INVITRO ACCLIMATIZATION OF CHRYSANTHEMUM AND SUGAR-BEET PLANTLETS BY TREATMENT WITH PACLOBUTRAZOL AND EXPOSURE TO REDUCED HUMIDITY

Methods are described to promote in vitro acclimatization of chrysanthemum and sugar beet. Plants were cultured at relative humidity levels of 58%, 81%, and 100% or with alternating combinations of these levels. The effect on plant growth of the addition to growth media of the anti-gibberellin paclobutrazol was also investigated. Leaves which were initiated and which developed on plants at relative humidity levels below 100%, or on plants cultured on growth media supplemented with 10.0-mu-M paclobutrazol, displayed increased epicuticular wax, improved stomatal functioning, and reduced leaf dehydration. Reduced humidity levels also increased trichome density in chrysanthemum and decreased the incidence of vitrification in sugar beet. Plant growth for both species was optimal at 81% relative humidity. The addition of paclobutrazol to the growth medium resulted in a reduction in plant height.