various genes. In gladiolus, the expression of senescence associated genes (SAGs) viz., GgCyP1 was down-regulated, while GgDAD1 expression was up-regulated by NO treatment during the senescence process (Dwivedi et al., 2016) (Table 6). It is
Conclusion and perspectives
In recent years the postharvest handling of horticultural crops is becoming hot issue and there are some considerable work done in this area on different horticultural products. The role of molecules could be of great importance in postharvest preservation. Some signaling molecules, like NO, H2O2, CO and H2S, were once regarded as toxic substances. They are now mostly considered as small molecule compounds essential for multiple functions to control growth and development in both animals and
Acknowledgements
This research was supported by the National Natural Science Foundation of China (no. 31160398 and 31560563), the Key Project of Chinese Ministry of Education (no. 211182), the Research Fund for the Doctoral Program of Higher Education (no. 20116202120005), the Natural Science Foundation of Gansu Province, China (no. 1606RJZA073, 1606RJZA077, 1308RJZA179, and 1308RJZA262) and Feitian and Fuxi Excellent Talents in Gansu Agricultural University in Lanzhou, P. R. China.
References (92)
- et al.
Extending the postharvest life of carnations with nitric oxide–comparison of fumigation and in vivo delivery
Postharvest Biol. Tec.
(2003) - et al.
Post-harvest treatment with citric acid or hydrogen peroxide to extend the shelf life of fresh sliced mushrooms
Lwt-Food Sci. Technol.
(2000) - et al.
Control of lemon postharvest diseases by low-toxicity salts combined with hydrogen peroxide and heat
Postharvest Biol. Tec.
(2013) - et al.
Combined effects of aqueous chlorine dioxide and ultrasonic treatments on postharvest storage quality of plum fruit (Prunus salicina L.)
Postharvest Biol. Tec.
(2011) - et al.
Effects of aqueous chlorine dioxide treatment on enzymatic browning and shelf-life of fresh-cut asparagus lettuce (Lactuca sativa L.)
Postharvest Biol. Tec.
(2010) - et al.
Carbon dioxide-enriched atmospheres during cold storage limit losses from Botrytis but accelerate rachis browning of ‘Redglobe’table grapes
Postharvest Biol. Tec.
(2002) - et al.
Effects of aqueous chlorine dioxide treatment on browning of fresh-cut lotus root
Lwt-Food Sci. Technol.
(2009) - et al.
Effect of nitric oxide on pericarp browning of harvested longan fruit in relation to phenolic metabolism
Food Chem.
(2007) - et al.
Effect of sodium nitroprusside on differential activity of antioxidants and expression of SAGs in relation to vase life of gladiolus cut flowers
Sci. Hortic.
(2016) - et al.
Reactive oxygen species and antioxidant machinery in abiotic stress tolerance in crop plants
Plant Physiol. Bioch.
(2010)