尖喙牻牛儿苗繁殖体外部形态特征

Morphological characters of Erodium oxyrrhynchum diaspore

尖喙牻牛儿苗(Erodium oxyrrhynchum)是古尔班通古特沙漠短命植物层片优势物种,其繁殖体能够在生物结皮上成功定居,借助扫描电镜等方法对其繁殖体形态进行了观察。结果表明:尖喙牻牛儿苗繁殖体表皮附属毛具4种不同类型,在保持水分和固定繁殖体等方面发挥作用,是对散布和定居的一种适应;果实与芒连结部位存在过渡区和分裂缝隙;芒吸湿后与种子长轴夹角逐渐减小,表皮细胞发生形变,是吸湿运动的形态基础,这种形态变化可以促使繁殖体在地面"行走",遇到适宜的生境时,推动种子钻入土壤而定居。本研究为揭示该种定居适应机制提供了形态学依据。

Erodium oxyrrhynchum is a dominant ephemeral plant in the Gurbantunggut Desert. Its diaspore can successively establish on soil bio-crust. In this paper, a laboratory experiment was conducted under controlled conditions, and scanning electron microscopy was used to observe the morphological changes of the diaspore following hygroscopic absorption. The appending hairs located on the epidermis of the diaspore had four types, playing important roles in the moisture retention and diaspore fixation, and being considered as an adaptation strategy to the dispersion and establishment of E. oxyrrhynchum. There existed transition areas and gaps in the conjunction of fruit and awn. During the process of hygroscopic absorption, the angle between awn and major axis decreased gradually, and the epidermal cells changed in shape, which were the basis of the hygroscopic movement. These morphological changes could promote the mobility of the diaspore on soil surface, and benefit the seed establishment when the habitat was suitable. Our results provided morphological evidences for the further study on the establishment mechanisms of E. oxyrrhynchum.