The Physiological And Biochemical Response Of Wheat To Phenanthrene And Its Accumulative And Distributive Characteristics

The test, which was conducted in the experimental ground of Yangzhou University during 2012-2013 on the basis of seedling test of thirty varieties, used Ningmai9 (phenanthrene tolerant variety) and Jinan 17 (phenanthrene sensitive variety) as materials and set six different concentration levels(0,50,100,150,200 and 350 mg·kg-1 soil) of phenanthrene. It aims to explore the growth and development, optical property and physiology and biochemistry of two types of genetic wheat under the different concentrations of the phenanthrene, as well as phenanthrene’s accumulative and distributive characteristics in the wheat plant. The main results showed as follows:1. The dry matter weight and grain yield of Jinanl7 were discovered to decrease with the increase of the concentrations of the phenanthrene. Under the high phenanthrene stress (350 mg·kg-1), the dry matter weight and grain yield decreased by 24.96% and 46.73% at filling stage, which was significantly different from that of CK. In terms of Ningmai9, the dry matter weight and grain yield at filling stage increased slightly by 1.83% and 4.30% under the low phenanthrene stress (50 mg·kg-1), which was not significantly different from that of CK. Under other concentrations of the phenanthrene, they were found to decrease with the increase of the concentrations. Under the high phenanthrene stress (350 mg·kg-1), the dry matter weight and grain yield in maturity reduced by 22.10% and 36.64%. However, the decreasing amplitudes of dry matter weight and grain yield of Ningmai9 were all less than Jinan 17 under the different concentrations of phenanthrene.2. The accumulative amount of phenanthrene in Ningmai9 and Jinan 17 would reach their maximum at jointing stage and then decreased to some extent. The accumulation of phenanthrene in every part of the plants presented an increasing trend with the increase of the concentration. Meanwhile, the enrichment coefficient exhibited a decreasing tendency when the concentration increased. The accumulative amount of phenanthrene was sequenced as follows: root> stem> leaf> spike. The phenanthrene in the spike mainly accumulated in chaffs at filling stage. The total amount of phenanthrene of Jinan 17 above the ground 1.16-1.62 more than that of Ningmai9. According to the national food and health standard of the BaP, the amount of phenanthrene in the kernels of Ningmai9 and Jinan17 exceeded the standard respectively under the stress of 150 mg~kg-1 and 100mg·kg-1.3. The values of SPAD of three top leaves of stem of Ningmai9 showed a tendency of increasing at first and then decreasing under the Phenanthrene stress. Under the low phenanthrene stress (50 mg·kg-1), the values of SPAD of Ningmai9 had a slight increase at every stage. The values of SPAD of three top leaves of stem of Jinan 17 presented a reducing trend under the stress. The greater concentration led to the higher decreasing amplitude, but no linear relationship was found between them. The inhibitive effect of three leaves was discovered as the third upper leaf> second upper leaf> flag leaf. Comparatively speaking, the inhibition effect of the values of SPAD of Jinan 17 was stronger than Ningmai9 on the same stress condition.4. The indexes of photosynthesis had a decreasing trend with the increase of the the concentration, such as Pn, Gs and Tr, while the values of Ci would present an increasing trend. This explained that the decrease of photosynthesis of wheat under phenanthrene stress was caused by non-limiting factors of stoma, and that the process of photosynthesis was inhibited and damaged by phenanthrene. Ci reached the maximum at flowering stage, filling stage and then declined, which indicated that wheat photosynthesis reduction might be caused by the interactions between limiting factors of stoma and non-limiting factors of stoma. In the meantime, the chlorophyll fluorescence parameters, Fv/Fm, Fv/Fo,Φ and qP presented a decreasing trend, while NPQ presented an increasing trend with the increase of the concentration. However, the increasing or decreasing values of Ningmai9 were less than Jinan17 under every stress level. The reduced OPSII caused by phenanthrene was one of the reasons that resulted in the decline of photosynthetic rate. The phenanthrene stress inhibition weakened in some way along with the growth period of the wheat. As a result, the mechanism of how phenanthrene stress influenced the wheat photosynthetic was the same, but there were some differences in the tolerance abilities of the wheat.5. The physiological and biochemical characteristics and antioxidant system of stress resistance were significantly affected by phenanthrene stress. The activity of SOD, POD and CAT of these varieties of wheat increased firstly and then decreased under the phenanthrene stress. In addition, the content of Pro and MDA, cell membrane permeability presented an increasing trend with the increase of the concentration of the phenanthrene stress. In terms of Ningmai9, the stress resistance was enhanced in some way under a low phenanthrene stress. Antioxidant capacity of both the two wheats decreased under high phenanthrene stress, which led to higher lipid peroxidation, and finally caused metabolic disturbance. Moreover, all the indicators had larger response differences in jointing stage than other growth periods and the stress response reduced in the latter stages.