| The fruit of Silybum marianum (L.) Gaertn., belonging to the Compositae family, is a traditional Chinese medicine. Pharmacological research show that silymarin, the main effective component of Silybum marianum, is widely applied in preventing and treating hepatobiliary disease, resisting oxidation, radiation and tumor. Widespread Silybum marianum plays an important role in utilizing saline-alkaline soil for its strong adaptability. In order to investigate the salt-tolerance mechanism, the alleviate effect of SNP on Silybum marianum under salt stress, and the accumulation law of silybin and total flavonoids in Silybum marianum, a series of researches were carried out with two types of Silybum marianum as experiment materials. Concrete results were as follows:1. The germination energy and germination rate of two Silybum marianums decreased under Nacl stresss.The low density Nacl showed promting function and high density Nacl expressed inhibitory function(HW:NaCl concentration>0.5%> SD:NaCl concentration≥0.3%) on the bud seedling growth.The content of malondialdehyde (MDA) increased in young leaves. The low density Nacl showed promting function and high density Nacl expressed inhibitory function(HW:NaCl concentration>0.9%>. SD:NaCl concentration>0.7%) on the seedling growth.The soluble sugar,soluble protein contents and activities of protective enzymes (including SOD, POD and CAT) increased at first and then decreased in young leaves,while Pro content increased continuously.2. Soaking seeds with 0.05-0.60 mmol·L’SNP could alleviate the damage of NaCl stress to Silybum marianum. Under this treatment, contents of photosynthetic pigment (including chlorophyll a,chlorophyll b, total chlorophyll and carotinoid) and osmosis substances (including soluble sugar,soluble protein and proline), activities of protective enzymes (including SOD, POD and CAT) in leaves were significantly increased, while malondialdehyde (MDA) content in leaves was decreased.3. From seedling to Initial bloom stage, plant grew quickly,and the content of photosynthetic pigment and silibinin and total flavonoid in leaf increased gradually;From Initial bloom stage to fruiting stage, growth was slower,and the content of photosynthetic pigment and silybin content in leaf decreased,and content of total flavonoids increased at first and then decreased.The distribution laws of silybin and total flavonoids in different organs of Silybum marianum showed that:at seedling, silybin:root> stem> leaf, total flavonoids:stem> root> leaf; From squaring period to full-bloom stage:inflorescence> leaf>stem> root; At fruiting stage:fruit>inflorescence> leaf>stem> root.From initial bloom stage to Fruiting stage, the contents of silybin and total flavonoids in the leaves of different positions increased gradually with closing to anthotaxy.4. Compared with the control, the growth of Silybum marianum was inhibited, and the plant dry weight decreased under NaCl, Na2SO4, Na2COP3, NaHC03 treatments, the decreasing range of shoot dry weight was higher than that of root dry weight. Whereas,50 mmol·L-1NaCl treatment had opposite effect. Photosynthetic pigment content of Silybum marianum leaf decreased in early stage, treated after 4 d, then increased with time passing under saline and alkaline treatments. O2- generating rate, H2O2, MDA, soluble protein and soluble sugar contents, SOD, POD and CAT activities of Silybum marianum leaf under saline and alkaline treatments were higher than that in the control, and showed an upward tendency with saline and alkaline concentrations increasing. These indexes increased first and decreased afterwards under neutral salt(NaCl and Na2SO4)treatments, whereas, increased continually under alkalic salt(Na2CO3 and NaHCO3). Pro content increased continually compared with the control in all treatments.NaCl, Na2SO4, Na2CO3, NaHCO3 treatments induced increase in Na+content and decreases in K+, Ca2+ and Mg2+ contents of every parts in Silybum marianum seedling, while high concentration of alkalic salt(Na2CO3 and NaHCO3) treatments induced increase in Ca2+ content. The ratios of K+/Na+, Ca2+/Na+and Mg2+/Na+decreased in all treaments. The distribution regularities of Na+and Ca2+ in all treatments were:aging leaves >young leaves> root, young leaves> aging leaves> root. The distribution regularity of K+ in neutral salt(NaCl and Na2SO4)treatments was:root>aging leaves, young leaves, while that showed an opposite tendency in alkalic salt(Na2CO3 and NaHCO3). The distribution regularity of Ca2+in neutral salt(NaCl and Na2SO4)treatments was:aging leaves>root, young leaves, while that in alkalic salt(Na2CO3 andNaHCO3) was:root>young leaves> aging leaves.5. Photosynthetic pigment content of Silybum marianum decreased, while O2-+ generating rate and MDA content increased under complex alkali-saline stress. Low salinity(≤80 mmol·L-1) and low alkalinity(pH<7.98) treatments induced increase in plant height of Silybum marianum, while the other treatments induced decrease. Three antioxidant enzyme activities increased drastically in all treatments, and SOD, CAT activities reached the maximum in full-bloom and squaring stage respectively, and POD activity was high at three stages.Low salinity and low alkalinity treatments induced increase in the contents of soluble sugar, soluble protein, reducing sugar and total nitrogen compared with the control, while high salinity and high alkalinity treatments took contrary action. Starch content was lower than that in the control and decreased continually in each stage. Sucrose content was higher than that in the control in squaring and fruiting stage, while lower in fruiting stage.Na content of Silybum marianum leaves increased compared with the control in all treatments, while B content showed an opposite tendency. The contents of Fe, P, Ca, K, Mn, Mg, Cu and Zn increased in low salinity and low alkalinity treatments, and decreased in high salinity and high alkalinity treatments. Whereas, Cu content decreased compared with the control in full-bloom and fruiting stage in all treatments, and this also happened on Fe, P, Ca and K in fruiting stage. Silybin content of Silybum marianum fruit was higher than that in the control when pH≤8.82, while lower when pH> 8.82. |
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