| Heilongjiang province is an important commodity grain production base and the main production areas of the high quality japonica rice in China.Total water resources are relatively less in the region and the regional distribution is uneven,it is become the bottleneck problem of limiting the further development of rice in heilongjiang province.Water and fertilizer is the most important two factors of rice production,and the interaction of water and fertilizer will change with the change of irrigation method.In this study,Dongnong428 was used to investigate the effects of two irrigation regimes(W1 and W2)and five nitrogen rate(N0,N1,N2,N3 and N4)on growth and yield formation,accumulation and distribution of NPK,Photosynthetic characteristics,and key enzymes in nitrogen metabolism of japonica rice in cold region.The rice root organ under the best nitrogen fertilizer treatment was transcriptome sequenced by the application of HiSeqTM-2000 sequencing platform.The main results are as follows:(1)Effect of water and nitrogen coupling on growth and yield of japonica rice in cold regionThe result indicate that plant height and tiller number were greatly influenced by nitrogen,and there were reached the maximum in N4 treatment;Different water and nitrogen treatment had a significant impact on the leaf area index,and the largest value of LAI appeared in N3 at both heading and ripening stage;Water and nitrogen had an impact on the growth process of rice.In comparison with conventional irrigation,the tillering stage,heading stage and ripening stage of plants under the control of water irrigation took place 2d in advance.Under the same water condition,the mature period of plant delayed 2-3d with the increased of N application rate.The rate of dry matter accumulation of rice was changed by the interaction of water and nitrogen.With the increase of nitrogen application rate,the dry matter accumulation increased firstly and then decreased.In the same nitrogen conditions,dry matter accumulation under the control of water irrigation was significantly lower than that of conventional irrigation at tillering stage,and it showed opposite trend at heading and ripening stage;Root shoot ratio and grain-straw ratio under the control of water irrigation were less than those of conventional irrigation;control of water irrigation compared with conventional irrigation promoted the accumulation of yield,With the increase of nitrogen application rate,yield,effective tillers,grain number and kernel weight increased firstly and then decreased,the highest yield under N3(150kg hm-2)treatment.(2)Effect of water and nitrogen coupling on photosynthetic characteristics of japonica rice in cold regionThe result indicate that photosynthetic characteristics was influenced by water and nitrogen coupling,the control of water irrigation could increased net photosynthetic rate of rice from 3.38%to 11.84%;With the increase of nitrogen,the net photosynthetic rate showed a parabolic curve,N3 had the highest net photosynthetic rate;Nitrogen application significantly increased transpiration rate,N4>N3>N2>N1>N0;Under the control of water irrigation,the water use efficiency of N3 treatment was the highest,which was significantly higher than that of other treatments;The SPAD value of leaf was the "M" curve at the growth stage,and two peaks appeared at 30d and 60d after transplanting,and the SPAD value of water control irrigation was significantly higher than that of conventional irrigation after transplanting 90d;The SPAD value increased with increasing N application rate;The photosynthetic nitrogen use efficiency of controlled irrigation was higher than that of conventional control.Photosynthetic nitrogen use efficiency increased gradually with the increase of nitrogen application rate,and N3 treatment was the highest.(3)Effect of water and nitrogen coupling on nutrient uptake of japonica rice in cold regionThe nitrogen,phosphorus and potassium contents of rice plants showed a downward trend with the development of the growth process.Compared with conventional irrigation,water control irrigation decreased the phosphorus content in the tillering and jointing stage and the nitrogen content in the mature stage;Nitrogen fertilizer could increase the content of nitrogen and phosphorus,and the nitrogen content of plant increased with the increase of nitrogen application rate at tillering and jointing stage;Nitrogen application could significantly increase nitrogen,phosphorus and potassium accumulation,and accumulation increased with the increase of nitrogen application rate.Under the same nitrogen application rate,water control irrigation decreased the accumulation of nitrogen in the tillering stage and increased the nitrogen accumulation in the heading stage and ripening stage;Nitrogen application decreased the proportion of nitrogen in the leaves and stems and increased the proportion of grain in the ripening stage;Water control irrigation increased the phosphorus accumulation in the whole growth period,and the potassium accumulation in the ripening stage;The amount of potassium accumulation in stem and sheath and its proportion in plants were higher than that of conventional irrigation,while the proportion of leaves and grains were opposite.(4)Effect of water and nitrogen coupling on key enzymes of nitrogen metabolism of japonica rice in cold regionThe effects of water control irrigation on the activities of glutamine synthase,nitrate reductase,glutamate synthase,glutamic oxaloacetic transaminase and glutamate pyruvic transaminase in rice were different;Water control irrigation can improve the activity of glutamine synthase,nitrate reductase,glutamic oxaloacetic transaminase and glutamate pyruvic transaminase at different growth stages.With the increase of nitrogen application rate,the activities of five enzymes were increased in varying degrees,and the most reasonable nitrogen application amount was 150kg/hm2.(5)Study on the differentially expressed genes in the root system of optimal nitrogen treatment under water control irrigationThe rice root organs under the best nitrogen fertilizer and no nitrogen fertilizer were transcriptome sequenced by the application of HiSeqTM-2000 sequencing platform.A total of 3650 differentially expressed genes(DEGs)were identified based on the comparison of fertilizer/no fertilizer nitrogen library with Fold Change?1.5 and FDR<0.05 as screening criteria.In these DEGs,1253 and 2397 genes were up-regulated and down-regulated,respectively.All the DEGs distributed on every chromosome with 199,125,112,112,74,90,107,69,82,80,73,79 for up-regulated and 388,281,379,178,199,192,171,145,105,118,99,81 for down-regulated,respectively.GO and Pathway analysis were performed for these DEGs and the results indicated that DEGs had COG classification and that could be dividedinto 47 classes;A total of 54 significantly enriched GO terms were obtained by hypergeometric test.DEGs involved in 108 metabolic pathways,and eighteen of them were significantly enriched based the criteria of Q-value ?0.05,and Os06g0335900(hydrolase),Os01g0508000(sucrose metabolism),Os06g0683300(glucosidase)involved in nitrogen metabolism pathway 9.2,4,2.6 times up-regulated expression under nitrogen treatment than under no nitrogen fertilizer,which indicating the absorption and utilization of nitrogen in rice plants could be regulated by Os06g0335900,Os01g0508000;Os06g0683300.Otherwise,Os 11 g0149200(peroxidase),Os06g0547400(peroxidase),Os06g0727200(catalase),Os04g0223300(ascorbate peroxidase)involved in antioxidant enzyme metabolism pathway 10,10,9.3,4.6 times up-regulated expression,which indicating the appropriate amount of nitrogen fertilizer could promote antioxidant enzyme gene expression. |
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