PBIO*3110 –Crop Physiology Topic 2 - Crop Phenology: Growth Stages and Rate of Development What is the difference between “growth” and “development”? What factors determine the rate of crop development? Learning Objectives 1.Understand how development is different from growth. 2.Be able to explain why it is important to be able to define the developmental stage of a crop. 3.Know the major environmental factors than can influence crop development. 4.Be familiar with two different systems for quantifying heat unit accumulation. Introduction Throughout this course, we will analyze the physiology of crop growth and yield primarily in quantitative terms (canopy interceptance of solar radiation, rates of dry matter production, partitioning of dry matter). However, these measurements must usually also be considered within the context of qualitative descriptions of crop development. In particular, it is necessary to be able to define the developmental stage at which measurements are made. In this regard, crop physiologists need to understand the phenologyof the plant species with which they are working. In this topic we will see how developmental stages of several crop species can be unambiguously identified, and we will examine some of the most important factors that determine rate of development. Some Definitions It is important for us to differentiate between the terms growthand development. Both can be seen as components of the process of morphogenesis(literally, the origin of form).