Effects Of 1,2,4-Trichlorobenzene And Naphthalene On The Growth And Grain Yield Of Rice And Their Mechanism

Organic pollutants could enter a crop field by many ways, such as wastewater irrigation, urban sludge for agricultural use or polluted air sedimentation. They have become one main group of chemical pollutants affecting the growth and development in crops, especially in rice. In this study, two rice cultivars, Shanyou 63 (indica hybrid) and Wuyujing 7 (japonica), were used, and the effects of two toxic organic chemicals, 1,2,4-trichlorobenzene (TCB) and naphthalene (NAP), on the growth and grain yield of rice and the mechanism for the plant to response to the chemicals were investigated. The agronomic approaches to improve the grain yield were also studied when rice was grown in the organic-contaminated soil.1. Effects of TCB and NAP on the growth of riceTCB and NAP had little effect on the seed germination. However, they could strongly affect plant height, root length, root number and dry matter weight, with root length more sensitive to the pollutants. TCB had more inhibition in the growth than NAP, indicating that TCB has more toxicity than NAP. NAP at a low concentration increased root number of Wuyunjing 7. Both TCB and NAP less affected rootα-NA oxidation ability at low concentrations, but they significantly reduced root activity at high concentrations. The amount of bleeding sap decreased significantly with the increase in pollutant concentrations, indicating that root bleeding sap is sensitive to organic pollutant stress during the heading period. Observation on root tip microstructure showed that TCB and NAP increased root thickness, which was mainly due to the increase in cell volume, not due to increase in cell number. The two pollutants made the cell wall anomalistic, and presumed that thickened cell wall would be a main reason for the inhibition of root growth. The results suggest that TCB and NAP at a low content in the irrigation water would significantly influence the growth of rice seedlings. Root length could be acted as a sensitive morphologic indicator for TCB or NAP influencing rice growth, and root bleeding sap be considered a useful biochemical indictor for diagnosing the toxicity of the two pollutants to rice plants.