The data on plant height at 150 days after transplanting (DAT) revealed significant differences among treatments with plant growth retardants (Table 1). At 30 DAT, no significant differences were observed. However, by 150 DAT, paclobutrazol at 0.1825 mg/pot (T3) resulted in the shortest plant height (47.53 cm), which was statistically similar to paclobutrazol at 0.25 mg/pot (T4) (47.70 cm). The tallest plants (53.01 cm) were recorded in the control treatment (T13), which was comparable to CCC at 500 ppm (T9) and 1000 ppm (T10).

The results showed that growth retardants significantly reduced plant height compared to control plants. Paclobutrazol was the most effective in retarding plant height in Aglaonema. This finding is consistent with previous studies on Dieffenbachia and Peperomia (Mansour and Poole 1987). Paclobutrazol works by inhibiting gibberellic acid biosynthesis, which regulates stem growth and shoot elongation (Rademacher, 1991). This results in shorter plants with reduced internode length, as observed in various studies (Davis, 1987; Kumar and Purohit 1998; Chen et al., 2002). 

The data on leaf number per plant at 30 and 150 DAT showed no significant difference among the treatments with different growth retardants (Table 1). 

The data in Table 1 show significant variation in canopy length among Aglaonema plants treated with different growth retardants from 30 to 150 DAT. At 150 DAT, paclobutrazol at 0.1825 mg/pot (T3) and 0.25 mg/pot (T4) resulted in significantly shorter canopy lengths (41.25 cm and 41.30 cm, respectively). In contrast, control plants had the longest canopy length (45.96 cm), which was comparable to cycocel treatments. The reduction in canopy length due to paclobutrazol is likely attributed to decreased petiole elongation and leaf length, consistent with previous studies (Hagildi and Watad 1992; Wang and Blessington 1990). Paclobutrazol suppresses growth by inhibiting gibberellin biosynthesis (Chaney, 2004), which may contribute to the observed reduction in canopy length.

Significant differences in canopy width were observed among Aglaonema plants treated with growth retardants at 150 DAT (Table 1). Paclobutrazol at 0.1825 mg/pot (T3) resulted in the shortest canopy width (44.63 cm), which was statistically similar to paclobutrazol at 0.25 mg/pot (T4) (45.60 cm). The control plants had the widest canopy (53.50 cm), comparable to CCC at 500 ppm, 1000 ppm, and 1500 ppm. The reduction in canopy width due to paclobutrazol might be attributed to decreased petiole and leaf length. According to Barrett and Bartuska (1982), paclobutrazol inhibits gibberellin synthesis by being absorbed by roots and translocated to actively growing tissues. Similar results have been reported in other studies (Emily Anna Stefanski, 2008; Li et al., 2009).

Plate 1: Relative growth Retardant effect on aglaonema cv. Ernesto’s Favourite.

Fig. 1. Effect of paclobutrazol, ancymidol, cycocel on growth performance of aglaonema cv. Ernesto’s Favourite.

The influence of plant growth retardants on leaf area was significant at 150 DAT (Table 1). Initially, at 30 DAT, leaf area did not differ significantly among treatments. However, by 150 DAT, paclobutrazol at 0.25 mg/pot (T4) resulted in the lowest leaf area (140.66 cm²), which was statistically similar to paclobutrazol at 0.1825 mg/pot (T3) (141.16 cm²). The control plants had the maximum leaf area (150.93 cm²). The reduction in leaf area due to paclobutrazol might be attributed to decreased leaf length, consistent with previous studies (Hagiladi and Watad 1992). Additionally, paclobutrazol's ability to bind to enzymes essential for gibberellin production and alter leaf morphology (Chaney, 2004) may also contribute to reduced leaf area. These findings are consistent with earlier reports (Mansour and Poole 1987).

