Effect of Low Phosphorus Stress on Endogenous Hormone Levels of Different Maize Genotypes in Seedling Stage

The study was aimed at revealing the effect of low phosphorus stress on endogenous hormone levels of maize lines and displaying the different regulars of hormone change under phosphorus starvation between high P-efficient lines and low P-efficient lines, as well as providing the theoretical foundation for identifying high P-efficient lines at the seedling stage. In the present research, two high P-efficient inbred lines of maize 178 and 129, two low P-efficient ones 9782 and 202, with the F1 generation of 178 and 9782 were conducted to assay for the dynamic change of endogenous hormones in immature leaves and roots under low-phosphorus treatment by the method of solution culture, sand culture and field cultivation. As a result, all of the hormones except ABA were observed more abundant in the high P-efficient lines and F1 hybrid than the low P-efficient lines. The contents of zeatin in leaves and roots decreased significantly by the stress of phosphorus starvation under all of the environments, contrarily the contents of gibberellic acid (GA3), Indol-3-acetic acid (IAA) and Abscisic Acid (ABA) increased after suffering the low-P stress. In addition, the change ranges of GA3 and IAA were greater in high P-efficient lines 178, 129 and the F1 hybrid than in low P-efficient 9782 line and 202 line, whereas it is the opposite case for Zeatin (ZT) and Abscisic Acid (ABA) contents. However, no significant difference of every hormone change was observed between the two high P-efficient inbred lines as well as the two low P-efficient ones. Which indicated that the distinction of the hormone sensibilities to phosphorus starvation were just specifically present among the lines with different P-availability and can be considered as an important reference basis for identifying phosphorus efficiency of maize lines. Each of the hormones in the F1 hybrid always displayed the highest or the lowest values among all the lines, indicating the heterobeltiosis of F1 generation in response to low starvation. So the method of cross breeding can be considered to applied to breeding higher P-efficient lines of maize.