Effects Of Seed Priming With Trehalose And Sodium Nitroprusside On Improvement Of Stress Resistance Of Tobacco Seeds And Seedlings And The Relationship With Proline Metabolism

Seed germination, seedling emergence and early growth are often very sensitiveto various environmental stresses, and seed priming is becoming an effectivetechnique to enhance seed quality, improve germination, seedling emergence andearly growth under environmental stresses. tobacco (Nicotiana tabacum L.), acting asone of the most important pillar industry of economic development in Yunnan, has animportant influence on the economic development of Yunnan. Low temperatureduring tobacco early seedling stage and drought when transplanted has been anserious problem for tobacco plantation and production. In this paper, using Yunyan203seeds as the experimental material, the effect of seed priming with trehalose (TH)and sodium nitroprusside (SNP) on the resistance of tobacco seed and seedlings tolow temperature and drought stress were investigated, as well as proline metabolismpathway involved in SNP priming to improve the resistance of tobacco seeds andseedlings to drought and chilling resistance were studied, the results are stated asfollows:1. Effects of trehalose primng on increasing the resistance of tobacco seed andseedlings under the low temperature and drought stress tolerance.Trehalose in5,10,15mmol·L-13concentration (TH) for priming, study TH onseed germination and seedling growth of tobacco seed under the normal culture,drought, low temperature and drought and low temperature double stress. The resultsshowed that, for the suited concentration of TH priming can significantly improve thetobacco seeds under drought, low temperature and drought and low temperature stressthe germination potential, germination rate, germination index, shorteninggermination time, increasing the seedling root length, seedling height and fresh anddry weight, especially which10mmol·L-1TH priming effect is most remarkable.Further studies show that10mmol·L-1TH priming increase the TTC reductioncapacity under low temperature, and decrease relative electric conductivity underdrought, especially in drought and low temperature stress effect is more obvious, cansignificantly improve the tobacco seedlings TTC reduction capacity and totalchlorophyll content, and decrease relative electric conductivity. As a conclusion, the seed priming with10mmol·L-1TH could enhance simultaneously the chilling anddrought resistance of tobacco seeds and seedlings.2. Effects of SNP priming on low temperature and drought stress resistance oftobacco seeds and seedlings.Using1,50,100,200μmol·L-14concentrations of sodium nitroprusside (SNP)for seed priming treatment, and the priming effects on seed germination and seedlinggrowth under the normal culture, drought, low temperature, drought and lowtemperature double stress were studied. The results showed that the seed priming withSNP could significantly improve the germination potential, germination rate andgermination index of tobacco seeds, shorten germination time, increase the root andshoot length, and fresh and dry weight of tobacco seedings under normal culture,drought, low temperature, drought and low temperature doubles stress conditions, andthe priming with100μmol·L-1SNP obtained the best effects in the presentexperiments. Further studies show that100μmol·L-1SNP priming can obviouslyincrease the proline content in tobacco seeds, increase GDH and P5CS activity,decreased PDH activity. On the other hand, the RT-PCR results also showed, by100μmol·L-1SNP priming seeds, P5CS upregulation, PDH downregulation. It isspeculated that proline accumulation is mainly by stimulating glutamate synthesispathway, while suppressing the degradation pathway. Results show that100μmol·L-1SNP priming can enhance both seeds and seedlings drought and cold resistance, andincrease the accumulation of proline to increased seed tolerance.3. Effects of proline metabolism pathway involved in SNP priming increase droughtand cold resistance of tobacco seeds and seedling.With the optimal concentration of sodium nitroprusside (100μmol·L-1SNP) forpriming, study effecte of100μmol·L-1SNP on proline content and key enzymeactivity of proline metabolic of tobacco seed under the normal culture, drought, lowtemperature, drought and low temperature stress. The results showed that,100μmol·L-1SNP priming can be different degrees increased proline content in normaland stress conditions, obviously in the early stage of germination of seedlings, whileGDH, P5CS and OAT also have varying degrees improvement, especially in droughtand low temperature double stress, can significantly improve the early germination (0~10d) of GDH and P5CS activity, decreased PDH activity. Further of geneexpression detection that, in normal, drought, low temperature and drought and lowtemperature conditions, compared with the dry seeds, the P5CS expression ofdistilled water and100μmol·L-1SNP priming caused increase in different degrees,the expression of OAT also have varying degrees of increase in different time periods,and the expression of PDH also decreased to different extent, especially in droughtand low temperature stress, the expression of PDH in the early stage of germination(0~10d) decreased obviously.100μmol·L-1SNP induced by glutamate synthesispathway can stimulate proline metabolism, part stimulate ornithine synthesis pathway,while suppressing the degradation pathway, the proline content increased in seeds andseedlings of tobacco in adversity, in order to increase the seed and seedling resistance.