Physiological Effects Of Different Light Intensity On Phosphorus Uptake At Seedling Stage

Phosphorus is an essential nutrient for plant growth,it also has important influence on plant growth and metabolism.Light plays an important role in influencing plant growth.When plants growing out of the soil to reach the sunlight,light activation of photoreceptor phy B results in rapidly combining with EIN3 protein,the master transcription factor in the ethylene signaling pathway,so that ethylene signal pathway will be inhibited.However,exogenous ethylene can increase phosphorus starvation response gene expression and root acid phosphatase activity.We think that phy B directly targets EIN3 protein for light-induced rapid degradation.Then,inhibited ethylene signal pathway will downregulate acid phosphatase activity.While,light regulates the absorption of phosphorus by plants negatively.Wheat and maize are the main food crops,and oil rape is the main oil crop.at the same time,take C3,C4,monocotyledonous and dicotyledon crops in to account,in this study,we selected maize,wheat and oil rape as the research object.In the pot,the light intensity was changed by the distance between the plant and the light source,let them under 800 umol m^-2s^-1,400umol m^-2s^-1and 200 umol m^-2s^-1 light intensity.Before the treatment,phosphorus was supplied as Ca(H₂PO₄)₂�H₂O at 1g plant^-1.The light intensity was changed by shading treatment in the field.Make the relative light intensity in the shading shelter 42%and15%of the natural light treatment,and apply superphosphate(100 kg/hm2)before treatment.Under different light intensity,we studied phosphorus absorption level,ethylene content,acid phosphatase activity and EIN3 protein content at seedling stage and so on.We will provide a scientific theory for agricultural production,applying phosphate fertilizer scientifically,and improving plant phosphorus absorption.The main conclusions are as follows:(1)The high light intensity inhibits the absorption of phosphorus,and reduce light intensity can promote the absorption of phosphorus.C4 plants have a longer low light tolerance than C3 plants,and monocotyledons have a stronger low light tolerance than dicotyledons.Among maize plants,biomass(fresh weight)reached the maximum after two weeks of medium light intensity treatment,while phosphorus content reached the highest after two weeks of low light intensity treatment.But biomass(fresh weight)just decreased by about 0.2 times.For wheat plants,similarly,the biomass(fresh weight)of wheat reached the maximum after two weeks of medium light intensity treatment.But the phosphorus content of wheat did not change significantly at the second week of light intensity,while the phosphorus content of wheat reached the maximum after one week of low light intensity treatment,and there was no difference between biomass.One low light intensity treatment for rape plants,phosphorus content was highest,but the biomass(fresh weight)is significantly reduced.In field,the effect of light intensity on plant phosphorus absorption had a similar trend,indicating that,in pot planting or field planting,the increase of light intensity will reduce the total phosphorus and cell phosphorus concentration of the plant.Decreasing the light intensity will increase the total phosphorus and cell phosphorus concentration.But too low light intensity will lead to the inhibition of plant growth.At the same time,take the balance of plant growth and phosphorus content,as a C4 plant,maize has a special dark reaction process that allows it to grow normally under low light intensity.Maize can accept low light intensity treatment for two weeks,and wheat can accept low light intensity for one week.For treatment,oil rape as a C3 crop can only be treated with medium light intensity(moderate shade)for one week.(2)Reducing light intensity can promote plant ethylene synthesis,but there are differences among plants.Compared with high light intensity,medium and low light intensity treatments can significantly increase the ethylene content in corn for one week.Similarly,after one week of low light intensity treatment,the ethylene content of wheat is also higher than that of high and medium light conditions.However,after one week of medium light intensity treatment,the ethylene content of rapeseed increased significantly.Those result showed that decreasing light intensity can promote plant ethylene synthesis,but there are differences between materials and processing time.(3)Decrease light intensity will contribute to the accumulation of EIN3 protein content.After maize was treated with high light intensity for one week,the protein content in high light conditions was significantly reduced.Under low light conditions,the EIN3 protein content was highest.And the second week of light treatment had similar trend with the first week.Among wheat and rape,the EIN3 protein content of wheat was the highest after one week of low light treatment,and the rapeseed rape had the highest EIN3 protein content after one week of medium light intensity treatment,the influence of the intensity of the EIN3 protein disappear after two weeks of treatment.Light intensity affects protein content and EIN3 protein content is reduced by high light intensity.(4)Reduce light intensity and promote plant acid phosphatase secretion.Under low light intensity,the BCIP staining of acid phosphatase secreted by the roots of maize,wheat and oil rape became significantly darker,and the color gradually increased as the light intensity weakened,indicating that acid phosphatase secretion was promoted under low light intensity.In general,in agricultural production,we can use shading net to change light intensity.we believe that when we applied phosphate fertilizer,under 200 umol m^-2 s^-1light intensity about 14 days,it is most beneficial for phosphorus absorption of maize.After applying phosphate fertilizer,under 200 umol m^-2 s^-1 light intensity about 7 days,it is most beneficial for phosphorus absorption of wheat.After applying phosphate fertilizer,under 700 umol m^-2 s^-1 light intensity about 7 days,it is most beneficial for phosphorus absorption of oil rape.