Seasonal Changes in Soluble Carbohydrates of Russian Knapweed’s Rhizomes

The soluble carbohydrates play a major role in germination, growth, reproduction, defense and survival of perennial plant species reproducing with rhizomes under normal and adverse environmental conditions. The information regarding the amount of carbohydrates present in the rhizomes of such species could provide valuable insights for making decisions regarding the best time to control these species. Therefore, seasonal changes in the concentrations of soluble carbohydrates (fructose, glucose, sucrose) and their sum termed as total amount of soluble carbohydrates (TSCs) in the rhizomes of Russian knapweed were investigated during 2013-2014. The TSCs were low at sprouting and then slightly increased until mid-June (beginning of flowering). Thereafter, TSCs were slightly decreased from mid-June to minimal values in August (flowering period) (6.2 mg/g), and then gradually increased until the highest values in January (170.6 mg/g). Fructose (131.5 mg/g) was detected as the main soluble carbohydrate, followed by sucrose (98.8 mg/g) and glucose (73.1 mg/g). Keeping in view the results of current study, the best time to control Russian knapweed is flowering, where the amount of TSCs in the rhizomes is minimal. It is therefore recommended that the species should be controlled either at flowering stage or during the production of first rhizomes for its sustainable management in the country.