Study On The Damage And Tolerance Mechanisms Of 1,2,4-trichlorobenzene And Naphthalene In Rice

In this paper, the damage and tolerance mechanisms of 1,2,4-trichlorobenzene and naphthalene in different rice varieties (Shanyou 63, Wuyunjing7)were studied. The results showed as follows: 1 The apparent damage of TCB and NAP to riceThe seed germinating percentage of rice didn't change remarkably, but the growth and development of rice seedling were inhibited proportionally to the concentration of TCB and NAP. The results showed that, the seedling height and dry weight decreased, the root elongation, root number and root activity was inhibited; the structure of the root was destroyed.TCB and NAP could affect yield components, decrease the final height of rice plant and the effective tiller number, postpone the earing time, reduce the seed setting rate ; The effective tiller number and seed setting rate were the main factors which decreased the grain yield.Effects of TCB and NAP on the quality of rice showed that: they could increase the chalky area of rice obviously, but decrease the rice rate, the head rice rate, while TCB and NAP showed little influence oh the content of protein and amylose.With the pollutant concentration increasing, the residues of TCB and NAP in rice seed were also added. 2.The damage mechanism of TCB and NAP in the riceTCB and NAP could increase the MDA content in rice leaf and root significantly, which indicated that TCB and NAP could cause membrane lipid-peroxidation, hence, the structure and physiological functions of membrane were damaged.TCB and NAP inhibited the photosynthesis of rice, it showed: chlorophyll content, net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO₂ concentration (Ci), photochemical efficiency (Fv/Fm), quantum yield of PSII (ΦPSII), potential activity of PSII (Fv/Fo) and photochemical quenching (qP) and non-photochemical quenching (qN) were decreased under TCB and NAP stress. The effects of TCB were more serious than that of NAP, while the sensitivity of Xianyou 63 was higher than that of Wuyunjing 7. Under the lower concentration organic pollutants, stomatal limitationwas a dominating factor for Pn decrease; under the higher concentration organic pollutants, the decrease of Pn was due mainly to stomatal limitation and the non-stomatal limitation. Among all of the chlorophyll fluorescence kinetics of parameters, both Fv/Fo and qN are more sensitive to TCB and NAP than the others parameters.The lower concentration of TCB and NAP could increase the respiration of rice root while the higher concentration could inhibit it. The effect mechanism of TCB and NAP on the respiration included that, the COD activity and COD isozymes of rice were induced by low concentration of TCB and NAP (10-20mg/L) , and with the concentration of TCB and NAP increasing, the COD activity and COD isozymes were both inhibited significantly, especially in roots. Likewise, effects of TCB and NAP on the expression of amylase isozymes showed the same pattern with COD isozymes, MDH isozymes express was also effected by TCB and NAP. Among the three enzymes, the change of COD activity and COD isozymes express showed the closest relativity with, the respiration change trend.TCB and NAP could influence the protein metabolism -The protein content in rice leaf and root decreased proportionally to the concentration of TCB and NAP. 3. The study on adaptability of rice to the TCB and NAP stressTreated for different time, the radioactivity of 45Ca in root increased under shorter treating time, and decreased under longer time with the TCB stress (40mg/L); the radioactivity of 45Ca in Wuyunjing7 leaf increased proportionally to the treating time while the radioactivity of 45Ca in Xianyou63 leaf appeared double peak curve. These showed that the absorption of calcium in root and the movement of calcium from root to leaf could be both enhanced.Treated with different concentration, the calcium content in protoplasm in Wuyunjing7 root increased proportionally to the treating concentration; while in Shanyou63 root the calcium content decreased under the lower concentration and increased under the...