Matching Sentences: [ Sen. 4, subscore: 1.00 ]: * Gas spaces ( aerenchyma ) form as an adaptation to submergence to facilitate gas exchange . In rice ( Oryza sativa ) , aerenchyma develop by cell death and lysis , which are poorly understood at the cellular level . * Aerenchyma formation was studied in rice stems by light microscopy . It was analyzed in response to submergence , ethylene and hydrogen peroxide ( H ( 2 ) O ( 2 ) ) treatment , and in the MT2b : : Tos17 mutant . O ( 2 ) . ( - ) was detected with nitroblue tetrazolium and an epinephrine assay . H ( 2 ) O ( 2 ) was detected with 3 , 3-diaminobenzidine . * Aerenchyma develop constitutively in all internodes of the deep-water rice variety Pin Gaew 56 , but are absent from the nodes . Constitutive aerenchyma formation was also observed in two lowland rice varieties , albeit to a lesser degree . A larger number of aerenchyma are present in older internodes , and at the top of each internode , revealing developmental gradients . Submergence or treatment with the ethylene-releasing compound ethephon promoted aerenchyma formation in all genotypes analyzed . Pre-aerenchymal cells contain less starch , no chloroplasts , thinner cell walls and produce elevated levels of O ( 2 ) . ( - ) and H ( 2 ) O ( 2 ) compared with other parenchymal cells . Ethephon promotes O ( 2 ) . ( - ) formation and H ( 2 ) O ( 2 ) promotes aerenchyma formation in a dose-dependent manner . Further-more , genetic downregulation of the H ( 2 ) O ( 2 ) scavenger MT2b enhances aerenchyma formation . [ Sen. 13, subscore: 1.00 ]: It was analyzed in response to submergence , ethylene and hydrogen peroxide ( H ( 2 ) O ( 2 ) ) treatment , and in the MT2b : : Tos17 mutant . O ( 2 ) . ( - ) was detected with nitroblue tetrazolium and an epinephrine assay . H ( 2 ) O ( 2 ) was detected with 3 , 3-diaminobenzidine . * Aerenchyma develop constitutively in all internodes of the deep-water rice variety Pin Gaew 56 , but are absent from the nodes . Constitutive aerenchyma formation was also observed in two lowland rice varieties , albeit to a lesser degree . A larger number of aerenchyma are present in older internodes , and at the top of each internode , revealing developmental gradients . Submergence or treatment with the ethylene-releasing compound ethephon promoted aerenchyma formation in all genotypes analyzed . Pre-aerenchymal cells contain less starch , no chloroplasts , thinner cell walls and produce elevated levels of O ( 2 ) . ( - ) and H ( 2 ) O ( 2 ) compared with other parenchymal cells . Ethephon promotes O ( 2 ) . ( - ) formation and H ( 2 ) O ( 2 ) promotes aerenchyma formation in a dose-dependent manner . Further-more , genetic downregulation of the H ( 2 ) O ( 2 ) scavenger MT2b enhances aerenchyma formation . * Aerenchyma formation is mediated by reactive oxygen species .
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