Effects Of Phosphorus Nutrition On Photosynthesis And Phosphorus Absorption And Accumulation In Soybean

Phosphorus is one of the most important elements,and plays an important role in soybean growth and development.Phosphorus deficiency had a significant effect on the formation of phosphorus metabolites,which seriously affected the growth and development of soybean.Phosphorus has obvious effect on the transformation and metabolism of chloroplast energy and the formation of photosynthetic capacity,which can promote the transport of photosynthate in leaves and occupy important physiological positions in photosynthesis.Therefore,different phosphorus nutrition levels have an impact on soybean photosynthesis,and further affect the formation of yield.In this experiment,Heinong 48 was used as materials,using sand pouring method of nutrient solution.The test set up 4 phosphorus levels: 1 mg·L-1(P1),11 mg·L-1(P11),21 mg·L-1(P21)and 31 mg·L-1(P31),treated in the whole growth period.At the same time,the change of phosphorus in soybean growth period was set up,from low phosphorus to high phosphorus treatment: emergence to V4 period pouring P1 nutrient solution,V4-R8 pouring P31 nutrient solution recorded as V4P1-31;Emergence to R2 stage pouring P1 level nutrient solution,R2-R8 pouring P31 level nutrient solution recorded as R2P1-31;from high phosphorus to low phosphorus treatment: emergence to V4 pouring P31 nutrient solution,V4-R8 pouring P1 nutrient solution recorded as V4P31-1;emergence to R2 period pouring P31 nutrient solution,R2-R8 pouring P1 nutrient solution recorded as R2P31-1.The experiment studied the effects of phosphorus levels on photosynthesis and phosphorus absorption and accumulation of soybean.The results showed:The absorption rate of CO2,leaf area and photosynthetic rate increased with the growth of soybean.The absorption rate of CO2 and photosynthetic rate reached the maximum at the R5 stage,and then tended to decrease gradually.The absorption rate of CO2 and leaf area increased with the increase of phosphorus nutrition level,but when the phosphorus nutrition level reached P21(21 mg·L-1),the phosphorus level had no obvious effect on it.The effects of phosphorus on photosynthetic rate were different.Under low phosphorus stress,the photosynthetic rate of soybean was significantly decreased in the early and middle stage of growth,but the effect was not significant when the phosphorus level was P11.From low phosphorus to high phosphorus treatment has a stimulating effect on the photosynthetic rate of soybean,the photosynthetic rate increased.The photosynthetic rate of soybean will not be reduced for some time under the from high phosphorus to low phosphorus treatment,the early high phosphorus treatment may has some phosphorus supplementation to later stage of low phosphorus.With the growth of soybean chlorophyll a,b content and total content gradually increased,and reached the highest in R4-R5 stage,then gradually decreased,showing a single peak curve changes.Only when the phosphorus nutrition level was very low,the chlorophyll content will be affected.From low phosphorus to high phosphorus treatment significantly improved soybean chlorophyll content,but in a short of time,it was impossible to reach the normal conditions of chlorophyll content level.From high phosphorus to low phosphorus treatment,there was still a higher chlorophyll content in a short of time,which was due to the accumulation of early results.With the increase of phosphorus nutrition level,the phosphorus accumulation of soybean organs showed a significant increase trend.With the development of soybean growth,the accumulation of phosphorus in roots,stems and handles increased rapidly in R2-R4 stage,and reached the maximum value in R4-R5 stage.The accumulation of phosphorus in leaves reached the maximum value in R6 stage,and then most of phosphorus transferred to the pods,the accumulation of phosphorus showed significant increase trend in R6 stage.From low phosphorus to high phosphorus treatment,not only can significantly improve the content and accumulation of phosphorus in each organ,but also caused the phosphorus content of some organs increased sharply because of the early starvation.From high phosphorus to low phosphorus treatment,due to the accumulation of phosphorus in the seedling stage,the phosphorus content of each part decreased relatively slow compared to the V4 treatment stage.The effect of phosphorus nutrition on vegetative growth stage was higher than that of reproductive stage.There was a positive correlation between the accumulation of dry matter and nutrient level of soybean.It can be concluded that low phosphorus stress can significantly inhibit the dry matter accumulation of soybean.The accumulation of dry matter in all organs of soybean increased with the growth of soybean firstly and then decreased.When the phosphorus nutrition level was P21(21 mg·L-1),the increase of phosphorus nutrition had no significant effect on the dry matter accumulation of soybean.The plant height,grain number,node number and yield of soybean increased gradually with the increase of phosphorus nutrition level,when the phosphorus nutrition level reached 21 mg·L-1,the increase of phosphorus nutrition had no effect on the plant height and yield.From low phosphorus to high phosphorus treatment had a certain promoting effect on soybean yield.In the vegetative growth stage,the phosphorus deficiency is easy to cause yield reduction,the longer the low phosphorus stress,the lower the yield.