METABOLISM OF REACTIVE OXYGEN DYNAMIC CHANGES DURING TOMATO FRUIT RIPENING AND SENESCENCE

Recently, reactive oxygen species (ROS) have been revealed to play an important role as signaling molecules in many processes, including hypersensitive response (HR) and senescence.
Some studies have confirmed that ROS acts in concert with ethylene in HR and senescence.
However, little is known about the source of ROS production and its metabolic dynamics in fruit ripening and senescence.
In this study, tomato (Lycopersicon esculentum Mill.) pericarp and seed were used to investigate changes of ROS and activities of antioxidant enzymes during fruit ripening and senescence.
Superoxide (O₂^–.) production rate and hydrogen peroxide (H₂O₂) content in seed were significantly higher than those in pericarp at all maturity stages, and the H₂O₂ content in the seed increased sharply after the pink stage.
Higher activities of superoxide dismutase (SOD), catalase (CAT) and glutathione reductase (GR) occurred in seeds than that in the pericarp.
At the beginning of fruit ripening, an increase of CAT activity followed the accumulation of H₂O₂, but its activity declined quickly by the end of ripening.
These patterns of enzyme activity suggest that the AsA-GSH cycle might play an important role in scavenging H₂O₂. The maximum malondialdehyde (MDA) content appeared in seeds earlier than that in the pericarp, the maximum being 1.5 fold of that in the pericarp.
High concentration of ROS in the seed is closely related with fruit ripening, and H₂O₂ might be an important factor in triggering senescence.

XXVII International Horticultural Congress – IHC2006: International Symposium on The Role of Postharvest Technology in the Globalisation of Horticulture

Lin Shen, Ying Ruan, Kailang Liu, Jiping Sheng

reactive oxygen species, seed, hydrogen peroxide, antioxidant enzymes, postharvest physiology, fruit quality

https://doi.org/10.17660/ActaHortic.2008.768.69