During the vegetative shoot stage, the untreated leaves contained more ethylene (1.4nLg-1h?1) than the treated plants, with the 2.5, 5, 1 and 0.5mg/L treated leaves containing 0.8, 0.9, 1.1, and 1.1nLg-1h?1 ethylene, respectively. During the 5th day of flowering, the ethylene production rate was 38%, 33%, 27%, and 16% lower in the 5, 2.5, 1, and 0.5mg/L TRIA treatment groups, respectively, compared to the control group. It was also observed that the ethylene production rate increased with the flowering advance as well as with the age of the Bougainvillea plants, and the production rate was significantly lower in the treated plants compared to the control plants (Figure 6).Figure 6The effect of TRIA treatments on ethylene production of Bougainvillea glabra leaves. BF: before flowering, DAF: day after flowering.In this two-year study, it was observed that several parameters were correlated in the TRIA-treated plants. A high degree of correlation was observed between the number of flowers and the leaf TSS (r = 0.80), as well as between the flowering required day and the leaf TSS (r = 0.92) (Figures 7(a) and 7(b)). Moreover, the flower weight (bract) was correlated with leaf sugar content (r = 0.93) as well as bract growth (r = 0.93), and dry matter production (r = 0.89) was positively correlated with the net photosynthesis rate of the treated plants (Figures 8(a), 8(b), and 8(c)). Furthermore, flower longevity was negatively correlated (r = 0.86) with ethylene production in Bougainvillea plants (Figure 8(d)).Figure 7Regression lines for the relationship between flower number and leaf TSS (a) and flowering day and leaf TSS (b) in the treated Bougainvillea plants.Figure 8Regression lines for the correlations between flower weight (bract) and leaf sugar content (a), between net photosynthetic rate and bract growth rate (b), between net photosynthetic rate and dry matter production (c), and between flower longevity and …4. DiscussionTriacontanol (TRIA) is a saturated long-chain alcohol that is known to have growth-promoting activities on a number of plants when applied exogenously. As an important growth regulator, TRIA has attracted much attention with respect to typifying its physiological effects on a number of agronomic crops. TRIA regulates various growth and developmental processes in plants under both normal and stress conditions [19]. Plants are sensitive to extremely low doses of TRIA; therefore, low concentrations of TRIA may be biologically active [20]. It has been reported that TRIA application enhances water uptake, cell division, cell elongation, and the permeability of plant cell membranes [21]. Our two-year study demonstrated that TRIA treatment increased leaf area, shoot length, flower bud, and bract growth of Bougainvillea plants. Reddy et al.