Specialization of Organelles and Compartmentation of metabolism between cells. Using immunohistochemistry to study plant metabolism: the examples of its use in the localization of amino acids in plant tissues, and of phosphoenolpyruvate carboxykinase and its possible role in pH regulation

To understand many aspects of the metabolism of complex plant structures such as leaves, fruit and roots it is important to understand how metabolic processes are comparmentalized between tissues. The aim of this article is to show how immunohistochemistry, in conjunction with biochemical and physiological studies, is useful in understanding both the function of an enzyme in a tissue and metabolic processes occurring in plant tissues. This is illustrated by two examples. Firstly, the use of immunohistochemisty in the localization of amino acids in plant tissues is described. Secondly, the use of immunohistochemistry in understanding the function of an enzyme in a tissue and the metabolic processes occurring within the tissue is described. To illustrate this the example of phosophoenolpyruvate carboxykinase (PEPCK), an enzyme which is present in many plant tissues in which its function is unknown, is used. Evidence is provided that PEPCK may play a role in pH regulation in tissues active in the metabolism of nitrogen.