a1 Wageningen Agricultural University, The Netherlands, and University of Siena, Italy.
Several ultrastructural changes occur during dehydration and subsequent rehydration of Arabidopsis thaliana pollen. The cytoplasmic channels, present in the outer part of the intine of the mature, dehydrating pollen grain, degenerate and develop into electron-dense inclusions. At the same time a large quantity of electron-dense material is deposited in the cavities of the exine. A large number of vesicles is produced in the vegetative cell, and they become predominantly located in the peripheral region near the intine. Starch of amyloplasts is consumed and the lipid bodies which originally surround the sperm cells become randomly distributed. In addition, the individual lipid bodies become enveloped by single rough endoplasmic reticulum cisterns.
c1 M. Cresti, Dipartimento di Biologia Ambientale, Università di Siena, via P.A. Mattioli 4, I-53100 Siena, Italy.
1 Department of Plant Cytology and Morphology, Wageningen Agricultural University, Arboretumlaan 4, NL–6703 BD Wageningen, The Netherlands.
2 Department of Environmental Biology, University of Siena, Via P.A. Mattioli, 4, 1–53100 Siena, Italy.