| In this study, with Shanyou 63 (an elite hybrid rice variety) as control, designed different water treatments during different growth stage from panicle initiation to 30 days after flowering, and determined soil moisture by W.E.T Sensor and electronic balance, six experiments cultivated in pots or pools were carried out for two years. The water sensitivity difference of different super rice varieties was researched, evaluated and classfied comprehensively by fuzzy function method, principal components and cluster analysis. In addition, the response of panicle organ growth and development, grain filling to water deficit were studied, based on machine vision detection technology, the grains morphological traits of full panicle and different position within a panicle under different water condition were inspected, and the relationship among these traits and their relation to grain weight was analyzed as well. The source and sink mechanism and partial physiological biochemistry characteristics for influence of water deficit on super rice yield were discussed primarily. The results showed as the following:Different water deficit during panicle initiation to grain filling had various degree influence on plant morphological traits, panicle characteristics, dry matter accumulation, yield and its components and other agronomic characters so on. Water deficit had the greatest influence during whole panicle growth period and 10-20d, 15-30d after panicle initiation, 0-15d and 10-20d after flowering, followed by 0-15d and 20-30d after panicle initiation, 0-10d and 15-30d after flowering, however, 0-10d after panicle initiation and 20-30d after flowering had the least influence. Water deficit during panicle initiation effected panicle development and inhibited the elongation of flag leaf and the 2nd leaf from top, which leaded to photosynthesis leaf area, plant height, panicle length decrease obviously and numbers of the secondary branches and spikelets reduce significantly. Water deficit during panicle initiation and grain filling leaded to the reduction of biomass and dry matter weight of each organ compared with normal water supply, total grain numbers, filled grain numbers, fertility rate and 1000-grain weight were influenced greatly, which caused the reduction of grain yields at last, even more than 20% of each variety. Sensitivity to water deficit varied from these varieties, the sensitive time interval and influence degree were difference in each variety, the order of water sensitivity is listed from hypersensitive to insensitive: Shanyou 63,â…¡you 602, Tianyou 998,â…¡you 7, Liangyoupeijiu and Guodao 6. Certain relationship exists among WSC (water sensitivity coefficient), WSI (water sensitivity index), WSV (water sensitivity subordinate values), and that of each three parameters with yield and other agronomic characters. The sensitivity of these rice varieties evaluated with different parameters had the same results to some extent, consisting with the yield reduction degree under different water conditions, it was effective to evaluate water sensitivity of various varieties by WSC, WSI, WSV, total grain numbers, filled grain numbers, the secondary branch numbers, fertility rate and 1000-grain weight, grain yield, biomass, panicle length, plant height and photosynthesis leaf area and other traits.During start to 30 days after panicle initiation, both different time intervals and levels water deficit influenced panicle growth and development obviously. Panicle length, the secondary branches, numbers of spikelets and filled grains, fertility rate and 1000-grain weight all decreased, which leaded to the reduction of panicle weight, grain yields, plant height, panicle-neck length, photosynthesis leaf area, and biomass. The distribution proportion of dry matter in panicles dropped with water deficit increasing, while culm and sheath, leaf showed rising trend. The reduction of spikelets numbers is one of the main reasons leading to yield drops, secondary, the drop of fertility rate and grain weight. A positive correlation existed between yield drop range and water deficit degree, heavier water deficit had the greater influence than middle water deficit, and lower water deficit had certain influence, too. Water deficit during entire period of panicle growth and 10-20d after panicle initiation had the greatest influence, nextly, 0-10d after panicle initiation, 20-30d after panicle initiation had little influence on the panicle growth, but certain influence on grain filling. The growth and development of lower and middle grains within a panicle were affected mainly by water deficit during this period, the effect on fertilizing and filling of upper grains existed also at a certain extent. Influence degree of super rice, Guodao 6, was lower than that of normal hybrid rice, Shanyou 63, and its automatic adjustment ability of growth compensation and yield component factors after enduring moderate water deficit was stronger.From flowering to 30d after flowering, both different time intervals and levels water deficit caused grain yield drop, the reduction of fertility rate and grain weight was the main