Changes in the ascorbate system in the response of pumpkin (Cucurbita pepo L.) roots to aluminium stress.
The involvement of the ascorbate (AsA) system in the response of pumpkin (Cucurbita pepo L.) roots to aluminium stress was studied. The treatment of 5-day-old pumpkin seedlings with 50 microM aluminium sulphate resulted in approximately 60% inhibition of root growth within 48-60 h of treatment, while aluminium accumulated in the roots reaching a maximum within 48h. During the same period, the hydrogen peroxide content of the roots was strongly enhanced. The increased level of hydrogen peroxide was matched by both increased ascorbate peroxidase (APX) (EC 1.11.1.11) activity and ascorbate free radical reductase (AFRR) (EC 1.1.5.4) activity, while dehydroascorbate reductase (DHAR) (EC 1.8.5.1) and glutathione reductase (GR) (EC 1.6.4.2) did not change. The levels of AsA in the roots were also increased by the Al treatment. It was concluded that an oxidative burst is probably involved in the toxicity of Al in pumpkin roots and that plants react to the enhanced production of reactive oxygen species by expressing higher levels of scavenging systems such as the AsA-APX system.
Dipierro
Nunzio
N
Department of Plant Biology and Pathology, University of Bari, via Orabona 4, Bari 70125, Italy.
Mondelli
Donato
D
Paciolla
Costantino
C
Brunetti
Gennaro
G
Dipierro
Silvio
S
D000534:Alum Compounds / Q000633:toxicity*; D001205:Ascorbic Acid / Q000378:metabolism*; D028464:Cucurbita / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D016166:Free Radical Scavengers / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism; D018384:Oxidative Stress; D018517:Plant Roots / Q000187:drug effects / Q000502:physiology*; D036226:Seedlings / Q000187:drug effects / Q000254:growth & development; D013997:Time Factors
D000534:Alum Compounds; D016166:Free Radical Scavengers; C041524:aluminum sulfate; D006861:Hydrogen Peroxide; D001205:Ascorbic Acid