Abstract:
To investigate the effects of citric and malic acids on the photosynthetic physiology of
Saraca dives seedlings under different cadmium stress levels, half-year-old
S. dives seedlings were used as experimental materials, and a two-factor completely randomized block design (5 cadmium concentrations × 3 organic acid treatment levels, including a blank control) was adopted to analyze the physiological characteristics of
S. dives seedlings under different treatments. The results showed that different cadmium concentrations and organic acid treatments had significant effects on the photosynthetic and physiological indexes of
S. dives seedlings. Cadmium stress significantly reduced the Chl a/b ratio, which tended to increase and then decrease when the cadmium concentration was higher than 50 mg/kg, and then increased with the addition of organic acids, Cadmium stress significantly reduced the Chl a/b ratio, which tended to increase and then decrease at cadmium concentrations higher than 50 mg/kg, and the Chl a/b ratio was elevated by the addition of organic acids, with the minimum values (Cd
150CA
4 and Cd
200MA
4 treatment groups) under citric and malic acid treatments increasing by 13.36 and 1.64%, respectively, compared with the same level of cadmium stressl;
Pn,
Gs, and
Tr decreased with the increase of cadmium concentration, and the addition of organic acids significantly increased Pn, Gs, and Tr; Ci in each treatment group showed a first decrease and then an increase with the enhancement of Cd stress, and reached a peak at the Cd
200 level; SS and SP content under Cd stress showed first increase and then decrease, in the Cd
50 treatment group all reached the peak, organic acid treatment significantly enhanced SS, and SP content, and the malic acid treatment effect is not as good as citric acid; Pro content increased with cadmium concentration, citric acid treatment in the Cd
100 when the maximum increase; cadmium stress to enhance the content of MDA, the imposition of organic acid was significantly reduced;The activities of SOD, POD and APX enzymes increased under Cd stress, and their activities were further enhanced by the application of organic acids, especially in the citric acid treatment group; in the analysis of the affiliation function, the Cd
100CA
4 treatment group had the best overall performance, followed by Cd
50CA
4. Therefore, in the Cd-contaminated environment, both organic acids were able to improve the photosynthetic physiological characteristics and stress tolerance of
S. seedlings, and citric acid was more effective than malic acid.