Biochemical changes in roots of coconut palms (Cocos nucifera L.) affected by lethal yellowing.
Respiration rates and protein concentrations of lateral and subtending roots of coconut palms were studied at various stages of development of lethal yellowing (LY) disease (caused by phytoplasmas), including LY-positive symptomless palms, and compared to respiration rates and protein concentrations of healthy palms. No visual symptoms were apparent in the roots of LY-positive symptomless palms. However, respiration rates and protein concentrations were already lower in LY-positive symptomless palms and they continued to decrease as the disease developed. The appearance of root necrosis coincided with the onset of leaf yellowing in aboveground parts. Implications of these findings are discussed in the context of root damage, as a central process in the mode of pathogenicity of the disease.