Moderate salinity facilitates the tillering in S.
alterniflora
As one of the most common abiotic stresses, soil salinization has been
proved to cause an inhibition on plant tillering or branching of
glycophyte even subjected to low salinity, such as rice (Kibria et
al. , 2017), wheat (Ruan et al. , 2008) and
lettuces
(Aroca et al. , 2013). However, a proper soil salinity is required
for halophyte growth.
In
the present study, we found that both of the S. alternifloraseedlings grown in the field and greenhouse exhibited more tillering
under the moderate salinity condition (13-18‰ or 15‰) than in low or
high salinity conditions (Figure 2, Figure 3, Figure 4). Similar with
our results, study conducted by Wang et al . (2006) showed thatS. alterniflora produced more tillers
under
15‰ salt treatment. Besides, Xiao et al . (2011) also found that
the tiller number of S. alterniflora were much higher in medium
salinity. Importantly, the common garden experiment performed by Zhanget al . (2012) found that the shoot density of S.
alterniflora , which in some extent represented the tiller number ofS. alterniflora , was much higher in mesohaline site (13‰-18‰
salinity) and polyhaline site (21‰-26‰ salinity) than that in
oligohaline site (0‰-6‰ salinity) and euhaline site (29‰-32‰ salinity).
Ruan et al (2012) reported that the removal of tiller profoundly
enhanced the salt tolerance in salt-sensitive wheat. This can be
explained by the reduction of tiller number in high salinity condition.
In addition, the plant height of S. alterniflora was gradually
decreased with the increase of salt treatments (Figure 2b; 4c), which
agreed with other studies (Wang et al. , 2006; Xiao et al. ,
2011; Zhang et al. , 2012). Plant height is an important character
for crops to determinate the yield. In rice, an opposite additive effect
on plant height and tiller number was dissected by using the
quantitative trait loci method (Yang et al ., 2006).
This
negative relationship between plant height and tiller number may due to
the trade-off of limited nutrient supply between tiller generation and
stem elongation (Cui et al ., 2004). In the present study, less
tiller but much taller of S. alterniflora seedlings under control
salinity condition may be due to the trade-off between tiller outgrowth
and plant growth. According to the above results and analyses, it can be
concluded that a proper moderate salinity was favorable for tillering
development in S. alterniflora .
Moreover, the asexual propagation by vegetative tillering in S.
alterniflora was regarded as one of the reasons for its fast spread in
salt marsh area (Proffitt et al ., 2003; Taylor et al .,
2004). Takahashi et al . (2019) reported that the lateral growth
(tiller production) of S. alterniflora colonies, rather than
seedling recruitment, was an important factor to control the expansion
of S. alterniflora . Ning et al . (2020) found that the
suitable salinity in soil with a higher propagule pressure conditions
provided a firm foundation for S. alterniflora seedling
establishment, which was the potential implications for controllingS. alterniflora invasions. Both of the results from previous
studies and our observation showed that S. alterniflora produced
more tillers in moderate salinity condition, suggesting the higher
invasive of S. alterniflora under such condition. These may
partly explain why S. alterniflora were more invasive in the
mesohaline area along the coastal intertidal wetland in China.