The Effect Of Low Root-zone Temperature On Absorption And Translocation Of Mineral Elements In Tomato Seedings

In early spring production in northern China,due to the buffering effect of soil and other factors,a slow rise in ground temperature has occurred.Under low temperature stress,plant roots are more sensitive to changes in root zone temperature.Small changes in the temperature of the root zone can directly cause a series of morphological and physiological and biochemical changes in the root system,reducing the absorption and transmission rate of water and nutrients.The root system can also sense and identify the low temperature signal of the root zone,and transmit it to the ground to reduce the photosynthetic rate,which in turn affects the growth and development of the ground.In this study,the tomato(Lycopersicon esculentum Mill.)variety named `Liaoyuan Dully' seedlings were used as test materials,and different root zone temperature treatments were performed to study the effect of low root-zone temperature on the mineral element content of tomato plants.The test results are as follows:1.Determine the effect of low root-zone temperature on the content of mineral elements in tomato seedlings.Low temperature(7°C and 13°C)treatment of tomato seedlings in the root zone: Inhibition of N,P,K,Mg element content in the root system,increase Ca content;Decrease in the content of 5 mineral elements in the stem;N,K,Ca,Mg in the leaf The content decreased,but the content of P element in the leaves increased;and with the increase of treatment time,the contents of various mineral elements showed different trends.The effect of 7? treatment was more significant,affecting the accumulation and distribution of elements in roots and stems.2.The effects of low root-zone temperature on the anatomical structure of tomato seedling roots and stems were determined.After 9 days of low temperature(7°C and 13°C)treatment,the number and diameter of tomato root system ducts were significantly reduced compared with the control(19°C),the ratio of vascular bundle to root diameter was reduced,the thickness of the cortex increased,and the diameter of the ducts in the stem is slightly reduced,which increases the radial resistance of the root system to absorb water and nutrients,and reduces the axial transport rate.3.The effects of low root-zone temperature on the content of aquaporins in tomato seedling roots were determined.Analysis of aquaporin gene expression in tomato roots by reverse transcription-polymerase chain reaction: SLTIP2.3,SLTIP3.2,SLTIP4.1,SLNIP1.7,SLNIP5.1,SLPIP1.2,SLPIP1.5,SLPIP2.10 expression was up-regulated,and SLTIP1.1 and SLNIP2.1 were down-regulated at 7°C;while at 13°C,only SLNIP2.1 expression was down-regulated,and all other genes were up-regulated.Increasing the content of these groups is beneficial to increase water transport in the cellular pathway.4.To clarify the effect of low root-zone temperature on hormones content and ABA signal component gene expression in tomato seedlings.After low temperature treatment in tomato root zone,the hormone content in roots,stems and leaves generally decreased to varying degrees.Among them,the higher contents of ABA,IAA and DHZR in various organs are more affected by low temperature,and ABA has the largest changes in various organs.Therefore,it is beneficial to improve the tolerance of plants to low temperatures.The expression levels of Sl PYL,Sl PP2 C and Sl Sn RK2 genes in ABA signal transduction components were detected.The results showed that the three family genes had different responses to the low root-zone temperature in different organs,some were induced and some were suppressed,indicating that the low temperature felt by the roots could be transmitted upward through the ABA signaling pathway,and then affect the growth and development of new shoots.