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1.
Influence of external zinc and phosphorus supply on Cd uptake by rice (Oryza sativa L.) seedlings with root surface iron plaque 总被引:1,自引:0,他引:1
Rice seedlings were grown in hydroponic culture to determine the effects of external Zn and P supply on plant uptake of Cd
in the presence or absence of iron plaque on the root surfaces. Iron plaque was induced by supplying 50 mg l−1 Fe2+ in the nutrient solution for 2 day. Then 43-day-old seedlings were exposed to 10 μmol l−1 Cd together with 10 μmol l−1 Zn or without Zn (Zn–Cd experiment), or to 10 μmol l−1 Cd with 1.0 mmol l−1 P or without P (P–Cd experiment) for another 2 day. The seedlings were then harvested and the concentrations of Fe, Zn, P
and Cd in dithionite–citrate–bicarbonate (DCB) extracts and in roots and shoots were determined. The dry weights of roots
and shoots of seedlings treated with 50 mg l−1 Fe were significantly lower than when no Fe was supplied. Adsorption of Cd, Zn and P on the iron plaque increased when Fe
was supplied but Cd concentrations in DCB extracts were unaffected by external Zn or P supply levels. Cd concentrations in
shoots and roots were lower when Fe was supplied. Zn additions decreased Cd concentrations in roots but increased Cd concentrations
in shoots, whereas P additions significantly increased shoot and root Cd concentrations and this effect diminished when Fe
was supplied. The percentage of Cd in DCB extracts was significantly lower than in roots or shoots, accounting for up to 1.8–3.8%
of the plant total Cd, while root and shoot Cd were within the ranges 57–76% and 21–40% respectively in the two experiments.
Thus, the main barrier to Cd uptake seemed to be the root tissue and the contribution of iron plaque on root surfaces to plant
Cd uptake was minor. The changes in plant Cd uptake were not due to Zn or P additions altering Cd adsorption on iron plaque,
but more likely because Zn or P interfered with Cd uptake by the roots and translocation to the shoots. 相似文献
2.
Effect of silicate on the growth and arsenate uptake by rice (Oryza sativa L.) seedlings in solution culture 总被引:1,自引:0,他引:1
A solution culture experiment was conducted to investigate the effect of silicate on the yield and arsenate uptake by rice. Rice seedlings (Oryza sativaL. cv. Weiyou 77) were cultured in modified Hoagland nutrient solution containing three arsenate levels (0, 0.5 and 1.0 mg L –1 As) and four silicate levels (0, 14, 28 and 56 mg L –1 Si). Addition of Si significantly increased shoot dry weight (P=0.001) but had little effect on root dry weight (P=0.43). Addition of As had no significant effect on shoot dry weight (P=0.43) but significantly increased root dry weight (P=0.01). Silicon concentrations in shoots and roots increased proportionally to increasing amounts of externally supplied Si (P < 0.001). The presence of As in the nutrient solution had little effect on shoot Si concentration (P=0.16) but significantly decreased root Si concentration (P=0.005). Increasing external Si concentration significantly decreased shoot and root As concentrations and total As uptake by rice seedlings (P <0.001). In addition, Si significantly decreased shoot P concentration and shoot P uptake (P <0.001). The data clearly demonstrate a beneficial effect of Si on the growth of rice seedlings. Addition of Si to the growth medium also inhibited the uptake of arsenate and phosphate by the rice seedlings. 相似文献
3.
