Non-destructive detection of the effects of DCPTA on maize seed germination under drought stress

2-(3,4-dichlorophenoxy)ethyl triethylamine (DCPTA) serves as one of the most important regulators to improve the stress resistance of crops. Taking the corn seeds as the research object, this study aims to investigate the effects of different DCPTA concentrations on drought stress in plant growth. Distilled water was taken as the control group. A 10% concentration of polyethylene glycol 6000 (PEG-6000) solution was as the control group of drought stress. The drought environment was then simulated during the growth of corn seeds. Three types of 10% PEG-6000 solutions were mixed with DCPTA at the concentrations of 0.5, 1.0, and 1.5 mg/L as three experimental groups. Corn seeds were also soaked in five solutions. Three experiments were conducted to verify the alleviating effect of DCPTA on maize seeds under drought stress. Firstly, the seed standard germination test was carried out to determine the germination rate, germination potential, as well as the average embryo and radicle length of maize seeds on the 8th day of germination. The drought resistance index of seed germination was also calculated for four experimental groups, except for the distilled water group. These germination indicators were selected to clarify the effects of DCPTA concentrations on the germination of corn seeds. Two LF-NMR experiments were used to reveal the internal causes of this pattern from a molecular perspective. Low-field nuclear magnetic resonance (LF-NMR) technology was used to obtain T₂ relaxation spectra during maize seed germination. According to the differences in T₂ relaxation spectra among five experimental groups, the differences were then obtained in the internal water and water migration patterns during maize seed germination in the solution environments. Finally, magnetic resonance imaging (MRI) technology was used to obtain a proton density-weighted image of corn seeds. The pseudo-color image was then obtained using pseudo-color processing. The color and area feature parameters were further extracted from the pseudo-color images. The color feature parameters R, G, and the sum of R and G were normalized by area in the pseudo color images. The trend was achieved in the changing pattern of water distribution in corn seeds. The experimental results showed that the germination rate of corn seeds increased by 34%, 20%, and 12%, respectively, while the germination potential increased by 18%, 8%, and 6%, respectively, and the germination drought resistance index increased by 26.29%, 16.33%, and 9.96%, respectively, as the addition of 0.5, 1.0, and 1.5 mg/L DCPTA increased, compared with the drought stress group. The length of the embryo and radicle also increased in the maize seeds. According to the T₂ relaxation spectrum of corn seeds, DCPTA reduced the proportion of semi-bound water in corn seeds, while increasing the proportion of free water and the content of total water, thereby promoting the transition of corn seeds to a more fluid state with a better conditions for the germination of corn seeds. According to the changes in the color characteristic parameters of corn seeds, DCPTA can be expected to make the water distribution of corn seeds more concentrated at the center of the embryo, thus promoting the germination of corn seeds. The relieving effect of DCPTA on drought stress in the maize seeds showed a trend of first increasing and then decreasing with the increase of the concentration. The most significant performance was found in the treatment with 1.0 mg/L DCPTA, followed by 1.5 and 0.5 mg/L DCPTA solutions. There was the highest proportion of free water, total water content, and the rightward shift of the T₂ relaxation spectrum. Therefore, DCPTA can be used to improve the drought resistance of corn seeds during germination, and then accelerate the storage rate of internal water, in order to promote the transformation of semi-bound water into bound water inside corn seeds. The necessary water conditions can be provided for the seed germination, thus reducing the damage caused by drought stress to corn seeds. This finding can greatly contribute to the internal factors that mitigate the effects of DCPTA on maize seeds. An important way can offer to improve the drought resistance in maize seeds.