Seed, cutting and air-layering reproductive inefficiency of noxious woody vine Merremia biosiana and its implications for management strategy

Abstract

Merremia boisiana (Gagnep) van Ooststr. is a noxious fast growing woody vine and is able to grow overtop other plants, causing the death of plants underneath and forming monospecies stands. To formulate management responses, we assessed its seed and vegetative reproduction efficacy through indoor and field experiments. The number of flowers counted from bagged infructescences in Guangzhou ranged from 25 to 172, with an average of 80.80. Counting the seeds of bagged infructescences had shown that there were only 1.58 hard testa seeds in each infructescence. Seed vitality tests using red ink indicated that only 68.6% of hard testa and filled seeds were viable. The emergence rate of scarified hard testa seeds in the sand bed was 31.96%. Under imitated natural conditions, 8% of hard testa seeds could germinate, and 9% still retained their germination potential in one year. Thus, seedlings should be monitored and removed in a timely fashion after any attempt of clearing. Moving soil or transplanting plant from infested patches should be strictly prohibited at least for several years. All considered, an infructescence contributed 0.3 seedlings. The investigation in the field found no seedlings either inside or at the perimeter of the patch, suggesting scant expansion by means of seed dispersal. Therefore, the elimination effort could be focused on a relatively restricted scale of patches. Of 630 cuttings of young shoots, old shoots and old lying shoots with or without growth regulators, there were only four (or 0.63%) established individuals. Air-layering shoots all died in two months. Poor cuttings and air-layering reproduction indicated that regeneration from fragments of removed stems or accidentally dropped ones was quite unlikely, and thus mechanical removal was safe.