Suaeda salsa

Overview

Suaeda salsa occurs in both intertidal and inland saline habitats in the Yellow River Delta. Controlled studies cover seeds, seedlings, established plants, and reproduction; a 200 mM NaCl pot study continued to mature seed, while higher-concentration results are interpreted by life stage and endpoint. [S13, S01, S02, S03, S11]

Name and taxonomy

Floras and the relevant primary studies use Suaeda salsa (L.) Pall.; seed and seedling results identify intertidal and inland sources separately. [S13]

Morphology and identification

Flora of China describes an annual herb 20–80 cm tall, with an erect stem branching mainly above. Linear semiterete leaves are usually 1–2.5 cm long; plants may be green or purple-red. Axillary flower clusters form interrupted spikes along branches. [S13]

Distribution, habitat, and phenology

The Yellow River Delta has both intertidal and inland saline populations. A 2021 field study reported total soil salts of 11.92±1.59‰ at intertidal sites and 3.84±1.63‰ above the tide line. A 2020 study also sampled plants and root-associated soil from both habitat types. [S01, S02, S03, S11]

Salinity in natural habitats

The species occurs at both intertidal and inland sites. Reported soil total salts in ‰ or g/kg are mixed-soil measures and remain separate from NaCl nutrient-solution concentrations; the review’s <5, 15–20, and >20 g/kg values remain secondary field summaries. [S01, S02, S07, S09, S11]

Salinity experiments

Guo et al. (2020) grew wild Dongying seeds in sand pots from sowing to mature seed under 200 mM pure NaCl nutrient solution, raised gradually and then supplied twice daily at three times the pot water-holding capacity. At 103–110 days, the study measured reproductive plants, ovule starch and sugars, and photosynthetic variables; treated plants produced larger seeds. Pore-water concentration was not measured directly. [S04]

Guo et al. (2019) separately grew Dongying-source plants in sand pots from sowing with 200 mM pure NaCl nutrient solution. Vegetative growth was assessed at day 100, followed by observations of flowers and seeds. At day 100, shoot dry mass was 40.7% above the control; fresh mass, height, and primary-branch number were 67.6%, 13.3%, and 12.3% greater, respectively. The study also recorded peak flowering at day 145 and later seed traits. The dry-mass comparison supports actual biomass gain rather than survival judged only at harvest. This protocol is a sand-pot result, not a field root-zone concentration. [S05]

Song et al. (2009) pre-cultured seedlings from Yellow River Delta intertidal and inland populations for 55 days, then gradually applied 10–600 mM NaCl for 18 days. Table 2 shows positive shoot and root relative growth rates at 600 mM in both populations, although rates were lower than at 100–200 mM. Intertidal root dry mass was lower at 600 mM, and leaf water content in the inland population declined at 400 and 600 mM. In a separate sand-culture experiment, Song et al. (2011) found lower shoot dry mass after 22 days at 600 mM; that study did not calculate net growth from initial and final dry mass, so this endpoint alone does not establish sustained growth. [S07, S09]

In Mori et al.’s hydroponic study, post-germination seedlings received nutrient solutions containing 0–800 mol m−3 NaCl for 46 days. Total dry mass was greatest at 50–200 mol m−3, declined above 200, and was extremely low at 800 mol m−3. The control used tap water with small amounts of Na and Cl; this paper reports mol m−3, while other studies use mM or soil-salinity measures. [S08]

Guo et al. (2021) compared plants inoculated with Sphingomonas prati or S. zeicaulis against uninoculated plants and reported 0‰ and 20‰ NaCl. At 20‰, dry mass in the S. prati-inoculated group was 102.25% higher than in uninoculated plants; the abstract also lists height, root length, fresh mass, and physiological endpoints. It does not report plant stage, culture medium, the basis for the salt solution, or treatment duration. The contrast includes an inoculation effect and cannot be generalized to uninoculated plants or converted to mM. [S06]

A one-time Yellow River Delta field survey compared green supratidal and purple intertidal ecotypes. Total salts in surface-site soils were 3.84±1.63‰ and 11.92±1.59‰, respectively; the paper also compared above- and belowground growth. These ‰ values describe mixed soil salts at plot scale, without a time series or a fixed exposure measurement for individual roots. They are not pure-NaCl solutions and are not converted to controlled-treatment concentrations. [S03]

Song and Wang’s review cites Gu (1999) for field communities in which S. salsa was not recorded below 5 g/kg dry soil, was described as suitable at 15–20 g/kg, and could dominate above 20 g/kg. The review does not identify the original plots, sampling duration, or analytical method. These total-soil-salt descriptions are secondary ecological information, not growth-treatment results. [S11]

The databases combine 800, 600, 400, and 200 mM entries with ‰ and mg/L values from independent studies. Song et al. (2009) measured positive relative growth at 600 mM, whereas growth was extremely poor at 800 mol m−3 in Mori et al. Database links also include an inoculation experiment or a biomass-processing paper, so the entries do not form a single dose–response curve. [S10, S14]

Song et al. (2008) exposed brown and black dimorphic seeds from intertidal and inland populations to 0.6–35.1 ppt NaCl for 20 days, with a separate 20-day sand-pot test of emergence and seedling growth. Germination of brown seeds exceeded 96% in both populations across the salinity treatments; 35.1 ppt significantly shortened shoots, with a larger effect on inland seedlings. Germination and short-term seedling growth are distinct endpoints. [S01]

Liu et al. (2020) measured root and leaf Cl− in Yellow River Delta intertidal and inland plants and treated seedlings from both populations with 0 or 300 mM NaCl for 7 or 35 days. Total soil salt was 12.35±1.91 g/kg at the intertidal site and 2.50±0.34 g/kg inland; root Cl− in field intertidal plants was about 2.9 times the inland value. Controlled studies also measured root/leaf Cl−, expression of SsCLCc, Ssperoxidase64, and SsCASP, and root endodermal structure. Gene and barrier roles are the authors’ interpretation, not single-factor functional proof. [S02]

Guo et al. (2018) sowed Yellow River Delta seeds in sand and applied 0, 200, or 400 mM NaCl from sowing through seed maturity, with 12 pots per treatment. The study measured flowering, seed set/yield, and ions in reproductive tissues; reproductive performance was greatest at 200 mM, with smaller gains at 400 mM. This full-cycle experiment differs in material and endpoints from the vegetative-growth trial of Guo et al. (2019). [S18]

Reported mechanisms and ecological adaptation

Studies report ovule and seed development, ion accumulation in leaves and roots, Cl− transport, and expression of genes related to root barriers. Populations differed in root/leaf Cl− allocation; the roles proposed for gene expression and the Casparian band remain interpretations that require functional tests. [S01, S02, S03, S04, S05, S06, S07, S08, S09]

Conclusions and evidence gaps

Sources support natural intertidal and inland populations. The 200 mM pure-NaCl sand-pot study continues into reproduction and covers the broadest developmental span among the available sustained-growth records. Short seedling experiments reached 600 mM, while Mori et al. reported very poor growth at 800 mol m−3; each result applies to its study’s stage and duration. Redondo-Gómez et al. (2008) applied 900 mol m−3 NaCl in S. splendens seed-germination tests, followed by a seedling-growth experiment with a maximum of 400 mol m−3. That paper studied S. splendens and provides no results for S. salsa. [S01, S02, S03, S04, S05, S07, S08, S09, S19]