Methane delays the senescence and browning in daylily buds by re-established redox homeostasis.

BACKGROUND: During the postharvest senescence of fruits and vegetables, redox imbalance occurs. Although the release of methane (CH4 ) has been observed for a long time and its antioxidant properties have recently been demonstrated in animals and plants, the corresponding physiological role of CH4 in regulating plant senescence has not yet been elucidated. RESULTS: Our results indicate that the postharvest deterioration of daylily buds during storage is greatly ameliorated by the exogenous application of CH4 , particularly in the inhibition of tissue browning. The results are supported by a decrease in the degree of browning and by the corresponding phenotype, which are correlated with the suppressed polyphenoloxidase activity. CH4 also maintains the re-establishment of redox balance, as indicated by the lower relative leakage rate, lipid peroxidation level, and reactive oxygen species accumulation in daylily buds. Furthermore, the decrease of the unsaturated/saturated fatty acid ratio and energy charge during storage was also attenuated. CONCLUSION: These results clearly suggest that the postharvest treatment with CH4 is an effective means of prolonging the storage life of daylily buds. © 2017 Society of Chemical Industry.

Signal regulation involved in sulfur dioxide-induced guard cell apoptosis in Hemerocallis fulva.

Chronic and acute exposure to SO2 is associated with increased risks of various damages to plants. In the present study, epidermal strip experiment was employed to investigate SO2-induced guard cells apoptosis and the signal regulation in Hemerocallis fulva. The results showed that with the increase of treatment concentrate of SO2 derivates (a mixture of sodium sulfite and sodium bisulfite, 3:1, mmol L⁻¹/mmol L⁻¹, 1.0-5.0 mmol L⁻¹), the physiological activity of the guard cells declined and cell death occurred. While the concentration of SO2 derivatives exceeded 2.0 mmol L⁻¹, the percentage of cell death increased significantly (P<0.05). Typical features of apoptosis including nuclear condensation, nuclear elongation, fragmentation etc. were found. Meanwhile, concomitant presence of nitric oxide (NO), reactive oxygen species (ROS) and Ca²âº level increment appeared. However, SO2-induced cell death can be effectively blocked by either of the following substances with their respective optimal concentrations: antioxidant ascorbic acid (Asc; 0.05 mmol L⁻¹) or catalase (CAT; 200 U mL⁻¹), nitric oxide (NO) scavenger 2-(4-carboxyphenyl)-4, 4, 5, 5- tetramethylmidiazoline-1-oxyl-3-oxide (c-PTIO; 0.20 mmol L⁻¹), nitrate reductase inhibitor NaN3 (0.20 mmol L⁻¹), Ca²âº chelating agent EGTA (0.05 mmol L⁻¹) or plasma membrane Ca²âº channel blocker LaCl3 (0.05 mmol L⁻¹). In addition to a significant decrease in cell death rate, a reduction in the levels of reactive oxygen species (ROS), NO and Ca²âº was observed. Further study showed that compared to treatment with SO2 alone, Asc treatment led to a decrease in NO and Ca²âº levels and NaN3 treatment led to a decrease in ROS and Ca²âº levels, but the NO and ROS levels of the LaCl3 treatment changed little. All results suggested that NO, ROS and Ca²âº were involved in the apoptosis induced by SO2 in H. fulva. The process might be related to the burst of NO or ROS, which would activate the plasma Ca²âº channel and result in the increase of intercellular Ca²âº.