Effect of environmental factors on rhizome bud germination and shoot emergence of invasive Imperata cylindrica

Abstract

Imperata cylindrica causes severe damage to the date palm and sugarcane fields of Iran. As the aggressive and invasive nature of this species is chiefly attributed to its rhizomes, a better understanding of the effect of environmental factors on rhizome sprouting and emergence can be very helpful for its management. Laboratory and greenhouse experiments were conducted to investigate the effect of environmental factors on Imperata cylindrica rhizome sprouting and emergence. Imperata cylindrica rhizomes showed greater sprouting (82.5%) under a light/dark regime compared with only 10% sprouting in continuous darkness. Exposure to a range of salinity levels showed that I. cylindrica rhizome sprouting was greater than 50% at 6 dS/m but only reached 15% at 15 dS/m, indicating the sensitivity of I. cylindrica rhizomes to salinity stress at sprouting stage. Sprouting was greater than 50% up to −0.9 MPa osmotic potential and even approximately 5% of buds sprouted at −1.2 MPa. Experiments on soil water availability in the greenhouse also showed that I. cylindrica plants even survived irrigation intervals as long as 24 days, indicating I. cylindrica has a greater tolerance to drought stress conditions than many crop and weed species. The viability of rhizomes was significantly reduced when exposed to temperatures ≥40°C, although complete rhizome mortality required temperatures >80°C. No shoot emergence was observed from rhizomes buried at depths ≥20 cm, which suggests that mouldboard ploughing to bury the rhizomes at greater depths is required to prevent I. cylindrica emergence and growth. Based on these results, managing depth placement of I. cylindrica rhizomes so they are either near the soil surface or buried >20 cm deep may assist in controlling its spread.