不同降水量处理时5种蒿属植物瘦果粘液溶出

Comparison of mucilage produced by achenes of 5 Artemisia species under different rainfall treatments

用粘沙法对科尔沁沙地西部5种蒿属植物冷蒿(Artemisiafrigida)、差巴嘎蒿(A.halodendron)、大籽蒿(A.sieversiana)、黄蒿(A.scoparia)、乌丹蒿(A.wudanica)进行了瘦果粘液溶出及粘沙量的比较。主要模拟埋深5mm、降水量为1、2、4、8mm时瘦果的粘液溶出。5种供试植物均有粘液瘦果。在降水量1mm时,供试植物的粘液瘦果就能溶出粘液。当降水量达到2～4mm时,典型的沙生植物乌丹蒿和差巴嘎蒿的粘液瘦果粘沙量平均值分别达到7.31～13.56mg、0.63～2.55mg。除冷蒿外,其它4种植物均有随降水增多、粘液溶出量加大的趋势。粘液瘦果比例从大到小的排序是冷蒿>乌丹蒿>差巴嘎蒿>大籽蒿>黄蒿。在各种处理时,粘沙瘦果百粒瘦果粘沙量由大到小的顺序是乌丹蒿>差巴嘎蒿>大籽蒿>冷蒿>黄蒿。溶出粘液粘沙后,冷蒿瘦果所形成沙团重量达到瘦果重量的5～7倍,差巴嘎蒿2～9倍,大籽蒿3～5倍,黄蒿5～8倍,乌丹蒿5～29倍。流沙先锋植物乌丹蒿和差巴嘎蒿百粒瘦果粘沙量较其它植物大、在较低降水量时这两种植物粘液瘦果粘沙量较大表明瘦果溶出粘液粘沙是植物针对沙地流动性的进化适应之一。

Myxospermy, a mechanism, where mucilage is produced upon being moistened, has been found in many species, and is frequently associated with species occurring in arid zones. There has been, however, little study on myxospermy with reference to rainfall amount. To analyze the ecological significance of myxospermy, a comparison was made with regard to mucilage producion and the capacity to hold sand particles of the achenes of 5 Artemisia species, i.e., Artemisia frigida, A. halodendron, A. sieversiana, A. scoparia and A. wudanica under different rainfall treatments. In the experiment, achenes were buried in a depth of 5mm, 1, 2, 4 and 8 mm water was added to simulate different rainfall amount. The amount of mucilage was judged by means of the capacity to hold sand particles. All species included were proved to have mucilaginous achenes. When the rainfall was 1 mm, achenes of the 5 species in the experiment began to produce mucilage. When the rainfall was 2～4 mm, the mean weight of the sand held by a single achene of the typical psammophytes, A. wudanica and A. halodendron was 7.31～13.56 mg and 0.63～2.55 mg, respectively. Except A. frigida, other 4 species exhibit a general trend that mucilage increased with rainfall rising. The descending order of the proportion of mucilaginous achenes was as A. frigida, A. wudanica, A. halodendron, A. sieversiana and A. scoparia. Under the different rainfall treatments, the descending order of the sand amount held by mucilaginous achenes showed the trend as Artemisia wudanica, A. halodendron, A. sieversiana, A. frigida and A. scoparia. After producing mucilage and adhering sand upon moistening, compared to achene weight, weight of the achene-sand conglomeration of A. frigida increased by 4～6 times, A. halodendron 1～8 times,A. sieversiana 2～4 times,A. scoparia 4～7 times and A. wudanica 4～28 times. The experiment showed that, achenes of pioneering species on sand dunes, A. wudanica and A. halodendron, had bigger capacity to hold sand particles after producing mucilage than other species, and much sand was held by the mucilaginous achene of these two species when only 2～4 mm rainfall occurred,meaning that the ability to produce mucilage from achenes upon being moistened is one of the adaptations of Artemisia species to shifting sand.