Changes in photosynthetic efficiency and carotenoid composition in leaves of white clover at different developmental stages

Sang Dong Yoo, Dennis Greer, William A. Laing, Michael T. McManus

Research output: Contribution to journalArticle

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Abstract

Changes in photosynthetic capacity and efficiency, and in carotenoid composition have been examined during leaf ontogeny in the pasture legume white clover, Trifolium repens (L.). Leaf chlorophyll, measured as 'g'1 FW, was used as an indicator of leaf maturity, with maximum levels of the pigment denoting the mature-green phase of leaf development, and an observed decrease in chlorophyll content accompanying leaf senescence. For chlorophyll a and b, a constant ratio (a/b) between the two pigments was observed in mature-green leaves, and in the early stages of senescence while the ratio increased during the later stages of leaf senescence. Measurement of the net photosynthetic CO2 assimilation rate (PN) as 'mol m'2 s'1 revealed a decrease in the photosynthetic rate that correlated with the decrease in total chlorophyll content. Measurement of chlorophyll fluorescence in vivo revealed that the optimal quantum efficiency of PSII (Fv/Fm) did not decline significantly, but the effective quantum efficiency of PSII in the light ((Fm' ' Ft)/Fm') did decrease significantly, with a concomitant increase in non-photochemical quenching (NPQ). In terms of changes in the accessory pigments during senescence, the total pool of carotenoids decreased when expressed per unit leaf area, but not as rapidly as total chlorophyll such that the chlorophyll/carotenoid ratio decreased. The relative abundance of the carotenoids comprising the xanthophyll cycle, zeaxanthin (Z), violaxanthin (V) and antheraxanthin (A) altered during leaf ontogeny. In mature-green leaves, violaxanthin was the more abundant pigment, but as leaf senescence progressed, zeaxanthin became the most abundant pigment, and the ratio of (Z + A)/(Z + A + V) increased. These results are discussed in terms of the role of the xanthophylls cycle in the protection of PSII during leaf senescence.
Original languageEnglish
Pages (from-to)887-893
Number of pages7
JournalPlant Physiology and Biochemistry
Volume41
Issue number10
DOIs
Publication statusPublished - Oct 2003

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Medicago
Carotenoids
Chlorophyll
Trifolium repens
carotenoids
developmental stages
chlorophyll
Xanthophylls
leaves
pigments
violaxanthin
Trifolium
zeaxanthin
ontogeny
Fabaceae
antheraxanthin
Fluorescence
xanthophylls
forage legumes
Light

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title = "Changes in photosynthetic efficiency and carotenoid composition in leaves of white clover at different developmental stages",
abstract = "Changes in photosynthetic capacity and efficiency, and in carotenoid composition have been examined during leaf ontogeny in the pasture legume white clover, Trifolium repens (L.). Leaf chlorophyll, measured as 'g'1 FW, was used as an indicator of leaf maturity, with maximum levels of the pigment denoting the mature-green phase of leaf development, and an observed decrease in chlorophyll content accompanying leaf senescence. For chlorophyll a and b, a constant ratio (a/b) between the two pigments was observed in mature-green leaves, and in the early stages of senescence while the ratio increased during the later stages of leaf senescence. Measurement of the net photosynthetic CO2 assimilation rate (PN) as 'mol m'2 s'1 revealed a decrease in the photosynthetic rate that correlated with the decrease in total chlorophyll content. Measurement of chlorophyll fluorescence in vivo revealed that the optimal quantum efficiency of PSII (Fv/Fm) did not decline significantly, but the effective quantum efficiency of PSII in the light ((Fm' ' Ft)/Fm') did decrease significantly, with a concomitant increase in non-photochemical quenching (NPQ). In terms of changes in the accessory pigments during senescence, the total pool of carotenoids decreased when expressed per unit leaf area, but not as rapidly as total chlorophyll such that the chlorophyll/carotenoid ratio decreased. The relative abundance of the carotenoids comprising the xanthophyll cycle, zeaxanthin (Z), violaxanthin (V) and antheraxanthin (A) altered during leaf ontogeny. In mature-green leaves, violaxanthin was the more abundant pigment, but as leaf senescence progressed, zeaxanthin became the most abundant pigment, and the ratio of (Z + A)/(Z + A + V) increased. These results are discussed in terms of the role of the xanthophylls cycle in the protection of PSII during leaf senescence.",
keywords = "Open access version available, Carotenoids, Leaf development, Leaf senescence, Photosynthetic yield, Photosystem II, Trifolium repens, White clover",
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Changes in photosynthetic efficiency and carotenoid composition in leaves of white clover at different developmental stages. / Yoo, Sang Dong; Greer, Dennis; Laing, William A.; McManus, Michael T.

