Telfer A, Bollman K M, Poethig R S
Plant Science Institute, Department of Biology, University of Pennsylvania, Philadelphia 19104-6018, USA.
Development. 1997 Feb;124(3):645-54. doi: 10.1242/dev.124.3.645.
Higher plants pass through several phases of shoot growth during which they may produce morphologically distinct vegetative structures. In Arabidopsis thaliana this phenomenon is apparent in the distribution of trichomes on the leaf surface. Leaves produced early in rosette development lack trichomes on their abaxial (lower) surface, leaves produced later have trichomes on both surfaces, and leaves in the inflorescence (bracts) may have few or no trichomes on their adaxial (upper) surface. Here we describe some of the factors that regulate this distribution pattern. We found that the timing of abaxial trichome production and the extent to which bracts lack adaxial trichomes varies in different ecotypes. The production of abaxial trichomes appears to be regulated by the age, rather than the size of the plant. This conclusion is based on the observation that mutations that affect either the rate (altered meristem programming1) or onset (paused) of leaf initiation respectively increase or decrease the number of leaves that lack abaxial trichomes, but have only a minor effect on the time at which the first leaf with abaxial trichomes is produced. The production of abaxial trichomes is coordinated with the reproductive development of the shoot as this trait is delayed by photoperiodic conditions and some mutations that delay flowering. The loss of adaxial trichomes is likely to be a consequence of floral induction, and is accelerated by terminal flower1-10, a mutation that accelerates inflorescence development. We demonstrate that gibberellins promote trichome production in Arabidopsis and present evidence indicating that abaxial trichome production is regulated by both the level of a trichome inducer and the competence of the abaxial epidermis to respond to this inducer.
高等植物在茎尖生长过程中会经历几个阶段，在此期间它们可能会产生形态上不同的营养结构。在拟南芥中，这种现象在叶表面毛状体的分布上很明显。莲座叶发育早期产生的叶片，其背面（下面）没有毛状体；后期产生的叶片两面都有毛状体；而花序中的叶片（苞片），其正面（上面）可能几乎没有或完全没有毛状体。在这里，我们描述了一些调节这种分布模式的因素。我们发现，不同生态型中，背面毛状体产生的时间以及苞片缺乏正面毛状体的程度各不相同。背面毛状体的产生似乎受植株年龄而非大小的调节。这一结论基于以下观察结果：分别影响叶片起始速率（改变分生组织编程1）或起始时间（暂停）的突变，会分别增加或减少缺乏背面毛状体的叶片数量，但对第一片有背面毛状体的叶片产生时间影响较小。背面毛状体的产生与茎尖的生殖发育相协调，因为这一特征会因光周期条件和一些延迟开花的突变而延迟。正面毛状体的缺失可能是花诱导的结果，并且会被加速花序发育的终端花1 - 10突变所加速。我们证明赤霉素促进拟南芥中毛状体的产生，并提供证据表明背面毛状体的产生受毛状体诱导剂水平和背面表皮对该诱导剂反应能力的共同调节。
