Effects of exogenous melatonin on the morphology, photosynthetic pigment, and reactive oxygen species parameters of rice seedlings under NaCl stress
As shown in Table 4, under NaCl stress, plant height (Figure 7), root length, fresh weight, dry weight, chlorophyll a, chlorophyll b, and total chlorophyll (chlorophyll a+b) content of seedlings were significantly reduced compared to those of the control. Further, the H2O2, O2- ·, and MDA contents increased by 47.404%, 57.277%, and 36.815%, respectively. Compared with salt treatment alone,
exogenous melatonin at different concentrations (50-800 μmol·L-1) significantly increased plant height (Figure 7), root length, fresh weight, dry weight, chlorophyll a, chlorophyll b, and total chlorophyll content (Table 4), whereas H2O2, O2-·, and significantly decreased MDA content to different degrees. The higher the melatonin concentration, the less obvious the alleviation effect under NaCl stress. These results indicate that exogenous melatonin could increase the chlorophyll content of rice seedlings under NaCl stress to a certain extent, enhance the photosynthetic rate and biomass of leaves, reduce the ROS content in seedlings, and promote the growth and development of seedlings.
TABLE 4 Effect of melatonin on the parameters of morphological, photosynthetic, and reactive oxygen species of rice seedlings under NaCl stress