The content of total iron, cuprum and boron in leaves of four chrysanthemum cultivars was studied in 12 growth cycles starting on the second day of each month throughout the year, from January to December. From the moment of potting, the plants were treated with a short day. In periods of naturally long days, the day was shortened to 10.5 hours using a black-out cover. No supplementary light was used. The time of culture associated with real insolation had a significant influence on micronutrients content. Maximum contents of cuprum and boron were recorded in the leaves of chrysanthemums grown in periods of light deficit. The reverse regularity in case of iron was observed.

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