The Effects Of CO₂ Fertilization On Photosynthetic Characteristics And Microstructure Of Tomato Leaves And Root System

In this study,an infinite-cultivated tomato variety "Xinghai 12" was used as a test material to study the effects of CO2 fertilization on photosynthetic characteristics,microstructure from different leaf ages and root system.The results of this experiment show that:(1)With the increase of treatment days,the photosynthetic rate is increased and then decreased.After 20 days,T2 and T3 was 29.08%and 29.36%higher than that of the control,respectively.The effects of elevated CO2 concentration to stomatal conductanc and transpiration rate are different at different growth periods.The water use efficiency is always higher at the high concentration.From the economical point of view,CO2 concentration of 800 μmol-mol-1 is more advantageous.(2)During the whole treatment period,elevate CO2 concentration promoted the increase of leaf area..After 40 days,the leaf area reached maximum,and T1,T2,and T3 were 7.16%,15.19%,and 12.04%higher than the CK,respectively.The effects of different CO2 concentrations on chlorophyll content were different.In the first 40 days of treatment,chlorophyll a content was higher than CK at high concentrations,and there was no significant difference in chlorophyll b,carotenoid content,and chlorophyll a/b.After 50 days of treatment,chlorophyll was significantly lower than that of the CK under T3 conditions.(3)Under high CO2 treatment,the initial fluorescence Fo,maximum fluorescence Fm,actual photochemical quantum efficiency Y(II),and photochemical quenching qP were consistently greater than CK.After 30 days,Fo and Y(II)were the highest,that were 15.88%and 51.70%higher than the CK,respectively.High CO2 concentration had no significant effect on PSII maximum quantum yield Fv/Fm.The non-photochemical quenching qN was significantly lower at high CO2 concentration.(4)Elevating CO2 concentration significantly promoted the increase of the sponge tissue,palisade tissue and total leaf thickness.High CO2 concentration promoted the increase of chloroplast number and volume;basal granules was clearly visible in the chloroplast,and the number and volume of starch granules were greater than that of the CK.Under the condition of high CO2,the degradation degree of chloroplast and basal granules was higher than that of the CK,while the degradation rate of starch granules was lower than that of the CK.(5)Elevating CO2 concentration favors increases in root length,root volume,root diameter,and surface area.After treatment for 30 days,root length,root volume,root diameter,and surface area were all greater than those of the CK,and the higher the concentration,the greater the root length,root volume,root diameter,and surface area.During the entire treatment period,Root activity first rose and then decreased.After 30 days of treatment,the root vigor was the highest,and the high concentration condition was greater than the CK.The root vitality under T3 condition was 20.45%higher than the CK.In summary,elevating the CO2 concentration promoted the increase of leaf area and chlorophyll content,increased the activity of PSII,promoted the increase of leaf thickness,chloroplasts,and the number and volume of starch grains and basal granules in the interior.At the same time,it is conducive to the growth of roots in the subterranean region.In turn,the photosynthetic rate of tomato was increased.From the economical point of view,CO2 concentration is 800 μmol·mol-1 better.