Genotypic Variation in the Thickness of Silica Deposition on Flowering Rice Spikelets

Abstract

Silicon may play an important role in regulating the transpiration rate of rice (Oryza sativa L.), particularly cuticular transpiration. The control of cuticular transpiration is important in rice spikelets because water stress at anthesis may severely disrupt fertility and grain yield. Data on the quantitative variation among rice cultivars in the thickness of the silica layer of the flowering spikelet were obtained in order to assess the potential for genetic selection for silica layer thickness as a potential means for increasing spikelet resistance to water loss. Flowering spikelets were collected from 17 genotypes and thickness measurements were made of the major anatomical layers in cross section. The silica layer of the lemma varied from 4·2 to 17·7 μm among cultivars. Similar variation was observed in the palea. Differences among cultivars were also found in the thickness of the epidermis and sclerenchyma-parenchyma layer. The total cross-sectional thickness of the lemma and palea averaged slightly over 100 μm. Total thickness was not significantly correlated with the length, width or product of length × width. Thickness of silica deposition was significantly correlated with spikelet length × width suggesting that these easily measured parameters may be useful in screening for silica thickness.