Response of Helianthus tuberosus L. to pinching techniques for ornamental containerized purpose

Abstract

Most Jerusalem artichoke (JA, Helianthus tuberosus L.) grown as edible functional food plant, produce more tubers with high stems (1.5-2.0 m). To develop them as potted plant it is necessary to control their height and to increase branches in order to create a more compact canopy. Two experiments were conducted under greenhouse conditions. Experiment 1 demonstrated that pinching seedlings at all position (2, 3, and 4 leaf pairs: LFP) increased canopy width, total leaf area, compactness index, number of branching and leaf and stem dry weight, but reduced plant height more than 40% when compared with non-pinching treatment. Leaving 2 or 3 LFP instead of 4 LFP after pinching only increased compactness index with marketable characters. None of the pinching times (10, 20 and 30 days after tuber planting: DAP) affected total leaf area, compactness index, number of branching and total leaf area. Pinching at 30 DAP gave the lowest leaf and root dry weight (DW). No interaction between pinching position and time in all growth parameters was seen, except in plant stem DW by leaving 2 or 3 LFP at 20 DAP after pinching. Experiment 2 showed that pinching seedlings with 2 LFP had low new tuber DW through all growth stages, however the underground part produced higher DW when reaching the harvesting stage. Higher reducing sugar accumulation in new tubers was found in normal plants (non-pinched) from flowering stage to senescence stage, thereafter its content declined compared to pinching plant at harvesting time. This result suggests that pinching technique might be partially a good horticultural practice to control JA height and canopy for the use as an ideal ornamental containerized plant.