APPLIED USES OF PLANT GROWfH REGULATORS (PGRs)
Plant growth regulators are used in the cut foliage industry for both traditional and nontraditional
purposes.
Plant propagation
Seedgermination. SoakingZamiaJloridana seeds for 48 hr in 1,000 mg'L-1 GA3 solutions
after treatment with sulphuric acid (H2S04) increased seed germination (1). Similar GA3
treatments also reduced the number of days to germination for Zamia fuifuracea (2).
Rooting of cuttings. Cut foliage producers often root cuttings of desirable clonal cut
foliage plant material. To do so, commercial products containing indole-3-butyric acid (IBA)
or IBA + naphthalene acetic acid (NAA) are often used.
Tissue culture. More and more selections of unique cut foliage species and cultivars are
being made so that tissue culture propagation is becoming more important to the industry.
Needless to say, auxins and cytokinins playa significant role in making those propagation
efforts successful.
Substitution for chilling requirement
Gibberellic acid treatments have been effective substitutes for low temperatures needed
to satisfy chilling requirements of crops such as potatoes in warm climates like Florida (11).
Research has shown that Florida/Holland/Israeli ruscus (Ruscus hypophyllum L.) must have
adequate chilling in order to produce new stems (12). For a related plant in Florida, Italian
ruscus (Danae'racemosa [L.] Moench), spring stem production was increased from one to 3.8
stems per plant by chilling for 8 weeks at 4°C. However, this plant did not respond to 2,500
mg'L-1 sprays of GA3 (Stamps, unpublished). The lack of response to GA3 may have been be
due to lack of penetration of the spray through the waxy coating of the leaves.