Phenotypic analysis and molecular markers of plant nodule senescence

Abstract

Leguminous crops can form nodules to fix atmospheric nitrogen (N2). Senescence of nodules is associated with a rapid decline in N fixation. During the process of nodule senescence, a number of visible or detectable changes on morphology, biochemistry, and physiology occur. Here we describe several methods for examining the senescing phenotypes of nodules, including rhizobium inoculation, nitrogenase activity determination with the acetylene reduction assay, leghemoglobin content determination, and apoptotic cell identification with TdT-mediated dUTP-biotin nick end-labeling (TUNEL) staining.