Study On The Response Of Seed Germination And Seeding Growth Of Cirsium Japonicum Fisch Ex DC To The PEG Stress

In order to investigate the mechanism of seedling drought resisting to the Cirsium japonicum Fisch.ex DC, evaluated drought resistance the seeds and seedlings, the data provided a theoretical basis and reference for introduction and cultivation and garden applications in arid and semi-arid regions. In this experimentation,taking the Cirsium japonicum Fisch.ex DC. as test material, used laboratory culture dish compare 6 concentration gradient (5%,10%,15%,20%,25%,30%) of PEG-6000 simulated drought stress affect seed germination rate, germination index and other indicators, hydroponic nutrient solution added PEG method to compare the above-mentioned six PEG concentration gradient the seedlings treated 24h,48h,72h, The leaf relative water content, the soluble sugar content, the free proline content,the relative conductivity, MDA, three large protective enzyme SOD, CAT, POD activity changes, combined with plant leaves wilt status, results showed:With PEG concentration increased, the germination rate, germination index, vigor index, drought index showed a decreasing trend. Among them, when the PEG concentration of 5% and 10% treated these five indicators showed no significant difference with CK ((p> 0.05), PEG concentration greater than 15%, with a gradient of increasing concentration indexes were significantly lower (p<0.05), when the PEG concentration of 20%, the germination rate, germination index, vigor index, drought index relative to CK decreased by 94.6%94.3%,89.5%,97.8%,98%, indicating that the conditions have reached lethal concentration seeds.With PEG concentration and treatment time, the leaf relative water content (RWC) decreased, compared with CK, PEG concentration gradient of 5% to 30% with the RWC declined 17.3%,31.4%,48.3%,55.1%,61.8%,72.2%; processed time with 24h, under PEG concentration of 5% treated, the RWC and CK was not significantly different, the next 10%～30% PEG concentration gradient between treatments were not significant, but lower than PEG 5% treatment (p<0.05), in 48h and 72h treatment, the RWC decreased significantly with the increasing concentration gradient.With PEG concentration and drought stress time, the leaf of soluble sugar (Ss) and proline (Pro) content showed trends firstly decreasing and then increasing, which PEG concentration gradient of 5% to 30% with the leaf soluble sugar and proline content higher than CK; when dealing with 24h and 48h, the Ss and Pro content increased with the PEG concentration of less than 20%, the largest increase was 63.1%,103%, with the PEG concentration of 25%,30%, the Ss and Pro content decreased, a decline of 12.8%,24.6% and 7.1%,12.9%; when dealing with 72h,the leaf of Ss and Pro content remains relatively high levels, indicating that under severe drought, the leaf of Ss and Pro early accumulation content, maintained a long time, which was a short-term drought stress can just and adapt initiatives to reduce injuries.With PEG concentration increasing, the leaf relative conductivity and MDA was a persistent increase in the trend, compared with CK, the PEG concentration gradient of 5% to 30% treatment, the leaf relative conductivity decrease was13.6%、21.2%、19.3%、 23.7%、28.3% and 23.4%, MDA decline 52.9%、42.5%、29.7%、24.2%、27% and 34.6%; with prolonged stress time the relative conductivity and MDA content with 5% to 30% of the difference more significant (p<0.05), dealing with 24h,48h and 72h, which the leaf relative conductivity and CK compared to the largest increase was 45.7%,59.1%,74.5%; the MDA content compared with CK largest increase was 123%,171%,186%; indicating that the MDA was more active than the leaf relative conductivity under drought stress.With the PEG concentration increasing, dealing with 24h, SOD activity increased gradually, CAT and POD activity the first increased after reduced, the PEG 30% treatment was maximum activity of SOD, increasing of 108%, the PEG 10% treatment was maximum CAT activity, increasing of 10.3%, the PEG 15% treatment was biggest POD activity, increasing of 14.3%; when processing 48h and 72h, the SOD, CAT and POD activity were first increased and then reduced, when the PEG concentration was less than 15% that the SOD, POD gradually increased, SOD activity of increases were 79.7%, 21.1%,6.6% and 135%,8.3%,46%, POD activity of increases were 10.3%,17.7%,32.4% and 42.2%,9.5%,14%, but the PEG 25% treatment, the SOD activity was highest that which was significantly higher than CK (p<0.05) at 48h concentration, when the PEG concentration greater than 15%,SOD and POD activity decreased, the biggest drop was 46.8%,40.3%; when the PEG concentration of less than 10%, the CAT activity increased gradually and the maximum CAT activity, compared to CK was increasing of 38.9%, while PEG concentration gradient of 10% to 30% with the next CAT activity decreased, the largest decline was 23.4% and 27.6%; with the stress time extend, the same PEG concentration, the SOD and POD risen, the largest increase were 565%,403%;but the CAT activity the first risen then reduced, the largest increase and decrease were 153%,24%; indicating when drought stress SOD and POD played an important role than the CAT.In view of the above findings, provide a theoretical basis of the introduction or expansion of cultivation for the Cirsium japonicum Fisch.ex DC. The seed ability mild drought stress (PEG concentration≤10%), and the PEG concentration of 15% with a certain tolerance; moderate drought (15%≤PEG concentration≤20%) is a seed germination and growth the threshold is exceeded,the indicators change of growing instability, severe drought (PEG≥20%), the plant of leaves began to wilt partly, not die mortality.