南方红豆杉水浸提液对喜树种子发芽和幼苗生长的化感作用

Abstract

化感作用是影响人工混交林种间关系的重要因素之一。已有研究表明：喜树南方红豆杉混交对喜树生长有明显促进作用，并从混交改善混交林地微气候角度解释了这种促进作用，但未从种间化感作用角度探讨这种作用。为了探究南方红豆杉是否对喜树具有潜在的化感促进作用，从而更全面了解喜树南方红豆杉混交林种间关系，考察了不同浓度（25、50 g/L和100 g/L）的南方红豆杉（Taxus chinensis var.mairei）鲜叶、凋落叶、枝和根水浸提液对喜树（Camptotheca acuminata）种子发芽和幼苗生长的影响。结果表明：（1）南方红豆杉凋落叶浸提液对喜树种子发芽和幼苗生长无显著影响（P>0.05），而鲜叶、枝和根浸提液对喜树发芽和幼苗生长均具有不同程度的促进作用（P<0.05），且作用强度大体与浓度呈正相关；（2）100 g/L的南方红豆杉鲜叶、枝和根浸提液浸泡的喜树种子，其发芽率比对照组分别提高8.1%、14.9%和25.6%；（3）南方红豆杉鲜叶浸提液只有在高浓度（100 g/L）时，对喜树幼苗基径生长具有促进作用（P<0.05），而对其株高、全株干重和净光合速率无显著影响；南方红豆杉根和枝浸提液对喜树幼苗株高、基茎、干重和净光合速率均具有促进作用（P<0.05），与对照组相比，100 g/L的根和枝浸提液浇灌喜树幼苗，可以使喜树幼苗株高分别提高14.2%和8.4%，基径分别提高19.0%和15.3%，干重分别提高23.1%和15.9%，净光合速率分别提高11.6%和6.1%。研究结果表明，在喜树南方红豆杉混交林中，南方红豆杉对喜树的正向化感作用可能是促进喜树生长的重要因素之一。;Allelopathy is one of the important factors that affect the interspecific relationship of artificial mixed forest. Previous studies have shown that Taxus chinensis var. mairei has a significant promoting effect on the growth of Camptotheca acuminata in the mixed forest of T. chinensis var. mairei and C. acuminata, which was explained from the perspective of improving the microclimate of mixed forest land, but not from the perspective of interspecific allelopathy. In order to explore whether T. chinensis var. mairei has potential allelopathy promoting effect on C. acuminata, so as to understand more comprehensively the interspecific relationship of T. chinensis var. mairei and C. acuminata mixed forest, the effects of water extracts from fresh leaves, litter leaves, branches and roots of T. chinensis var. mairei with different concentrations (25 g/L, 50 g/L, and 100 g/L) on seed germination and seedling growth of C. acuminata were studied in this study. The results showed that (1) the litter extract of T. chinensis var. mairei had no significant effect on seed germination and seedling growth of C. acuminata (P>0.05), but the fresh leaves, branches and roots extracts had the promoting effects on C. acuminata germination and seedling growth in different degrees (P<0.05), and the intensity was positively correlated with the concentration of extracts. (2) The germination percentage of C. acuminata seeds soaked in 100 g/L extracts of fresh leaves, branches and roots from T. chinensis var. mairei was 8.1%, 14.9% and 25.6% higher than that of the control group, respectively. (3) The fresh leaves extract of T. chinensis var. mairei could promote the basal diameter growth of C. acuminata seedlings at high concentration (100 g/L) (P<0.05), but had no significant effect on plant height, total dry weight and net photosynthetic rate regardless of extracts concentration. The root and branch extracts of T. chinensis var. mairei had the promoting effects on plant height, basal stem, dry weight and net photosynthetic rate of C. acuminata seedlings (P<0.05). Compared with the control group, 100 g/L of root and branch extracts could increase the height of C. acuminata seedlings by 14.2% and 8.4%, the basal diameter by 19.0% and 15.3%, the dry weight by 23.1% and 15.9%, and the net photosynthetic rate by 11.6% and 6.1%, respectively. The results showed that the positive allelopathy of T. chinensis var. mairei to C. acuminata may be one of the important factors to promote the growth of C. acuminata in the mixed forest of the two trees.