Photosynthesis and protective mechanisms during ageing in transgenic tobacco leaves with over-expressed cytokinin oxidase/dehydrogenase and thus lowered cytokinin content

Title:

Photosynthesis and protective mechanisms during ageing in transgenic tobacco leaves with over-expressed cytokinin oxidase/dehydrogenase and thus lowered cytokinin content

Creator:

Mýtinová, Z., Haisel, D., and Wilhelmová, N.

Identifier:

https://cdk.lib.cas.cz/client/handle/uuid:ba23e454-edf5-42b0-9efc-7c2a56fe8895
uuid:ba23e454-edf5-42b0-9efc-7c2a56fe8895
issn:0300-3604
doi:10.1007/s11099-006-0078-6

Subject:

chlorophyll fluorescence, Nicotiana tabacum, photosynthetic efficiency, senescence, and xanthophyll cycle

Type:

model:article and TEXT

Format:

bez média and svazek

Description:

The content of cytokinins (CKs), the plant inhibitors of the final phase of plant development, senescence, is effectively controlled by irreversible degradation catalysed by cytokinin oxidase/dehydrogenase (CKX). In transgenic tobacco, denoted as AtCKX, with over-expressed CKX causing lowered CK content, we investigated changes in the time courses of chlorophyll (Chl) and xanthophyll (violaxanthin, antheraxanthin, zeaxanthin, neoxanthin, and lutein) contents. We also determined parameters of slow Chl fluorescence kinetics such as minimum Chl fluorescence yield in the darkadapted state F0, maximum quantum yield of PS2 photochemistry (Fv/Fm), maximum ratio of quantum yields of photochemical and concurrent non-photochemical processes in photosystem 2 (PS2), Fv/F0, non-photochemical quenching (NPQ), and effective quantum yield of photochemical energy conversion in PS2 (Φ2). We used three different developmental leaf stages, old, mature, and young, and compared this with time courses of these characteristics in leaves with natural CK levels. The parameters Fv/Fm, Fv/F0, and Φ2 were unchanged during ageing in AtCKX plants in contrast to control ones where a significant decrease in old leaves was found. In control plants F0 increased during ageing, but in the oldest leaf a considerable decrease was observed. This could indicate progressive damage to PS2 reaction centres and then detachment and rapid degradation of Chl. This is in agreement with time course of Chl content. NPQ decreased with age and was similar in both plant types. We observed a decline of xanthophyll contents in the oldest leaves in both plant types, but the contents were enhanced in AtCKX compared to control plants, especially of neoxanthin. The higher xanthophyll contents in the transgenic plants contribute to a better photoprotection and the fluorescence parameters indicated that photosynthetic apparatus was in better condition compared to control and it consequently postponed the onset of leaf senescence. and Z. Mýtinová, D. Haisel, N. Wilhelmová.

Language:

Multiple languages

Rights:

http://creativecommons.org/licenses/by-nc-sa/4.0/
policy:public

Coverage:

599-605

Source:

Photosynthetica | 2006 Volume:44 | Number:4

Harvested from:

CDK

Metadata only:

false