The influence of drought on the free radical contents of fruits of there types of strawberry (Fragaria vesca L. cv. Semperflorens, Fragaria ananassa cv. Elsanta and cv. Symphony) and there types of tomato (Lycopersicon esculentum cv. Gold Königin, cv. Gartenperle and cv. Kremser Perle) was investigated over an extended period of time. In addition, the influence of ozone, as another abiotic stress, was investigated with one tomato cultivar (Lycopersicon esculentum cv. Gartenperle). Four or five harvests of fruits were made in order to get time-dependent information on any relationship between the duration of the stress and free radical production. Determination of free radical levels was carried out using EPR spectroscopy on frozen fruit samples at 77 K and freeze-dried fruit samples at room temperature. Spin trapping using 4-POBN as a spin trap was used for detecting the generation of unstable free radicals in crushed strawberry samples. Information on the stress status of the plants was obtained from stomatal conductance measurements and fruit and soil water contents. The results showed no effects of drought or time of harvest on the total free radical contents of frozen fruit of strawberry (investigated with one cultivar. Fragaria ananassa cv. Symphony), or on the amounts of unstable free radicals generated, in crushed fruits of a second cultivar (Fragaria vesca cv. Semperflorens). In contrast, with freeze-dried strawberry samples, distinct effects of drought stress were seen with two out of there varieties studied, and there were also differences between harvests. The free radical levels were approximately ten times higher in the freeze-dried fruits, than in the equivalent frozen samples (expressed on a dry weight basis). Massive free radical generation, therefore, accompanies the freeze-drying process and the differences between stressed and control strawberry samples may indicate an effect of drought stress on the levels of free radical scavenging compounds in the fruit. In tomato fruits no influence of drought was seen on the free radical levels in frozen samples, whereas exposure to elevated ozone levels led to higher free radical signals. In conclusion, it appears that elevated ozone might have a greater influence than drought on free radical production in fruits of tomato plants, especially during a short period after commencing the stress. However, this was a limited experiment and the harvests of drought stressed fruits might have been chosen at times when increased antioxidant production had already occurred, thereby compensating for any stress-induced free radical production.
|Publikationsstatus||Veröffentlicht - 2002|
- Nicht definiert