木薯块根膨大初期淀粉体形态及发育的扫描电镜观察

Observation on the structure and development of amyloplast in early stage of cassava storage root with scanning electronic microscope

对华南木薯3个品种(SC124、SC8、Arg7)膨大初期的木薯块根淀粉体的大小、形态、分布排列和发育等特性进行了扫描电镜观察。结果表明:淀粉主要沉积在木薯块根的次生韧皮部和木质部的薄壁细胞中。木薯块根淀粉体形态品种间没有明显差异,主要为球形,常见有椭球体、不规则的半球体、多极球体等形态,但淀粉体大小及空间排列在3个品种间差异显著。SC124淀粉体平均直径最小,淀粉体的变异系数大,淀粉体间空隙较大,呈层状排布;SC8淀粉体大小较为一致,变异系数小,淀粉体排列紧密,呈束状排布;Arg7淀粉体大小及变异系数都较小,淀粉体排列较为疏松,成团状排布。结论:淀粉体的大小、形态、空间排列及增殖方式可能是影响木薯块根淀粉充实程度和品质特性直接原因。

In this study,it has been observed and compared the size,pattern,distribution,arrangement and development of the amyloplasts in early stage of storage root in 3 varieties of cassava（SC124、SC8、Arg7） under scanning electron microscope（SEM）.The results show that the starch grains mainly deposite in parenchyma of the secondary and pholem xylem.There are no detectable differences in shape of 3 cassava varieties,but the size（the average diameters）,pattern and arrangement are diversity,in which the main shape of the amyloplasts is sphere,but many transient shapes such as hemispheroid,orellipsoid,multidimensional sphere are found.Among the three varieties,the average size of amyloplasts in SC124 is smallest,but its coefficient of variation and interspace is the largest;the granule size of amyloplasts in S8 is relative uniform with small coefficient of variation and tight arrangement;however in Arg7,the granule size and coefficient of varation is small,while the interspace are large.SEM image of the amyloplasts show that they are stratiformly arranged in zylem parenchyma in SC124,sarciniformly arranged in SC8;and granularly arranged in Arg7.The natural fractured image of root chips by cryodesiccation reflects the real structure of the amyloplasts in parenchyma of cassava.The size,pattern,arrangement and development of the amyloplasts in early stage may be the efficient amse of character differenties.