reason during this period. Heavier water deficit had the greatest influence, while lower water deficit had comparatively small yield drop. The effect of water deficit during middle stage of grain filling (10-20d after flowering) was greater than that of prophase stage (0-10d after flowering), while influence of prophase stage was greater than that of anaphase stage (20-30d after flowering), water deficit in prophase and middle stage caused the drop of fertility rate and 1000-grain weight obviously. Heavier and middle water deficit during different period from flowering to 20d after flowering all decreased GFD (grain filling degree), more obviously influence appeared under water deficit of middle filling stage, the effect of water deficit in different stage to GFD of different position was related with the grain filling course in each position, GFD in middle and lower grain position was affected mainly. Under different water condition from panicle initiation to grain filling stage, obvious difference of grain filling characteristic was existed, water deficit leaded to reduce the initial position of grain filling, average filling rate, and move up the time arriving maximum filling rate, accelerate the preliminary filling speeds, and reduce the filling rate in middle and anaphase stage, and active filling time as well, finally, grain weight reduced remarkably, and the initial filling level of superior or inferior grains decreased, while filling rate raised, the asynchronous filling characteristic was more obvious.Under different water deficit condition during panicle growth and development stage, the grain length, area, perimeter, equivalent diameter and 1000-grain weight responded more obviously to siol moisture, the change of GRWA (ratio of grain weight to area) was caused by the effect of water deficit on grain area and weight, the response of ratio of grain length to width manifested complexity at a certain extent, and that of grain width and equivalent diameter to water deficit varied from varieties. The grain morphological traits, 1000-grain weight, yield and its components showed a drop trend of different extent with enhanced degree of water deficit, these grain morphological traits and grain weight reduced observably while controlling soil moisture from beginning to 30 days after panicle initiation, the effect of different water deficit was most significant during 0-30d, secondary, heavier or middle water deficit during 10-20d and heavier water deficit during 0-10d or 20-30d. The expressive laws of the effect of water deficit at different stage on grain morphological traits and weight of different position within a panicle was basically inosculated with the order of panicle initiation and growth. These morphological traits except for width showed significant positive correlation at 0.01 probability level, while the relationship of grain width with other morphological traits was significant negative correlation at 0.01 or 0.05 probability level, respectively. The correlativity existed significantly between grain weight and grain length, projective area, perimeter, equivalent diameter and ratio of grain length to width at 0.01 or 0.05 probability level, respectively. Therefore, these traits can be used as effective grain morphological indexes to evaluate drought-resistance in rice.Water deficit will influence obviously the source and sink mechanism of yield formation in super rice, and the response exists in partial physiological biochemistry characteristics. Under middle water deficit at different growth stage during panicle initiation to 30 days after flowering, the content of malondialdehyde (MDA, membrane lipid peroxidation product), free proline (Pro) and soluble sugar (SS) in rice leaf increased significantly with growing course and process of leaf function, while that of chlorophyll (Chla, Chlb, Chla+b) and carotenoid showed drop trend, the physiological response of different varieties to water deficit is different at a certain extent. Water deficit of different growth stages all accelerated membrane lipid peroxidation and leaded to MDA content raise, moreover, the influencing degree enhanced with growing process and lasting days of water controlled. On the other hand, the MDA content in different leaves showed rising trend with leaf position fall, that of the 3rd leaf from top was higher, secondarily, the 2nd leaf from top, and the MDA content in flag leaf was relevantly lower. The MDA content in rice leaf was enhanced by water deficit, especially under-layer leaf, which obviously leaded to damage of enzyme and cell membrane, accordingly affected cell normal physiological metabolism. The effect of water deficit on MDA, Pro, SS, chlorophyll and carotenoid in different rice varieties showed difference because of different sensitivity to water stress, the influence of Shanyou 63 was greater, followed byâ…¡you 602 and Liangyoupeijiu, that of Guodao 6 was less. Not only the relationship of stress degree and effect, stress lasting time and effect, but also growing course and effect are existed in the response to water deficit.
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