Two Stages in the Redifferentiation of Amyloplasts in the Microspores of Lilium

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Abstract
The first stage in the redifferentiation of plastids in the meiocytes of Lilium occurs late in meiotic prophase and involves the formation of an association between particles and membranous cisterna. The distribution of carbohydrate within this association has been examined cytochemically, and the particles are demonstrated to contain a high proportion of carbohydrate. The osmiophilic globules of the stroma also react with the cytochemical probe for carbohydrate, indicating that they must, at least in part, be composed of glycolipid. Structure within the organelles remains unchanging until the break-up of the tetrad, when elements of the membrane—particle association expand to fill the stroma. Electron microscopic evidence suggests that the particles form the nuclei of the starch grains which then swiftly develop. It is proposed that the association represents the limit of differentiation possible in the tetrad of microspores, and that the callosic special wall restricts the availability of materials from the thecal fluid required for full development of the amyloplast. The association should thus be more correctly termed the proamyloid body.

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