Physiological effects of tree growth regulators on several tree species

Shuju Bai, Purdue University

Abstract

Physiological effects of two tree growth regulators (TGRs), flurprimidol and paclobutrazol, on eleven species located in Indiana and Louisiana were studied. Five experiments were designed with mature trees, saplings, seedlings, or isolated mitochondria to investigate effects of TGRs on wound healing, cambial growth, vegetative growth of progeny seedlings, and electron transport by leaf mitochondria. Species investigated were: Quercus rubra L., Q. alba L., Q. falcata var. pagodaefolia Elliott, Juglans nigra L., Alnus glutinosa L., Liquidambar styraciflua L., Fraxinus americana L., Pinus strobus L., P. taeda L., Liriodendron tulipifera L., and Platanus occidentalis L. Closure of bark wounds was reduced in paclobutrazol-treated white oak, red oak, sweetgum, black walnut and white ash in Indiana, and sweetgum and cherrybark oak in Louisiana. There was no difference in bark wound closure between treated and untreated European black alder, yellow poplar, white pine, or American sycamore. Closure of pruning wounds was reduced in white oak, red oak, sweetgum, European black alder, and black walnut in Indiana, and sweetgum and cherrybark oak in Louisiana. The inhibitory effect on closure of both bark and pruning wounds in some species persists at least three or four years. TGRs were transported to developing seeds of silver maple and reduced growth of the progeny when the seeds were collected one month after treatment. The growth of progeny seedlings was enhanced when seeds were collected one year after treatment and was not affected when seeds were collected two years after treatment with TGRs. The effect of paclobutrazol on cambial growth, annual shoot growth, and total tree height growth varied with species and treatment duration. Paclobutrazol reduced cambial growth in white oak, red oak, cherrybark oak, sweetgum, European black alder, and white pine with the effect varying among species, vertical location of the cross-section, and years after treatment. TGRs accumulated in seeds of treated European black alder and silver maple reduced or stimulated electron transport in leaf mitochondria of the progeny seedlings. The inhibition and stimulation effects depending on the number of growing seasons after treatment of the parent trees related to growth responses, indicating another mode of action of TGRs.

Degree

Ph.D.

Advisors

Chaney, Purdue University.

Subject Area

Forestry|Plant sciences

COinS