In their development leaves exhibit plastic responses in both shape and size. Variations in shape are often associated with changes in size also but the reverse is not always true. Plastic responses in leaf form resulting from ontogenetic or external influences are initiated very early in primordial development and are brought about by effects on the rate and direction of cell division and expansion in different regions of the primordium. Effects on leaf size are often induced over much longer periods including the phase of lamina expansion. In Phaseolus vulgaris the primary leaves exhibit increases in size when one of the pair is removed or when the stem is decapitated above the primary leaf node. These compensatory growth effects are not the result of a change in cell number but are caused by an increase in mean cell size. Cell wall extensibility is not increased by treatment and the evidence suggests that a small increase in the (turgor-wall yield stress) term may be the cause of the very rapid response to defoliation. The usefulness of leaf systems for the analysis of plastic responses of shape and size is indicated and the importance of a better understanding of the factors determining the siting and development of the cell wall is stressed.
在其发育过程中，叶片在形状和大小方面都表现出可塑性反应。形状的变化通常也与大小的变化相关，但反之则不一定成立。由个体发育或外部影响导致的叶片形态可塑性反应在原基发育的早期就开始了，并且是由对原基不同区域细胞分裂和扩展的速率及方向的影响所引起的。对叶片大小的影响通常在更长的时期内诱导产生，包括叶片扩展阶段。在菜豆中，当一对初生叶中的一片被摘除或在初生叶节上方将茎去顶时，初生叶的大小会增加。这些补偿性生长效应不是细胞数量变化的结果，而是由平均细胞大小的增加引起的。处理并没有增加细胞壁的伸展性，证据表明（膨压 - 壁屈服应力）项的小幅增加可能是对去叶非常快速反应的原因。文中指出了叶片系统对于分析形状和大小可塑性反应的有用性，并强调了更好地理解决定细胞壁位置和发育的因素的重要性。
