Selenium Distribution and Translocation in Rice (Oryza sativa L.) under Different Naturally Seleniferous Soils

Abstract

Selenium (Se) accumulation in plant foods may be providing dietary Se to minimize the health problems related to Se deficiency. In this study, rice plants were cultivated in different naturally seleniferous soils (0.5–1.5 mg Se kg−1). Se concentration in rice plant tissues was analysed, and the distribution and translocation of Se in rice were also studied. The effect of exogenous Se on yield and Se concentration in rice grain was also investigated by spraying Na2SeO3 (15 mg L−1, 15 g ha−1). Results show that Se concentration in root, straw and grain of rice was increased with increased concentrations of Se in seleniferous soils. The root accumulated higher Se than straw and grain under the same naturally seleniferous soil. Spraying Se significantly increased Se concentration in grain, hull, brown rice and polished rice compared with spraying water. Se concentration in the grain fractions was in the following order: Bran > brown rice > whole grain > polished rice > hull. About 13.7% Se in wholegrain was discarded by milling process if about 6.9% of it was polished as bran. Se-enriched rice could be produced in naturally seleniferous soils with Se concentration from 0.5 to 1.0 mg kg−1, and this polished rice would provide enough Se (60–80 μg day−1) to satisfy the human requirement. Therefore, naturally seleniferous soils may be an effective way to produce Se-enriched rice without spraying Se fertilizer, which will be more economically feasible and environmentally friendly for without exogenous Se added to the soils or plants. However, the polished rice and brown rice, produced by spraying Na2SeO3 (15 g ha−1) or grown in soil with total Se upto 1.5 mg kg−1 was not suitable for daily human consumption, unless diluted with Se-deficient rice to meet the standard (≤0.3 mg Se kg−1). This study imparted a better understanding of the utilization of seleniferous soils and Se-enriched rice for human health and food safety.

Effects of Selenium Fertilizer Application on Yield and Selenium Accumulation Characteristics of Different Japonica Rice Varieties

“…Hu et al [43] reported that when adding exogenous selenium to make the soil selenium concentration reach 0.5 and 1.0 mg Se kg −1 , no changes are found in the weight of rice roots, straw and grains. Similar results were reported by Shen et al [14], who confirmed that foliar spraying of NaSeO 3 (0 and 15 mg L −1 ) would almost make no change to the rice yield. However, Zhang et al [44] indicated that while 50 g Se ha −1 of the selenite fertilizer was applied, the rice yield could significantly increase.…”

“…The content of N, P and K in the soil, the primary conditions of the experimental site and the variety and management measures could affect the yield of rice [41,42]. However, selenium may have a specific impact on rice yield [8,14,43,44]. For example, Boldrin et al [8] found that the rice yield would not be significantly affected by applying either selenate fertilizer or selenite fertilizer.…”

“…There is evidence [13] that compared with low-selenium soils, rice grown on high-selenium soils grains can accumulate more selenium. There are also research studies showing that the grains produced from natural selenium-rich soils (soil selenium content 0.5-1.0 mg kg −1 ) can meet people's daily demand for selenium (60-80 ug d −1 ) [14]. However, about 72% of the soil in China contains deficient selenium, and the selenium content of the plants growing on it is shallow [15].…”

“…Studies have shown that rice has the strong ability to enrich selenium [22,23], and the selenium fertilizer applied will lead to a significant rise in the selenium content of rice [14,20,24,25]. There are two types of selenium fertilizers applied to rice: soil application and foliar spraying [7,25,26].…”

“…China stipulates that the selenium content standard of seleniumenriched rice is 0.04 to 0.3 mg kg −1 according to the standard GB/T22499-2008 [35]. Many studies [8,14,36,37] indicate that rice grains will contain more selenium as the selenium fertilizer application increases. For producing safe selenium-rich rice, the amount of selenium fertilizer is significant.…”