大麦根边缘细胞发育的生物学特性

Biological Characters of Root Border Cell Development in Barley

FDA PI(fluoresceindiacetate propidiumiodide)检测结果表明 ,在大麦种子萌发过程中 ,根边缘细胞 (bor dercells)活性约为 95 %。 0 .5mol/L甘露醇有利于离体边缘细胞的生存。第一个边缘细胞几乎与初生根根尖同步出现 ,当根长为 2 0～ 2 5mm时 ,边缘细胞数目达到最大值 (约 140 0 ) ;移去全部边缘细胞 48h后 ,又有新的边缘细胞形成。与 2 5℃相比 ,15和 35℃明显抑制根的伸长 ,但不明显抑制边缘细胞的发育。在边缘细胞诱导和发育过程中 ,边缘细胞的游离与根冠果胶甲基酯酶活性有密切的正相关性。

The developmental biology of root border cells in higher plants is one of the newly emerged research fields. The viability, number, induction, and response to temperature of border cells were investigated during seed germination in barley (Hordeum vulgare L. cv. Humai 8). The viability of border cells attached to the root tip was (95±3)% using FDA-PI method (Fig.1A). CC medium and 0.5 mol/L mannitol solution were beneficial to border cell survival (Fig.1B). During normal seed germination, the first formation of border cells occurred almost synchronously with primary root tip emergence in barley. The number of border cells increased with root elongation, and reached its maximum value (about 1 400) when the root was 20-25 mm long (Fig.2A). When a full set of border cells was removed, a new set of border cells was induced within 48 h (Fig.2B). Further studies showed that there existed no specific extracellular inhibitor in border cell secretions (Fig.2C). Compared with 25℃, 15 and 35℃ could significantly inhibit root elongation, but not border cell development (Fig.3). Changes in pectin methylesterase (PME) activity in root caps were closely related with border cell separation in barley (Fig.4). These results revealed that the response of root elongation to temperature was more sensitive than border cell development in barley, which was an induced process and whose separation was mediated via PME activity expression in root caps.