Effects of plant growth regulators on growth, yield and lodging of sweet sorghum

Sweet sorghum [Sorghum bicolor (L.) Moench] has been widely regarded as a potential feedstock for producing bio-fuel. Lodging is a limiting factor due to its height, particularly in susceptible varieties and hybrids. An experiment was performed in order to study the influence of plant growth regulators (PGRs) on lodging and yield of sweet sorghum lodgingsusceptible variety Yuantian 1. The experiment was carried out in a randomized block design. Treatments of ethephon (ETH 90, 180 and 360 g/ha), uniconazole (S-3307 22.5, 45 and 90 g/ha), chlormequat chloride (CCC 225,450 and 900 g/ha), 2, 3, 5-triiodobenzoic acid (TIBA 45, 90 and 180 g/ha) and a control (water) were used in this study. The results indicate that ETH, among the four PGRs, had significant dwarfing effects on the stalk length, resulting from a significantly shorter stalk length increment before 14 days after treatment (DAT). A reduction in internode length was observed at the orders between 6* and 15^th (not significant for 8^th, 9^th and 10^th) from the base. The ETH treatments significantly reduced lodging rate of sweet sorghum plants with an increase in ETH dose. It is in agreement the ETH treatments exhibited significantly higher stem bending strength compared that in the control. There was no significant difference in between the ETH treatment and the control. The ETH treatment exhibited lower grain yield (not significant), stem and biomass yield (significant) than the control. However, the leaf blades at the 3 ^rd and 4^th orders from the top were significantly shorter after treated with ETH. The leaf orientation value (LOV) of the two leaves was significantly higher than the control. The improvement in leaf blade length and LOV after the ETH treatments opened a new possibility for increasing yields through increasing plant density. This study contributes to the knowledge and importance of PGR usage, especially ETH hormone in lodging enhancement.