The Anatomical And Chemical Characteristics Of A Culm-brittleness And A Leaf-rolling Mutants Of Rice And Their Ecophysiological Properties

Creating and establishing a saturated rice mutant population and establishing a specific mutant research system as well as positioning and cloning different developmental and physiological process genes are a major focus for rice research,by which new varieties or lines with high-yield and quality,multi-resistance,and high efficient and environmentally friendly features will be expected.In the present research,two typical rice mutants,brittle culm rice and leaf rolling mutant,were considered to understand the anatomical and chemical characteristics and some ecophysiological properties such as photosynthesis dynamics and apoplastic transport ability when rice plants had a culm-brittleness or leaf-rolling mutation respectively.Brittleness culm is an important agronomic trait that has a potential usefulness in agricultural activity as animal forage while the developmental mechanism is not clear yet.In the present study,the anatomical and chemical characteristics as well as some ecophysiological features in the brittleness culm mutation of rice(Oryza sativa L.) were investigated.Compared with the wild type(WT),the brittleness culm mutant (bcm)exhibited higher culm vascular bundle distance and lower culm wall thickness, leaf interveinal distance and leaf thickness.Ratio of bundle sheath cell/whole bundle and areas of whole vascular bundles and bundle sheath of leaves were reduced while ratios of xylem and phloem to whole bundles were elevated in bcm.The Fourier transform infrared(FTIR)microspectroscopy analysis and further histochemical and physiological measurements revealed that the different contents and depositions of cell wall components such as pectins,lignin,suberin and cellulose were participated in the mutation of brittleness.However,the mutant presented no significant changes in leaf photosynthetic dynamics and apoplastic transport ability.These results strongly indicate that the alterations in anatomical and chemical characteristics rather than the changes in major ecophysiological features such as photosynthesis and apoplastic transport were involved in the brittleness mutation of rice. The anatomical and chemical characteristics of a rolling leaf mutant(rim)of rice (Oryza sativa L.)and its ecophysiological properties in photosynthesis and apoplastic transport were also investigated.As compared to the wild type(WT),the increased areas of whole vascular bundle and xylem,the higher ratios of xylem/whole vascular bundle and xylem/phloem,as well as the lower area and width of foliar bulliform cell were observed in rlm.The fourier transform infrared microspectroscopy spectra (FTIR)of foliar cell walls differed greatly between the rim and Wild-Type,and the rim exhibited lower protein and polysaccharide contents of foliar cell wails compared with the Wild-Type.An obvious reduction of pectin contents was also observed in the rim by biochemistry measurement.The rate of photosynthesis in rlm was depressed, whereas the conductance of stoma and concentration of intercellular CO₂ were hoisted compared with Wild-Type in all three growing stage.In addition,the PTS fluorescence which represents the ability of apoplastic transport,was decreased by 11%compared with the Wild-Type.These results suggest that the changes of anatomical and chemical characteristics of foliar vascular bundles,such as the reduction of protein,pectin,and other polysaccharide of foliar cell walls were participated in the leaf rolling mutation,and consequently might involve in the reduced photosynthetic dynamics and apoplastic transport in the mutant.