PREWINTER AND POSTWINTER CHANGES IN THE ROOT-NODULES OF LATHYRUS-MARITIMUS (L) BIGEL WITH SPECIAL REFERENCE TO STORAGE ORGANELLES

Histological and ultrastructural studies of the root nodules of natura lly growing beach pea (Lathyrus maritimus [L.] Bigel.), an arctic/suba rctic legume from the shorelines of Newfoundland, revealed considerabl e seasonal variation in the presence of storage organelles, such as am yloplasts and oleosomes (lipid bodies). Three successive years of samp les taken during late autumn and early spring were processed for both light and electron microscopy. After fruiting, large numbers of amylop lasts with starch grains and oleosomes were observed in the uninfected interstitial cells and parenchyma cells of the nodule tissues. These storage organelles could not be seen in the cells of nodules sampled d uring postwinter periods before aerial shoots emerged, indicating thei r importance in overwintering. Persistent infection threads with rhizo bia could be seen, and rod-shaped rhizobia in senescent cells were ind icative of reversion of bacteroids to rod forms within the nodule tiss ue.