| Ground-cover chrysanthemum(Chrysanthemum morifolium)is a cultivar group of Chrysanthemum with high ornamental value and strong resistance.A few of cultivars have drinking and medicinal value,which could be used for tea.In this study,the salt-tolerant physiological mechanism of ground-cover chrysanthemum was analyzed and the nutritional quality was evaluated.It is of great significance for the breeding and application of salt-resistant ground-cover chrysanthemum.The first part of this study,The morphological characteristics of 7 ground-cover chrysanthemum cultivars under the treatment of 5 salt concentration gradient were observed.Meanwhile,the salt tolerance physiology of ground-cover chrysanthemum was studied by measuring 22 physiological indexes.Then,the salt tolerance of 7 species of ground-cover chrysanthemum was comprehensively evaluated.'Yuanguanzi' and 'ty51' were selected to study their characteristics in ion absorption and transport,and the mechanism of salt tolerance of ground cover chrysanthemum was further revealed.The second part of this study,3 excellent varieties of ground-cover chrysanthemum were used as materials.The nutritional composition of chrysanthemum head in tea field was analyzed and compared with ' Hangbai '.It provides a theoretical basis for the promotion and application of fine ground-cover chrysanthemum.The main findings are as follows:(1)At the concentration of 50mmol/L salt,the tested ground-cover chrysanthemum basically showed a normal growth state.With the increase of salt concentration,ground-cover chrysanthemum began to lose water,yellowing and even die.The salt damage on the whole plant level of ground-cover chrysanthemum is shown as follows:the leaves at the bottom of stem first wilted and yellowed,and then the young tissue at the top gradually appeared.The salt damage on the leaf level of ground-cover chrysanthemum was manifested as:water loss and yellowing occurred firstly at the leaf edge and tip,and gradually extended to the leaf interior.(2)The physiological response of ground-cover chrysanthemum under salt stress was:the relative conductivity and soluble sugar content of ground cover chrysanthemum increased significantly,while other physiological indexes did not change significantly under the treatment of 50mmol/L NaCl concentration.In 100?150 mmo/L salt concentration processing,the ground-cover chrysanthemum leaf water content,specific leaf weight significantly reduced,osmoregulation substance(soluble sugar,free proline),plasma membrane permeability(relative conductivity)MDA),a significant rise in antioxidant enzymes(SOD,POD)activity;Chlorophyll photosynthesis was inhibited:chlorophyll(chla,chlb)content decreased,photosynthetic parameters Pn,Ci,Gs,Tr decreased;chlorophyll fluorescence parameters Fv/Fm,?PS?,qP decreased,NPQ increased.Under the treatment of 200mmo/L salt concentration,the water content and specific leaf weight of ground cover chrysanthemum reached the minimum value,and the activities of osmotic regulatory substances and antioxidant enzymes began to decrease and were significantly lower than those of the control group.The photosynthesis of ground cover chrysanthemum was still inhibited:chlorophyll content,Pn,Gs,Tr,Fv/Fm,?PS? and qP were significantly decreased,but Ci was significantly increased.(3)With the increase of salt concentration,the total flavonoids content in the leaves of ground cover chrysanthemum first increased and then decreased.There was no obvious consistent rule between the total phenol and chlorogenic acid content and the salt treatment concentration.(4)Yuanguanzi','ty51 ' ion absorption,transportation research results showed that:with the increase of concentration of salt treatment,'Yuanguanzi','ty51 ' Na+content in roots,stems and leaves increased significantly,K+,Ca2+content decreased significantly;The selective transport capacity of K+/Na+,Ca2+/Na+ ratio and K+ and Ca2+ was also significantly reduced.Compared with Yuanguanzi',the root,stem and leaf of 'tys1'had lower Na+ content and higher K+ and Ca2+ content.Moreover,it has a strong selective transport capacity for K+ and Ca2+ and a more stable K+/Na+ and Ca2+/Na+ion balance ratio.(5)The salinity tolerance of 7 ground-cover chrysanthemum ranged from high to low was:'ty51'>'Maoxiangyu'>'Fanbailu'>'Zaobailong'>'Jinruhe '>'yy3'>'Yuanguanzi'.(6)The selected indicators of ground-cover chrysanthemum salt tolerance were:SLW(X1),Relative conductivity(X2),MDA(X3),Fv/Fm(X4).The salt tolerance evaluation equation constructed is as follows:y=3.13-0.90 X1-0.08 X2-0.87 X3+0.27 X4,R2=0.929.(7)The salt tolerance threshold of chrysanthemum was preliminarily determined:'ty51 ','Fanbailu','Zaobailong','Jinruhe','yy3','Yuanguanzi' were 100mmol/L of NaCl;'Maoxiangyu' was 150mmol/L of NaCl concentration.(8)The nutritional quality of the four varieties of tea-chrysanthemum was successively from high to low:'ty51 '>'yy3 '>'Hangbai'>'Zaobailong'.Among them,the nutritional quality of 'ty51' and 'yy3' is superior to 'Hangbai'.Based on the research results,This study preliminarily analyzed the salt-tolerant physiological mechanism of ground-cover chrysanthemum.The salt tolerance of the tested ground-cover chrysanthemum was also evaluated.And 2 cultivars of tea-chrysanthemum were selected.It provides guidance and reference for the popularization and application of ground-cover chrysanthemum. |
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