Seasonal changes in perennial nodules of beach pea (Lathyrus maritimus [L.] Bigel.) with special reference to oleosomes

Beach pea (Lathyrus maritimus [L.] Bigel.), a potential cold-climate circum polar legume crop, grows along the shorelines of Newfoundland, Canada. The nodules undergo winter dormancy and become active in the spring season. The nodules sampled in winter show dormant tissue and bacteria without any los s of structural integrity. In the senescent zone, bacteroids are found to b e disintegrated. Oleosomes (lipid bodies) are clearly localized in the meri stem, invasion zone, interstitial cells of the symbiotic and senescent zone , vascular tissue, and cortical cells of both winter and summer nodules. In all the tissues, significantly large numbers of oleosomes are seen in hist ological preparations of nodules sampled in winter compared with nodules sa mpled in summer. As winter approaches, the nodules show increasing accumula tion of lipids. The nodule tissues are protected from winter stress and pat hogen attack by suberized peridermal cells. We propose multipurpose functio ns of oleosomes in root nodules of beach pea, including the release of ener gy for Various metabolic functions in the cells, to prevent freezing in the localized microenvironment of the cells, and to insulate the cells and sup ply fatty acids for membrane synthesis during cell growth.