Effect of ancymidol in combination with temperature regime, calcium nitrate, and cultivar selection on calcium deficiency symptoms during hydroponic forcing of tulip

Abstract

Experiments were conducted to determine the effect of ancymidol, as impacted by temperature, Ca(NO 3) 2, and cultivar, on the prevention of Ca deficiency symptoms during hydroponic forcing of tulip ( Tulipa gesneriana L.). In all treatments where tulips were forced in distilled water, Ca deficiency symptoms occurred. Symptoms included scape topple; flower abortion; and chlorosis, water soaking, cracking, exudation, and purple pigmentation of the lower leaves. All symptoms except topple were avoided when tulips were forced in 5 mM Ca(NO 3) 2 solution. Topple was prevented by Ca(NO 3) 2 in a low temperature regime (21°C day–18°C night) in two of three experiments. Ca deficiency was not prevented in a high temperature regime (24°C day–21°C night). Plants forced in Ca(NO 3) 2 were too tall for commercial use. When forced in a solution of ancymidol, topple was prevented but all other symptoms of Ca deficiency persisted. An ancymidol rate of 0.25 mg per 650 ml pot containing five bulbs caused abortion, unrelated to Ca deficiency, in the cultivar Oscar. Forcing in a combination of 5 mM Ca(NO 3) 2 plus ancymidol prevented all symptoms of Ca deficiency in all experiments except in the high temperature regime of one. Ancymidol rates of 0.0625 and 0.125 mg per pot did not always provide adequate height control. A rate of 0.18 mg per pot in combination with 5 mM Ca(NO 3) 2 was sufficient to prevent Ca deficiency symptoms and provide adequate height control in all but one cultivar. `Jingle Bell' required an ancymidol rate of 0.24 mg for adequate height control. Prevention of topple by ancymidol did not appear to be due to the correction of Ca deficiency since ancymidol added to Ca(NO 3) 2 resulted in lower total Ca uptake per shoot. It was likely due to shorter, stronger scapes masking this Ca deficiency symptom.