ABSTRACT
I. INTRODUCTION Dicot leaf ontogeny is a complex process that is regulated by a variety of exogenous factors (e.g., light) and endogenous factors (e.g., hormones, developmental signals) [1,2]. Striking alterations occur in photosynthetic rates during leaf development, and these changes have been used to monitor the progression of this process. In general, increasing photosynthetic rates are coincident with leaf expansion; a phase of maximal rates occurs at full expansion; and finally, a prolonged senescence phase of declining rates takes place in the fully expanded leaf [3]. The senescence phase is marked by a progressive yellowing of the leaf, loss of protein (most notably of Rubisco), and the translocation of resources to growing parts of the plant [4-8].
