Nitric Oxide Expansion Of Cold Damage And Mechanisms, Anti-absorption Of Tomato Seeds

Before the 1980's, NO was known as a toxic molecular to both human beings and the environment. In the following research it is found that NO is a ubiquitous messenger and effective molecule in biology. NO plays an important role in both animals and plants. The research in animals is obvious to all of us. It plays various functions including the relaxation of blood vessels, inflammation, neurotransmission and defense during immune response and distributing in brain, lung and generative apparatus. The research of NO in plants is later than animals. But the research of NO in plants became fashionable since it was chosen as "Molecule of the year" in 1992. It participates in a series of key physiological processes such as respiration, stomatal movement, seed germination, leaf and root development, lateral root development, the growth of hypocotyls, leaf and fruit senescence, programmed cell death, responses to biotic and abiotic stresses such as pest and disease challenge, drought, salinity and low temperature. However, information is still lacking regarding NO resisting against chilling imbibition. In the present study, tomato seeds were used as plant material, and treated in 4℃distilled water and SNP for 12 h respectively, in order to clarify the effect of 100μmolL^-1 SNP on chilling imbibition tomato seeds, germination indexes and physiological indexes were analyzed and investigated and it was found that it had an obvious alleviate effect on chilling imbibition. In addition, treated with NO scavenger Hb, NOS inhibitor L-NAME and NR inhibitor Na₂WO₄ in both 25℃and 4℃for 12 h, and the use of laser-scanning confocal microscopy, it was found that endogenetic NO also plays an important role in seed germination.The main results were followed:1. Chilling imbibition had a serious inhibitory effect on the germination and root growth of tomato seeds. It indicated that this tomato seed is sensitve to temperature. Exogenous nitric oxide donor SNP enhances seed germination, average root length, germination index and vigor index. The results indicated that exogenous NO can obviously alleviate the inhibited effect of chilling imbibition on tomato seed.2. Another kind of NO donor GSNO could enhances seed germination, average root length, germination index and vigor index of chilling imbibition seeds, which is similar to the effect of SNP. They had the same cleavage product -NO, the result showed it was NO but not others played an important role. With the result of laser-scanning confocal microscopy, it showed the reason of germination inhibitory was that endogenetic NO was inhibited by chilling imbibiton.3. The addition of exogenous NO could dramatically decreased the REC and MDA content, at the same time increased the activities of SOD and CAT after 12 h of chilling imbibition. The results show that the main aim of chilling imbibition is cell membrane and the protecting effect of SNP against imbibitional may be due to improving the activation of the two enzymes.4. There are no differences among the activities of SOD and CAT of the seeds treated with RNA synthetical inhibitor actinomycin D (or protein inhibitor cycloheximide) together with SNP and SNP alone. These results suggest that NO has no affect on the synthesis of the two enzymes during chilling imbibition in tomato seeds and NO could induce a rapid increase in the activity through the activation of the enzymes5. Seed germination, average root length, germination index and vigor index of treatments of NO scavenger Hb, NOS inhibitor L-NAME and NR inhibitor Na₂WO₂ in both 25℃and 4℃for 12 h are less than CK. The results indicated again that the reason of germination inhibitory was that endogenetic NO was inhibited by chilling imbibiton. and endogenetic NO also plays an important role in seed germination and NO may be produced from both the NOS and NR pathways.