The Effect of Paclobutrazol on Growth and Response to Water Stress of Apple Seedlings

in Journal of the American Society for Horticultural Science
Authors:
Dariusz SwietlikAppalachian Fruit Research Station, ARS, U.S. Department of Agriculture, Kearneysville, WV 25430

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Stephen S. MillerAppalachian Fruit Research Station, ARS, U.S. Department of Agriculture, Kearneysville, WV 25430

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Abstract

The addition of (2RS, 3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-1,2,4-triazoI-1-yl-) pentan-3-ol) (paclobutrazol, PP333) at 0.05 or 0.20 ppm to a nutrient solution in which 4-month-old apple (Malus domestica, Borkh.) seedlings were growing, reduced terminal growth and increased root to leaf ratio. Plants pretreated with 0.20 ppm PP333 did not show a reduction in transpiration due to subsequent applied water stress induced by polyethylene glycol (PEG), whereas untreated plants decreased their transpiration in response to PEG stress at −0.5 and −0.75 MPa. The PP333 pretreatment at 0.20 ppm improved water balance of the seedlings since they had a higher water potential than untreated seedlings at equal or higher transpiration rates. Leaf osmotic adjustment to lower water potentials was shown to be leaf age-dependent irrespective of PP333 pretreatment.

Contributor Notes

Visiting Research Horticulturist, Research Institute of Pomology, Skiemiewice, Poland.

Research Horticulturist.

Received for publication April 22, 1983. Mention of a growth regulator in this paper does not constitute a recommendation for use by the U.S. Department of Agriculture nor does it imply registration under FIFRA as amended. Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that also may be suitable. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.

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