Effect Of Phosphorus Aluminum Treatment On Indole Acetic Acid (IAA) In The Root System Of Tea Plants (Camellia Sinensis)

Tea plant is a poly-aluminum-tolerant plant,and an appropriate concentration of aluminum can promote the growth of tea roots.Phosphorus is an essential element for plant growth.Under phosphorus-deficient conditions,some plants will adapt to adversity by increasing root area or changing root morphology.In this experiment,we investigated the pH conditions and the contents of phosphorus and aluminum in some tea garden soils.And the tea plant was treated with different phosphorus and aluminum concentration to explored the expression of auxin Indole acetic acid（IAA）content and auxin response factors in the roots and leaves.The effects of phosphorus and aluminum treatment on tea plant’s root growth were further studied by combined with the changes of tea plant’s root growth status and elements in different organs of tea plant.Our results provide a theoretical basis for further guiding the rational and efficient fertilization of tea garden.Through the investigation of pH and elements in the soil of some tea gardens in Yixing City,Jiangsu Province,it was found that the pH of the investigated tea garden soil was less than 5,the tea garden soil less than 4.5 accounted for 60.7%,and the average pH was 4.39.The total content of phosphorus in tea garden soil was between 0.78 g·kg^-1 to 6.44 g·kg^-1,the content of phosphorus was significantly negatively correlated with soil pH,and the content of available phosphorus was between 40.8 and 58.4 mg·kg-1,which met the requirement of"gradeⅡ"of fertility index of tea garden with high quality,high efficiency and high yield.The content of aluminum was distributed in the range of 10.26 g·kg^-1 to 31.74 g·kg^-1.The content of aluminum was negatively correlated with soil pH,and the content of Al³⁺was distributed in the range of 160.9 to 628.6 mg·kg^-1.The content of aluminum is in the range of 10.26 to 31.74 g·kg^-1,the content of aluminum is negatively correlated with soil pH,and the content of Al³⁺is distributed in the range of 160.9 to 628.6 mg·kg^-1.The content of Al（OH）₂⁺and Al（OH）²⁺is distributed between 31.5 to 105 mg·kg^-1,the content of Al（OH）₃is between 42.2 to 953.4 mg·kg^-1,the content of aluminum humate is between 199.8 to 1001.3mg·kg^-1.Different phosphorus and aluminum concentration gradients were designed to explore the effects of phosphorus and aluminum on the growth of tea plants and the contents of phosphorus and aluminum in tea plant’s roots and leaves.The tea plants of’Longjing 43’（10to 12 leaves）and’Shu Chazao’（5 to 7 leaves）were used as materials to carry out culture experiments The treatments were divided into 16 groups:high phosphorus(0.5 mmol·L^-1),normal phosphorus(0.05mmol·L^-1),low phosphorus(0.01 mmol·L^-1),no phosphorus(0mmol·L^-1),high aluminum(1 mmol·L^-1),normal aluminum(0.25 mmol·L^-1),low aluminum(0.1 mmol·L^-1)and no aluminum(0 mmol·L^-1).The results showed that there was a positive correlation between root elongation and aluminum concentration,and the absence of aluminum would seriously inhibit the growth of tea plant’s root.The root growth of tea plant was the best under the treatment of high aluminum,and the treatment of low concentration of phosphorus could promote the root elongation.The root elongation of’Shuchzao’was the highest in the treatment of low phosphorus and high aluminum,and the treatment of no phosphorus and high aluminum of’Longjing 43’was the maximum.The biomass increase of’Shuchzao’was positively correlated with aluminum concentration,and’Longjing 43’was positively correlated with aluminum concentration only under the condition of low phosphorus and no phosphorus.The results of determination of phosphorus and aluminum content in tea plant showed that the absorption of phosphorus and aluminum by tea plant’s roots and leaves under low phosphorus treatment was positively correlated with aluminum concentration,and the phosphorus content of tea leaves under low phosphorus treatment was positively correlated with aluminum concentration.The phosphorus content of tea leaves under low phosphorus and high aluminum treatment reached the maximum value of all treatment groups,which was significantly higher than that of tea leaves under high phosphorus treatment.There was a significant difference in IAA content in the root between the two varieties.The IAA content in the root of’Longjing43’in CK group was 2.72 times higher than that of’Shuchzao’,but the change trend was basically the same under the influence of treatment.Different concentrations of phosphorus and aluminum had a great influence on the IAA content of tea plant’s root.Under the condition of low phosphorus,the IAA content in the root of’Longjing 43’and’Shuchazao’was the highest under high aluminum treatment,which was 13.2%and 75.2%higher than that under normal phosphorus and aluminum condition,and 54.1%and 41.7%higher than that without phosphorus and aluminum,respectively.IAA content was closely related to aluminum concentration.The root IAA content of’Shuchazao’increased with the increase of aluminum concentration under the treatment of no phosphorus,low phosphorus and normal phosphorus,but the promoting effect was weakened under the treatment of high phosphorus.The content of IAA in the root of’Longjing 43’was positively correlated with aluminum concentration only under low phosphorus treatment,and reached the maximum at normal aluminum concentration,and high aluminum inhibited the increase of IAA content under normal and high phosphorus conditions.After analyzing the expression of auxin response factor CsARF5 gene and Cs ARF10gene,it was found that aluminum and phosphorus treatment had a certain effect on the expression of these two genes.Generally speaking,the increase of aluminum concentration could promote the expression of Cs ARF5 in root under the condition of no or low phosphorus,and the expression of Cs ARF10 was also closely related to aluminum concentration.The relative expression of Cs ARF5 in the root of the two tea varieties was the highest under the condition of low phosphorus and high aluminum,which was consistent with the content of IAA in the root.The expression of Cs ARF5 in the root of’Shuchazao’increased with the increase of aluminum concentration under the condition of no phosphorus and low phosphorus,and the change trend of gene expression was basically consistent with the content of IAA in the root.The relative expression of Cs ARF5 gene in the root of’Longjing43’was consistent with that of’Shuchazao’under low phosphorus conditions,but the change of aluminum concentration had no significant effect on its expression under the treatments of no phosphorus,normal phosphorus and high phosphorus.The expression of Cs ARF10 gene in root system of’Shuchzao’could be induced by high concentration of aluminum,but the change of phosphorus concentration had no significant effect on its expression.However,the expression of Cs ARF10 gene in root system of’Longjing 43’was consistent with that of’Shuchazao’under the condition of no phosphorus,and the change of aluminum concentration had no effect on its expression under the condition of low phosphorus.Under normal phosphorus and high phosphorus treatment,the expression of Cs ARF10 increased with the increase of aluminum concentration,but under the condition of high phosphorus,the gene expression of normal aluminum treatment reached the maximum.