Effect Of Low Phosphorus On Root Morphology And Root Exudation Of Zygophyllum Xanthoxylum

Phosphorus?P?is one of the nutrients necessary for plant growth and development,but the effective phosphorus content in the soil is very low,its concentration is<10?M,which only accounts for 1/600¹/100 of the total phosphorus content of the soil,and it is easily fixed in the soil,while phosphorus resources are not renewable and have become limited.It is necessary to select plants with high phosphorus uptake and utilization characteristics and understand their adaptation strategies for low phosphorus environment.In this study,the super xerophytic shrub Zygophyllum xanthoxylum were studied.The seedlings germinated for three days were pre-cultured in phosphorus deficiency?-P?solution for 5 days,and then were transplanted into split-root pots.Three treatments were performed:phosphorus deficiency?-P-P?,phosphorus supply?+P+P?and localized phosphorus supply?-P+P?,phosphorus concentration was supplied at 0mmol/L in the phosphorus deficient compartment and 0.25 mmol/L in the phosphorus sufficient compartment.After 13 days culturing,plants were collected to study the effects of low phosphorus on the root morphology and root exudation of Z.xanthoxylum.The main findings are as follows:?1?There was no significant difference in the root/shoot ratio of Z.xanthoxylum among phosphorus deficiency,phosphorus supply and localized phosphorus supply.The dry weight of shoot and root increased synchronously with the increase of phosphorus concentration,which was the reason for the no significant difference in the root/shoot ratio.Under phosphorus deficiency,the chlorophyll and soluble sugar content of Z.xanthoxylum leaves increased significantly,but there was no significant difference between roots.Under phosphorus deficiency,different from most plants,the soluble sugar transported to the root wasn't increased in Z.xanthoxylum.?2?The phosphorus deficiency resulted in a decrease in the roots area,roots volume,roots length and roots total number of Z.xanthoxylum.The root morphological indicators did not increase under P deficiency,which were related to the increase of GA₃ and CK,and the decrease of ABA in both shoot and root.When phosphorus was locally supplied,Z.xanthoxylum preferentially increased the length and total number of roots.The Z.xanthoxylum does not increase root morphological indicators to respond to low phosphorus.?3?The root physiology altered significantly with the change of the external phosphorus environment:under phosphorus supply,the intracellular APA activity increased,indicating that Z.xanthoxylum had strong phosphorus transport ability;under phosphorus deficiency,the root secretion APA activity and malic acid increased,indicating that Z.xanthoxylum had strong activation effect to environmental phosphorus.The Z.xanthoxylum responds to low phosphorus by increasing root exudation.?4?Under localized phosphorus supply,Z.xanthoxylum inhibited malic acid secretion rapidly,and the effect of rhizosphere acidification was weakened,indicating that it was a P-sensitive plant with flexible regulation mechanism to cope with the external phosphorus environment.