Effects of soil water saturation on rice growth and development

Transcription

1 THE ROYAL SOCIETY OF CROP SCIENCE Indian J. Crop Science, 1(1-2): (2006) Effects of soil water saturation on rice growth and development Longxing Tao, Xi Wang, Huijuan Tan, Junhui Shen and Shihua Cheng RSCS 2006 Longxing Tao et al. State Key Laboratory of Rice Biology, China National Rice Research Institute, Effects P of R soil China water saturation in rice Abstract Intersubspecific hybrid rice Xeiyou 9308 and Liangyoupeijiu were used as the test materials, three level of soil water content were designed during filling in irrigated field to observe their effects on translocation and allocation for carbohydrate. The results showed that in conventional flooding or non flooding cultivation, the exported rates of stored carbohydrate from stem and photophate from the leaves were 60 % and 90 % respectively. The exported rate of carbohydrate was decreased significantly in the non-flooding cultivation. The filling s were the major sinks for carbohydrate storage during filling stage. Grains received nearly 50% leaf-sheath-stored carbohydrate and 80 % leaf-stored photophate. At the non flooding condition, the absorbing rates of s were significantly decreased by 10 % and 20 % from leaf sheath and from leaves photophate, respectively. Dry stress caused much decrease in absorbing ability for inferior s. It was also observed that one time water saturation during filling stage, the degradation of both root respiration and root exudates was significantly slowed down with little effects on the decreasing process of zeatin content in roots exudates. Key words: Introduction Soil water saturation; Hybrid rice, cytokinin, root exudates, carbohydrate allocation. China is one of the most water deficient countries in the world; more than 72% of the total land suffers from water stress. The average water resource per unit lowland is only 67% of the average world level, and the average water volume per unit irrigation area is only 19% of the world level (Qu, 1998). Recently almost half of the fresh water was used for rice irrigation, resulting in very low water use efficiency (so-called half kg rice with one ton water ) and high cost of rice production. It is time to limit irrigation water in rice production by non-flooding rice farming technique (NFRF). Non-flooding rice farming technique has been studied for many years, but the yield of NFRF was always not as high and stable as the traditional flooding rice farming (TFRF) (Luo and Zhang, 2001). The main cause may be from premature senescence of NFRF during filling stage. It was reported that those phenomena as leaf yellowing, stem soften and early lodging were usually associated with NFRF during maturing stage (Zhang and Liu, 1988, Huang et al., 1999, Yang et al., 2002). Some field trials conducted by Zhang in Hunan, Anhui and Jiangsu provinces showed similar results. Wang compared with the root system and root activity between NFRF and TFRF, he pointed out that NFRF usually showed a bigger root system but lower root physiological activity and early stem senescence than that of TFRF (Wang et al., 2004). By different irrigation treatments, different soil water contents were built to study their effects on transportation and distribution of both the stored carbohydrate in leaf sheath and the photophate in leaves. This paper tries to get some useful physiological data to support and improve irrigation technique, and increase -filling enrichment of non-flooding rice farming technique. Materials and methods Plant materials: Three-line inter-sspecific hybrid rice Xeiyou 9308 (Released from China National Rice Research Institute) and two-line intersubspecific hybrid rice Liangyoupeijiu (Released by The Academy of Agricultural Sciences of Jiangsu Province) were used as the tested materials. The yield potential of above two hybrids was very high on large-scale farmer s field. Xieyou9308 was typical for big panicle and lower tillering ability, and Liangyoupeijiu was a typical type for more panicles and strong tillering ability. 3 H-glucose used in this experiment was D-[6-3 H] glucose, produced by China Institute of Atomic Energy, irradiation intensity was 18ci/mM, and irradiation concentration was Bq/ml. Treatments: The experiments were conducted in experimental station of China National Rice Research Institute. Hybrid rice was planted in cement slots with 2 20 m and bottom sealed with cement. A shield (made of transparent plastic film) was built to prevent rainwater. Water irrigation was controlled and monitored by water meter. The seedlings were single planted in the slots, and plant density, fertilizer, irrigation and agro-chemical application were same as main field management before heading stage (Wang et al., 2004). After heading, three irrigation treatments were conducted: Flooding irrigation (treatment A). Dry cultivation (full stop watering after heading, treatment B), dry-watering alternation (based on the B treatment, but giving a pass-through irrigation at 15 days and 30 days after full heading stage, treatment C), with three repeats. Taking soil samples at a fixed time from treatment A to monitor the soil water content at normal irrigation condition (soil water content 63.5%, equal to the volume of soil water saturation). Treatment B was dry cultivation, with soil water content above 30.0%

