Foliar Application of Gibberellic Acid and Methyl Jasmonate Improves Leaf Greenness in Hesperantha coccinea (syn. Schizostylis coccinea), a Rare Ornamental Plant

Abstract

Hesperantha coccinea (Iridaceaea) is a little-known ornamental plant recommended for cultivation in pots, gardens and for cut flowers. The species produces narrow, decorative green leaves that sometimes turn yellow as the plants begin to anthesis. A solution to the problem may be the application of plant growth regulators (PGRs), and so far none have been studied in Hesperantha cultivation. The study assessed the effect of foliar application of gibberellic acid solutions (GA3; 50,100 and 200 mg dm−3) and methyl jasmonate (MeJA; 100, 500 and 1000 µmol dm−3) on the leaf greenness index (SPAD index), leaf number, leaf length and leaf width of H. coccinea. Control plants were not treated with PGRs. It was found that both GA3 and MeJA applied at all tested concentrations significantly increased the greenness index of H. coccinea leaves. In addition, GA3 increased the number of leaves without affecting the length and width of the leaves. MeJA had a growth inhibitory effect. When compared to the control, plants sprayed with MeJA solutions produced fewer leaves that also had reduced length and width. These findings indicate that both regulators (GA3 and MeJA) positively affected plant quality by improving leaf greenness.