EFFECTS OF ETHYLENE ON RUDIMENTARY LEAF AND PANICLE PRIMORDIUM IN LITCHI: ANTIOXIDANT ENZYMES, HYDROGEN PEROXIDE AND NITRIC OXIDE
The floral bud of litchi (Litchi chinensis Sonn.) is a mixed bud that consists of leaf primordia, rudimentary leaves and panicle primordia. From field observations, the fate of the mixed bud is largely dependent upon environment. If litchi plants are exposed to high temperatures, the rudimentary leaves may develop to fully expanded leaves and the axillary panicle primordia may cease to develop and shrink. Suppressing the development of the rudimentary leaves by spraying with ethephon encourages panicle development. In this study, litchi trees at the panicle primordia emergence stage were transferred to a controlled environmental growth chamber at 28/23°C (day/night temperature, 12 h day and 12 h night) to induce a leafy panicle. Ethephon at a rate of 200 mg/L was sprayed onto the trees to suppress the growth of the rudimentary leaves in the panicles. All the elongating but unexpanded leaves abscised in 8 d while the axillary panicle primordia continued to develop. Before the rudimentary leaves abscised, leaves and panicle primordia were sampled for the determination of antioxidant enzymes, hydrogen peroxide (H2O2) and nitric oxide activity (NO). H2O2 and NO imaging indicated that H2O2 and NO levels were both higher in the apical dome of the buds, the petioles and the stems in ethylene-treated trees than in control trees. Ethylene treatment also increased the activities of superoxide dismutase (SOD) and peroxidase (POD) in both the rudimentary leaves and the panicle primordia. However, the treatment did not significantly increase the activity of ascorbate peroxidase (APX) in rudimentary leaves but did significantly increase it in panicle primordia. POD activity in panicle primordia was much lower than that in rudimentary leaves. The results suggested that the senescence and abscission of the rudimentary leaves promoted by ethylene might be related to the increase in POD, H2O2 and NO. The continuous development of the panicle primordia which also had high levels of H2O2 after ethephon treatment, might be related to the low level of POD activity in the primordia and the increase in the activity of APX, a scavenger of H2O2.
Biyan Zhou, , Huang, X., Chen, H., Shu, W., Hu, Z., Liu, W., Xiang, C. and Zhang, S. (2013). EFFECTS OF ETHYLENE ON RUDIMENTARY LEAF AND PANICLE PRIMORDIUM IN LITCHI: ANTIOXIDANT ENZYMES, HYDROGEN PEROXIDE AND NITRIC OXIDE. Acta Hortic. 975, 247-254
antioxidant enzyme, hydrogen peroxide, litchi, nitric oxide, panicle primordium, rudimentary leaf