Diagnosis and prognosis of manganese deficiency in Lupinus angustifolius L

Abstract

Relationships diagnostic of manganese (Mn) deficiency in Lupinus angustifolius were examined in growth chamber experiments by studying the effects of Mn supply on plant growth and on photosynthesis and Mn concentrations in young leaves and whole shoots. A critical Mn concentration in youngest fully expanded leaves (YFEL) of 30 8g/g dry matter was found to be diagnostic of reduced dry matter production. A similar critical concentration was found for whole shoots, and the criteria were consistent over a wide range of ontogeny until at least early flowering. A less sensitive criterion of Mn deficiency was that for chlorophyll 'a' fluorescence characteristics of YFEL's (17 8g/g in YFEL), which estimates photosynthetic dysfunction in relation to Mn supply. The distal segments of lupin leaves best reflected changes in fluorescence in relation to their Mn status. The prognosis of impending Mn deficiency in maturing lupin plants was also examined in field and growth chamber experiments by studying the effects of Mn supply on the relationships between the concentrations of Mn in plant components at anthesis, and the subsequent appearance of Mn deficient ('split') seed on maturing plants. The absence of Mn deficient seed in main axis and first-order lateral inflorescences of maturing lupins could be predicted by Mn concentrations in stems at anthesis of >20 8g/g. Manganese concentrations of buds, leaves and tissues containing a high proportion of leaf, were found to be poor predictors of subsequent Mn deficiency in maturing lupins.