Figure 2. Tiller number and plant height of Spartina alterniflora in three study sites. (a) The number of tillers per seedlings and (b) plant height were recorded every month. The solid square represents seedlings grew at oligohaline (0-6‰) site, the open circle represents seedlings grew at mesohaline (13-18‰) site, the solid triangle represents seedlings grew at euhaline (29-32‰) site.
The field survey showed that both of the transplanted seedlings in mesohaline site (salinity: 13-18‰) produced more tiller than that in oligohaline site (salinity: 0-6‰) and euhaline site (salinity: 29-32‰) (Figure 2a). In addition, the number of tillers in oligohaline site was the lowest. Besides, plant height of S. alterniflora was decreased with the salinity increased (Figure 2b). To further confirm the effect of salinity on tillering, S. alterniflora seedlings subjected to different salinities (0‰, 15‰, 30‰) were grown in greenhouse. Similarly, we also found the S. alternifloraseedlings under 15‰ salinity showed more tillers than the seedlings under 0‰ and 30‰ salinity (Figure 3, Figure 4). It was noticeable that the first axillary bud was early observed at the basal node of S. alterniflora seedling under 15‰ salinity treatment around 30th days (Figure 3a). To quantify the effect of salinity on tillering, the percentage of tillering, tiller number per seedlings and plant height of S. alterniflora seedlings were recorded (Figure 4). The results showed that the percentage of tillering in 15‰ salinity treatment was sharply increased from 30 days to 90 days (Figure 4a) and the tiller number per seedlings was gradually increased from 90 days to 150 days (Figure 4b). The moderate increases of the percentage of tillering and the number of tillers per seedling were observed under 30‰ salinity treatment. For 0‰ salinity treatment, the percentage of tiller was slightly increasing and the number of tillers per seedling was almost no change. Similar with the field results, the plant height of S. alterniflora grown in greenhouse were decreased with the salinity increased (Figure 4c). These results indicate that the moderate salinity could promote the tillering process in S. alterniflora seedlings, while low salinity or high salinity are likely to inhibit the tillering process.