Study On Mechanism Of Seedling Rooting And Root Growth Of Rice After Transplanting

By experiments of water, pot and field, three hybrid rice varieties of significant rooting ability difference, Gang You 22, II You 162 and K You 047, were used to study the influence factors of seedling rooting ability, and characteristics in matter and energy metabolism, carbon and nitrogen metabolism, root morphology and physiology as well as their relationships with seedling rooting and root growth after transplanting, in laboratory, pot place and DaXing town of Sichuan agricultural university. Physiology and ecological mechanism after rice seedling transplanting was found, and regulating technique were experimented, such as seedlings raised and transplanted methods, seedling ages, transplanting and water management methods, and different organs cutting off on root growth of rice after transplanting. The main results showed as follows:1. The RA (rooting ability) of rice was influenced by the external environmental conditions and rice nutrition and physiology characteristic. The lower and upper temperature was 15℃ and 40℃ separately for seedling rooting, and the fittest temperature was 30-31 ℃ from the parabola equation (y=ax²+bx+c) of the properties of RA of seedling and temperatures fitted. Rice could root under 0 lux, but RA of seedling was reduced rapidly. Weak light restrained strongly the average root length, on the adverse to the number of root. At the water stress second day, RA of rice dropped rapidly, and root nearly rooted at the water stress third day. The RA of seedling that transplanted in sandy loam was higher significantly than that in heavy loam. As far as the nutrition elements, the fittest NH₄NO₃ and K⁺ content were 40mg/L to seedling rooting, 20-80mg/L KH₂PO₄ promoted significantly seedling to root and the effect strengthened with the days of culturing increasing.Among the three varieties, the RA of GangYou22 was best strong, KYou047 secondly, and IIYou162 was the lowest. The RA of DSR (dry land seedling raising on beds) was stronger than WSR (wet land seedling raising on beds) and PSR (wet land seedling on plastic trays), which properties of RA of seedling was improved significantly as seedling age increasing, such as root length per plant, root number, root weight. Those main lay in seedling quality in different varieties, seedlings-raising ways and seedling ages. There were fine linear fit (y=ax+b) among the properties of seedling qualities, such as tiller number, DW (dry weight) of stem and sheath, DW of leaf, and properties of RA, and the correlation coefficient of the equation had reached to the highly significant level. Meanwhile, the RA was influenced significantly by the organs of seedling cutting off, and the more organscutting off, the weakest the RA of rice.The significant positive correlation was found between the NC (nitrogen content) of root, stem, leaf, and new root number. There were significant or highly significantly between NA (nitrogen accumulation) and root length per plant, root number, root weight. SSC (soluble sugar content) was correlated with properties of RA, SSC of leaf and it negatively, SSC of stem and it positively. The amylase activity of root was positive significant and highly significantly correlated with root length per plant, root weight and root number. There was significant correlation between amylase activity of stem and sheath and ATPase activity of rooting joint and root, furthermore, the correlation coefficient of ATPase activity of root and RDW/PDW was 0.8407**(significantly correlation). The root vigor of DSR was higher than WSR and PSR, which ABA content of root was lower, while the content of endogenous hormone promoting growth and cell fission was higher than that of WSR and PSR. There was significant negative correlation between ABA content of root and root per plant, significant or highly significantly correlation between GA content of rooting joint, root and properties of RA.2. In initial stage after transplanting, the stem and sheath was the main source organs of seedling, and new root, tillers and new leaf were the main sink organs. After 10 days of label, 7.6%-9.8% 3H assimilates of stem and sheath labeled at 4d after transplanting was used in new root rooting and growing, 6.7%-15.6% in new leaf of main stem, and 6.9%-9.9% in the stem and leaf of tillers. After 30 days of label, about 12% 3H assimilates of stem and sheath labeled at 4d after transplanting was distributed to new root, and 10%-14% to the stem and leaf of tillers. The 3H assimilates of redistribution during 10-30d of label came from stem and sheath of main stem, and was imported to tillers and new root. After the rice seedling turned green and survives, the leaf as source organs exported photosynthetic production to other organs. At 20d after transplanting, there was 19%-28% 3H assimilates of leaf labeled after lOd of label used in new leaf of main stem growing, and about 4.6%-13.4% in tiller growing, moreover, still 3%-5% in new root growing.In earlier stage after transplanting in the field, both DW accumulation dynamics of root and top part could well be fitted for the index model (y=aebx). At the same time, DW of root could well fit for the linear model