Institute of Botany, Academia Sinica, Taipei, Taiwan 115, Republic of China.
J Chem Ecol. 1992 Dec;18(12):2285-303. doi: 10.1007/BF00984951.
A unique pattern of weed exclusion was found under the canopy ofDelonix regia, which was planted in many places as an ornamental tree in the south of Taiwan. A quadrat method was employed to examine the botanical composition between the area underneathD. regia and its adjacent control grassland. The number of species and coverage of understory species were significantly lower in the area of theD. regia than that of the grassland, indicating the growth of understory species was suppressed byD. regia. A series of aqueous extracts of leaves, flowers, and twigs ofD. regia were bioassayed against three species to determine their phytotoxicity, and the results showed highest inhibition in the flowers. A water-culture experiment indicated the aqueous extract of flowers ofD. regia on two local understory species (Isachne nipponensis andCentella asiatica) inhibited growth of both species by more than 70%. The phytotoxicities of fallen leaves and flowers ofD. regia were not significantly affected by temperature. When the plant material was subjected to temperatures above 70°C, however, phytotoxicity was decreased, indicating that the allelopathic nature ofD. regia could easily be decomposed by fire. By means of paper, thin-layer, and high-performance liquid chromatography, and UV-visible spectrophotometry, responsible phytotoxins present in leaves, flowers, and twigs ofD. regia were identified as 4-hydroxybenzoic, chlorogenic, 3,4-dihydroxybenzoic, gallic, 3,4-dihydroxycinnamic, 3,5-dinitrobenzoic, and L-azetidine-2-carboxylic acids, and 3,4-dihydroxybenzaldehyde. The findings of bioassays and the number and amount of responsible allelopathic compounds found inD. regia are well correlated, thus permitting the conclusion that the exclusion of understory plants under the canopy ofD. regia trees was due primarily to the allelopathic effect of the fallen flower, leaves, and twigs of theD. regia. A possible mechanism of action is discussed.
在台湾南部，许多地方都将王棕作为观赏树种种植，在其树冠下发现了一种独特的杂草排除模式。采用样方法研究了王棕下区域与其相邻草地之间的植物组成。王棕下区域的物种数量和林下物种覆盖率明显低于草地，表明林下物种的生长受到王棕的抑制。对王棕的叶、花和嫩枝的一系列水提取物进行了对三种物种的生物测定，以确定其植物毒性，结果表明花的抑制作用最高。水培实验表明，王棕花的水提取物对两种当地林下物种（Isachne nipponensis 和 Centella asiatica）的生长抑制作用均超过 70%。王棕落叶和落花的植物毒性受温度的影响不显著。然而，当植物材料的温度高于 70°C 时，植物毒性会降低，这表明王棕的化感性质很容易被火分解。通过纸、薄层层析和高效液相色谱以及紫外可见分光光度法，鉴定出王棕叶、花和嫩枝中的有害物质为 4-羟基苯甲酸、绿原酸、3,4-二羟基苯甲酸、没食子酸、3,4-二羟基肉桂酸、3,5-二硝基苯甲酸和 L-氮杂环丁烷-2-羧酸以及 3,4-二羟基苯甲醛。生物测定的结果以及在王棕中发现的有害物质的数量和种类与王棕的化感作用密切相关，因此可以得出结论，王棕树冠下林下植物的排除主要是由于王棕落花、落叶和嫩枝的化感作用。讨论了可能的作用机制。