2 [ 60 ] Longxing Tao et al. at heading stage, and was decreasing to less than 20% (equal to 70% of volume of soil water saturation) after 10 days time, and was a critical volume of water requirement for rice plant (Zhang and Liu, 1988). The water stress was getting serious during maturation. Treatment C was a dry -watering alternation; there was no standing water in field, and the soil water content was always higher than the critical volume. Sampling for superior and inferior s: Superior and inferior s sampling followed the method as the reference (Wang et al., 2001; Wang et al., 2003), that is, s from the top three primary branches of one panicle are defined as superior s, usually most of those spikelets finish their flowering in the first or second day during heading stage, and very few of them (less than 5%) flower at third day during heading stage. Those s from secondary branches of 3 base primary branches are defined as inferior s, usually those spikelets start flowering at 5 th to 9 th days after heading stage. Each sample contained 50 panicles. Isotope trace experiments: Isotope trace materials were sampled from different treatments (A, B, C). Five uniform shoots were labeled each hill for 20 plants at initial heading stage, and cut the other shoots of the labeled plant. Using 5% Teween-20 as dilute daub 20 ul 3 H-glucose to each leaf sheath for main shoot and the five labeled shoots each hill at pollen cell maturity stage. Do the same daub to each flag leaf of the main shoot and the five labeled shoots each hill? 3 H-glucose daubed to the leaf sheaths was considered as stored carbohydrate; and 3 H-glucose daubed to the flag leaf was considered as a synthesizing photophate. Whole plant (above the ground) was sampled at yellow maturity stage. The method of radioactive sample preparation and measurement was followed as Yu et al. (1995), 50 mg dried and smashed sample was wet-oxidized and measured by LKB-1217 Liquid Scintillation Counting (LSC) instrument. The scintillation liquid was: Toluene: Trition.X-100=2:1(v/v) containing PPO 6g.L -1. Drying of the samples: First the samples were quickly killed at C for 15min, and then dried at 80 0 C for 24h. Root respiration measurement: Dig out one whole plant with 50 cm uninjured root system from field, cut and select the root slice beginning from 6 cm to 15 cm of the root downward direction. Care was taken during the clearing the roots with clean water. The root respiration rate was determined with Warburg Manometer (Wang et al., 2003). Root exudates intensity: Ten uniform plants were selected for each treatment, cut the plant at 10 cm upward position of stem and cover each stem with a small plastic bag containing absorbent cotton soon after cutting in late afternoon. Bags were collected after 12 h, cutting and squeezing out the root exudates for zeatin analysis (Wang et al., 2003). Zeatin measurement: Zeatin analysis was conducted using HPLC (HP1100 Chemical Station) with HP-ODS C-18 column (12.5 mm Á4.6 mm) DAD detector at 270 nm (Wang et al., 2003 and Ding et al., 1985). Results and discussion Effects of soil water content on root respiration: Root respiration intensity was down after initial heading stage (Fig.1). The respiration intensity was down from 320 O 2 l h -1 g -1 FW at initial heading stage to O 2 l h -1 g FW within 8 weeks in treatment A for Xieyou9308, and even more decrease was happen to another hybrid Liangyoupeijiu. Root respiration rate (O 2 Ìl/hr.g.FW) x x Xieyou Fig. 1 Effect of different irrigation methods on root respiratory intensity during filling stage Time after initial heading (week) Flooding irrigation Dry cultivation Liangyoupeijiu D----- D Dry-wet alternation Initial heading stage At initial heading stage, the root respiration intensity was higher in the dry cultivation (treatment B) than in treatment A, but it decreased faster than treatment A during filling for Xieyou9308.The root respiration intensity of Liangyoupeijiu showed a faster decrease tendency than that of Xieyou9308 in the B treatment. Two time pass-through irrigation at 3 weeks after heading (Treatment C) showed a significant better effect in increasing root respiration intensity (recovery from decrease) than treatment B: (1) Root respiration intensity of treatment C for Xieyou9308 was recovered to level of treatment A after a pass-through irrigation; (2) Root respiration intensity of treatment C for Liangyoupeijiu was higher than the level of treatment A after conducting a pass-through irrigation. Effects of water content in soil on root exudates volume and zeatin level: The volume of root exudates was going down during maturation for both hybrids, and the decreasing rate was higher in treatment B (Fig. 2). The treatment C could retard this process and the root exudates volume was between treatment A and treatment B.

