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The formation and distribution pattern of lipid bodies was investigated in spring and summer-grown seeds of Solanum nigrum. L. Lipid bodies were first formed in endosperm cells abutting the young globular embryo. The initial distribution pattern resembled an inverted cone with the 'tail' of the cone pointed away from the embryo. As the seed developed, lipid body formation commenced in the endosperm cells immediately adjacent to the cone and then in the remaining endosperm cells. RER cisternae were frequently found appressed to one side of the lipid body and sometimes continuous with the electron-lucent zone which separated the electron dense osmiophilic core from the surrounding half-unit membrane. The electron-lucent zone was of variable width and more noticeable in spring-grown seeds. In summer-grown seeds only, the osmiophilic cores of adjacent lipid bodies were joined by bridges of similar osmiophilic material. When the cotyledons of the torpedo-stage embryo had curved (approx. 14 d after anthesis), the osmiophilic stainability of the lipid bodies began to disappear as they were converted into oleosomes. Glyoxysome-like organelles were found only in the endosperm's 'Zone of Separation and Secretion' and arose earlier in the spring-grown seeds than in the summer-grown seeds. The early formation of lipid bodies, the spatial and temporal deposition pattern and the occurrence of glyoxysome-like organelles only in the Zone of Separation and Secretion suggests that the lipid bodies act as a reserve to be utilized during periods of uneven or low transfer of photosynthetic products.Copyright 1993, 1999 Academic Press |
