title: The functional significance of black-pigmented leaves: photosynthesis, photoprotection and productivity in Ophiopogon planiscapus 'Nigrescens'.
abstract: Black pigmented leaves are common among horticultural cultivars, yet are extremely rare across natural plant populations. We hypothesised that black pigmentation would disadvantage a plant by reducing photosynthesis and therefore shoot productivity, but that this trait might also confer protective benefits by shielding chloroplasts against photo-oxidative stress. CO2 assimilation, chlorophyll a fluorescence, shoot biomass, and pigment concentrations were compared for near isogenic green- and black-leafed Ophiopogonplaniscapus 'Nigrescens'. The black leaves had lower maximum CO2 assimilation rates, higher light saturation points and higher quantum efficiencies of photosystem II (PSII) than green leaves. Under saturating light, PSII photochemistry was inactivated less and recovered more completely in the black leaves. In full sunlight, green plants branched more abundantly and accumulated shoot biomass quicker than the black plants; in the shade, productivities of the two morphs were comparable. The data indicate a light-screening, photoprotective role of foliar anthocyanins. However, limitations to photosynthetic carbon assimilation are relatively small, insufficient to explain the natural scarcity of black-leafed plants.
authors.affiliation: School of Biological Sciences, University of Auckland, Auckland, New Zealand.
authors.forename: Jean-Hugues B
authors.initials: JH
authors.lastname: Hatier
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Clearwater
authors.forename: Kevin S
authors.initials: KS
authors.lastname: Gould
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D002940:Circadian Rhythm / Q000528:radiation effects; D005453:Fluorescence; D031441:Ophiopogon / Q000254:growth & development / Q000502:physiology* / Q000528:radiation effects*; D010788:Photosynthesis / Q000528:radiation effects*; D045332:Photosystem II Protein Complex / Q000378:metabolism; D010858:Pigmentation / Q000528:radiation effects*; D018515:Plant Leaves / Q000502:physiology* / Q000528:radiation effects*; D013472:Sunlight; D013696:Temperature
chemical_list: D045332:Photosystem II Protein Complex; D002734:Chlorophyll; D002245:Carbon Dioxide; D000077194:Chlorophyll A