Pre- and Postwinter Changes in the Root Nodules of Lathyrus maritimus (L.) Bigel. with Special Reference to Storage Organelles

Abstract

Histological and ultrastructural studies of the root nodules of naturally growing beach pea (Lathyrus maritimus [L.] Bigel.), an arctic/subarctic legume from the shorelines of Newfoundland, revealed considerable seasonal variation in the presence of storage organelles, such as amyloplasts and oleosomes (lipid bodies). Three successive years of samples taken during late autumn and early spring were processed for both light and electron microscopy. After fruiting, large numbers of amyloplasts 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 during postwinter periods before aerial shoots emerged, indicating their importance in overwintering. Persistent infection threads with rhizobia could be seen, and rod-shaped rhizobia in senescent cells were indicative of reversion of bacteroids to rod forms within the nodule tissue.