Growth and Phytochemical Content of Cynodon dactylon (L.) Pers. as Affected by Trinexapac-ethyl and Paclobutrazol

Abstract

Bermudagrass [<em>Cynodon dactylon</em> (L.) Pers.] is a perennial grass and has been long used as a medicinal herb in Iranian traditional medicine to treat varied ailments. Different parts of bermudagrass such as leaves, stolons, rhizomes and culms are rich sources of metabolites such as proteins, carbohydrates, mineral constituents, β-sitosterol, flavonoids, alkaloids, glycosides and triterpenoides. Growth regulators change plant physiological processes such as phytochemical accumulation. Paclobutrazol (PBZ) and Trinexapac-ethyl (TE) are two popular growth retardant that inhibit gibberellic acid (GA) biosynthesis. This greenhouse experiment was conducted to determine effects of TE and PBZ application on bermudagrass growth and phytochemical content. Paclobutrazol was applied twice at four weeks intervals at 0, 1, 2, 3 and 4 g a.i. (active ingredient) /100 m² and TE treatments (0, 0.25, 0.5, 0.75 and 1 g a.i. /100 m2) were applied biweekly over 8 weeks period. Shoot and root growth, were decreased with increasing PBZ and TE application rates except for TE_0.5treatments that showed higher root growth than control plants. Chlorophyll, Total non-structural carbohydrates, soluble flavonoids and protein content were increased with increasing PBZ and TE application rates unless TE₁ treatment that exhibited lower total non-structural carbohydrates (TNC) content than untreated plants. The results suggest that TEand PBZ treatments were beneficial for bermudagrass phytochemical content enhancement. However, puclobutrazol application, because of higher phytotoxity than trinexapac ethyl (lower plant quality and sever shoot depression), seems to be less effective in raising medicinal properties.