CYTOLOGICAL STUDIES IN DORMANCY II. PATHOLOGICAL AGEING CHANGES DURING PROLONGED DORMANCY AND RECOVERY UPON DORMANCY RELEASE.

Seeds with a chilling requirement were maintained fully imbibed at 22-25° C for more than 6 years without germination. Similar seeds stored air-dry at the same temperatures were dead by the second year. Cytological changes in the radicle meristem cells during the first year included the development of complex associations of ER with protein bodies. After 2 years imbibition, cytolysomes were formed, and by the fifth year membrane systems were extensively damaged. Upon release from dormancy, germination was delayed compared with that of normal, unaged embryos. During this delay, the vacuoles acted as lysosomes, engulfing and hydrolysing cytoplasmic organelles, Renewal was by sub-division of existing organelles, separating damaged from apparently normal zones by the formation of partition membranes. The relationship between lysosomal systems and the plant cell vacuole is discussed. The extended viability of imbibed seeds compared with dry seeds is discussed in relation to the possibilities of running repairs to membrane and genetic systems whilst the tissue is hydrated. [ABSTRACT FROM AUTHOR]