## 4 Discussion  
### Response of Growth Morphology of Halophytes to Salt Stress  
Plants undergoing adverse stress can reduce the harm of adversity to themselves in different ways. Three different types of halophytes have special plant organs, which can be adjusted by their own organs to survive in the face of salt stress. (i) Euhalophytes: _Haloxylon ammodendron_. Salt can be accumulated in the vacuoles of green tissue cells through the regionalization of salt ions, thus reducing the salt in the body. (ii) Recreteohalophytes: _Tamrix chinensis_. Salt glands, or salt vesicles, can be used to directly excrete excessive salt ions from the body, thus avoiding salt damage. (iii) Pseudohalophytes: _Phragmites australis_. Salt can be accumulated in vacuoles of parenchyma or parenchyma of root xylem, which reduces the upward transport of ions and reduces the salt in the body [10]. The environment in the northwest of China is harsh, and the salinity is high. When halophytes are stressed by adversity, their external morphology will change to adapt to the harm caused by the harsh environment [21]. Plant height, stem diameter, and biomass are all significant indicators that can directly reflect plant growth and are also the most direct basis for evaluating plant salt tolerance. Although eulahophytes, recretohalophytes, and pseudohalophytes all have special plant organs, when the salt concentration is too high, they will still have a direct impact on the growth of three different types of plants. In this study, with the increase in salt concentration, the plant height, stem diameter, and biomass of three different types of halophytes were inhibited to varying degrees, showing a decreasing trend. However, [PERSON] et al. found that with the increase in salt concentration, the biomass of five garden salt-tolerant plants not only showed an upward trend but also made the soil desalination rate of saline-alkali land reach 31%, and according to this result, the environmental greening and landscape restoration effects in saline-alkali areas were improved [22]. This may be due to the different plants studied and the different salt concentration ranges, leading to different research conclusions. At present, many studies show that with the increase in salt concentration, the growth of plants will be clearly inhibited, which is consistent with the conclusion of this study. For example, [PERSON] et al. analyzed the salt tolerance of _Oryza sativa_ in California and found that with the increase in salt concentration, the growth rate of _Oryza sativa_ gradually decreased [23]. [PERSON]'s research in Brighton shows that the plant height of crops will be notably shortened when it is stressed by salt [24]. [PERSON] et al. found in India that with the increase in salt concentration, the biomass of _Brassica juncea junccea_ decreased gradually, and the salt tolerance of different varieties of _Brassica juncea_ was different [25]. [PERSON] et al. also found that when the salt concentration was high, the biomass of _Coleus hybridus_ also showed a downward trend [26]. This is because when the salt concentration is high, osmosis, ion stress, and oxidation stress are enhanced, and plants absorb a lot of harmful ions, which hinders cell division and destroys metabolism, thus affecting the absorption and utilization of water and nutrients in plants, then leading to plant growth damage and slow development.