Effects Of Sodium Silicate On Castanopsis Hystrix Seedings Under Manganese Stress

Manganese contamination of the soil is particularly widespread in China.Manganese contamination in the soil can limit plant development and possibly cause mortality.Silicon can reduce manganese buildup in plants and improve plant stress tolerance.In southern my nation,Castanopsis hystrix is a valuable and high-quality natural timber and greening tree species with good decorative and greening benefits.Castanopsis hystrix seedlings were employed as test trees,and five manganese concentrations(0,200,600,1500,3000 mg/kg)and four silicon concentrations(0,500,1000,2000 mg/kg)were set using a two-factor experimental design.Castanopsis hystrix was studied for its resistance to heavy metal manganese and the influence of silicon on heavy metal manganese stress.The following are the conclusions:(1)Castanopsis hystrix seedlings with lower Mn concentrations had a greater rise in plant height,ground stem biomass,root biomass,stem biomass,total biomass,total root length,total root surface area,and root biomass.The phenomena of "poor promotion and strong inhibition" was evident in the total projected area and total root volume.Castanopsis hystrix toxicity can be reduced by 500 mg/kg sodium silicate,but Castanopsis hystrix growth is inhibited by 2000mg/kg sodium silicate.(2)With the rise in Mn content,the MDA content of Castanopsis hystrix seedlings decreased at first,then increased,while the activity of four antioxidant enzymes,SOD,POD,CAT,and APX,increased at first,then decreased.The activities of Castanopsis hystrix SOD,POD,CAT,and APX were greatly enhanced when 500 mg/kg and 1000 mg/kg sodium silicate were administered.The SOD,POD,and CAT of Castanopsis hystrix seedlings were greatly enhanced when 2000 mg/kg sodium silicate was administered.The activity of APX was drastically reduced.After the administration of Mn,the level of soluble protein increased first,then declined,peaking at 200 mg/kg,while the content of soluble sugar fell.(3)Chlorophyll and carotenoids reduced as Mn concentration increased.With increasing Mn concentration,the net photosynthetic rate(Pn),intercellular carbon dioxide concentration(Ci),stomatal conductance(Gs),and transpiration rate(Tr)increased initially,then dropped.Pn,Ci,Gs,and tr of Castanopsis hystrix treated with high concentration Mn increased when 500 mg/kg and 1000 mg/kg sodium silicate were applied;at 2000 mg/kg sodium silicate,the stress degree of the red cone was worsened,resulting in a reduction in chlorophyll content,Pn,Ci,Gs,and Tr.(4)Fv/Fm,Y(II),q N,q P,and ETR all increased first,then declined as Mn concentration increased.Fv/Fm,Y(II),q P,and ETR were considerably reduced at high dosages of 1500 mg/kg and 3000 mg/kg.Castanopsis hystrix can enhance its Fv/Fm and Y(II)under high Mn stress by using a modest concentration of sodium silicate.(5)With the rise in Mn concentration,the content of mineral elements in Castanopsis hystrix leaves displayed a distinct pattern.The content of K,Ca,Mg,and Cu increased at first,then declined,whereas the concentration of Fe fell at first,then increased.The level of Zn rose dramatically during stress,and the content of Zn showed an increasing trend.The concentrations of K,Ca,Mg,and Fe often reduced after the application of Si,while the contents of Zn and Cu generally rose initially and later declined.(6)Mn absorption and enrichment in Castanopsis hystrix seedling roots were lower than in stems and leaves.The level of Mn in the roots,stems,and leaves of Echinacea rubra reduced dramatically following treatment with high doses of1500 mg/kg and 3000 mg/kg Mn after applying 1000 mg/kg sodium silicate.The Castanopsis hystrix seedlings scored higher and grew better when low concentrations of Mn and sodium silicate were applied;however,when high concentrations of Mn and high concentrations of sodium silicate were applied,the comprehensive scores of Castanopsis hystrix seedlings were generally lower,and growth was inhibited.