CO₂-induced P Uptake Is Mediated By Increased Strigolactones Biosynthesis And AM Parasitism In Tomato Plants

Since the industrial revolution, as a result of a sharp drop in forest area and the use of fossil fuels, the CO2 concentration in the atmosphere has been increasing. As the main material of photosynthesis, the CO2 concentration has an important influence on changing the growth and resistance of the plant. There are a lot of studies aim to reveal the CO2 enrichment effect on plant growth and development, but the research of CO2 enrichment on the effect of plant nutrient stress and symbiotic plants with fungi, is still relatively few, the mechanism also remains to be elucidated. In this study, we use tomato (Solanum lycopersicum L.) as the research object, which was cultured in the artificial illumination incubator with a hydroponic and sand vermiculite mixed cultivation mode, to elucidate the effect of elevated CO2 and inoculated mycorrhizal fungi on growth of tomato in low phosphorus environment by using photosynthetic rate, oxygen sensitivity, GUS staining, blue staining, fluorescence microscope, dry matter weight, atomic spectrophotometer and other techniques. This study indicated the important underlying mechanisms of elevated CO2-induced P uptake is mediated by increased strigolactones biosynthesis and AM(Arbuscnlar mycorrhizal) parasitism in tomato plants. The prominent features of current study are as follows:1. First of all, we found that the CO2 enrichment could alleviate the low phosphorus stress, and promoted the absorption of phosphorus in the low phosphorus environment. We found that in the environment of different phosphorus concentration, the plant growth, dry matter weight and photosynthetic capacity of tomato in the environment of high CO2 (900 ?L/L) was significantly higher than that in the control (CO2:450 ?L/L) environment. By atomic spectrophotometer, we determined phosphorus content of the tomato plants and found that tomato plants grown in elevated CO2 environment, the phosphorus concentration and the phosphorus content of which are significantly higher than that of the control. These results indicate that CO2 can improve the absorption of phosphorus in the low phosphorus environment. These results indicate that CO2 enrichment can improve the absorption of phosphorus in the low phosphorus environment. At the same time, through the further experiments,we could conclude that the expression of RBOH, WFI, FZY, IAAI5, MAX1, MAX2, CCD7, CCD8, the accumulation of ROS in roots and the synthesis amount of auxin can be increased by CO2 enrichment.2. We have made it clear that the mycorrhizal fungi(Arbusular mycorrhizal) can promote the absorption of phosphorus in tomato under low phosphorus stress. Through experiments, we found that the photosynthetic rate, oxygen sensitivity and dry weight of tomato were significantly increased after inoculation with mycorrhizal fungi in low phosphorus environment. These results indicated that mycorrhizal fungi could significantly relieve the stress caused by low phosphorus environment. At the same time, we also found that the CO2 enrichment and the low phosphorus environment can promote the growth of tomato root mycorrhizal fungi:The infection rate and infection density of mycorrhizal fungi in CO2 enrichment and low phosphorus environment were significantly higher than those in other treatment groups. The results showed that mycorrhizal fungi and tomato root symbiosis could promote the absorption of phosphorus, and the promotion of the relationship in CO2 enrichment could be more significant, so it might be related to the increase synthesis of IAA and SLs by CO? enrichment.3. According to the results of previous experiments, we did experiments to explore the mechanism of CO2 enrichment promoting the growth of the mycorrhizal. In this study, compared with the pTRV plants, the photosynthetic rate, oxygen sensitivity, dry matter weight, dry matter weight, mycorrhizal fungal infection rate and the infection density of the SLs synthetic gene silencing tomato plants were significantly decreased in the environment of CO2 enrichment and low phosphorus These results showed that, when the SLs synthetic gene silenced, the effect of CO2 enrichment on the growth of mycorrhizal fungi was significantly decreased or even disappeared, which resulted in the decrease or disappearance of the resistance of tomato to low phosphorus environment.