Effect of desiccation on isolated embryos of maize. Onset of desiccation tolerance during development

The research described in this paper was designed to define the stage of development during which the excised embryo of maize acquires desiccation tolerance.The applied desiccation stress corresponded to a period of 2 days at 35 °C (during which the isolated embryos reached a water content around 3.8 %).The experiments led to the following conclusions : at stages where precocious germination is fully evident, the embryo can still be desiccation-intolerant ; -desiccation tolerance is acquired by the embryo at a very precise developmental stage, between 20 and 25 days after pollination (DAP) during which the dry weight increases by a I' ' .ctor of 5 to 10.In terms of DAP the onset of desiccation tolerance was found reproducible for 2 years and for the 4 genotypes tested.Normal development of the coleoptile and embryonic root originating from a dried embryo depends on the stage of excision : the younger the embryo is desiccated, the more abnormal are the coleoptile and the embryonic root originating from it.Acquisition of desiccation tolerance and of insensitivity of the embryo to desiccation damage is probably the result of two independent physiological processes : the first property is acquired rapidly and at earlier stages than the second.A set of proteins has been identified that is specifically expressed only at stages of development when the embryo is desiccation-tolerant.This may open possibilities for approaching the biochemistry of desiccation in the maize embryo.