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

Silicon may play an important role in regulating the transpirationrate of rice (Oryza sativa L.), particularly cuticular transpiration.The control of cuticular transpiration is important in ricespikelets because water stress at anthesis may severely disruptfertility and grain yield. Data on the quantitative variationamong rice cultivars in the thickness of the silica layer ofthe flowering spikelet were obtained in order to assess thepotential for genetic selection for silica layer thickness asa potential means for increasing spikelet resistance to waterloss. Flowering spikelets were collected from 17 genotypes and thicknessmeasurements were made of the major anatomical layers in crosssection. The silica layer of the lemma varied from 42 to 177µm among cultivars. Similar variation was observed inthe palea. Differences among cultivars were also found in thethickness of the epidermis and sclerenchyma-parenchyma layer. The total cross-sectional thickness of the lemma and palea averagedslightly over 100 µm. Total thickness was not significantlycorrelated with the length, width or product of length width.Thickness of silica deposition was significantly correlatedwith spikelet length width suggesting that these easily measuredparameters may be useful in screening for silica thickness. Oryza sativa L., rice, panicle, silicon, lemma, palea, husk