伊乐藻和黑藻断枝根和芽的发生及生长研究

为了解外来种伊乐藻的无性繁殖力、评价其生态安全性,采用插植方式比较研究了伊乐藻(Elodea nuttallii)和本土种黑藻(Hydrilla verticillata)两种沉水植物不同节数(1至4节)和不同节位断枝的不定根和新芽的发生及生长情况。通过室内4周的3次平行实验,结果表明:两者顶芽段均有形成不定根继而形成新植株的能力,而顶芽以下茎段只有本身具有腋芽的断枝才有形成新芽和不定根的能力。两者具相同节数的断枝形成不定根的百分率及根、芽长度,以具顶芽断枝的均明显高于不具顶芽断枝的,具顶芽四节断枝的不定根生成率最高达到90%以上。不具顶芽断枝形成新芽和不定根的百分率及长度随着断枝节数的增加均呈显著递增趋势,每类断枝的发芽率显著大于其生根率;伊乐藻和黑藻枝条一般分别每7节和5节具有一个腋芽,只有具腋芽断枝才能存活,因此,对不具顶芽断枝,7节和5节分别是其形成新苗所需的最短断枝长度。根和芽的长度随节位的下降大致呈递增的趋势。但是节数对形成根、芽的影响显著大于节位的影响。具顶芽断枝的顶芽的增长量和具顶芽4节断枝的生物量增量伊乐藻的高于黑藻,其余指标伊乐藻均显著低于黑藻。伊乐藻断枝的繁殖力总体上低于黑藻。  

REGENERATION OF FRAGMENTS OF ELODEA NUTTALLII AND HYDRILLA VERTICILLATA

In order to identify the ability of asexual reproduction of the alien species Elodea nuttallii, and evaluate its ecological safety, the formation and growth of adventitious roots and buds of two submerged macrophytes, E. nuttallii and native species Hydrilla verticillata, were compared in an experiment. Intact shoots of the two species were cut into different fragment types, including 1-4 nodes. Observed in the laboratory for 4 weeks, we found that the fragments with apical buds showed the ability to form adventitious roots and young plants for both species. While the fragments without apical buds were not able to survive unless the axiliary bud was originally present. The percentage of adventitious roots' formatted, and the lengths of roots and buds of the fragments were signifi-cantly higher for shoots with apical buds than those without apical buds of same nodes. The formation rate of ad-ventitious roots for 4 node apical fragments in both species exceeded 90%. For the fragments without apical buds in the two species, the percentage and the length of buds and adventi-tious roots increased significantly with the increase of node number of the fragments. The bud percentage of all fragments were significantly greater than their rooting rate. In general, the shoots of E. nuttallii and H. verticillata had an axillary bud in every 7 nodes and 5 nodes respectively. The formation rate of new bud of both plants was from their axillary bud. Therefore, seven and five nodes were the shortest fragment size for E. nuttallii and H. verticillata without apical bud respectively to survive and regenerate. The vertical position of the node showed an appreciable effect on the growth of the root and bud in both species. The lengths of the roots and buds increased with the node-position's closing the bottom of the fragment. However, the position effect was lower than the size effect in both species. The lengths of all-sized apical shoots and the biomass of 4 nodes apical shoots of E. nuttallii were signifi-cantly higher than those of H. verticillata. Other indices of E. nuttallii were significantly much lower than that of H. verticillata. In concluding, the reproductive capacity of E. nuttallii was lower than that of H, verticillata.