Physiological effects of Solanum rostratum Dunal extract and cadmium chloride complex stress on rye seedlings under freeze-thaw conditions

Abstract

Background: Affected by global warming, freeze-thaw occurs more frequently in Northeast China. Meanwhile, as a major grain-producing area, this region is influenced by the invasive plant Solanum rostratum Dunal. Moreover, due to the long-term application of chemical fertilizers, soil cadmium pollution has been aggravated. Therefore, crops in Northeast China may suffer from compound stress simultaneously. However, the impact of combined stress on plants has not been given enough attention, and the interrelationships between different stresses have not been thoroughly studied. This experiment adopted the indoor simulation method. By determining the changing trends and amplitudes of relative conductivity (RC), soluble protein (SP), chlorophyll (Chl), malondialdehyde (MDA) content, and the activities of superoxide dismutase (SOD) and peroxidase (POD), the influence effects of the combined stress of freeze-thaw, S. rostratum extract, and cadmium chloride on the growth and metabolism of seedlings could be judged.

Results: Under the combined stress of freeze-thaw, cadmium chloride, and S. rostratum extract, the growth of rye seedlings was inhibited; The relative conductivity (RC) increased by 1.92-71.07%, and the content of malondialdehyde (MDA) increased by 17.34-28.11%; The soluble protein (SP) content decreased by 17.82-22.14%; The activities of superoxide dismutase (SOD) and peroxidase (POD) both increased, but POD activity was inhibited at the lowest point of freeze-thaw (-5℃); The chlorophyll (Chl) content decreased by 9.68-19.67%.

Conclusion: Stress affects osmotic pressure, and seedlings need to accumulate osmoregulatory substances to maintain cell osmotic balance. Compared to a single stress factor, the combined stress of freeze-thaw, cadmium chloride, and S. rostratum extract further enhanced the physiological damage to plants. This compound stress leads to electrolyte leakage, intensified membrane lipid peroxidation, inhibition of protein synthesis, increased osmotic pressure, and disruption of cell osmotic balance. Combined stress further promotes the accumulation of reactive oxygen species (ROS) in the seedlings, leading to oxidative damage and inhibiting photosynthesis.

Keywords: Allelopathy; Cadmium stress; Combined stresses; Freeze-thaw; Invasive plant; Plant physiology.

Fig. 1

Effects of cadmium (CS), S. rostratum extract (SES), freeze-thaw (FT) and composite stress on the relative conductivity (RC) of rye seedlings. In the horizontal coordinate, T1, T2, and T3 indicate the temperature of 10°C, − 5°C, and 10°C during freezing and thawing, respectively. The lowercase letters in the figure represent significant differences between groups at the same time (P < 0.05). The result represents the mean ± standard error (SE) (N = 3)

Fig. 2

Effects of cadmium (CS), S. rostratum(SES) and freeze-thaw (FT) combined stresses on malondialdehyde (MDA) content in rye seedlings. In the horizontal coordinate, T1, T2, and T3 indicate the temperature of 10°C, − 5°C, and 10°C during freezing and thawing, respectively. The lowercase letters in the figure represent significant differences between groups at the same time (P < 0.05). The result represents the mean ± standard error (SE) (N = 3)

Fig. 3

Effects of cadmium (CS), S. rostratum(SES) and freeze-thaw (FT)combined stresses on the soluble protein content (SP) of rye seedlings. In the horizontal coordinate, T1, T2, and T3 indicate the temperature of 10°C, − 5°C, and 10°C during freezing and thawing, respectively. The lowercase letters in the figure represent significant differences between groups at the same time (P < 0.05). The result represents the mean ± standard error (SE) (N = 3)

Fig. 4

Effects of cadmium (CS), S. rostratum extract (SES) and freeze-thaw (FT) combined stresses on peroxidase (POD) activity in rye seedlings. In the horizontal coordinate, T1, T2, and T3 indicate the temperature of 10°C, − 5°C, and 10°C during freezing and thawing, respectively. The lowercase letters in the figure represent significant differences between groups at the same time (P < 0.05). The result represents the mean ± standard error (SE) (N = 3)

Fig. 5

Effects of cadmium (CS), S. rostratum extract (SES) and freeze-thaw (FT) combined stresses on superoxide dismutase (SOD) activity in rye seedlings. In the horizontal coordinate, T1, T2, and T3 indicate the temperature of 10°C, − 5°C, and 10°C during freezing and thawing, respectively. The lowercase letters in the figure represent significant differences between groups at the same time (P < 0.05). The result represents the mean ± standard error (SE) (N = 3)

Fig. 6

Effects of cadmium (CS), S. rostratum extract (SES) and freeze-thaw (FT) combined stresses on chlorophyll (Chl) content in rye seedlings. In the horizontal coordinate, T1, T2, and T3 indicate the temperature of 10 °C, − 5 °C, and 10 °C during freezing and thawing, respectively. The lowercase letters in the figure represent significant differences between groups at the same time (P < 0.05). The result represents the mean ± standard error (SE) (N = 3)

Fig. 7

Pearson correlation analysis between MDA, SP, RC, POD, SOD, Chl in rye seedlings under FT environment (*P < 0.05, **P < 0.01)