3 Zeatin content was also going down during maturation, but there was some difference among treatments: (1) In the treatment A, the zeatin level of Liangyoupeijiu was higher than that of Xieyou9308 before heading stage, therefore this status was reversed, and zeatin level in Liangyoupeijiu decreased much sharply than Xieyou9308 after heading till maturity. (2) In the treatment B, the zeatin level in this treatment was higher than treatment A for Xieyou9308, and lower than treatment A for Liangyoupeijiu, but the zeatin level for both hybrids was lower in treatment B than treatment A at yellow maturity stage. (3) Treatment C had avantage to maintain the zeatin level for both hybrids. Root exudate (g/hill.12h) Zeatin content (pmool) IH: H: Xieyou930 8 IH H MR WR YR Initial heading stage Heading stage Flooding stage Development stage WR: MR: x x Wax ripening stage Milk ripening stage Dry cultivation Fig.2 Effect of irrigation model on root exudates and zeatin content. Transportation and allocation of labeled carbohydrates stored in leaf sheath: 3 H-glucose was fed to leaf sheath at pollen maturity stage. This 3 H-glucose represented as stored carbohydrates. About 40~50% was Effects of soil water saturation in rice [ 61 ] allocated to s, less than 10% was translated to leaf and panicle branch. This distribution was affected by irrigation pattern (Table 1). Of the two tested hybrids in this experiment, 60% of the stored carbohydrates was translated out in flooding irrigation treatment (treatment A), and less stored carbohydrates was translated out in dry cultivation (Treatment B). With dry cultivation, the export of stored carbohydrates was decreased 31% (P<0.01) and 18% (P<0.05) for Liangyoupeijiu and Xieyou9308 respectively when compared with flooding irrigation (Treatment A). There were different affects of dry -watering alternation treatment (Treatment C) on the transportation rate of the stored carbohydrates for two hybrids. For Liangyoupeijiu, the export of stored carbohydrates was 18% (P<0.05) decreased compared with that of flooding irrigation, and there was no significant affect to that of Xieyou9308. The transporting efficiency of stored carbohydrates to, which was also considered as a physiological activity of spikelets (Lu et al., 1988), was affected by the irrigation pattern in this experiment. Import rate of the stored carbohydrate to was 17% (P<0.05) and 23% (P<0.01) decreased for Xieyou9308 and Liangyoupeijiu respectively by dry-cultivation (Treatment B) compared with that of the treatment A. In dry -watering alternation treatment (Treatment C), import rate of the stored carbohydrate to was 13% (P<0.05) decreased for Liangyoupeijiu when compared with that of the treatment A, and no significant affects to Xieyou9308. Table 2 shows an up-taking rate of panicle for the stored carbohydrate. In the flooding irrigation treatment (A), the up-taking rate of panicle for carbohydrate, Xieyou9308 was lower than that of Liangyoupeijiu. The dry-watering alternation (C) had no affect to carbohydrate up-taking rate of panicle for both hybrids. The dry cultivation treatment (B) decreased a panicle up-taking rate for carbohydrate of 1.3Bq (8.9% decreased, P<0.05) and 4.0Bq (26% decreased, P<0.01) for Xieyou9308 and Liangyoupeijiu respectively. The superior spikelets showed a stronger up-taking ability for the stored carbohydrate than that of Table 1. Effects of irrigation patterns on the transportation of 3 H-glucose during filling stage (Bq 10 4 per stem) Combination Treatment Stem and sheath Leaf Stalk Grain Bq % Bq % Bq % Bq % Xieyou 9308 A B ** * * C * Liangyoupeiju A B ** ** C * * Labeling part. A=Water irrigation; B=Dry Cultivation; C=Dry-wet alternation. *,** : Significant at 0.05 and 0.01 level respectively. The same as below. Liangyoupeiji u IH H MR WR YR YR: Yellow maturity stage D---- D Dry-wet alternation

