Effects Of Titanium Treatments On The Growth,Photosynthetic Apparatus And Yield Of Soybean (Glycine Max L.) Under Light And Shade Conditions

In this study,the effects of ionic Titanium（Ti）under light and shade condition on growth and yield of soybean[Glycine max（L.）Merr.]were investigated.The five different concentration of Ti solution were sprayed on soybean plants both under light and shade conditions.Three experiments were conducted including hydroponic,soil pots and field experiment.In the hydroponic culture experiment three treatments（T₀:0,T₁:125 and T₂:250 mg/L）were chosen.However,in soil and field experiment five treatments（T₀:0,T₁:125,T₂:250,T₃:500 and T₄:1,000 mg/L）were used.Different agronomic and physiological parameters were measured with the help of instruments such as(Li-COR6400 for leaf net photosynthetic rate（Pn）,transpiration（Tr）,stomatal conductance（Gs）and intercellular CO₂（Ci）;SPAD-502 for chlorophyll content;WinRhizo scanner for root architecture measurements and Fluor-Image for chlorophyll fluorescence parameters.Our results revealed that shade significantly reduced the root length,volume,surface area and diameter.Additionally,shade significantly reduced leaf area,leaf thickness,stem breaking strength,and stem diameter and lignin biosynthesis.Shade affected the physiological parameters including,chlorophyll contents,photosynthesis,stomatal conductance and transpiration rate.Such reduction in photosynthesis occurred probably due to the smaller leaf area and lower chlorophyll contents.Additionally,shade interrupted the chlorophyll fluorescence parameters by disturbing the leaf anatomy,chloroplast and thylakoid structure.The reduction in Chl fluorescence occurred due to decrease in photochemical quenching（qp）,effective quantum yield of PSII photochemistry（ФPSII）and electron transport rate（ETR）.However,Ti had significant stimulatory and inhibitory effects on soybean growth under low and high concentrations.Under low concentration,Ti enhanced the root length,volume and surface area under both normal light and shade conditions.However,high concentration negatively affected the plants growth.Moreover,our results showed that foliar application of Ti（125 and 250 mg/L,T₂ and T₃）significantly improved leaf area,chlorophyll contents,photosynthesis（Pn）,stomatal conductance（Gs）,transpiration（Tr）,photochemical quenching（qp）,effective quantum yield of PSII photochemistry（ФPSII）and electron transport rate（ETR）both under normal light and shade conditions.The total soluble sugar also increased significantly in Ti treated plants.The increased number of pods and seeds per plants of the T₂ and T₃ plants led to higher final grain yield.The optimal soybean yield per hectare was 2630.48 kg/hm² in T₂ that was by 19.84%higher than that of T0（control）.Whereas,the lowest soybean grain yield was1597.36 kg/hm² in T₅ that was by 24.25%lower than T0.In conclusion,lower concentrations of Ti promoted the plant growth by accelerating activity of photosynthetic apparatus both under normal light and shade conditions.