| Abstract: | This paper reports on an ultrastructural study of peroxisomesin infected nodule cells of Lupinus albus L cv Multolupa plantsgrown with and without nitrate (in short-term experiments) Cytochemicallocalization of catalase and peroxidase was performed applyingthe diamino-benzidine (DAB) technique in these tissues The infected cells presented a mean of seven peroxisomes, themaximum being 16 in some cells Peroxisome shapes proved to befairly round or egg-shaped, with maximum and minimum diametermeans of 0-35 and 0 18µm, respectively They were preferentiallypositioned on the cell periphery. The intense osmiophilic stainingobtained by applying the DAB technique indicates a strong catalaseactivity reaction in these microbodies The addition of nitrate (20 mol m–3) to the growing plantsexerted a negative effect on nitrogenase activity, which diminishedby 31 6% after 5 d of treatment Severe alterations in the ultrastructureof microbodies, bacteroids, and penbacteroidal membranes wereobserved Cytochemical data show a reduction in catalase localizationin peroxisomes and an increased peroxidase activity in the cytosol Finally, leghaemoglobin (Lb) localization was studied in nitrate-grownplants, confirming our previous observation of a decrease inthis protein Discussion focuses on the involvement of theseresults in tissue senescence of the nodules following nitrateapplication Key words: Peroxisomes, diamino-benzidine, nitrate, catalase, leghaemoglobin |
