What can cell cycle and ultrastructure tell us about desiccation tolerance in Leucaena leucocephala germinating seeds?

Abstract

Desiccation tolerance (DT) is the ability to tolerate dehydration to levels below 0.1 g(H2O) g−1(dry mass) and subsequent rehydration without lethal damage. Here, it is proposed that Leucaena leucocephala, a tree species, has potential to be model tolerant species in seed research. Using flow cytometry and transmission electron microscopy, cytological changes related to loss of DT in Leucaena primary roots were followed during germination. Leucaena seeds lost their DT at the end of germination and this coincided with an increase in cellular 4C DNA content. A negative correlation between the 8C DNA content and the capacity of germinating Leucaena seeds to tolerate desiccation was also observed. Apparently, the seeds of Leucaena underwent extra cycles of endoreduplication and accumulated a high content of DNA — an event not previously linked to DT. The ultrastructural damage imposed by drying overcame Leucaena primary root cell resilience and their ability to resume normal growth. Nuclear DNA content may be used as indicator of progress of germination and loss of DT in Leucaena.