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Abstract：
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.
摘要：
在肖尔顶点上形成原基的过程是控制（1）生长速率的过程，(2)划分平面。（3）表面微观结构，和(4)表面的延伸性。生长速率和分裂平面的变化可能伴随着原基的形成，但被认为本身可能不是因果关系。表面微观结构的变化可能是必要的，以界定初始原基所占据的位置和面积。然而,注意表面延展性的变化，这可能是原基形成的最重要因素。然而，原基的位置和形式也将取决于生长速度，师平面,表面微观结构是允许的。这四组过程的相对重要性可能因物种而异，也因发育阶段的不同而不同。首先，可能需要在顶点内进行化学和代谢变化，以确定表面是否可以充分延伸以形成任何原基。但是他们的位置和启动时间可能更多地取决于其他因素。当图案化在发育中的花朵中详细且精确时，表面微结构可能变得更加重要。而依赖于形态发生原（生长素？）合成的局部诱导的较不精确的机制可能提供足够的信息来确定营养顶点中原基起始的一般位置和界限。在确定先端原基的模式时，起始时的原始面积很重要，并总结了相信生长素可能参与确定的原因。原基的不同发育途径似乎从开始时就有所不同。原基的发育命运取决于实际上可能是异慢性基因的基因。到目前为止，这些调节基因如何控制不同类型原基分化所涉及的过程尚不清楚。内容摘要1一、导言2二.原基形成的机制：是什么导致了顶端表面的生长？2III。连续原基的位置:是什么决定了它们的大小和定位，所以产生了模式？11IV。是什么决定了原基的发育途径？13V。结论15VI。致谢16七.参考文献16.
