Application of Paclobutrazol to Mitigate Environmental Stress of Urban Street Trees

Abstract

Paclobutrazol is a tree growth regulator that is frequently applied by arborists to control tree growth in utility rights of way. Paclobutrazol is also marketed to mitigate tree stresses associated with urban environments. In this study we applied paclobutrazol as a soil drench to honeylocust (Gleditsia triacanthos L var. inermis (L.) Zab.) and Callery pear (Pyrus calleryiana Decne.) trees planted as street trees on two sites in Lansing, Michigan USA. We evaluated physiological and morphological responses for two years after treatment. Application of paclobutrazol increased SPAD chlorophyll index of trees of both species in both years, compared to untreated control trees. Application of paclobutrazol increased leaf water potential of trees on one study site (Downtown) but not the other (Old Town). Paclobutrazol increased gas exchange (net photosynthesis and stomatal conductance) of Callery pear trees on one of four measurement dates (gas exchange was not measured on honeylocust trees). Leaf size of Callery pear trees was reduced following paclobutrazol application whereas leaf size of honeylocust trees was unaffected by paclobutrazol. These results indicate that paclobutrazol can help to reduce stress of trees and improve physiological function under urban conditions. However, paclobutrazol should be viewed as part of a suite of options for arborists and landscapers to manage trees on stressful sites, rather than as a replacement for proper overall care.

Growth and physiology of ornamental sunflower under salinity in function of paclobutrazol application methods

“…These authors report that the rise in this index by PBZ reflects the increase in the intensity of the green color of the leaves, enabling greater contrast with the yellow of the inflorescence, which increases visual attractiveness and, after that, the commercialization, indicating that PBZ application via soil is a viable alternative for sunflower cultivation. This change in leaf color, promoted by PBZ, was also found in Paeonia lactiflora (Xia et al, 2018) and forest species (Cregg & Ellison-Smith, 2020).…”

“…The higher net photosynthesis promoted by the application of PBZ via soil may be related to the more efficient action of this growth regulator on the xylem and phloem vessels (Jaleel et al, 2007), favoring greater availability of water and nutrients to the roots for the aerial part, which contributed to photosynthesis rate, since PBZ interferes in the source-sink relationship (Silva et al, 2020). PBZ induced improvement in gas exchange was also observed in plants of Catharanthus roseus (Jaleel et al, 2007), Paeonia lactiflora (Xia et al, 2018), Solanum lycopersicum (Silva et al, 2020), and forest species (Cregg & Ellison-Smith, 2020) in the absence of stress, besides Chenopodium quinoa under salt stress (Waqas et al, 2017).…”

Zinc and Paclobutrazol Mediated Regulation of Growth, Upregulating Antioxidant Aptitude and Plant Productivity of Pea Plants under Salinity

“…In addition, the seeds are an excellent source of carbohydrates, minerals (calcium and iron), and vitamins (thiamin, tocopherols, niacin, and folic acid) [ 22 ]. Earlier reports have individually documented that zinc or PBZ, as cost-effective agents, have multiple biochemical functions in plant development under stressful conditions [ 14 , 23 , 24 ]. Conversely, their integrative application on inducing pea salt tolerance, to our knowledge, has not been documented and required more exploration.…”

Paclobutrazol reduces growth and increases chlorophyll indices and gas exchanges of basil (Ocimum basilicum)

“…The effect of reduced transpiration area and more roots absorbing water results in greater plant vigor (Miller, 2016). PBZ can be applied via soil or foliar, however, it is more efficient via soil, as it is translocated almost exclusively by the xylem, where it is absorbed by the roots and taken to the growth points (Xia et al, 2018;Cregg and Ellison-Smith, 2020;Lima et al, 2020;Guimarães et al, 2021).…”