Biophysics of Development of the Plant Shoot

植物的多细胞发育涉及基因组和宏观表型之间的一条长的因果链。细胞行为是一个关键的中间阶段。一方面，基因组为细胞行为提供了基础。另一方面，当细胞的行为在时间和空间上整合时，就会产生连续的发育阶段。格林博士专门研究因果关系链后面的这些方面。格林博士从生长细胞壁上的纤维素定向强化的角度来研究枝条的发育。细胞在有丝分裂时维持或重新定向纤维素合成的方向。一种解释叶的起源和间距的生物物理理论--叶序分类--正在开发中。它的主要原理是，新近形成的叶子的生长通过拉伸其细胞来影响顶端圆顶，然后在圆顶上建立新的加固模式。这可以解释后续叶片的位置。现在，他提议通过改变器官拉伸模式和研究细胞反应来实验测试细胞拉伸和强化行为之间的明显关键关系。他还建议找出目前的理论是否可以扩展到更多的系统发育模式，以及它是否可以应用于叶的形式的产生。生物物理学解释的充分性将通过一个有限元程序进行检验，该程序将物理力和模型分生组织中的细胞反应联系起来。应该会得出枝条发育的一般生物物理理论。这个项目的研究集中在植物继承其几何特征的方式上。最著名的植物枝条图案的例子是向日葵花头上的螺旋线和松果上鳞片形成的螺旋线。在生长在温带地区的大多数植物的叶片图案中也发现了这些螺旋图案。显然，植物有一个“发育引擎”，它以植物特有的模式产生叶子。本研究涉及这些模式形成的细胞基础。这些模式是由茎尖端的一次活动循环产生的。在茎顶端，叶或其他附属物出现在细胞表面周围强化图案的不连续点处。这些强化图案是纤维素微纤维的结果。一旦叶子形成，它的根基的生长就会作用于邻近的组织，伸展它。这会在相邻单元中引起响应，从而产生新的不连续。因此，表面的不规则性导致器官，器官产生不规则性。这个循环可能会延续一种固定的模式。这项研究旨在扩展对所有模式的这种解释，并检查物理拉伸和细胞反应之间明显的关键联系，细胞反应改变了强化的方向。

Multicellular development in plants involves a long causal chain between genome and macroscopic phenotype. Cell behavior is a key intermediate stage. One the one hand the genome provides the basis for the cell behavior. On the other, the cell behavior, when integrated through time and space, produces the successive developmental stages. Dr. Green specialize in these later aspects of the causal chain. Dr. Green studies the development of the shoot in terms of the directional reinforcement, by cellulose, in the walls of growing cells. Cells maintain, or reorient, the direction of cellulose synthesis at mitosis. A biophysical theory to explain the origin and spacing of leaves, phyllotaxis, is being developed. Its main tenet is that growth of recently formed leaves influences the apical dome by stretching its cells which then establish new reinforcement patterns on the dome. This can explain the placement of subsequent leaves. Now he proposes to test experimentally the apparent key relationship- between cell stretch and reinforcement behavior by altering organ stretch patterns and studying cell responses. He also proposes to find out if the present theory can be extended to additional phyllotactic patterns and if it can be applied to the generation of form in leaves. Sufficiency of the biophysical explanations will be tested by a finite element program which correlates physical forces and cell responses in model meristems. A general biophysical theory for shoot development should result. %%% Research in this project centers on the way that plants inherit their geometrical features. The best known examples of pattern in plant shoots are the spiral lines seen in the heads of sunflowers and the helical lines made by the scales on a pine cone. These spiral patterns are also found in the leaf patterns of most plants growing in temperate zones. Obviously, plants have a "developmental engine" that produces leaves in a pattern specific to the plant. The present research is concerned with the cellular basis of the formation of these patterns. The patterns are generated by a cycle of activity at the stem tip. At the stem tip, leaves or other appendages, arise at points of discontinuity in the reinforcements patterns around cell surfaces. These reinforcement patterns are a result of cellulose microfibrils. Once a leaf is establishes, the growth of its base act of the adjacent tissue, stretching it. This causes a response in neighboring cells which create new discontinuities. Thus surface irregularities lead to organs and the organs make irregularities. The cycle can go on to perpetuate a fixed pattern. This research is to expand this interpretation of all patterns and to examine the apparently key connection between physical stretch and the cell response which alters reinforcement direction.