[Effects of silicon supply on diurnal variations of physiological properties at rice heading stage under elevated UV-B radiation].

A pot experiment was conducted to investigate the effects of silicon( Si) supply on diurnal variations of photosynthesis and transpiration-related physiological parameters at rice heading stage under elevated UV-B radiation. The experiment was designed with two UV-B radiation levels,i. e. ambient UV-B( ambient,A) and elevated UV-B( elevated by 20%,E),and four Si supply levels,i. e. Si0( control,0 kg Si O2·hm-2),Si1( sodium silicate,100 kg Si O2·hm-2),Si2( sodium silicate,200 kg Si O2·hm-2),Si3( slag fertilizer,200 kg Si O2·hm-2). The results showed that,compared with ambient UV-B radiation,elevated UV-B radiation decreased the net photosynthesis rate( Pn),intercellular CO2concentration( Ci),transpiration rate( Tr),stomatal conductivity( gs) and water use efficiency( WUE) by 11. 3%,5. 5%,10. 4%,20. 3% and 6.3%, respectively,in the treatment without Si supply( Si0level),and decreased the above parameters by 3. 8%-5. 5%,0. 7%-4. 8%,4. 0%-8. 7%,7. 4%-20. 2% and 0. 7%-5. 9% in the treatments with Si supply( Si1,Si2 and Si3levels),respectively. Namely,elevated UV-B radiation decreased the photosynthesis and transpiration-related physiological parameters,but silicon supply could obviously mitigate the depressive effects of elevated UV-B radiation. Under elevated UV-B radiation,compared with control( Si0level),silicon supply increased Pn,Ci,gsand WUE by 16.9%-28. 0%,3. 5%-14. 3%,16. 8%-38. 7% and 29. 0%-51. 2%,respectively,but decreased Trby 1. 9%-10. 8% in the treatments with Si supply( Si1,Si2 and Si3levels). That is,silicon supply could mitigate the depressive effects of elevated UV-B radiation through significantly increasing Pn,Ci,gsand WUE,but decreasing Tr. However,the difference existed in ameliorating the depressive effects of elevated UV-B radiation on diurnal variations of physiological parameters among the treatments of silicon supply,with the sequence of Si3!Si2!Si1!Si0. This study suggested that fertilizing slag was helpful not only in recycling industrial wastes,but also in effectively mitigating the depressive effects of elevated UV-B radiation on photosynthesis and transpiration in rice production.