Abstract
Biochemical aspects of senescence were studied in coconut leaf tissue from palms affected by lethal yellowing a disease with a suspected mycoplasma aetiology. By comparison with water controls, gibberellic acid, copper zinc, iron administered separately and kinetin supplied alone or with indoleacetic acid increased the longevity and/or caused re-greening of detached diseased pinnae. Healthy pinnae responded only to gibberellic acid or a mixture of amino acids. The failure of yellow diseased pinnae to respond to a mixture of amino acids, taken together with the much reduced catalase activity in chlorotic pinna suggests a disturbed protein metabolism in palms affected by lethal yellowing. The likelihood of a hormonal imbalance associated with lethal yellowing inducible by mycoplasmas or micronutrient deficiencies is discussed as is the possibility of ethylene involvement.
