Mitigation Effect Of Extraneous Salicylic Acid On Zinnia Elegans Under Low Potassium Stress

In this paper,the effect of different potassium levels(0,100,200,300 and 400mg·kg^-1)on the growth and development of Zinnia elegans was studied by using a field pot experiment.And the low and proper potassium concentrations of the Zinnia elegans seedlings were determined through studying the effects of different concentrations of potassium nutrition?0,4,8,12 and 16 mM?on growth of Zinnia elegans seedlings.Then the effect of salicylic acid on the flowering of Zinnia elegans was studied by pot experiment in the field.Alleviating effect of silicon of salicylic acid on Zinnia elegans seedlings under low potassium stress was explored by using sand culture method.The main results were showed as follows:1.In the range of this experiment,potassium application improved the plant height,leaf number,shoot dry weight,root dry weight,the number of flowers and flower dimeter,all these indexes increased first and then decreased with potassium levels raise,and reached the maximum when the potassium level was 300 mg·kg^-1.Potassium application improved dry matter accumulation,contents of N,P in shoots and roots,accumulation of N,P,and K.The variation of dry matter accumulation and the accumulation of N,P,and K were consistent,they first increased and then declined with the potassium levels raise,the indicators reached the highest in the treatment of 300 mg·kg^-1,and then decreased when the potassium level was 400 mg·kg^-1,these indexes at 400 mg·kg^-1 were still significantly higher than those of control;the content of potassium increased with the increase of potassium application rate.Under the condition of this experiment,the 300 mg·kg^-1 is the most appropriate potassium level to Zinnia elegans.2.Different concentrations of SA have different effects on the flowering of Zinnia elegans.Under the condition of this experiment,0.5 mM SA treatment significantly increased the plant height,biomass,leaf number and flower number of Zinnia elegans,while 1.0 mM treatment had no significant difference compared with the control.In conclusion,the appropriate concentration of exogenous SA has a significant promoting effect on the growth and flowering of Zinnia elegans.3.In the range of this experiment,the index of Zinnia elegans seedling growth increased firstly and then declined with the increasing K⁺concentration,the indicators reached the highest when K⁺concentration was 12 mM.The plant height of Zinnia elegans seedlings treated with K⁺were significantly higher than that of control,and when K⁺concentration was 12 mM,it was the highest,with an increase of 80.52%compared with the control.K⁺treatment increased the root length,root surface area and root volume,and all these indicators were the highest under 12 mM K⁺treatment.The suitable concentration of K⁺?12 mM?had promotive effect on the growth of Zinnia elegans seedlings,the promoting effect on underground growth was greater than that of aboveground,higher concentration of K⁺had negative effects on growth of Zinnia elegans.4.Spraying salicylic acid improved the plant height,fresh and dry weight,all these indexes increased first and then decreased with the concentrations of SA raise,and reached the maximum when the concentration of SA was 0.75 mM.Total root length,total surface area,the length and surface area of fine roots?diameters?0.3 mm?of Zinnia elegans seeding treated by 0.75 mM SA concentrations were significantly higher than the control.It indicated that SA could significantly alleviate the inhibitory effect of low potassium stress on the growth of Zinnia elegans seedlings,especially with 0.75 mM,higher concentration of SA had negative effects on growth of Zinnia elegans.5.The plant height,dry and fresh weight,root length and root surface area,the content of chlorophyll and carotenoid were declined with low potassium on seedling period of Zinnia elegans,while the content of soluble protein,proline and malondialdehyde were increased,and inhibited the absorption and accumulation of N,P and K.Spraying 0.75 mM salicylic acid treatment increased root length and root surface area,the content of pigment,soluble protein and proline on seedling period of Zinnia elegans under low potassium stress,reduced the content of abscisic acid,and promoted nutrient uptake and accumulation of N,P and K,it demonstrated that spraying 0.75 mM salicylic acid could alleviate the adverse effects of low potassium stress on the seedlings of Zinnia elegans to a certain extent.The key factor to alleviate the adverse effects of low potassium stress were the whole dry weight and the content of IAA through using principal component analysis?PCA?.