4 [ 62 ] Longxing Tao et al. Table 2. Effects of irrigation patterns on allocation of 3 H-glucose from sheath to s during filling stage (Bq 10 4 per stem) Hybrids Treatment Total s per panicle the inferior spikelets, and this up-taking ability for the stored carbohydrate of the superior spikelets was irresponsible to the irrigation pattern. There were significant effects of irrigation patterns on the up-taking ability for the stored carbohydrate for inferior spikelets. In the dry-cultivation treatment (B), the stored carbohydrate up-taking ability of inferior spikelets were decreased 5.2 Bq (41.9%, P<0.01) and 6.8Bq (51.9%, P<0.01) for Xieyou9308 and Liangyoupeijiu respectively when compared to the flooding irrigation treatment. The similar results was also obtained in dry-watering alternation treatment, and a 1.1Bq (8.4%, P<0.05) decrease was observed on hybrid rice Liangyoupeijiu compared with treatment A. Transportation and allocation of the labeled photophate from flag leaf: The data showed in Table 3 were based on data collected from up-ground part of rice plant. 80~90% of the labeled photophate was translated out from labeled leaf and the two hybrids showed no significant difference on it. However the irrigation pattern affected the export rate of the labeled photophate. The photophate export rate was Superior s Inferior s Other s () () () () Xieyou 9308 A B * ** C Liangyoupeiju A B ** ** * C * decreased 62% and 61% for Xieyou9308 and Liangyoupeijiu respectively in dry cultivation (Treatment B) when compared with the flooding irrigation (Treatment A). Almost 80% of the labeled photophate was allocated to for both hybrids, but it was affected by irrigation pattern. 9.2% and 11.5% (P<0.01) decreased for Xieyou9308 and Liangyoupeijiu respectively caused by the dry cultivation when compared with the flooding irrigation treatment. The export rate from the labeled flag leaf to other part except was not significantly affected by the irrigation pattern. Up-taking of the labeled photophate per single was affected by irrigation pattern (Table 4) more on Liangyoupeijiu than Xieyou9308, and Liangyoupeijiu showed a 6.9 Bq (20.2%, P<0.01) decrease in the dry cultivation (Treatment B) compared with the treatment A. There was no significant effect of the treatment C on the labeled photophate up-taking per single for two hybrids. Up-taking of the labeled photophate per single superior was not significantly affected by the irrigation pattern for Xieyou9308, but Table 3. Effects of irrigation pattern on translocation and allocation of 3 H-glucose from flag leaf to organs during filling stag (Bq 10 4 per stem) Combination Treatment Flag leaf* Other leaves Stem and sheath Stalk Grains Bq % Bq % Bq % Bq % Bq % Xieyou 9308 A B * ** C Liangyoupeijiu A * Labeling part, **Significant at 0.01 level. B * ** C

5 6.8Bq (18.6%, P<0.01) was decreased for Liangyoupeijiu caused by the dry cultivation treatment compared with that of the flooding irrigation treatment. Up-taking of the labeled photophate per single inferior was negatively affected by the dry cultivation treatment, it was 6.5Bq (decrease 36.7%, P<0.01) and 7.6Bq (decrease 41.7%, P<0.01) decreased for Xieyou9308 and Liangyoupeijiu respectively when compared with that of the flooding irrigation treatment. Grain weight and seed setting rate of superior and inferior s: Seed setting rate of superior s for both hybrids were decreased in the dry cultivation treatment, and more negative effects of the dry cultivation was observed for Liangyoupeijiu than Xieyou9308 so far as seed setting rate is concerned. There were less negative effects on seed setting rate in the dry-watering alternation treatment (Treatment C) compared with that of the treatment B. A