THE RECALCITRANT PLANT-SPECIES, CASTANOSPERMUM-AUSTRALE AND TRICHILIA-DREGEANA, DIFFER IN THEIR ABILITY TO PRODUCE DEHYDRIN-RELATED POLYPEPTIDES DURING SEED MATURATION AND IN RESPONSE TO ABA OR WATER-DEFICIT-RELATED STRESSES

In constrast to seeds of orthodox species, those of recalcitrant speci es do not acquire desiccation tolerance during their development and a re shed from the parent plant at high water contents, Dehydrin product ion in seeds of recalcitrant species was examined during development a nd germination, in response to abscisic acid (ABA), and following the imposition of various water-deficit-related stresses, including desicc ation, water stress, high salt, high osmolarity, and low temperature. Two tropical species exhibited a differential capacity to produce dehy drin-related proteins during seed maturation. Dehydrins were present i n axes and cotyledons of Castanospermum australe seeds during mid-matu ration and at maturity. In Trichilia dregeana, no dehydrin-related pol ypeptides were detected in the mature seed. During the development of C. australe seeds, the nature of the dehydrin-related polypeptides acc umulated in the cotyledons and axis changed and new polypeptides were detected in the mature seeds that were not present during mid-maturati on. The dehydrins present in cotyledons of mature seeds (31, 37 and 40 kDa) were still detectable after germination (i.e. in untreated seedl ings). These dehydrins became less abundant in the cotyledons of C. au strale seedlings following ABA and all stress treatments except cold, although most of the dehydrins were still detectable, An exception was the desiccation-treated seedlings, in which no dehydrins were detecte d. In the roots of C. australe seedlings, no dehydrins were found afte r germination nor were they induced in the root by ABA or any of the s tress treatments imposed on seedlings. Seedlings of Trichilia dregeana did not produce dehydrins in the roots or cotyledons when exposed to ABA or water-deficit-related stresses.