Oxidative injury and antioxidant responses were investigated in two banana genotypes (Musa AAA 'Berangan' and Musa AA 'Mas') subjected to 40 % PEG-induced water stress. PEG treatment resulted in oxidative injury, as expressed in increased lipid peroxidation and reduced membrane stability index, in both cultivars; however, greater oxidative injury was detected in 'Mas'. Under PEG treatment, catalase activity and glutathione reductase activity were enhanced in both cultivars, but were higher in 'Mas'. Ascorbate peroxidase activity was enhanced in 'Berangan' under water stress, but was unaffected in 'Mas'. Meanwhile, superoxide dismutase activity was inhibited in both cultivars under water stress, but higher activity was detected in 'Berangan'. Higher ascorbate peroxidase and superoxide dismutase activities were associated with greater protection against water stress-induced oxidative injury.Additional key words: oxidative stress, ascorbate peroxidase, superoxide dismutase, glutathione reductase, catalase, lipid peroxidation.

The net primary productivity of Bruguiera parviflora dominated mangrove forest at Kuala Selangor, Malaysia was estimated from the average yearly biomass increment and litter production. The average yearly biomass increment in saplings and trees was 0.58 and 16.51 t ha À1 , respectively, and the annual amount of total litter production was 10.35 t ha À1 . The biomass increment in saplings and trees was not significantly different (t-test, p > 0.05) in 2 successive years and the estimated net primary productivity was 27.44 t ha À1 year À1 . The ratio (2.65:1) of net primary productivity and litterfall suggests that this mangrove forest is at a juvenile stage. #

Oysters Isognomon alatus containing high concentrations of Zn, Cu, Pb and Cd were collected from the Sepang Besar River, and transferred to the Sepang Kecil River where the native oysters contain low metal concentrations. Concentrations of heavy metals in oysters were measured monthly over six months. The concentrations of all metals decreased significantly ( p<0.05) for Cd 87%, Pb 83%, Cu 78%, and Zn 59%. In addition, metal depuration in oysters was investigated under laboratory conditions. Oysters were exposed to 100 mg g À1 of metals for two weeks followed by one week of depuration. Our studies suggest that metals in oysters tend to be lost in the order, Cd>Pb>Cu>Zn. A comparison between laboratory and field data showed that depuration of metals under the laboratory conditions is significantly faster than in the field.

Field experiments were conducted to measure the accumulation of heavy metals (Zn, Cu, Pb, Cd) in oysters Isognomon alatus transferred from the Sepang Kecil River (clean area) to the Sepang Besar River (polluted area), for a period of 6 months. Oysters were placed in an area near an effluent from pig farm. There were increase in all metals studied in the oysters introduced to the Sepang Besar River. The metals accumulated by transplanted oysters indicated chronic pollution by metals from the pig farm effluent. A significant difference was found between the accumulation rate of Zn and accumulation rates of the Cu, Pb and Cd. Accumulation rates of metals by oysters under field conditions were found to be 42.70, 1.77, 0.95 and 0.84 mg g À1 month À1 for Zn, Cu, Pb and Cd, respectively. It was also found that oysters have abilities to regulate their internal concentrations of metals over a range of external metal concentrations.

Unsynchronized flowering behavior and low fruit set are phenomenon that resulted in low production of mango fruit. The effects of a chemical inducing substance, potassium nitrate (KNO3), on enhancement of flowering on the mango clone 'Chok Anan' (MA 224) and, ultimately, the fruit production were studied. Initially, 12-month-old and 5-year-old mango trees were sprayed with 1%, 2%, and 5% KNO3. The 5-year-old mango trees showed earlier flowering and higher fruit set with 2% KNO3 followed by 5% and 1% KNO3. However, only 1% KNO3 initiated flowering on young mango trees. In conclusion, the flowering response to KNO3 depends on the age of tree.