decrease in weight was also caused by the dry cultivation treatment for two hybrids, and Liangyoupeijiu was more significant in weight decrease (P<0.05) than that of Xieyou9308. Inferior s suffered more from the dry cultivation treatment than superior s as seed setting rate and weight are concerned, it was significantly decreased in seed setting rate and Effects of soil water saturation in rice [ 63 ] Table 4. Effects of irrigation pattern on 3 H-glucose from flag leaf translocation into s during filling stage (Bq 10 4 per panicle) Combination Treatment Total s per panicle Superior s Interior s Other s Xieyou9308 A B ** C Liangyoupeijiu A B * ** ** * C Table 5. Effect of irrigation pattern on setting of rice s during -filling stage weight for both Xieyou9308 (P<0.05) and Liangyoupeijiu (P<0.01); It was significantly better in the dry-watering alternation treatment (Treatment C) when seed setting rate and weight of superior and inferior s were concerned. Scientists conducted many studies on hybrid rice, especially on intersubspecific hybrid rice. They cut their leaves, did spikelets thinning or conducted isotope tracing experiments or dry matter accumulation measurement of organs, to explore physiological reasons of lower seed setting rate and pre-mature plant senescence during maturing stage It was reported that those phenomena such as early leaf senescence, decline of photosynthesis or biomass accumulation rate and lower seed setting rate were always associated with hybrid rice, especially for intersubspecific hybrid rice with big sink and large source (Lu et al., 1988, Wang et al., 1966). As concerning with effects of export of stored carbohydrate in leaf sheath on seed setting rate, some scientists thought it was not a major cause for lower seed setting rate of the hybrid rice including intersubspecific hybrid rice. However, other scientists held an opposite opinion. The authors of this paper had reported that a drawing potential (or physiological activity) of spikelets for photophate (or all kinds of carbohydrate) was important to seed setting rate Combination Treatment Grain setting rate % 1000 weight (g) Superior s Inferior s Superior s Inferior s Xieyou9308 A B * * * C Liangyoupeijiu A B ** ** * ** C

6 [ 64 ] Longxing Tao et al. (Wang et al., 2000). There were a little reports regarding to the physiological effects of water stress on seed setting of hybrid rice. This paper showed a physiological mechanism of drought stress during rice filling stage on seed setting. At a normal flooding irrigation condition (treatment A), exports rate of stored carbohydrates from leaf sheath (radioactive isotope labeled) and photophate (radioactive isotope labeled) of flag leaf were 60% and 90% respectively, of which 50% and 80% respectively were distributed to s. At the Dry cultivation (treatment B) however, the exports rate of stored carbohydrates from leaf sheath to s were 16.7% (P<0.05) and 23.0% (P<0.01) decreased respectively for Xieyou9308 and Liangyoupeijiu; And the exports rate of photophate from flag leaf to s were also 9.3% (P <0.05) and 11.5% (P <0.01) decreased for Xieyou9308 and Liangyoupeijiu respectively. Therefore it was considered that under the dry-cultivation conditions, translocation of carbohydrates from source to sink was jammed, leading to more percentage of photophate un-moved. It was also considered in this paper that under the dry-cultivation conditions, the physiological activity of spikelets were decreased (Yang et al., 2001, Beltrano et al., 1998, Parthier et al., 1990), therefore the draw-ability for photophate from source of the filling s were come down (Wang et al., 2000). In this experiment, the draw-ability for photophate of superior spikelets was relatively stable for two hybrid combinations. There was a little affect of drought