Effect of light stress on the homoiochlorophyllous resurrection plant Craterostigma wilmsii

• Main Author: Loffell, D A
• Other Authors: Farrant, Jill M
• Format: Others
• Language: English
• Published: University of Cape Town 2017
• Subjects: Botany
• Online Access: http://hdl.handle.net/11427/26005

The effect of light stress during drying, experienced by the homoiochlorophyllous resurrection plant Craterostigma wilmsii, was examined in this study. Inner-whorl leaves, which become shaded from light when dry, and outer-whorl leaves, the abaxial surfaces of which receive light in the dry state, as well as leaves which had been restrained from curling during drying, were separately examined. Differences in chlorophyll ( a + b) content, carotenoid (x + c) content, anthocyanin content, ascorbate peroxidase activity, and ultrastructure, were assessed. Shaded inner whorl leaves do not experience lightchlorophyll interactions, carotenoids and anthocyanin pigments do not accumulate and ascorbate peroxidase activity remains low in them during drying. Outer whorl leaves accumulate light-filtering pigments such as anthocyanins and carotenoids to mask their chlorophyll, and the activity of the enzyme ascorbate peroxidase is increased. Neither inner nor outer whorl leaves suffer subcellular damage during drying but leaves prevented from curling and shading their abaxial surfaces suffer damage to the subcellular environment on drying. Although such leaves accumulated reflective pigments and increase ascorbate peroxidase activity, these mechanisms are unable to provide adequate protection of the leaf tissue without concurrent shading provided by curling. Leaves that shaded their abaxial surfaces by curling and leaves that where shaded completely by other curled leaves decreased their content of chlorophyll in the dry state. Leaves that were restrained from curling had increased chlorophyll contents. Although chlorophyll decline in normal dry C. wilmsii leaves appears to be an artefact of shading, this decline in photopigment content concurrent with shading by leaf movements and light filtering pigments, is suggested to assist in protecting against free radical damage in the dry state.