BB and BL plants were both collected from outskirts Danzhou (Hainan, China), authenticated by Mr. Ying-Bo Zhang and Dr. Xiao-Lu Chen. Voucher specimens have been deposited at the Traditional Medicinal Plant Germplasm Nursery of South China, Tropical Crops Genetic Resources Institute, Chinese Academy of Tropical Agricultural Sciences, Hainan, China.

・ Frozen section

Fresh and healthy immature leaves and stems about one to three centimeters nearby the stem tips were cut from the BB and BL plants. They were directly cut into 4 × 4 mm or 5 mm long without fixed. Each pieces of tissues were embedding on a sample table with Jung tissue freezing medium (Leica, German) under −18˚C for 10 min, and then cut with Leica CM1900 under −18˚C. The thickness ranges from 10 μm to 30 μm. The sections were observed with a computer-equipped microscope.

・ Data collection and analysis

Lengths were measuring with a computer equipped microscope with an electronic scale. Statistical analysis of the data was carried out by using the SPSS 19.0 software. The results were expressed as mean ± SD (standard deviation). Data were analyzed by one-way ANOVA followed by Duncan’s multiple range tests or the independent sample t-test using Statistical Package for Social Sciences 19.0 (SPSS, Chicago, IL, USA). A P-value of less than 0.05 was considered statistically significant.

Both BB and BL are covered by epidermal trichomes, including non-glandular and glandular hairs. Results showed in Table 1 indicated that two types of trichomes were growing on the BB plant, while three were on BL plant.

According to Table 2 and Table 3, the lengths of non-glandular hairs on BB were usually longer than 500 μm, which were much shorter on BL plants, typically ranges from 100 μm to 500 μm. The lengths of non-glandular hairs in BB and BL were significantly different by the independent sample t-test at P < 0.05 level.

*Values are expressed as mean ± SD. Data followed by different letters are significantly different by the independent sample t-test at P < 0.05 level.

The non-glandular hairs on BB leaf were lender (Figure 1(A)) and whose on BL leaf were shorter and thicker (Figure 1(B) and Figure 1(C)). Both of them were composed of several cells arranged in a line. Though the “bell-like” shade was not obvious on BL leaf under stereomicroscope (Figure 1(B)), it can be recognized by performing Frozen section (Figure 1(C)).

The length of glandular hairs on BB and BL plants were found to be significantly different. The BB plants grows only SGH with a length of about 56 μm, while the BL plants growth two kinds of glandular hairs, with length of approximately 92 μm, and 257 μm, respectively (Table 4 and Table 5).

*Values are expressed as mean ± SD. Data in the same column followed by different letters are significantly different by Duncan’s test at P < 0.05 level.

On BB plants, a short glandular hair is comprises of a head with two columns of secretory cells, a short stalk with some smaller cells, and one or two basal cell(s) (Figure 2(A)). In another word, it is a glandular capitate trichome. On BL plants, a short glandular hair is similar with the one on BB plant, except the stalk cells are larger (Figure 2(B)). The long glandular trichome on BL plant is a glandular peltate trichome (Figure 2(C)), which did not found on BB plant. It was consists of a head with about tour to twenty secretory cells (Figure 2(D)), a long stalk with two to eight stalk cells, and one or two basal cell(s).