| In this research,the root pressure chamber,the open exchange system LI-6400 Portable Photosynthesis System was used to determine the relationship between the root hydraulic conductivity(Lpr) and the leaf photosynthesis(Pn), transpiration rate(Tr),the water use efficiency(WUE) in Maize and Oats seedlings under different phosphorus levels solutions.The main results as follows:1 It will form aerenchyma in maize(Zea may L.) roots under phosphorus (P) deficiency and the change of root structure is earlier than that of plant biomass and root to shoot ratio.Maybe it is one of the mechanisms that the plant adapt to P-stress. Maize Lpr decrease sharply under P-deficiency besides it tends to increase under P-sufficient. Therefore it is indicated that the lowed Lpr was related to the aerenchyma formation under P-deficiency.2 As the oats root age increasing of whether P-deficiency or P-sufficient Lpr tends to decline and the former Lpr decrease faster than the latter.When adding HgCl2, Lpr is hardly affected in the P-deficiency treatment , but Lpr decrease sharply in the P-sufficient treatment that is still bigger than that of P-deficiency and decreasing range extend gradually with treatment time.3 Pn of P-deficiency Oats is lower obviously than that of P-sufficient after 6 days and changing time was later than that of Lpr decreased; WUE of P-deficiency oats became lower than that of P-sufficient after 2 days and changing time was earlier than that of Lpr reduced.4 Lpr is different obviously among yuan12, Taifeng, Baoluo, Neiyan-3, Neinong-1,8809-1-1-8-3; The six oats varieties Lpr with Pn,WUE,Tr and Gs show positive correlation under low phosphorus stress. And it is showed that whole plant water situation and photosynthetic assimilation's relative parameter will lower as Lpr decreased under the condition of low phosphorus. Besides, relative coefficient of Lpr and Pn is maximum (R2=0.7752) and reach prominent level (P=0.0206<0.05).
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