Studies On Resistance To Overwinter Of Weedy Rice Seed And The Features Of Photosynthesis In Northeast Rice Area

In this paper, the change of occurrence amount and distribution scale of weedy rice over the past few years in the northeast are investigated by fixed point follow-up survey, at the same time, the adversity resistance characteristics are studied , and the photosynthesis characteristic has carried on the preliminary discussion, and obtain the following main conclusions:After the weedy rice experiencing appear, spread, and outbreaks in the northeast, recently showed a declining tendency. Between 2010 and 2013, except the east area of Heilongjiang province that based on the light-duty farming, the northeast area of Jilin province and the mid-west area of Liaoning province that the rainfall is lower in the late autumn and early winter, the weedy rice disappeared and the disaster lightened in other areas. in recent years, occurrence amount of weedy rice related to the rainfall and temperature in late autumn and early winter.The weedy rice seeds ripe earlier and faster, have a strong cold tolerance and have no dormancy as cultivated rice seeds. The survival ability of weedy rice seeds is far higher than that of cultivated rice seeds in 3℃ . After three-months cold soak a large number of weedy rice seeds will be killed.The freezing effect of weedy rice seeds has a positive correlation with soaking temperature , soaking time, freezing temperature and freezing time. When the seed soaked at 10℃ and lasted 3-5days, the seed soaked at 5℃ and lasted 7-10 days, more than 90% of the weedy rice seeds will be killed in the rice paddy that the average temperature is below 5℃. Pouring water to paddy timely and duly in the autumn can improve the seed moisture content, and lead to the death of weedy rice seeds.Water-absorption speed of the weedy rice seeds is related with thickness and weighted ratio. The weedy rice seeds could survive safely in the winter because of the high amylase activity in the low temperature, but have nothing with the content of fat, protein and amylose.The area of the first leaf of the weedy rice is 2.7 times larger than that of cultivated rice. The area of the second leaf of the weedy rice is 1.3 times larger than that of cultivated rice. The chlorophyll content of the first leaf of weedy rice is higher than that of cultivated rice. The weedy rice has stronger photosynthetic capacity than cultivated rice, and reach the heading stage sooner than cultivated rice.With the increased of light, the photosynthetic rates of weedy rice is always higher than that of cultivated rice, but with the increased of CO2 concentration, it is lower than cultivated rice before and higher than cultivated rice after. So it result in the yields of weedy rice is lower than that of cultivated rice.Under the low light intensity, the photosynthetic rate of the weedy rice are stronger affected by light intensity, under the high light intensity, the photosynthetic rate of the weedy rice are stronger affected by stomatal conductance and transpiration. When the light intensity constant, the photosynthetic rate of the weedy rice are stronger affected by CO2 concentration.