Leaf yellowing, an indicator of senescence, reduces commercial value of Chinese flowering cabbage after harvest. Hydrogen peroxide (H2O2) plays a dual role in mediating plant stress responses, but it is not clear whether and how it affects leaf senescence when exogenously stimulating the plants before harvest. Here, we found that preharvest application with low concentrations of H2O2 to root delays leaf senescence. Around 10 mM H2O2 reduced leaf yellowing rate by 8.2 and 26.4% relative to the control following 4 and 8 days storage, respectively. The H2O2-treated cabbages showed higher chlorophyll and lower relative expression of senescence-associated gene (SAG) BrSAG12 than the control. Proteomic analysis revealed 118 and 204 differentially expressed proteins (DEPs) in H2O2-treated plants at 4 and 8 days of storage, respectively. The main DEPs are involved in chlorophyll degradation and synthesis, water deprivation, antioxidant activity, and protections on chloroplast membranes. Decline of water loss in H2O2-treated cabbages was coincide with increase of proline contents and modulation of leaf stomatal aperture. Alleviation of oxidative stress was indicated by suppression of respiratory burst oxidase homolog and upregulation of reactive oxygen species (ROS) scavenging-related genes. These results were also supported by the alleviation of lipid peroxidation and the protections on cell integrity and photochemical efficiency in H2O2-treated group. Collectively, preharvest H2O2 treatment alleviates water loss and activates antioxidant defense system, protects chloroplast membrane from oxidative damage, and ultimately delays leaf senescence during storage. This study provides novel insights into the roles of H2O2 for regulating leaf senescence of Chinese flowering cabbage.
Chinese flowering cabbage is prone to senescence and
yellowing
after harvest, leading to a huge postharvest loss. Nitric oxide (NO)
is a multifunctional plant growth regulator, but the effect of preharvest
application of NO on the storage quality of Chinese flowering cabbage
remains unclear. Preharvest application of 50 mg L–1 sodium nitroprusside (SNP, a NO donor) to the roots obviously reduced
leaf yellowing in Chinese flowering cabbage during storage. Proteomic
analysis reveals 198 differentially expressed proteins (DEPs) in SNP-treated
plants compared to the control. The main DEPs were significantly enriched
in chlorophyll metabolisms, phenylpropanoid synthesis, and antioxidant
pathways. SNP treatment enhanced chlorophyll biosynthesis and suppressed
chlorophyll-degradation-related proteins and genes. It also modulated
flavonoid-biosynthesis-related genes, and 21 significantly regulated
flavonoids were identified in SNP-treated plants. The enhanced antioxidant
capacity in SNP-treated plants was able to decrease chlorophyll catabolism
by inhibiting peroxidase-mediated chlorophyll bleaching. Collectively,
preharvest SNP treatment modulated chlorophyll metabolism and preserved
chlorophyll content in leaves during storage. Moreover, SNP treatment
enhanced flavonoid synthesis, suppressed reactive oxygen species accumulation,
and delayed the senescence process, thereby maintaining leaf greening
in Chinese flowering cabbage. These findings highlight the role of
exogenous NO in alleviating yellowing of leafy vegetables.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.