EFFECT OF RATE AND TIMING OF PGR-1V APPLICATION ON COTTON GROWTH AND DEVELOPMENT

D.N. Oosterhuis and D. Zhao

ABSTRACT

The effects of rate and timing of application of the plant growth regulator PGR-IV on cotton growth and development were investigated in pot experiments in the greenhouse at the Altheimer Laboratory in Fayetteville, Arkansas. Treatments consisted of three rates of PGR-LV (1, 2, and 4 oz./acre) and application at five times (infurrow at planting, cotyledon, second true leaf, fifth true leaf and pinhead square growth stages). Application of PGR-LV during early growth stages increased plant height, leaf area, square numbers per plant, and dry weight especially of roots and squares. The leaves of plants receiving PGR-LV had higher stomatal resistance and lower transpiration rate than control plants before watering, and the opposite results after watering. The most appropriate times of applying PGR-LV were in-furrow at planting, or at the second true leaf and pinhead square stages of growth. The optimal rates were 1-2 oz./acre before the second true leaf stage, and 4 oz./acre between the second true leaf and pinhead stages. With optimal rate and timing of application, the plant growth regulator PGR-IV caused significant beneficial effects on cotton growth.

Cotton cell lines were selected in vitro for increased resistance to chilling temperature (5EC). Shoot tips of plants regenerated from these cell lines were able to root normally at 22EC whereas those of the control cell lines did not. After prolonged passage in the absence of the selection pressure, the selected cell lines retained the acquired





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Document last modified July 8, 2004