Journal Article

Chill-Induced Decrease in Capacity of RuBP Carboxylation and Associated H<sub>2</sub>O<sub>2</sub> Accumulation in Cucumber Leaves are Alleviated by Grafting onto Figleaf Gourd

Yanhong Zhou, Lifeng Huang, Yili Zhang, Kai Shi, Jingquan Yu and Salvador Nogués

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 100, issue 4, pages 839-848
Published in print October 2007 | ISSN: 0305-7364
Published online August 2007 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcm181
Chill-Induced Decrease in Capacity of RuBP Carboxylation and Associated H2O2 Accumulation in Cucumber Leaves are Alleviated by Grafting onto Figleaf Gourd

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  • Ecology and Conservation
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Background and Aims

Chilling results in a significant decrease in Rubisco content and increased generation of reactive oxygen species (ROS) in cucumber (Cucumis sativus), a chilling-sensitive species. The role of roots in the regulation of the tolerance is unknown. Here, cucumber plants grafted onto figleaf gourd (Cucurbita ficifolia), a chilling-tolerant species were used to study the role of roots in the regulation of shoot functioning and the associated root-to-shoot communication.

Methods

Gas exchange and chlorophyll fluorescence were measured using an infrared gas analyser combined with a pulse amplitude fluorimeter during chilling at 14 °C or 7 °C and subsequent recovery. At the same time, Rubisco content and activity and ROS generation were spectrophotometrically assayed. Abscisic acid and cytokinin concentrations in xylem sap were also determined by enzyme-linked immunosorbent assay.

Key Results and Conclusions

Grafted plants showed a significantly higher light-saturated rate of CO2 assimilation (Asat) than own-rooted plants when roots were gradually cooled, but no differences were detected when shoots were cooled. Chill at 7 °C irreversibly reduced Asat, and significantly decreased maximum carboxylation activity, Rubisco content and initial Rubisco activity. However, grafted plants showed weaker inhibition, together with decreased electron flux in the water–water cycle. Higher activity of antioxidant enzymes with less ROS production was found in grafted plants. In addition, ABA concentration increased by 48·4-fold whilst cytokinin concentration decreased by 91·5 % in the xylem sap of own-rooted plants after exposure to a 7 °C chill. In comparison, ABA and cytokinin concentrations increased by 10·5-fold and 36·9 %, respectively, for the grafted plants. Improved plant growth was also observed in grafted plants after the chill. These results suggest that some signals coming from chilling-resistant roots (i.e. ABA and cytokinins) protect leaf photosynthesis in shoots of chilling-sensitive plants.

Keywords: Chilling; chlorophyll fluorescence; Cucumis sativus; electron transport flux; grafting; photosynthesis; reactive oxygen species; water–water cycle

Journal Article.  7009 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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