Changes in wheat seed germination ability, soluble carbohydrate and antioxidant enzyme activities in the embryo during the desiccation phase of maturation
Résumé
Soluble sugar contents and antioxidant enzyme activities were measured in the embryo of wheat (Triticum aestivum) seeds throughout the desiccation phase of maturation in 2003 and 2004 to investigate whether they were related to seed quality. Whatever the date of harvest after the end of filling, seeds tolerated artificial drying in the ears, and almost all of them germinated at 10 °C whereas they were dormant at 30 °C. Their sensitivity to 5 day accelerated ageing treatment (45 °C, 100% relative humidity) slightly decreased during desiccation. This phase of development was associated with an accumulation of sucrose and raffinose, and an increase in the raffinose/sucrose ratio in the embryo. Artificial drying in the ears resulted in an increase in both sugars, but especially raffinose, and in the maintenance of a high value (around 0.6–0.7) of the raffinose/sucrose ratio. Superoxide dismutase, catalase and glutathione reductase activities did not change markedly in the embryo after mass maturity. They were sufficiently active to maintain malondialdehyde and H2O2 contents at very low levels. No clear relationship existed between the antioxidant enzyme activities and seed quality, whereas seed tolerance to ageing seemed to be related to a high value of the raffinose/sucrose ratio.