Effect of Silicon Deficiency from Panicle Stage on Formation of Cell Fraction Containing Nucleus of Rice Spikelets

Inanaga Shunji, Sakashita Kotomi, Sameshima Hirotaka, Chen Nengchang, Chishaki Naoya

doi:10.20710/dojo.78.1_7

We attempted to clarify existing forms of silicon in cells of rice plant spikelets before heading. Plants were grown with and without silicon addition from the panicle stage, and spikelets were harvested 10 and 5 days before heading and on the day of heading. The spikelets homogenized in cold water were filtered by nylon mesh, and the filtrate was centrifuged first at 600×g for 10min, and then at 10,000×g for 30min. The residue on the nylon mesh was referred to as F1 fraction, the precipitate from centrifugation at 600×g was F2, the precipitate from 10,000×g as F3 and its supernatant as F4. The main organ of F1 was the cell wall, while that of F2 was the nucleus. After freeze drying, the weight of each fraction and its silicon content were determined ; UV and IR spectra of higher molecular nucleic acids (HMNA) from the nucleus, and the IR spectra of residue extracted the HMNA were recorded. Ten days before heading, there was no significant difference in weight of any fraction outside the F2 fraction among the treatments, but it was greater in the higher silicon spikelets at each day than in the lower ones. The level of silicon in the F2 fraction in every treatment was the same as, or more than, that in the cell wall, and was higher than in other fractions. The level of silicon in the HMNA was slightly more in the higher compared with lower silicon level, while that in the extracted residue was lower in low silicon spikelets, indicating that silicon in the nucleus fraction contains more in the HMNA than in the extracted residue. A bathocromic effect in UV spectra, namely the shifting of the absorption maximum to a longer wavelength, and absorbance bands at 1208, 1137 and 810cm^<-1> in the IR spectra, suggesting the existence of Si-OCH_3, were observed in the HMNA from higher silicon spikelets. While absorbance bands at 790 and 470cm^<-1> in the IR spectra were found in the residue extracted from the HMNA from F2 fraction with silicon supply, there was no peak at 1090cm^<-1> indicating silica gel. These findings suggest that silicon may play an important role in the formation of the nucleus through association with nucleic acid, and as a result, a decrease in the number of spikelets occurs through silicon deficiency in rice plants.

Effect of Silicon Deficiency from Panicle Stage on Formation of Cell Fraction Containing Nucleus of Rice Spikelets

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