Enzymatic and non-enzymatic protective mechanisms in recalcitrant seeds of Araucaria bidwillii subjected to desiccation.
The changes in several antioxidants as well as in the level of C-centered free radicals and thiobarbituric acid reactive substances (TBARS) were studied in seeds of Araucaria bidwillii Hook desiccated to 37%, 28% and 21% moisture content. The lowest-safe moisture content for the seedling establishment was 37%. The embryo, besides double amounts of free radicals, showed higher levels of both enzymatic and non-enzymatic antioxidants than endosperm. Lutein decreased in both organs whereas alpha-tocopherol values were not affected by desiccation. In the embryo at 37% seed moisture content the antioxidant defense system increased giving rise to a decrease in free radicals. Beyond this point, free radicals and TBARS increased in agreement with the umpiring of the ascorbate/glutathione cycle by the decrease in reduced glutathione and glutathione reductase activity (GR, EC 1.6.4.2). At 21% moisture GR decreased. In the endosperm during desiccation, the consumption of ascorbate, total glutathione and lutein prevented the rise in free radicals and TBARS till 28% moisture, at which an increase in oxidized glutathione was also observed.
Francini
A
A
Dipartimento di Scienze Botaniche, Università di Pisa, via L. Ghini 5, 56126 Pisa, Italy.
Galleschi
L
L
Saviozzi
F
F
Pinzino
C
C
Izzo
R
R
Sgherri
C
C
Navari-Izzo
F
F
D000975:Antioxidants / Q000378:metabolism; D001205:Ascorbic Acid / Q000378:metabolism; D003890:Desiccation; D018525:Germination / Q000502:physiology; D005978:Glutathione / Q000378:metabolism; D010940:Plant Proteins / Q000378:metabolism; D012639:Seeds / Q000201:enzymology* / Q000502:physiology*; D064028:Tracheophyta / Q000201:enzymology*
D000975:Antioxidants; D010940:Plant Proteins; D005978:Glutathione; D001205:Ascorbic Acid