Functional role of pigments in mature nigrescent leaves of Ophiopogon planiscapus 'nigrescens' nakai

Show simple item record Hatier, Jean-Hugues Bertrand 2021-08-25T09:05:42Z 2021-08-25T09:05:42Z 2006
dc.description Full text is available to authenticated members of The University of Auckland only.
dc.description.abstract Black-leafed plants occur only infrequently in nature, and are apparently confined to certain bryophytes growing in marginal habitats. However, ornamental cultivars of black-leafed vascular plants are common. Therefore, the reason for their rarity in nature is uncertain. Nothing is known of the physiology of black leaves. The aim of this thesis was to compare effects of different stressors on black leaves using near isogenic green and black phenotypes of Ophiopogonplaniscapus 'Nigrescens' Nakai. Black Ophiopogon planiscapus 'Nigrescens' had high concentrations of anthocyanins, up to 56% greater than those in anthocyanic leaves of three other species. There were no obvious structural differences between black and green leaves. The combination of anthocyanins and chlorophylls resulted in chromaticity coordinates comparable to a black paint standard. Constituent anthocyanidins comprised delphinidin (47%), petunidin (35%) and malvidin (18%). The leaves of both phenotypes had comparable concentrations of carotenoids. Black leaves absorbed 95% PAR and green leaves 90%. Green light penetrated deeper within green than black leaves. When exposed to low, medium or high light intensities, black plant productivity was less than the green. However, in high light intensities, the productivity of primary shoots of black plants was greater, but green plants produced more secondary shoots. After cold stress, black leaves were less vulnerable than green leaves to photoinhibition and photooxidation. The AF7Fm’ of plants exposed to 1500 pmol photon m'2-s'' white light was 62% greater at 20°C and 40% greater at 5°C in black than in green leaves. In both leaves phenotypes, FvZFm recovered completely when returned to darkness at 20°C. At 5°C, however, the Fy/Fm of the black phenotype recovered totally, but that of the green leaves remained 7% lower. The AF/Fm' of plants exposed to full sunlight after acclimation in either low, medium or high light intensities were up to 32% higher in black than in green leaves. AF/Fm’ of black leaves also recovered completely faster after sunset. SOD, APX and CAT were enhanced in black compared with green leaves. The DPPH scavenging capacities of methanolic extracts were up to eight times higher in black than in green leaves and were correlated with anthocyanin concentrations. After acclimation at 16°C, exposure to a 4°C night caused a greater surge of lipid peroxidation in green than in black leaves. The anthocyanins in dark pigmented plants may play a role in signalling. By absorbing green light, which is highly energetic and deeply penetrating, the black pigmentation may reduce the ROS produced in response to high light intensities. In addition to directly scavenging ROS, anthocyanins may protect antioxidant enzymes.
dc.publisher ResearchSpace@Auckland
dc.relation.ispartof PhD Thesis - University of Auckland
dc.relation.isreferencedby UoA99175844914002091
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dc.rights Restricted Item. Full text is available to authenticated members of The University of Auckland only.
dc.title Functional role of pigments in mature nigrescent leaves of Ophiopogon planiscapus 'nigrescens' nakai
dc.type Thesis Biological Sciences The University of Auckland Doctoral PhD
dc.rights.holder Copyright: The author

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