Regulation mechanism of lanthanum chloride on germination characteristics of wheat (Triticum aestivum L.) seeds and physiological response of seedlings

Abstract The purpose of this study to investigate the regulatory effects of exogenous 18 lanthanum chloride (LaCl 3 ) on wheat seed germination and seedling physiological 19 characteristics, in order to screen for the optimal treatment concentration that is most 20 conducive to its growth and development.Wheat seeds were used as experimental 21 materials, and a blank control group (CK) and six gradient treatment groups (T1 to T6) 22 were set up, with three biological replicates in each group. Inoculate 25 seeds into 23 each culture dish and apply 10 mL of LaCl3 solution at concentrations of 0 (CK), 60, 24 120, 180, 240, 300, and 360 mg·L⁻¹, respectively, while keeping the filter paper moist. After 3 days of germination, relevant indicators will be measured. In the pot experiment, when the seedling height reaches 5 cm, 10 mL of corresponding treatment solution is sprayed every 3 days. After 20 days of cultivation, the root length, number of fibrous roots, fresh weight, plant height, chlorophyll content, as well as key enzyme activities such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) are measured.The experiment showed that lanthanum chloride exhibited a dual effect of "Minimal stimulation and strong suppression" on wheat growth. Among them, the T4 to T6 groups suffered severe growth inhibition due to excessive concentration, and effective enzyme activity data could not be obtained. Physiological indicators testing showed that compared with the CK group, the low concentration T1 group (60 mg·L -1 ) significantly increased the activities of SOD, POD, and CAT by 31.43%, 71.82%, and 69.74%, respectively (P<0.05). The synergistic effect of the medium concentration T3 group (180 mg·L -1 ) was more significant, with the activities of the three enzymes increasing by 44%, 135.16%, and 114.47%, respectively. The chlorophyll content in T1, T2, and T3 groups also significantly increased by 39.84%, 20.86%, and 33.69%, respectively. Correlation analysis revealed that the activities of SOD, POD, and CAT were negatively correlated with seed germination rate, number of fibrous roots, and root length. There was also a significant negative correlation between chlorophyll content and number of fibrous roots. In summary, the optimal concentration for this experiment was 180 mg·L -1 LaCl3 treatment. Under these conditions, the germination rate of wheat seeds and the comprehensive physiological growth indicators of seedlings showed the best performance.