狐尾藻属狭域种和广布种断枝的生长与再生能力比较研究

SURVIVAL STRATEGIES OF STEM FRAGMENTS IN NARROW ENDEMIC AND WIDESPREAD PLANTS OF THE AQUATIC GENUS MYRIOPHYLLUM

对比研究了广布种穗花狐尾藻(Myriophyllum spicatum L.)和狭域种扬子狐尾藻(M.oguraense Mikisubsp.yangtzense Wang)不同长度(5、10和15 cm)和不同位置(顶枝、中枝和底枝)断枝的生长和再生能力。研究结果显示,两物种由断枝生长所形成植株的总生物量、分枝生物量、分枝数均随断枝长度的增加而增大;在由不同位置的断枝生长所形成的植株中,顶枝所形成植株的总生物量最大,中枝所形成植株的分枝生物量、分枝数和平均分枝长最大。由断枝所形成植株的总生物量、分枝生物量、分枝数、平均分枝长和新分枝所处位置在种间均存在显著差异,穗花狐尾藻顶枝和中枝的生物量较大,顶枝所产生的分枝位于断枝基部;扬子狐尾藻的分枝生物量、分枝数及平均分枝长较大,新产生的分枝多位于断枝顶端附近。研究结果表明穗花狐尾藻和扬子狐尾藻断枝的再生对策不同,前者是增加对断枝总生物量的投资,而后者是增加对断枝产生新分枝的投资。研究结果可为进一步开展水生植物广布种与狭域种的生活史对策研究提供资料,也为湿地物种多样性保护与管理提供科学指导。

For some aquatic macrophytes,stem fragment formed by disturbance plays a key role in the dispersal and establishment of the species.Previous studies have been focused on the regeneration abilities of sterm fragments of a range of aquatic species.However,the information on regeneration ability of fragments between narrow endemic and its congeneric widespread species is lacking.Our study examined the combined effects of fragment length and fragment location on regeneration performances of narrow endemic（Myriophyllum oguraense Miki subsp.yangtzense Wang） and widespread（M.spicatum L.） species,two submerged macrophytes in shallow lakes of the lower Yangtze River basin of China,by an outdoor experiment.Stem fragments from one genotype of population were planted separately in plastic pots by three fragment lengths（5 cm,10 cm and 15 cm） and three fragment locations（apex,midstem and bottom）.The objective of this study were to determine（1） whether fragment length and location correlate with the growth and regeneration abilities of the studied species,and（2） whether the growth and regeneration abilities of fragments differ between the narrow endemic and its congenetic widespread species.The results showed that total plant biomass,total branch biomass and branch number increased significantly with increasing fragment length between all treatments at the fragment level for both species.Total plant biomass,total branch biomass and branch number were greatly different between three length treatments,which were the greatest for fragments of 15 cm in length compared with the other two fragment length treatments.Additionally,the growth and regeneration performance of the studied species were significantly affected by fragment location.There were remarkable differences between the growth of sterm fragments with apices and those without apices.Plant from apical fragments had the largest plant biomass,and midstem fragments regenerated the largest branch biomass,the most lateral branches and the longest branches.Fragments without apices showed significant greater branch number and branch biomass compared with the ones with apices,except that those traits of bottom fragments were intermediate.Meanwhile,plant biomass,branch biomass,branch number,average branch length and branch position inserted at the stem were found to be significantly different between the species studied.For M.oguraense Miki subsp.yangtzense Wang,fragments regenerated larger branch biomass,more lateral branches and longer branches,while fragments produced larger total plant biomass for M.spicatum L.,indicating that different regenerative strategies of fragments occurred between the two species.Moreover,apical fragment of M.spicatum L.regenerated lateral branches at the bottom of the stem,while all fragments of M.oguraense Miki subsp.yangtzense Wang produced lateral branches at the top of stem.The present data confirmed the previous conclusion that larger fragments had higher regeneration abilities than smaller fragments and the regeneration potential of fragments with an apical tip was greater than fragments without an apical tip.Our study implied that the regrowth patterns differ between the studied species.M.spicatum L.was prone to increase investment in plant biomass while M.oguraense Miki subsp.yangtzense Wang was prone to invest more to reproduction of lateral branches.This suggested that regeneration performances of fragments of the studied macrophytes were species-specific and fragment trait-dependent,and the results might provide reference for biodiversity conservation and wetland vegetation management.