Lyndon Robert F
Institute of Cell and Molecular Biology, Division of Biological Sciences, University of Edinburgh, Edinburgh, EH9 3JH, Scotland, UK.
New Phytol. 1994 Sep;128(1):1-18. doi: 10.1111/j.1469-8137.1994.tb03981.x.
The processes involved in the formation of primordia on the shoor apex are those controlling (1) growth rate, (2) division plane. (3) surface microstructure, and (4) extensibility of the surface. Changes in growth rate and division planes may accompany primordium formation but are considered as probably not in themselves being causal. Changes in surface microstructure may be necessary to delimit the position and area occupied by an incipient primordium. However, attention is directed to changes in surface extensibility as perhaps being the overriding factor in primordium formation. Nevertheless, the position and form of the primordia will also depend on growth rate, division plane, and surface microstructurc being permissive. The relative importance of these four sets of processes may differ from species to species and from one stage of development to another. Chemical and metabolic changes within the apex may first be necessary to determine whether the surface can extend sufficiently for any primordia to form at all, but their positions and time of initiation may depend more on the other factors. The surface microstructure may become more important when patterning is detailed and precise as it is in the developing flower, whereas a less precise mechanism dependent on localized induction of synthesis of a morphogen (auxin?) may provide sufficient information to determine the general position and liming of primordium initiation in vegetative apices. In determining the pattern of primordia on the apex, primordial area at initiation is important and reasons for believing that auxin may be involved in determining this are summarised. The different developmental pathways of primordia seem to diverge from the moment of initiation. Developmental fate of primordia is determined by the hamcotic genes which may in fact be heterochronic genes. How these regulatory genes control the processes involved in differentiation of different types of primordia is so far unknown. Contents Summary 1 I. Introduction 2 II. The mechanism of primordium formation: what causes an outgrowth of the apical surface? 2 III. The positions of successive primordia: what determines their size and localization, so giving rise to pattern? 11 IV. What determines the developmental pathways of the primordia once initiated? 13 V. Conclusions 15 VI. Acknowledgements 16 VII. References 16.
茎尖原基形成过程中涉及的过程包括控制（1）生长速率、（2）分裂平面、（3）表面微观结构以及（4）表面伸展性的那些过程。生长速率和分裂平面的变化可能伴随原基形成，但它们本身可能并非因果关系。表面微观结构的变化对于界定初始原基所占据的位置和面积可能是必要的。然而，人们注意到表面伸展性的变化可能是原基形成中的首要因素。尽管如此，原基的位置和形态也将取决于生长速率、分裂平面以及表面微观结构是否适宜。这四组过程的相对重要性可能因物种不同以及发育阶段不同而有所差异。茎尖内部的化学和代谢变化可能首先是决定表面是否能充分伸展以使任何原基形成的必要条件，但其位置和起始时间可能更多地取决于其他因素。当图案化如在发育中的花中那样详细而精确时，表面微观结构可能变得更为重要，而依赖于形态发生素（生长素？）合成的局部诱导的不太精确的机制可能提供足够信息来确定营养茎尖中原基起始的大致位置和时间。在确定茎尖上原基的图案时，起始时原基的面积很重要，并且总结了认为生长素可能参与确定这一点的原因。原基的不同发育途径似乎从起始时刻就开始分歧。原基的发育命运由同源异型基因决定，而这些基因实际上可能是异时基因。到目前为止，尚不清楚这些调控基因如何控制不同类型原基分化所涉及的过程。内容摘要1. 引言2. 二、原基形成的机制：是什么导致茎尖表面长出？2. 三、相继原基的位置：是什么决定它们的大小和定位，从而形成图案？11. 四、原基一旦起始，是什么决定其发育途径？13. 五、结论15. 六、致谢16. 七、参考文献16.
