ISSN:
1365-3040
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
Abstract. The effect of SeO3 and SeO4 on NO3 assimilation in 8-d-old barley (Hordeum vulgare L.) seedlings was studied over a 24-h period. Selenite at 0.1 mol. m− in the uptake solutions severely inhibited the induction of NO3 uptake and active nitrate reductases. Selenate, at 1.0 mol m−3 in the nutrient solution, had little effect on induction of activities of these systems until after 12 h; however, when the seedlings were pretreated with 1.0 mol m−3 SeO4 for 24 h, subsequent NO3 uptake from SeO4-free solutions was inhibited about 60%. Sulphate partially alleviated the inhibitory effect of SeO3 when supplied together in the ambient solutions, but had no effect in seedlings pretreated with SeO3. By contrast, SO4 partially alleviated the inhibitory effect of SeO4 even in seedlings pretreated with SeO4. Since uptake of NO3 by intact seedlings was also inhibited by SeO3, the percentage of the absorbed NO3 that was reduced was not affected. By contrast, SeO4, which affected NO3 uptake much less, inhibited the percentage reduced of that absorbed. However, when supplied to detached leaves, both SeO3 and SeO4 inhibited the in vivo reduction of NO3 as well as the induction of nitrate reductase and nitrite reductase activities. Selenite was more inhibitory than SeO4; approximately a five to 10 times higher concentration of SeO4 than SeO3 was required to achieve similar inhibition. In detached leaves, the inhibitory effect of both SeO3 and SeO4 on in vivo NO3 reduction as well as on the induction of nitrate reductase activity was partially alleviated by SO4. The inhibitory effects of Se salts on the induction of nitrite reductase were, however, completely alleviated by SO4. The results show that in barley seedlings SeO3 is more toxic than SeO4. The reduction of SeO4 to SeO3 may be a rate limiting step in causing Se toxicity.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-3040.1990.tb01093.x
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