Studies On Growth Characteristics Of Rice Root System Under Dry Cultivation(0ryza Sativa L.)

Rice is a staple grain crop in China. Its production stands for about 40% of national grain production. In the north of China, decreasing water shortage limits the development of rice production and the increase of rice yield. It is important to develop the water saving cultivation in rice production to raise and maintain rice production in China. Rice root plays a very important role in the increase of water use efficiency. However, less knowledge about rice root growth and function under dry cultivation is available.This paper studies the root growth characteristics and its relation with leaf growth, yield and its componenets. Experiments were carried out with Xieyou63 and YangdaoNo.6 in the experiment farm of Anhui Agricultural University in 1999 and 2000. In pot experiment. Water content in soil was field capacity(FC)(check,CK)> 65%-70% of FQlight water stress,T1) and 55%-60% of FC(heavy water stress.!,).in the tillering stage, the jointing stage, the heading and grain filling stage, the milk riping stage. In field experiment. Planting type was Dry cultivation with plastic film mulching(PFM), Dry cultivation(DC), Traditional paddy cultivation(TPC). Root samples were taken in different stage through nylon net bag that was embedded in field before planting rice.The results showed that: light water stress stimulated root growth. Compared to check and heavy water stress. Roots grown deeply and percentage of deep root was high and the ratio of root to shoot high. Rice under light water stress shown drought resistance. Rice under PFM had more white roots and its root activity was strong.The total area and active absorption area of roots increased before jointing stage, then decreased. The active absorption area of roots contributed 46-50% of the total absorption area., the respiratory activity of rice roots under dry cultivation and plastic film mulching cultivation was greater than that under water cultivation. This results in leaf senescence of rice under under dry cultivation and plastic film mulching cultivation . Bleeding sap of root appeared with two-peaks curve during the growth period. The first peak appeared at the end of productive tiller, and the second peak heading stage. After heading stage, the bleeding sap of all treatment decreased, but decreased rapidly after 17 day after heading stage.Under PFM, tiller number per plant is higher. But percentage of productive tiller was lower. Root activity under dry cultivation was greater than that with plastic film mulching cultivation. Leaf area index(LAI) of rice under plastic film mulching cultivation was larger that than other treatments, during the milk riping stage. Peak of grain filling under dry cultivation and plastic film mulching cultivation appeared early, grain filling period of rice was shorter than that under traditional padd\ cultivation by about 7 days. Growth duration of rice under dry cultivation and plastic film mulching cultivation was later than Normal paddy field by about ~ dayss Due to the severe leaf senescence by water stress under dry cultivation, the number of grain per panicle, grain fertility and grain weight of traditional p,idd> cultivation was higher . Yield under plastic film mulching cultivation was similar to one under traditional paddy cultivation. Variation of yield under drv cultivation \va;. larger. This showed that yield may be gotten through plastic film mulching cultivation in water shortage region.It was discussed that plastic film mulching dry cultivation for rice is appli x1 in water shortage region and the role of rice root is played in dry cultivation.