Study On Germination Chatacteristics And Ability Of Antifreeze Of Weedy Rice In Shanghai

The weedy rice （Oryza sativa f. sopontanea）is a type of rice betweenthe wild rice and cultivated rice. It is a kind of plant which similar tocultivated rice in the appearance and physiology characteristic. It is firstdiscovered in North America. Weedy rice has strong environmental suitabilityand high adverse resistance. In the rice field, weedy rice shows strongbiology competitiveness which may affect the growth of cultivated rice andlead to huge loss in agricultural production and social economy. Today,weedy rice has become one of the main weeds in rice field all over the world.In China, many provinces such as Jiangsu, Liaoning, Guangdong andShanghai have reported that weedy rice has the existence in these areas whichharms to local agriculture production. In different regions, weedy riceshowed great phenotypic diversities.The lab experiment with weedy rice was carried in order to study theeffect of environment factors such as temperature, soil and water depth on theseed germination of weedy rice. The results are as follow:1. From the temperature condition of15to40℃, the seed of weedy ricecould germinate normally. Under the same temperature, seed of weedy ricegerminate faster than cultivated rice. The germination threshold temperatureof weedy rice and cultivated rice are close, but the effective accumulatedtemperature of weedy rice is lower. At low or high temperatures, the germination rate of weedy rice seed is significantly higher than cultivatedrice.2. Under the conditions of24hours lighting,24hours dark and12hourslighting/12hours’ dark, the seed of weedy rice could all germinate normally.The influence of light on the seed geemination of weedy rice is not obivious.3. Acidic or alkaline conditions both have a certain influence on thegermination of weedy rice seeds. But the seeds of weedy rice have higerresistence to both acidic and alkaline environment than cultivated rice.4. The covering soil layer depth has signigicant influence on seedgermination of weedy rice. When the covering soil layer was over8cm, theseed germination was decreased by80%. Compared to weedy rice of otherregions and cultivated rice, the resistance ability of deep buried of weedy ricein Shanghai area is much higher. At the same time, deeper soil covering alsodelayed the seed germination of weedy rice.5. The germination of weedy rice had high tolerance to waterlogging.The water depth had less influence on the germination of weedy rice.6. Weedy rice seeds had strong salt resistance. Under higher saltconcentration (300mmol/L), the seeds could still keep a certain germinationrate. The salt tolerant ability of weedy rice is stronger than cultivated rice.7. Seeds of Weedy rice had a strong ability of antifreeze. After beingprocessed under the low temperature condition for a whole week they stillcould germinate and maintain high germination rate. At the same time, theexperiment revealed that the water content of the seed is one of the importantfactors affecting its freezing resistance. The higher the water content of seedshad lower germination rate after low temperatuer processed.