Abstract
The effect of plant age on accumulation of calcium, magnesium, zinc, copper and manganese in elongating leaf sheaths of ix sugar-cane varieties (11= 1154) was studied in Hawaii. Calcium and Mg concentrations in the sheaths of each variety were negatively correlated with age, and a quadratic equation was derived for each function. Sheath Mn levels were also negatively correlated with age but not in a clearly delineated manner. There were two periods of maximum Mn accumulation during the 34 month crop cycle, i.e., 2·5 to 8 months, and 15 to 18 months. Zinc accumulation in heath tissue was independent of age except in the case of cv. H54-775. In this cultivar sheath Zn levels declined linearly with age from an average of 32·4 ?g/g dry wt at 2·5 months to 26·9 ?,g/g dry wt at 34 months of age. Copper concentration of leaf sheaths was independent of plant age for all six varieties investigated. Boron accumulation was likewise unaffected by age, but in this case the data for all varieties were combined for statistical analysis since the number of samples was much smaller (n=477). The importance of having knowledge of the effects of plant age on nutrient accumulation in the plant tissues is evident in that such effects can have a profound effect on the accurate interpretation of tissue analysis data. It is recognized, however, that factors such as tissue moisture content and levels of other nutrients in the plant may also affect micronutrient accumulation. Therefore, the data presented should be viewed as a contribution towards explaining the variation of tissue nutrient levels, but certainly not as the sole explanation.
