Silicon has versatile functions in plant biology, especially in plant defense and tolerance to both biotic and abiotic stressors. In this study, it was investigated if silicon could reduce the toxic effect of aluminum on rice. Aluminum was applied to OM4900 rice seedlings, and then their growth and sugar metabolism were determined. At doses of aluminum chloride of 100 and 200 µM, plant height was significantly enhanced and root elongation was reduced. The accumulation of photosynthetic pigments was tightly correlated with the aluminum concentration showing highest amounts at 400 µM. Sugar levels in roots and endosperm decreased upon aluminum addition. Aluminum toxicity in rice seedlings was relieved by addition of silicon in the form of sodium silicate. In the presence of 200 µM aluminum chloride, the addition of 100 mg/L sodium silicate to the hydroponic solution showed no contribution to plant growth or buildup of photosynthetic pigments. At this concentration, root development was not affected while it was at higher concentrations. Sodium silicate addition did not alter the reduction in sugar levels by aluminum. The presence of 200 µM aluminum chloride with or without sodium silicate in the growing solution significantly decreased silicon content in rice husks.

Vitamin E is an important oxidant for both plant and animal and a lipid soluble vitamin which occurs naturally in edible plant oils and able to be synthesized by oxygenic bacteria. Besides, cooking oils and edible oil containing seeds, human can intake vitamin E via pharmaceutical products. With simply spectral method, vitamin E contents in tablets were quantified easily during storage. Vitamin E levels in medical products sold on Vietnamese market varied among producers ranging from 15 mg up to about 360 mg/tablet. Vitamin E in eight selected products was degraded gradually with prolonged storage time but much more rapidly in scatter light exposure condition than in the dark. The more vitamin E in the tablets, the quicker degradation occurred. Tablets exposed to natural sun light or UV source depleted vitamin E significantly within 5 h, approximately 50% for both lighted conditions. There was a relatively high tight correlation (R 2 = 0.8266) between tablet price and its vitamin E content. Customer should buy the higher price products rather than the cheaper ones to get sufficient amount of vitamin E. Pharmaceutical vitamin E products should be used up soon after being bought or kept away any light sources.

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SUMMARYRice production in the Mekong Delta, Vietnam is threatened by future water scarcity caused by changing rainfall patterns and increasing irrigation costs. To improve resilience of the triple rice farming system to future climate-related stresses, profitability needs to be increased through water use efficiency, fertilizer management and planting methods.During four cropping seasons in 2011–13, alternate wetting and drying (AWD) irrigation was applied in the triple rice production area within An Giang Province, Vietnam. An issue with the application of AWD is the prevalence of acid sulphate soils in the Mekong Delta. Three types of irrigation management were tested; continuously flooded (CF) where the water in the paddy was maintained at 5 cm; AWD where the water level was allowed to fall to 15 cm below the ground surface, at which point the field was irrigated until the water level was at 1 cm above the ground surface (designated −15 cm); AWD where the water level was allowed to fall to 30 cm below the ground surface before irrigation until the water level was at 1 cm above the ground surface (designated −30 cm). Two further experiments were also undertaken which examined the planting method (transplant v. direct sowing) and phosphorus rate on rice yield. There was no effect on yield caused by P fertilizer rate and irrigation management in any year, and there was no significant effect on soil pH or salinity caused by irrigation management. Overall net profitability was greatest for the AWD treatments because of the reduction in pumping and labour costs in the dry season. Transplanted rice improved yields, but the labour cost reduced overall profitability. The study shows that AWD (−15 cm) can be safely applied in acid sulphate soil areas within the triple rice areas of An Giang Mekong Delta and saved at least 0·27 of total irrigated water quantity used during three of the six cropping seasons. The increased profitability of the AWD rice production system will help to improve the resilience of triple rice cropping systems to future water scarcity.

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