with DW of stem and sheath, DW of leaf, DW of rooting joint and DW of top part, their correlation coefficient (R2) was all above 0.95 (0.01 significant correlation). DW of root system increased fast after elongating stage and was up to apex between booting stage and heading stage, and then dropped slowly. The DW of root of CTTR (Conventional tillage transplanting rice) was higher than that of CTCTR (Conventional tillage cast-transplanting rice) and NTSCTR (No-tillage with high standing stubbles cast-transplanting rice) before heading, but it was the lowest in three tillage and cultivation methods after heading. Among the three varieties, DW of root of Gangyou22was the highest, and that of Kyou047 was the lowest.3. During 40d after transplanting, NA tendency of root system and top part increased accord to the index model. There was significant positive correlation between NC of stem and sheath, rooting joint, and root system and DW of root system, but NC of leaf was highly significant negative correlation with DW of root system. Moreover, NA dynamics of all organs assumed good consistency with DW of root system, their positive correlation were significant. The SSC of stem and sheath, and rooting joint was significant positive correlated with DW of root system, but SSC of leaf and root was significant negative correlation with DW of root system. NA dynamics of plant in growth duration was well fit for logistic (y=a/(l+be'cx)) equations, all of the relation coefficients R2 of the equation were above 0.988, meanwhile, there were significant positive correlation between NA and DW of root, while the growth stage was more early, the relation coefficients was higher. From elongating stage to mature stage, SSC of stem and sheath, and rooting joint was significant correlated with DW of root respectively, further, SSC of stem and sheath was significant positive correlated with SSC of rooting joint and root, therefore, SSC of rooting joint and root stemmed from the export of stem and sheath.There was significant correlation between the amylase activity of stem and sheath and DW of root in 15d after transplanting. Meanwhile, the amylase activity of stem and sheath was significant positive correlated with ATPase activity of rooting joint, therefore, the decomposition of starch of stem and sheath had important function to strengthen the ATPase activity of rooting joint. The ATPase activity of NTSCTR was the highest in three tillage and cultivation methods, but the root vigor of CTCTR was higher than that of other two tillage and cultivation methods. Among three varieties, the root vigor of II you 162 was the lowest.Among three tillage and cultivation methods, the effective panicles of CTTR and CTCTR were higher than that of NTSCTR, which assumed good consistency of root growth and tillers dynamics in growth duration. From the Richards equation for the grain filling, there was little difference of superior grain filling dynamics about three tillage and cultivation methods, but the inferior grain weight of NTSCTR was the highest, and that of CTTR was the lowest. Therefore, the yield of CTTR was the highest due to more effective panicles and next was NTSCTR lay in higher grains per panicle and grain weight.4. In the conditions of NTSCTR, the root number, DW of root, and root length in cast-transplanting rice by DSR were higher that of cast-transplanting rice by PSR, at the same times, its root vigor and ATPase activity was higher too. All of the root length per plant, DW of root and root number decreased while seedling age was shorter, at the same time, the root vigor and ATPase activity of long-age seedling was higher in initial stage (lOd) after transplanting, but after 20d after transplanting, the short-age seedling displayedthe superiority of physiology.Under heavy loam with sulfide, the root length per plant and DW of root in the transplanting rice was very low and the root system displayed black for the rooting joint was dept in soil, otherwise, the damage of cast-transplanting rice was relatively light for the rooting joint uncovered. The root length per root of cast-transplanting rice with water stress grew fast and its length was longer than other treatments, but the root number of that was less than others. The root length, root number and DW of root system of cast-transplanting rice with straw mulching were the highest in four treatments. The root vigor of transplanting rice and cast-transplanting rice in deeper water whose root system was poisoned by soil was higher than others, but the ATPase activity of rooting joint and root system of seedling with water stress was the highest in the treatments.The treatment of reduction sink (tillers cutting off) was stronger in root system growing in 20d of transplanting, and it's root vigor, amylase activity of stem and sheath and ATPase activity of root system were higher than CK too. Otherwise, the treatments of reduction source (leaf cutting off and half upper stem cutting off) and reduction both of source and sink (root and leaf cutting off, root and leaf and tiller cutting off, root and half upper stem cutting off etc.) was restrained obviously to root system growing, and their new root length, root number and DW were largely less than CK.