Observation on the epidermis of leaves by scanning electron microscope and the determination of contents of aloin in three species of Aloe

The leaves of three species (Aloe vera,A.arborescens,A.saponaria) of Aloe were used as material.The structure of stoma and cuticle of the epidermis were observed by scanning electron microscope and the contents of aloin were determined by HPLC.The results showed that all the epidermises of the leaves were covered with heavy cuticle and sunken stomata,which were the typical characteristics of xerophytes.However the decorative pattern and the thickness of cuticle varied differently among the three species.The cuticle surface was in shape of tumour in Aloe arborescens,comparatively,the cuticle surface was smoother in Aloe vera and A.saponaria.The thickness of cuticle in Aloe arborescens was 5~6 μm,3~4 μm in Aloe vera,and 8~10 μm in Aloe saponaria.The order of the three species in the contents of aloin was that Aloe arborescens,Aloe vera and A.saponaria.The relationship between the structure of epidermis and content of aloin was also discussed in this paper.