The involvement of silicon deposition in salinity-induced white head in rice (Oryza sativa L.)

White heads and silicon deposition in spikelets were observed in three rice varieties (IR28, IR4595-4-1-13 and Mangasa), which were different in vulnerability to white heads under salinity conditions. Plants were grown in three-liter pots with two nitrogen fertilizer levels (HN: high nitrogen and LN: low nitrogen) and subjected to salinity by submerging the soil in a 100mM sodium chloride solution from booting to seven days after panicle emergence. White heads occurred in IR4595-4-1-13 and Mangasa but not in IR28 under the salinity condition, and the vulnerability to white heads was higher with the HN treatment than the LN treatment. Silicon deposition in spikelets, measured by energy-dispersive X-ray analysis with a scanning electron microscope, was correlated to the vulnerability to white heads. White heads inhibited flower opening and thus induced high sterility. It was concluded that low silicon deposition in spikelets was responsible for the occurrence of white heads under salinity conditions in rice.