M.-J. Tseng’s research while affiliated with National Chung Hsing University and other places

Plantlets of wax apple (S. samarangense) propagated from cuttings were used to study changes in protein synthesis in roots under different flooding durations. Root tips of plantlets were labelled with ³⁵S-methionine, and the polypeptide patterns were analysed using two-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and fluorography. Labelling patterns of non-flooded controls and specimens of different flood durations (12, 24, 72 and 120 hours of flooding) were similar. Approximately, 200-300 polypeptides could be discerned. However, there were differences in individual polypeptides among the various flood treatments. Compared to the polypeptide profile of non-flooded controls, there were 15, 20, 12 and 16 enhanced polypeptides and 5, 9, 11 and 5 repressed polypeptides in 12, 24, 72 and 120 hours of flood treatments, respectively. Changes in polypeptides among treatments were classified into five groups. Group 1 proteins were those that were enhanced or repressed only at certain flooding durations. Group 2 proteins were those that remained enhanced or repressed for 12 or 48 hours. Group 3 proteins were those unique to flooding stress. Group 4 proteins comprised those that remained constant under aerobiosis and flooding stress, and group 5 proteins were those unique to the aerobic environment.

The present study associates the response to flooding of potted wax-apple trees, Syzygium samarangense Merr. et Perry, with changes in carbon and nitrogen metabolism. In wax-apple leaves, the starch content conspicuously increased after 14 days of flooding, and the total nitrogen content decreased after 35 days of flooding. In roots, concentrations of total soluble sugars significantly increased after 14 days of flooding. The accumulation of starch in flooded, wax-apple leaves and increased soluble sugar content in roots apparently were the result of the reduction of growth and metabolic activities in roots after flooding, which reduced the sink demand of carbohydrates. Soluble protein concentration significantly decreased after 7 days of flooding, but remained similar among 14-, 28- and 42-day flooding treatments. Free amino acid content of flooded plants was significantly higher than that of the control at all sampling dates. The activity of glutamine synthetase in leaves significantly decreased after 7 days of flooding, but was higher than the control's at 14, 28 and 42 days of flooding. In wax-apple roots, content of soluble protein, free amino acids, ammonia and the activity of nitrate reductase and glutamine synthetase all decreased significantly after flooding. Apparently, nitrogen metabolism was restricted in the roots during flooded conditions.

The vegetative growth of the wax-apple (Syzygium samarangense Merr. et Perry) tree was correlated with its physiological responses under flooding stress. Container-grown wax-apple trees were treated with various intervals of flooding. Growth response of new shoot and root system as well as leaf gas exchange among various treatments were compared. The first flush growth of new shoots for the treatments of 14-42 days of flooding were significantly lower than those of the control. The shoots of 14-, 28-, and 42-day flooded plants started the second flush growth at the 37th, 44th, and 72nd day, respectively. The second flush growth of the 42-day treatment was significantly lower than that of non-flooding control, 14-, and 28-day flooded treatments. The root dry weights of 14-, 28-, and 42-day flooded plants were 78.5, 72.9, and 61.7% of the control, respectively. The stomatal conductances, CO2 exchange rates, and transpiration rates of wax-apple leaves had similar variation trends during flooding. Their values decreased after 24 h of flooding but returned to the level of the control after 14 days of deflooding, while the internal CO2 concentration in leaves remained similar. Oxygen consumption rates of fibrous roots of 7-, 14-, 28-, and 42-day flooded plants were lowered to 64, 53, 47, and 46% of the level of the control, respectively.

The wax-apple [Syzygium samarangense (BI.) Merr. and Perry] is a vigorous tropical fruit tree species that has five to six growth flushes per year. One-year-old, root-bearing wax-apple trees were grown in different-sized containers filled with potting mixture to test if container volume restricts shoot and/or root growth and thereby lends itself to forcing culture. The trunk cross-sectional area (TCSA) at 15 cm above the soil was measured to assess vegetative growth. After 6 months, the TCSA had increased quadratically with container volume. At the end of the first and second year, leaf count, leaf area, leaf dry mass, stem dry mass, shoot dry mass, and root dry mass were positively correlated with container volume. However, the shoot: root ratios remained fairly constant among treatments during the experimental period. Thus, root restriction is an effective means of reducing shoot and root growth of the wax-apple.