白皮松针叶内皮层在盐胁迫中的屏障作用研究

应用荧光显微技术、傅里叶变换显微红外光谱分析(FTIR)、扫描电镜及X-射线能谱微区分析等手段,对白皮松(Pinus bungeana)子叶、初生叶及2a生针叶内皮层细胞径向壁的显微结构特征、化学成分,以及在叶子横切面上Na和Cl的微区分布进行分析。通过荧光显微观察发现,白皮松子叶内皮层不具凯氏带,而初生叶及2a生针叶均存在凯氏带加厚现象。根据FTIR的检测结果显示:子叶内皮层细胞径向壁不含木栓质或极少,2a生针叶内皮层细胞径向壁木栓质含量高于初生叶。对相应区域的X射线微区分析表明,子叶内皮层对Na和Cl在质外体运输中不起障碍作用,而初生叶与2a生针叶内皮层阻碍Na和Cl以质外体途径进入维管组织。研究结果表明:具凯氏带加厚的内皮层细胞壁中木栓质含量决定其在质外体运输过程中的生理功能。

The Function of Pinus bungeana Foliar Endodermis as Apoplastic Barrier under Salt Stress

The cellular structure, chemical nature of foliar endodermis and element cellular distribution were investigated in Pinus bungeana leaves by the fluorescence microscope, Fourier transform infrared (FTIR) microspectroscopy and energy-dispersive X-ray analysis. The fluorescence microscopy showed that Casparian strips were absent from cotyledon endodermis, while the radial wall of endodermis in primary and two-year-old leaves were occupied with Casparian strips. The FTIR analysis indicated that there was no or very little suberin in endodermis radial wall of cotyledon compared with primary and two-year-old leaves. Furthermore, the content of suberin in endodermis of the primary leaves was lower than that of two-year-old leaves. The energy-dispersive X-ray analysis showed that the endodermis with Casparian strips in primary and two-year-old leaves functioned as apoplastic barriers against Na and Cl. However, no blockage of Na and Cl in cotyledon was observed when they passed through endodermis. It was suggested that physiological function of endodermis with Casparian strips as apoplastic transportation depended on the content of suberin in endodermis cell wall.