stress on the draw-ability, only a slightly decrease. However there was significant decrease of the draw-ability caused by drought stress for inferior spikelets (P<0.01).This was an Inter- apical superiority (Wang et al., 2001). Under dry-cultivation conditions, the physiological activity of superior spikelets was stronger than that of inferior spikelets, so did the draw-ability for photophate. Usually the filling duration of superior spikelets was 10~20 days shorter than that of inferior spikelets, in other words, superior spikelets was suffered a shorter time from drought stress than inferior spikelets. So blight affects caused by draught stress during filling stage were mostly associated with inferior spikelets, resulting in lower seed setting rate and lower weight. This may be a main cause for lower yield by water stress. It was showed in this experiment that there was a less effect of water stress during filling stage on Xieyou9308 than Liangyoupeijiu. It seemed that Xieyou9308 showed a higher drought resistance than that of Liangyoupeijiu, further experiment is needed to understand its physiological mechanism. Acknowledgement The research work was supported by The Agricultural Planting Structure Adjustment Project of MOA ( B) and by the Agricultural Integration Exploitation Project of Zhejiang provincial government. References Beltrano J. Ronco M.G. and Montalaldi E.R Carbone. Senescence of flag leaves an ears of wheat hastened by Methyl Jasmonate.J Plant Growth Regul., 17: Ding J. and Shen Z.D Cytokinin substances in cotton exudate. Acta Phytophysiologica Sinica, 11: Duan J., Liang C.Y. and Huang Y.W Studies on Leaf Senescence of Hybrid rice at Flowering and Grain Formation Stage. Acta Phytophysiologica Sinica., 23: Huang Y.D., Zhang Z.L. and Wei F.Z Ecophysiological effect of dry-cultivated and plastic film-mulched rice planting. Chinese Journal of Applied Ecology, 10: Lu D.Z., Pan Y.C. and Ma Y.F Physiological and Biochemical Studies on Leaf Senescence at Heading and Formation Stage in Hybrid Rice. Scientia Agricultura Sinica, 21: Luo L.J. and Zhang Q.F The status and strategy on drought resistance of rice (Oryza sativa L). Chinese J Rice Sci., 15: Parthier B.J Hormonal regulators or stress factors in leaf senescence. J plant Growth Regul., 9: Qu G.P Some problems of water environmental management in China. China Environmental Science, 8:-4. Wang H.X., Zhang Z.L. and Ren G.G Study on the Distribution of Photosynthetic Products and Plumpness of two Line Intersubspecific Hybrid Rice. Acta Agriculturae Nacleatae Sinica., 10: Wang X., Tao L.X., and Huang X.L Seed setting characteristics and Physiological bases of subspecies Hybrid rice Xieyou Acta Agronomica Sinica, 29: Wang X., Tao L.X. and Tian S.L The Absorption For Carbohydrate Between Vigorous And Weak Spikelets In Hybrid Rice And Its Restorers. Acta Agriculturae Naclwatae sinica., 14:76-84 Wang X., Tao L.X. and Xu R.S Apical- superiority in hybrid rice. Acta Agronomica Sinica., 27: Wang Xi, Tao Longxing and Huang Xiaolin Study on Non-Flooding Farming Technique in paddy Field :Technique Specification and Formation of yield components. Scientic Agriculturae Sinira, 37: Yang J.C., Wang Z.Q. and Liu L.J Growth and development characteristics and yield formation of dry-cultivated rice. Acta Agronomica Sinica, 28: Yang J.C., Zhang W.H. and Wang Z.Q Source-sink Characteristics and the translocation of Assimilates in New Plant Type and Japonica/Indica Hybrid Rice. Scientia Agricultura Sinica, 34: Yu M.Y., Wang X. and Tao L.X Effect of S-07 on 14 CO 2 -assimilation and distribution of assimilates during ripening stage of wheat. Acta Agriculturae Nacleatae Sinica., 9: Zhang R.K. and Liu B.K Dry-cultivated rice production and cultivation techniques. Hunan Journal of Agricultural Science, 2:30-36.