秋季水位波动频率对喜旱莲子草、粉绿狐尾藻和水龙的影响

Effect of water level fluctuation frequency on Alternanthera philoxeroides, Myriophyllum aquaticum and Ludwigia adscendens in autumn

水位波动对水生植物的生长有显著影响。该文通过设置0次(对照)、1次、2次和4次水位波动频率,研究了入侵种喜旱莲子草(Alternanthera philoxeroides)、外来种粉绿狐尾藻(又称聚叶狐尾藻,Myriophyllum aquaticum)和乡土种水龙(Ludwigia adscendens=Jussiaea reppens)对水位波动的形态和生理响应策略。结果显示:水位波动对喜旱莲子草的分枝数、根冠比和最大光化学量子产量(Fv/Fm)无明显影响,但明显增加了株高(水位波动1次除外),降低了生物量和叶绿素含量;粉绿狐尾藻的分枝数和Fv/Fm在不同水位波动下无明显变化,但株高在2次水位波动下明显增加,根冠比在1次和4次水位波动下明显增加,生物量和叶绿素含量(4次水位波动除外)在水位波动后明显降低;水位波动明显降低了水龙的分枝数(2次水位波动除外)、株高(1次和2次水位波动除外)、总生物量(2次水位波动除外)和叶绿素含量,但对水龙的根冠比和Fv/Fm无明显影响。水龙的分枝数、株高、总生物量、叶绿素含量和Fv/Fm在绝大部分水位波动处理下都明显大于喜旱莲子草和粉绿狐尾藻,而且后二者间没有显著区别。以上结果说明在秋季这3个物种的生长都受到水位波动的抑制,喜旱莲子草和粉绿狐尾藻在秋季水位波动生境中并不能表现出较强的生长能力,但对水位波动具有较强的耐受性和可塑性,这与入侵种较强的入侵性有关。应加强防范外来种粉绿狐尾藻的入侵。

Aims In wetlands, water levels can fluctuate, which often disturbs local organisms, such as aquatic plants. The responses of Alternanthera philoxeroides, Myriophyllum aquaticum, and Ludwigia adscendens to water level fluctuations of different frequencies were examined here. Methods Water level fluctuations were simulated at four frequencies： static（0 frequency）, one cycle（1 frequency）, two cycles（2 frequency）, and four cycles（4 frequency）, and with fluctuation amplitudes（± 25 cm） during a 60 day experiment. Morphological and physiological traits of plants, including branching number, shoot length, total biomass, shoot root ratio, chlorophyll content, and maximum PSII quantum efficiency（Fv/Fm） were assessed. Important findings Water level fluctuation was found to have no significant impact on branching number, root shoot ratio, or Fv/Fm of A. philoxeroides, but all scenarios except 1 frequency were significantly associated with longer shoots and lower total biomass and chlorophyll content. The traits of M. aquaticum showed different responses to water level fluctuation： branching number and Fv/Fm showed no changes, but shoot length（2 frequency） and root shoot ratio（1 and 4 frequency） increased significantly, and total biomass and chlorophyll content（expect 4 frequency） decreased. In L. adscendens, water level fluctuation was associated with lower branching number in all scenarios except 2 frequency, shoot length in all scenarios except 1 and 2 frequency, total biomass in all scenarios except 2 frequency, and chlorophyll content but had no significant effects on root shoot ratio orFv/Fm. Under most water level fluctuation conditions, the branching number, shoot length, total biomass, chlorophyll content, and Fv/Fm of L. adscendens were significant higher than those of A. philoxeroides and M. aquaticum, and the latter two had no significant differences. Results suggested that water level fluctuations were the limiting factor for the growth of three species in autumn. Alternanthera philoxeroides and M. aquaticum did not show higher invasiveness in environments in which the water level fluctuated in autumn but did show higher tolerance and plasticity in response to water level fluctuations in general. This was related to the invasiveness of introduced species. Results also indicated that preventive efforts focusing on potential invasion by M. aquaticum should be strengthened.