The growth retardant treatments had a significant impact on stem diameter of Aglaonema at 150 DAT (Table 1). Paclobutrazol at 0.25 mg/pot (T4) resulted in the highest stem diameter (2.90 cm), followed by paclobutrazol at 0.1825 mg/pot (T3) (2.72 cm). In contrast, the control plants (T13) had the lowest stem diameter (1.46 cm). The observations suggest that paclobutrazol (0.25 and 0.1825 mg/pot) had a pronounced effect on reducing stem growth, resulting in thicker stems. This is consistent with previous findings that growth retardants like paclobutrazol can reduce internode elongation, leading to shorter plants with thicker stems (Dole and Wilkins 2004).  These results are in consonant with earlier findings of Wang and Gregg (1994) in golden pothos with paclobutrazol. 

Fig. 2. Influence of Paclobutrazol, Ancymidol, and Cycocel on Chlorophyll Content in Aglaonema cv. Ernesto's Favourite.

The data in Table 2 show significant differences in chlorophyll content among growth retardant treatments. At 150 DAT, paclobutrazol at 0.1825 mg/pot (T3) resulted in the highest chlorophyll 'a' content (18.50 mg/g fresh wt.), which was statistically similar to paclobutrazol at 0.25 mg/pot (T4) (17.80 mg/g fresh wt.). The control plants (T13) had the lowest chlorophyll 'a' content (8.26 mg/g fresh wt.). Similarly, paclobutrazol at 0.1825 mg/pot (T3) resulted in the highest chlorophyll 'b' content (6.78 mg/g fresh wt.), which was comparable to paclobutrazol at 0.125 mg/pot (T2) and 0.25 mg/pot (T4). According to Chaney (2004), the increased chlorophyll content in treated plants might be due to smaller cell size, resulting in more concentrated chlorophyll, or an increase in phytyl production, which is essential for chlorophyll synthesis.

The data in Table 2 show significant differences in visual plant grade among treatments. Treatment T3 (paclobutrazol at 0.1825 mg/pot) recorded the highest visual quality rating (4.57) at 150 DAT, which was on par with T2 (4.42), T4 (4.30), and T1 (4.21). The lowest plant grade was observed in the control (T13) (3.38), which was comparable to T10 (3.38) and T9 (3.43). These findings confirm that paclobutrazol-treated plants exhibit superior visual quality. Paclobutrazol's ability to delay senescence by inhibiting hydrolases and reducing lipid peroxidation (Malik and Thind 1994) likely contributed to the improved plant quality. This delay in senescence enables leaves to maintain photosynthetic activity for a longer period and retain their color (Kumar and Purohit 1998). The persistence of paclobutrazol in the soil also helps maintain plant size (Cox and Whittington 1988). Our results are consistent with previous studies on angel-wing begonia (Conover, 1994) and golden pothos (Conover and Satterthwaite 1996).

Regarding color grade, treatment T3 (paclobutrazol at 0.1825 mg/pot) resulted in a dark green color (4.60), which was comparable to T2 (4.50), T4 (4.45), and T1 (4.25). The lowest color grade was recorded in the control (T13) (3.30). The deep green color of paclobutrazol-treated leaves may be attributed to increased chlorophyll synthesis (Table 1) or reduced leaf area (Table 5) (Kumar and Purohit, 1998). Paclobutrazol has been reported to reduce leaf abscission and intensify green leaf color (Cox and Whittington 1988; Wang and Blessington, 1990). Overall, our results suggest that soil drench application of paclobutrazol at 0.1825 mg/pot or 0.25 mg/pot effectively reduces growth and improves the quality of Aglaonema cv. Ernesto's Favourite.

Table 1:  Growth Response of Aglaonema cv. Ernesto's Favourite to Paclobutrazol, Ancymidol, and Cycocel at 30 DAT and 150 DAT.

Table 2: Influence of Paclobutrazol, Ancymidol, and Cycocel on Chlorophyll Content (Chlorophyll-a and Chlorophyll-b), Plant Grade, and Color Grade in Aglaonema cv. Ernesto's Favourite.

Plant grade system where 1 = Dead, 2 = Poor quality, 3 = Fair quality, 4 = Good quality and 5=Excellent quality

Colour grade system where 1= Poor colour, 3 = Good, light green, 5 = Excellent, dark green & silver contrast.