Antitranspirant Treatments of Stock Plants do not alter Growth and Adventitious Rooting of Shoots of ‘Montaigne’ Lilac and White Fringetree

Abstract

Abstract Antitranspirants were evaluated for their effectiveness as a stock plant treatment to improve adventitious rooting of softwood cuttings of Syringa vulgaris L. ‘Montaigne’ (Montaigne lilac) and Chionanthus virginicus L. (white fringe tree). New shoots of S. vulgaris ‘Montaigne’ and C. virginicus were sprayed with one of two film-forming antitranspirants including Clear Spray® (aqueous acrylic emulsion) and sodium silicate; or Atrazine®, a herbicide that acts as a stomate-regulating antitranspirant. Shoot caliper of antitranspirant-treated lilacs increased more slowly than controls. Thirty days after treatment cuttings were taken from both taxa. All treatments resulted in 80 to 85% rooting of cuttings in lilac after 6 weeks, but cuttings from Clear Spray®-treated plants rooted more quickly. Chionanthus virginicus cuttings treated with Clear Spray® had significantly lower rooting (16%) than cuttings taken from Atrazine® treated plants (50%). In a subsequent experiment, antitranspirant treatment had no significant effect on shoot length or caliper of ‘Montaigne’ lilac. Photosynthetic rate, transpiration rate, and location of cutting on the stock plant were all positively correlated with shoot length, shoot caliper, and cutting diameter. Shoot length and caliper and cutting diameter, however, were all negatively correlated with root number and root length. There were no significant treatment effects on rooting percentage, root number or root length.