Efficacy of Plant Growth Regulators for Potted Plant Production of Sunflower Cultivars
Abstract
While economically important as a food and oil crop, sunflowers are equally as important as a cut flower and ornamental crop. A majority of sunflowers create one large infloresence, however, new ornamental sunflower varieties and hybrids recently released have improved branching and flowering habits, allowing for season-long cultivation. Due to their growth habits during greenhouse production, early vegetative stages must be controlled with plant growth regulators. A variety of non-chemical and chemical growth manipulation tools have been utilized to influence plant physiology and growth habit when ideal growth is not achieved naturally. Manual pinching remains an important tool; however, growers may not obtain the desired results, and the labor associated with pinching can be costly. The work in this thesis evaluated the efficacy of various plant growth regulators applied at commercially recommended timings and the effects of chemical pinching during early vegetative growth stages.
All plant growth regulators significantly reduced plant height and diameter on Helianthus hybrida ‘Sunfinity’ and ‘Suncredible’ except the paclobutrazol foliar spray to ‘Sunfinity.’ In contrast, foliar applications of paclobutrazol provided a significant reduction in plant height and diameter for ‘Suncredible.’ A tank mix application of daminozide and chlormequat chloride provided growth similar to the current production standard, a paclobutrazol drench, for both cultivars.
Applications of dikegulac sodium at 400 mg•L-1 at the first and third vegetative leaf stage, along with 500 mg•L-1 at the second vegetative leaf stage proved to be effective regarding chemically pinching. Chemical pinching did not occur when applied at 400 mg•L-1 at the V2 stage and 500 mg•L-1 at the V3 stage, but resulting growth created a well-rounded canopy. Results in this experiment show that chemical pinching of ‘Sunfinity’ is possible when applications are made at early stages of growth.
Citation
Marshall, Mason Lynn (2022). Efficacy of Plant Growth Regulators for Potted Plant Production of Sunflower Cultivars. Master's thesis, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /197301.