In: Plant Physiology and Biochemistry, Vol. 41, No. 10, 10.2003, p. 887-893.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Changes in photosynthetic efficiency and carotenoid composition in leaves of white clover at different developmental stages

AU - Yoo, Sang Dong

AU - Greer, Dennis

AU - Laing, William A.

AU - McManus, Michael T.

N1 - Imported on 12 Apr 2017 - DigiTool details were: month (773h) = Oct 2003; Journal title (773t) = Plant Physiology and Biochemistry. ISSNs: 0981-9428;

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N2 - Changes in photosynthetic capacity and efficiency, and in carotenoid composition have been examined during leaf ontogeny in the pasture legume white clover, Trifolium repens (L.). Leaf chlorophyll, measured as 'g'1 FW, was used as an indicator of leaf maturity, with maximum levels of the pigment denoting the mature-green phase of leaf development, and an observed decrease in chlorophyll content accompanying leaf senescence. For chlorophyll a and b, a constant ratio (a/b) between the two pigments was observed in mature-green leaves, and in the early stages of senescence while the ratio increased during the later stages of leaf senescence. Measurement of the net photosynthetic CO2 assimilation rate (PN) as 'mol m'2 s'1 revealed a decrease in the photosynthetic rate that correlated with the decrease in total chlorophyll content. Measurement of chlorophyll fluorescence in vivo revealed that the optimal quantum efficiency of PSII (Fv/Fm) did not decline significantly, but the effective quantum efficiency of PSII in the light ((Fm' ' Ft)/Fm') did decrease significantly, with a concomitant increase in non-photochemical quenching (NPQ). In terms of changes in the accessory pigments during senescence, the total pool of carotenoids decreased when expressed per unit leaf area, but not as rapidly as total chlorophyll such that the chlorophyll/carotenoid ratio decreased. The relative abundance of the carotenoids comprising the xanthophyll cycle, zeaxanthin (Z), violaxanthin (V) and antheraxanthin (A) altered during leaf ontogeny. In mature-green leaves, violaxanthin was the more abundant pigment, but as leaf senescence progressed, zeaxanthin became the most abundant pigment, and the ratio of (Z + A)/(Z + A + V) increased. These results are discussed in terms of the role of the xanthophylls cycle in the protection of PSII during leaf senescence.

AB - Changes in photosynthetic capacity and efficiency, and in carotenoid composition have been examined during leaf ontogeny in the pasture legume white clover, Trifolium repens (L.). Leaf chlorophyll, measured as 'g'1 FW, was used as an indicator of leaf maturity, with maximum levels of the pigment denoting the mature-green phase of leaf development, and an observed decrease in chlorophyll content accompanying leaf senescence. For chlorophyll a and b, a constant ratio (a/b) between the two pigments was observed in mature-green leaves, and in the early stages of senescence while the ratio increased during the later stages of leaf senescence. Measurement of the net photosynthetic CO2 assimilation rate (PN) as 'mol m'2 s'1 revealed a decrease in the photosynthetic rate that correlated with the decrease in total chlorophyll content. Measurement of chlorophyll fluorescence in vivo revealed that the optimal quantum efficiency of PSII (Fv/Fm) did not decline significantly, but the effective quantum efficiency of PSII in the light ((Fm' ' Ft)/Fm') did decrease significantly, with a concomitant increase in non-photochemical quenching (NPQ). In terms of changes in the accessory pigments during senescence, the total pool of carotenoids decreased when expressed per unit leaf area, but not as rapidly as total chlorophyll such that the chlorophyll/carotenoid ratio decreased. The relative abundance of the carotenoids comprising the xanthophyll cycle, zeaxanthin (Z), violaxanthin (V) and antheraxanthin (A) altered during leaf ontogeny. In mature-green leaves, violaxanthin was the more abundant pigment, but as leaf senescence progressed, zeaxanthin became the most abundant pigment, and the ratio of (Z + A)/(Z + A + V) increased. These results are discussed in terms of the role of the xanthophylls cycle in the protection of PSII during leaf senescence.

KW - Open access version available

KW - Carotenoids

KW - Leaf development

KW - Leaf senescence

KW - Photosynthetic yield

KW - Photosystem II

KW - Trifolium repens

KW - White clover

U2 - 10.1016/S0981-9428(03)00138-4

DO - 10.1016/S0981-9428(03)00138-4

M3 - Article

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EP - 893

JO - Plant Physiology and Biochemistry

JF - Plant Physiology and Biochemistry

SN - 0981-9428

IS - 10

ER -