Optimizing spray application rates of abscisic acid for height control of jalapeño transplants
Abscisic acid (ABA) applied as a foliar spray was evaluated for height control of jalapeño pepper (Capsicum annuum L.) seedlings. At the one- to two-leaf stage, ABA was applied in a factorial combination of three concentrations (0, 3.8, or 7.6 mM) and three spray volumes (0.2, 1, or 2 L m-2), providing up to 4.7 mg ABA plant-1. Although the final stem height decreased proportionally to the amount of ABA by up to 24%, the tested rates excessively suppressed the overall shoot growth, reducing the total leaf area by up to 52%. The reduction in leaf area was due mostly to cotyledon abscission, which was significantly induced with ≥1.18 mg ABA plant-1. To determine the optimal application rate with minimal negative side-effects, an additional test was conducted using four concentrations (0, 1.3, 2.5, or 3.8 mM) and three spray volumes (0.2, 0.4, or 0.6 L m-2), with up to 0.71 mg ABA plant-1. These rates reduced the final stem height by up to 23% without inducing cotyledon abscission. Although ABA inhibited leaf expansion and reduced total leaf area by up to 27%, the reduction in the photosynthetic area did not affect post-planting growth or yield. Our results suggest that excess levels of ABA in a single foliar spray induce undesirable growth inhibitions or excessive shoot growth reductions. With optimal rates, however, this method can provide effective height control and its extent can be easily modified by changing the concentration or spray volume.
Agehara, S. and Leskovar, D.I. (2018). Optimizing spray application rates of abscisic acid for height control of jalapeño transplants. Acta Hortic. 1204, 235-242
ABA, Capsicum annuum, chlorosis, leaf area, height control, internode elongation, stem elongation