Differential Responses of Dimorphic Seeds and Seedlings to Abiotic Stresses in the Halophyte Suaeda salsa

Abstract

The period between seed germination and seedling establishment is one of the most vulnerable stages in the life cycle of annuals in the saline environments. Although germination characteristics of Suaeda salsa seeds have been reported, the comparative germination patterns of dimorphic seeds and seedling growth to different abiotic stresses remain poorly understood. In this study, germination responses of dimorphic seeds to light and temperature were compared. Meanwhile, responses of dimorphic seeds and thereafter seedlings of S. salsa to different concentrations of NaCl and Na2SO4 were also tested. The results showed that the light did not significantly affect germination percentage of brown seeds, but significantly promoted germination of black seeds. Brown seeds could reach high germination percentage over a wide temperature range, however, germination of black seeds gradually increased with the increase of temperature. Brown seeds had higher germination percentage and velocity than black seeds under the same salt conditions. However, black seeds had higher recovery germination than brown seeds when transferred to deionized water. Young seedlings had lower salt tolerance than germinating seeds. At the same concentrations, Na2SO4 had stronger inhibitory effect on seed germination and seedling growth than NaCl. This study comprehensively compared germination traits of dimorphic seeds and seedling growth of S. salsa, and then developed a conceptual model to explain their adaptation to harsh saline environment.

Differences in Physiological Characteristics, Seed Germination, and Seedling Establishment in Response to Salt Stress between Dimorphic Seeds in the Halophyte Suaeda liaotungensis

“…POD and CAT activities, as well as MDA content, in black seeds significantly decreased during germination under salt stress ( Figure 6 A–C), which would lead to a lower germination rate of black seeds. After transferring to deionized water, a germination recovery experiment showed that the percentage of black seeds that germinated steadily increased, and the recovery germination rate of brown seeds was lower than that of black seeds ( Table 1 ), which is consistent with results reported in other halophytes [ 10 , 14 , 43 ]. Moreover, brown seeds had a significantly higher germination index than black seeds at the same salt concentration ( Table 2 ).…”

“…The germination percentages of dimorphic seeds decreased as salinity increased. Brown seeds germinated significantly higher than black seeds at the same salt concentration, which was similar to that of Suaeda salsa [ 14 , 42 ]. Under 1400 mM NaCl treatment, the germination of brown seeds was still 19.3%, while the black seeds did not germinate at all ( Table 1 ), suggesting that brown seeds were more salt-tolerant than black seeds at the germination stage.…”

“…For the time of seed germination and seedling establishment in desert plants, temperature is essential [ 13 ]. Compared to dormant seeds, non-dormant seeds have a wider temperature range for germination [ 13 , 14 ]. High salinity can inhibit seed germination and delay the time of germination [ 15 , 16 ].…”

“…High salinity can inhibit seed germination and delay the time of germination [ 15 , 16 ]. In addition, the ionic composition in soil also affects seed germination and seedling development [ 14 , 17 ]. At present, there have been many studies on heteromorphic seed germination and seedling establishment, but most have mainly focused on environmental factors such as light, temperature, and salt [ 18 , 19 , 20 ].…”

Can allelopathy of Phragmites australis extracts aggravate the effects of salt stress on the seed germination of Suaeda salsa?

“…This study demonstrated that aqueous extracts from aboveground and belowground biomass, soil, and litter of P. australis exhibited allelopathic activity on S. salsa seed germination and seedling growth, while the strength of the response depended on the habitat of the plants. Especially in halophytes, different habitat conditions can cause seed dimorphism and polymorphism (Khan et al, 2001;Zhang et al, 2021). In the present study, the seed weight of the intertidal zone was greater than that of the brackish wetland.…”