外来红树植物拉关木对乡土种桐花树和正红树的化感作用研究

为了探究外来红树植物拉关木对乡土红树植物的化感作用,该研究观察了不同浓度(0.1、0.3、0.5g·mL~(-1))的拉关木根、叶水浸提液对乡土红树植物桐花树和正红树的胚轴(种子)萌发、幼苗生长及叶片抗氧化酶活性的影响。结果表明:(1)拉关木水浸提液对桐花树种子的成苗率、萌发指数和根长均存在抑制作用,其中对根长的抑制作用随水浸提液浓度的提高而增强。(2)根水浸提液对桐花树幼苗的根长、苗高、生物量等生长指标的影响总体上均表现为低浓度促进,高浓度抑制。(3)拉关木水浸提液对正红树胚轴的萌发率、萌发指数、生长指标均表现为促进作用,且根水浸提液0.1、0.3 g·mL~(-1)处理组的芽长以及根、叶水浸提液0.1、0.3 g·mL~(-1)处理组的生物量显著大于对照组;拉关木水浸提液对正红树幼苗的生物量也表现为促进作用。(4)抗性生理方面,随着拉关木水浸提液浓度的升高,桐花树和正红树幼苗SOD活性降低,正红树幼苗POD活性在根水浸提液0.3 g·mL~(-1)和叶水浸提液0.1 g·mL~(-1)处理组显著高于对照组。以上结果表明,不同乡土植物对拉关木化感作用的敏感性不同,拉关木水浸提液抑制了桐花树的生长,而对正红树的生长则表现出一定程度的促进作用。

Allelopathic effects of exotic mangrove plant Laguncularia racemosa on native species Aegiceras corniculatum and Rhizophora apiculata

To explore the allelopathic effects of exotic mangrove species Laguncularia racemosa on the native species, it was observed that the effects of three concentrations(0.1, 0.3, 0.5 g·mL^-1)of aqueous extracts from L. racemosa roots and leaves on the germination, seedling growth and leaf antioxidase activity of the two native mangrove species Aegiceras corniculatum and Rhizophora apiculata. The results were as follows:(1)The aqueous extracts of Laguncularia racemosa had inhibitory effects on seedling rate of seeds, germination index and root length of Aegiceras corniculatum, in which the inhibitory effects on root length increased with the concentration of aqueous extracts increasing.(2)In addition, effects of root aqueous extracts on the growth indexes of root length, seedling height and biomass of A. corniculatum seedlings were positive in lower concentration and negative in higher concentration.(3)Meanwhile, the aqueous extracts of Laguncularia racemosa had promoting effects on the germination rate, germination index and growth index of Rhizophora apiculata hypocotyls. Bud length in the groups treated by the root aqueous extracts of 0.1 and 0.3 g·mL^-1 and biomass in the groups treated by the root and leaf aqueous extracts of 0.1 and 0.3 g·mL^-1 were significantly larger than those in control. The aqueous extracts of Laguncularia racemosa had promoting effects on the biomass of the Rhizophora apiculata seedling as well.(4)In stress physiology, the SOD activities of Aegiceras corniculatum and Rhizophora apiculata seedlings decreased with the concentration of aqueous extracts increasing, while and the POD activities of R. apiculata seedlings in treatment group with 0.3 g·mL^-1 root aqueous extract and in the group with 0.1 g·mL^-1 leaf aqueous extract were significantly higher than those in control. The results indicate that the sensitivities of the two native species to the allelopathy of Laguncularia racemosa are different. The aqueous extracts have inhibitory effect on the growth of Aegiceras corniculatum, while have promotional effect on the growth of Rhizophora apiculata to some extent.