THE INFLUENCE OF NITROGEN NUTRITION ON KEEPING QUALITY OF POT PLANTS

Experiments with Rosa-Hybrids ‘Ruby’ and Impatiens-New-Guinea-Hybrids ‘Veronika’ show that premature bud drop under interior conditions is advanced by an increasing supply of nitrogen. Euphorbia pulchemma ‘Fireking’ reacts by dropping not only cyathias but also leaves prematurely when the nitrogen supply is rising. As expected, an excessive fertilization with nitrogen leads to an increased salt content of the substrate. Control experiments with increasing potassium supply show, however, that the observed plant injuries are a specific nitrogen effect and that plants tolerate a high potassium supply better.

Besides the amount of nitrogen its form seems to be responsible for leaf drop as well as drop of buds under interior conditions. First experiments indicate a heightened bud and leaf drop when the nutrient solution consists a high amount of ammonium. Furthermore, an increased damage to the root system is observable with increasing ratio of ammonium to nitrate.

The experiments so far let assume that the influence of nitrogen on the keeping quality of pot plants can be traced back to salt effects and specific endogenous nitrogen effects. Also, the nitrogen fortification and disruption of the conversion process cause a rather strong impairment of root health and, therefore, indirectly the deterioration of the keeping quality.

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