Internode elongation and strobili production of Humulus lupulus cultivars in response to local strain sensing

William L Bauerle

doi:10.1038/s41598-021-88720-8

Abstract

Three different cultivars of Humulus lupulus L. were subjected to a regime of internode touch and bending under greenhouse conditions. Experiments were performed to assess intraspecific variability in plant mechanosensing, flower quality, and yield to quantify the thigmomorphogenic impact on plant compactness and flowering performance. Touching and/or touching plus bending the plant shoot internodes located in the apical meristem zone decreased internode elongation and increased width. The growth responses were due partly to touching and/or touching plus bending perturbation, 25.6% and 28% respectively. Growth of new tissue within the local apical portion of the bine continued to remain mechanosensitive. The number of nodes and female flowers produced was unaffected by either type of mechanical stress. The study provides evidence that thigmomorphogenic cues can be used as a hop crop management tool to increase bine compactness and increase node density per unit area. The findings have broad implications for hop production; production can more readily take place in a confined greenhouse space with the aid of mechanical stimulation to control plant growth without sacrificing yield or flower quality.

Highlights

Three different cultivars of Humulus lupulus L. were subjected to a regime of internode touch and bending under greenhouse conditions
Greenhouse conditions were programmed to a set point air temperature of 26 °C during photoperiod and 20 °C during the dark with a 45 min temperature step change between the two, 50% relative humidity (RH; %), and supplemental photosynthetically active radiation (PAR) of 100—700 umol m−2 s−1 during the photoperiod (Philips lighting, Amsterdam, The Netherlands)
The T45 and N45 treatments had a 27.9% and 26.6% reduction in internode elongation compared to the FC, FN, and F45 treatments

Summary

Introduction

Three different cultivars of Humulus lupulus L. were subjected to a regime of internode touch and bending under greenhouse conditions. The findings have broad implications for hop production; production can more readily take place in a confined greenhouse space with the aid of mechanical stimulation to control plant growth without sacrificing yield or flower quality. The author knows of no published data to substantiate or refute whether hops demonstrate a thigmomorphogenic response induced by “artificial” mechanical signals Hop production, whether it take place outdoors or within a controlled environment confined space, presents a challenge imposed primarily by the plant’s physical size (length). In comparison with small stature species, hop bines require a certain node count to flower This is due to a protracted variety-specific juvenile phase during which they are incapable of flowering unless 12–25 nodes are visible to the naked eye[7]. Transformation stipulation results in non self-supporting bines that are of significant length and morphological complexity, making them difficult subjects for experimental work or production in a confined space

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