Ea. Golovina et al., The competence to acquire cellular desiccation tolerance is independent ofseed morphological development, J EXP BOT, 52(358), 2001, pp. 1015-1027
Acquisition of desiccation tolerance and the related changes at the cellula
r level in wheat (Triticum aestivum cv. Priokskaya) kernels during normal d
evelopment and premature drying on the ear were studied using a spin probe
technique and low temperature scanning electron microscopy. During normal d
evelopment, the ability of embryos to germinate after rapid drying and rehy
dration was acquired after completion of morphological development, which i
s a few days before mass maturity. The acquisition of desiccation tolerance
, as assessed by germination, was associated with an upsurge in cytoplasmic
viscosity, the onset of accumulation of protein and oil bodies, and the re
tention of membrane integrity upon dehydration/rehydration. These features
were also used to assess cellular desiccation tolerance in the cases when g
ermination could not occur. Slow premature drying was used to decouple the
acquisition of cellular desiccation tolerance from morphogenesis. Upon prem
ature drying of kernels on the ears of plants cut at 5d after anthesis, des
iccation-tolerant dwarf embryos were formed that were able to germinate. Wh
en plants were cut at earlier stages poorly developed embryos were formed t
hat were unable to germinate, but cellular desiccation tolerance was nevert
heless acquired. In such prematurely dried kernels, peripheral meristematic
endosperm cells had already passed through similar physiological and ultra
structural changes associated with the acquisition of cellular desiccation
tolerance. It is concluded that despite the apparent strong integration in
seed development, desiccation tolerance can be acquired by the meristematic
cells in the developing embryo and cambial layer of endosperm, independent
ly of morphological development.