Photosynthesis and Chloroplast Breakdown

Abstract

This chapter discusses the photosynthesis and breakdown of chloroplast, and also gene expression of plastid during senescence, and regulation of chloroplast senescence. Chloroplasts on the one hand are subject to degradation and on the other hand they still have to perform photosynthesis during senescence. Minimization of mutual disturbances of these two processes requires a well-tuned coordination at different levels, ranging from gene expression to degradation of proteins and pigments. When senescence is induced untimely-by growth of the plants at elevated CO2 or by various stress situations including dark treatment-the balanced progression of senescence associated events are disturbed. Under these conditions photosynthesis and nitrogen reallocation are less efficient than during developmentally induced senescence. Chloroplast senescence is not a linear sequence of changes but a complex syndrome of parallel processes that are more or less tightly coupled and to some extent regulated independently. The interrelations among the different senescence-associated events occurring in plastids are severely influenced by environmental conditions. © 2004 Elsevier Inc. All rights reserved.