TRADE-OFF RESPONSES OF THE CLONAL PLANT WATER LETTUCE (PISTIA STRATIOTES L.) TO THE ALLELOPATHY OF CROFTON WEED (EUPATORIUM ADENOPHORUM SPRENG)

Gao, Lei

ISRAEL JOURNAL OF ECOLOGY & EVOLUTION

2012

58

4

Gao, L

Allelopathic interference is considered an ecologically acceptable and effective means of biological control of invasive weeds, but little is known about phenotypic plasticity and the physiological integration of clonal plants in response to allelopathic interference. We used the clonal invasive aquatic water lettuce as a target for allelopathic control by spraying it with a crofton weed filtrate that contained strong allelochemicals. The growth of single-parent water lettuce was inhibited early on in the experiment when adult leaves gradually faded and new leaves grew slowly. However, as offspring ramets grew, the total number of ramets, leaf coverage, and biomass were all significantly greater in allelopathic treatments than in the control, although individual offspring ramets were smaller on average than in the control. This is an indication that the effects of allelopathic control on the water lettuce are: overcompensation in growth, and a trade-off between average size and the number of offspring. The pressure of allelopathy resulted in the water lettuce producing more small ramets, but total biomass was not different from the control. The water lettuce increased investment in root growth and also the capacity for absorbing resources to counteract growth loss due to allelopathy. This possible trade-off suggests that the clonal traits of invasive species should be considered before using allelopathic control.