Sucrose degradation in sink and source poplar leaves treated with sulfite

Abstract

Sulfite at concentrations from 0.5 to 5.0 mM was supplied to illuminated, detached poplar (<em>Populus deltoides</em> Bartr. ex Marsh) leaves via the transpiration stream. Concentrations of chlorophyll <em>a</em> and <em>b</em>, carotenoids, glucose, fructose, sucrose and starch, and extractable specific activities of sucrose synthase (SuSy), acid invertase (AI) and neutral invertase (NI) were measured. In sink and source leaves chlorophylls and carotenoids appeared to be increased by sulfite at concentrations ranging from 0.5 to 5.0 mM. In source leaves the application of 5.0 mM and ≥ 2.5 mM sulfite led to a decrease in total nonstructural soluble sugars (sTNC) and starch, respectively. The specific activity of SuSy was enhanced by ≥ 0.5 mM sulfite. There was only a slight decline in the activity of Al and N1.In sink leaves sTNC decreased and starch increased under the influence of sulfite at concentrations ≤ 1.O mM and ≥ 0.5 mM, respectively. The effect of sulfite on the activity of At, NI and SuSy was negligible. However, in both development groups of leaves alterations in sucrose, glucose and fructose contents were observed. On the basis cf the obtained results we postulate that sulfite changes the sucrolytic activities primarily in source leaves and only marginally in sink leaves

Effect of SO2 on sugars, indicators of Maillard reaction, and browning in dried apricots during storage

“…The enzyme degrading the sucrose in SDAs could be invertase due to its high stability against SO 2 and the suitable pH of the samples for this enzyme . Similarly, Lorenc‐Plucinska et al . reported that total sucrolytic activities (acidic invertase activity + neutral invertase activity + sucrose synthase activity) in poplar leaves increased by increasing SO 2 concentration.…”

“…Before storage, the SO 2 concentrations of the samples were 451, 832, 1594, 2112 and 3241 mg kg −1 ( Table 1). To reach the targeted SO 2 concentrations, except for 3241 mg kg −1 , the same amount of apricots (125 kg) was exposed to the same amount of SO 2 gas (300 g) for different times (30,45,180 and 360 min, respectively). However, when 300 g SO 2 gas was used, the SO 2 concentration of the apricots could not have reached approximately 3000 mg kg −1 , which represents the SO 2 concentration in SDAs stored for at least 1 year in Malatya.…”