Effects Of Water Regulation On Grain Filling Characteristics And Yield Of Spring Wheat Under Drip Irrigation

【Object】The objectives of this study were(1) to confirm the effects of different amounts and irrigation frequency on root characteristics and physiological changes in photosynthesis and grain filling of drip-irrgrated spring wheat in northern in Xinjiang.(2) To reveal grain filling characteristics of spring wheat under drip irrigation condition.(3)To prove the differences among parts(strong and inferior grains) in grain filling.(4) To confirm the changes and possible role of endogenous plant hormones during grain filling, to reveal the mechanism of water regulation in drip irrigation wheat growth and development at metabolomics level. We aimed to provide a theoretical basis for the irrigation of wheat cultivation and management.【Method】 In this study, Xinchun 6, Xinchun 22 were used as tested materials, setting filling volume with two-factor multi-level test: three irrigation frequencies, 13 days(D1), 10 days(D2), 7 days(D3), three water amount treatments: W1(3750m~3 / ha), W26000m~3/ha), W3(8250m~3 / ha). In the whole growth period, dry matter accumulation and leaf area index were measured. At flowering stage, root characteristics were measured. At filling stage, filling parameters were analyzed, endogenous hormones determination and metabolomics were also analyzed.【Results 】(1) The dynamic changes of drip irrigation wheat was in line with "S" shaped curve. Transfer rate of vegetative organs before anthesis and the contribution rate to grain of W1 and W2 treatments were higher than W3 treatment under D1 treatment, indicated that at low frequencies of irrigation conditions, low irrigation amount limited the yeild due to biomass accumulation and production capacity after flowering. Comparison among different irrigation frequency in the D1 and D2 treatments, dry matter in the stems and leaves in mature increased, showedthat low frequency of irrigation is not conducive for the formation of the final grain yield. Comparison of biomass and yield found moderate frequency and high-frequency irrigation irrigation will significantly increase crop biological yield and grain yield, but excessive irrigation amount was unuseful to improve the yield.(2) With the growth period extended, the flag leaf Pn of two varieties showed a downward trend. We found that in D1, D2 treatment at early grain filling stage and the D3 treatment the main factor limiting process photosynthesis were the stomatal factors and in the grain filling stage in D1, D2 treatments was major factor limiting photosynthesis was non-stomatal limitation. After flowering stage, with advancing crop growth, Fv / Fm and Fv / Fo ratio decreased. In comparison among differentirrigation frequencies Fv / Fm values is manifested D3> D2> D1. This suggested that low irrigation frequency will inhibit the PSⅡphotochemical activity of flag leaf,make primary photochemical efficiency of PSⅡin wheat leaves reduced, so that leaves hurt. Under low irrigation frequencies, increasing the amount of irrigation can ease the flow of electrons to photosystem Ⅱ reaction center by suppressing a certain extent. High frequency irrigation of wheat flag leaf photosynthesis is mainly limited by stomatal factors, increase the frequency of irrigation can increase photosynthetic rate and reduce leaves of reactive oxygen species, thereby enhancing the photosynthetic efficiency.(3) RLD was greater in D1 and D2 than in D3 in shallow soil layer and on the contrary in deep soil. The amount of water in the 0-20 cm depth was not enough for plant growth when irrigation was in low frequent. RWD and root-shoot ratio were greater in D2 than in D1 and D3. The soil is relatively arid under W1 treatment, wheat plants grown mainly by increasing root length in 20-40 cm soil depth to protect water demand. Wheat roots had a very significant impact on wheat production.The RWD in 0-20 cm soil depth and RLD in 20-40 cm soil depth and yield of wheat drip irrigation had a corrletion relationship. Drip-irrigation wheat responded to drier soil conditions by increasing the proportion of roots deeper in the soil so wheat maintained the majority of the roots near the soil surface regardless of water deficit stress. With optimum irrigation amount, increasing drip irrigation frequency can make wheat root length and root weight increased, aboveground biomass accumulation increased, thereby improving the yield and water use efficiency.(4) Central spike in grain weight had obvious advantages. The two varieties under different treatments showed a significantly correlation between the central filling parameters spikelets and grain weight greater than between the upper and lower spikelets. Mid part filling rate> lower part filling rate > upper part filling rate, grain weight showed mid part> lower part> upper part. Increased irrigation frequency make theoretical maximum grain weight reduced, especially in the central spikelets, thereby reducing the overall spike weight. There was no significant difference among the upper and lower spikelets filling rate with the increase of irrigation amount, while the central filling rate showed that with the increase of irrigation amount increased and then decreased, indicating that moderate the irrigation can make the filling rate of central spikelets increased, thereby improving yields.(5) Middle spikelets had high ABA content in D2 and D3 treatments in the early filling stage and rapid decreased in the mid and late filling. This is useful for grain filling. Under different water treatments found higher IAA content in W1 treatment, which may cause the grain weight increased. And W2 and W3 treatments had higherCTK content, which was positively correlated with grain weight.(6) In the early, metabolites in mid and late grain filling, changed significantly. Compared with the metabolic pathway activity, in the early grain filling had a higher metabolic pathway activity,and in the late filling α- linolenic acid metabolic pathway arachidonic acid synthesis pathway, linolenic acid synthesis pathway, arginine and ornithine synthesis pathway activity increased among different water treatments. There were less metabolic differences between W2 and W3 treatments. IAA content increased may due to the precursors of IAA(tryptophan) increased. The reason ABA, CTK contents increased was that the increased β- carotene content and isopentenyl accumulated. Comparison of sugar and starch metabolic pathways, in W2 treatment glucose-6-phosphate, glucuronic activity increased, caused glucose, maltose, and fructose content increased. Compared 8 essential amino acids in the W1 and W2 water treatments in late grain filling stage indicated that they increased the amount of irrigation will make essential amino acids decreased.【Conclusion】 In arid regions,we can by increasing the frequency(7-10days) of irrigation to increase production, but after in the filling stage should appropriately reduce irrigation frequency(13days). In the grain filling stage, moderate irrigation(6000 m~3/ha) made the central spikelets filling rate increased, thereby improving yields. Excessive irrigation make grain essential amino acids declined and production was not increased.