| In recent years, hydrogen sulfide (H2S) has been extensively concerned and studied as the third gasotransmitter. H2S had been regarded as a vital role in animals initially and took significant physiological functions in cardiovascular system, respiratory system, nervous system and so on. With the deepening study of H2S, it had been confirmed that H2S played an essential role in regulating plant growth and responding to stresses. Currently, the main object of H2S generation enzymes in plants are L/D-cysteine desulfhydrase enzyme (LCD, DCD) and O-acetylserinelyase (DES1). The research found it was H2S that took an important part in lots of plant growth stages, including seed germination and root growth. Besides, the content of inner H2S would increase when plants were response to drought, heavy metal and other stresses, in order to improving the abilities of stress tolerance.For making a further understanding of physiological mechanism on the response to chilling stress in Chinese Cabbage (Brassica rapa var. pekinensis), this study explored the H2S production and changes in cabbages under chilly stress, and the influence of seedling growth pretreated with exogenous H2S. The results were as follows:1. With the gradual extension of 4℃, the inhibition of cabbage seedling growth was increasingly apparent by the low temperature stress and its height and leaf width was significantly reduced. Furthermore, antioxidant enzyme activity was increased to answer the higher ROS caused by chilling stress. After going through the stress, the production of H2S was also activated, which matched well with the related genes up-regulation of major H2S generation enzymes such as LCD, DCD and DES1, the higher production rate and more content of H2S, which were identified as the main genes for endogenous H2S emission.2. The cabbage seedlings pretreated with H2S showed obvious advantages in the aerial part height, the leaf width and the relative water content under chilling stress. And the cabbage seedlings had higher photosynthetic pigments, and bigger improvement of the photosynthetic rate. In addition, the coding genes of some light-harvesting protein, ferredoxin and thioredoxin were up-regulated dramtically after being pretreated with H2S. It could be concluded that physiological concentration H2S could raise the photosynthesis through up-regulating the photosynthesis related-genes and adding Pn caused by cold which was able to maintain the growth of cabbages under chilling stress.3. Pretreated with H2S the osmotic adjustment of the proline and the soluble sugar content in the cabbage seedlings increased obviously, but the content of H2O2, MDA and PCO changed inversely compared with the cabbages exposed to chilly stress directly. And that meant the oxidative stress had decreased. However, the antioxidant enzyme activity had little improvement due to the pretreatment of H2S under chilling stress. In conclusion, the pretreatment of H2S could relieve the oxidative stress directly which may not because of the antioxidant enzyme activation and H2S may protect the cabbage seedlings from chilly stress. |
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