Edelmann H G, Sievers A
Botanisches Institut, Universitat Bonn, Germany.
Planta. 1995 May;196(2):396-9. doi: 10.1007/BF00201401.
In various studies, auxin (IAA)-induced coleoptile growth has been reported to be closely correlated with an increased occurrence of osmiophilic particles (OPs) at the inner surface of the outer, growth-limiting epidermal cell wall, indicating a possible function related to the mechanism of IAA-induced wall loosening. In order to test whether changes in cell elongation rates of upper and lower flanks (UFs, LFs, respectively) during graviresponsive growth are reflected in appropriate changes in the occurrence of OPs, rye (Secale cereale L.) coleoptiles either as segments or as part of intact seedlings, were gravitropically stimulated by positioning them horizontally for 2 h. Ultrastructural analyses within the UFs and LFs of the upward-bending coleoptiles revealed a distinct imbalance in the occurrence of OPs. The number of OPs per transverse epidermal cell section of the elongation-inhibited UF on average amounted to twice the number of OPs counted in epidermal cell sections of the faster-growing LF. As a hypothesis, the results lead us to suggest that OPs are involved in the mechanism of wall loosening and that temporary growth inhibition of epidermal cells of the UF during upward bending is mediated by inhibition of OP entry into the cell walls. Thereby, more OPs accumulate near the inner surface of the outer wall of epidermal cells of the UF compared with the LF.
在多项研究中，据报道生长素（吲哚 - 3 - 乙酸，IAA）诱导的胚芽鞘生长与生长受限的外侧表皮细胞壁内表面嗜锇颗粒（OPs）出现频率的增加密切相关，这表明其可能具有与IAA诱导的细胞壁松弛机制相关的功能。为了测试在向重力性生长过程中，上侧和下侧（分别为UFs、LFs）细胞伸长率的变化是否反映在OPs出现的相应变化中，将黑麦（Secale cereale L.）胚芽鞘切段或作为完整幼苗的一部分水平放置2小时进行向重力性刺激。对向上弯曲的胚芽鞘的UFs和LFs进行超微结构分析，结果显示OPs的出现存在明显失衡。伸长受抑制的UF的每个横向表皮细胞切片中的OPs数量平均是生长较快的LF的表皮细胞切片中OPs数量的两倍。作为一种假设，这些结果使我们推测OPs参与了细胞壁松弛机制，并且向上弯曲过程中UF表皮细胞的暂时生长抑制是由OPs进入细胞壁受到抑制介导的。因此，与LF相比，更多的OPs积累在UF表皮细胞外壁的内表面附近。
