Effects of Pi deficiency on characteristics of resistant physiology in different sugar beet (Beta vulgaris L.) genotypes

The effects of phosphorus stress on the physiological properties of the individual attached leaves of sugar beet plants (Beta vulgaris L., cv.14, cv.17 and cv.20 with different resistance to phosphorus stress) was studied using the sand culture in growth chambers. The results were showed as follows: P deficiency constrained P uptake, consequently, the P contents in plant and biomass in all three varieties were decreased significantly among which, P content and biomass of cv.14 decreased most, followed by cv.17 and cv.20. Pi deficiency resulted in different physiological responses which was genetic dependent: First, the contents of MDA, Pro and POD activity were increased significantly in cv.14 and cv.17, while the content of MDA and Pro decreased significantly in cv.20. The activity of POD changed slightly; Second, the activity of Mg2+-ATPase in all three varieties were decreased with the order of cv.20cv.17cv.14; Third, compared with the normal Pi supply（P 100 μmol/L）, the contents of CaM content in sugar beet leaf was significantly increased in cv.20 andcv.17 under Pi deficiency, but it kept stable in cv.14. Fourth, different Pi nutrient levels had a big influence on the resistant ability of sugar beet to harsh environment which was also genetic dependent, Plasma membrane permeability of individual attached leaves in cv.14 and cv.17 increased significantly under higher temperature (40℃), while it decreased significantly in cv.20 indicating resistant ability to heat stress was improved.