Effect of iron plaque outside roots on nutrient uptake by rice (Oryza sativa L.): Phosphorus uptake 总被引:1,自引:0,他引:1
Under anaerobic conditions, ferric hydroxide deposits on the surface of rice roots have been shown to affect the uptake of
some nutrients. In the present experiment, different amount of this iron plaque were induced on the roots of rice (Oryza sativa
L. cv. TZ88-145) by supplying different Fe(OH)3 concentrations in nutrient solutions, and the effect of the iron plaque on phosphorus uptake was investigated. Results showed
that 1) iron plaque adsorbed phosphorus from the growth medium, and that the amount of phosphorus adsorbed by the plaque was
correlated with the amount of plaque; 2) the phosphorus concentration in the shoot increased by up to 72% after 72 h at concentration
of Fe(OH)3 in the nutrient solution from 0 to 30 mg Fe/L, corresponding with amounts of iron plaque from 0.2 to 24.5 mg g-1 (root d. wt); 3) the phosphorus concentration in the shoots of rice with iron plaque was higher than that without iron plaque
though the concentration in the shoot decreased when Fe(OH)3 was added at 50 mg Fe/L producing 28.3 mg g-1 (root d. wt) of plaque; and 4) the phosphorus concentrations in Fe-deficient and Fe-sufficient rice plants with iron plaque
were the same, although phytosiderophores were released from the Fe-deficient roots. The phytosiderophores evidently did not
mobilise phosphorus adsorbed on plaque. The results suggest that iron plaque on rice plant roots might be considered a phosphorus
reservoir.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
4.
In the Xinjiang province of western China, conventional methods of iodine (I) supplementation (i.e, goiter pills and iodinated
salt) used to mitigate I deficiencies were ineffectual. However, the recent addition of KIO3 to irrigation waters has proven effective. This study was conducted to determine the effects of I form and concentration
on rice (Oryza sativa L.) growth, I partitioning within the plant, and ultimately to assist in establishing guidelines for
incorporating I into the human food chain. We compared IO3
− vs. I− in order to determine how these chemical species differ in their biological effects. Rice was grown in 48 L aerated tubs
containing nutrient solution and IO3
− or I− at 0, 1, 10, or 100 μM concentrations (approximately 0, 0.1, 1, and 10 mg kg−1 I). The IO3
− at 1 and 10 μM had no effect on biomass yields, and the 100 μM treatment had a small negative effect. The I− at 10 and 100 μM was detrimental to biomass yields. The IO3
− treatments had more I partitioning to the roots (56%) on average than did the I− treatments (36%), suggesting differences in uptake or translocation between I forms. The data support the theory that IO3
− is electrochemically or biologically reduced to I− prior to plant uptake. None of the treatments provided sufficient I in the seed to meet human dietary requirements. The I
concentration found in straw at 100 μM IO3
− was several times greater than seed, and could provide an indirect source of dietary I via livestock feeding on the straw.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
5.
Effect of iron plaque outside roots on nutrient uptake by rice (Oryza sativa L.). Zinc uptake by Fe-deficient rice 总被引:6,自引:0,他引:6
This solution culture study examined the effect of the deposition of iron plaque on zinc uptake by Fe-deficient rice plants. Different amounts of iron plaque were induced by adding Fe(OH)3 at 0, 10, 20, 30, and 50 mg Fe/L in the nutrient solution. After 24 h of growth, the amount of iron plaque was correlated positively with the Fe(OH)3 addition to the nutrient solution. Increasing iron plaque up to 12.1 g/kg root dry weight increased zinc concentration in shoots by 42% compared to that at 0.16 g/kg root dry weight. Increasing the amount of iron plaque further decreased zinc concentration. When the amounts of iron plaque reached 24.9 g/kg root dry weight, zinc concentration in shoots was lower than that in shoots without iron plaque, implying that the plaque became a barrier for zinc uptake. While rice plants were pre-cultured in –Fe and +Fe nutrient solution in order to produce the Fe-deficient and Fe-sufficient plants and then Fe(OH)3 was added at 20, 30, and 50 mg Fe/L in nutrient solution, zinc concentrations in shoots of Fe-deficient plants were 54, 48, and 43 mg/kg, respectively, in contrast to 32, 35, and 40 mg/kg zinc in shoots of Fe-sufficient rice plants. Furthermore, Fe(OH)3 addition at 20 mg Fe/L and increasing zinc concentration from 0.065 to 0.65 mg Zn/L in nutrient solution increased zinc uptake more in Fe-deficient plants than in Fe-sufficient plant. The results suggested that root exudates of Fe-deficient plants, especially phytosiderophores, could enhance zinc uptake by rice plants with iron plaque up to a particular amount of Fe. 相似文献
6.
B. Xu J. Y. Yu T. Xie Y. L. Li M. J. Liu J. X. Guo H. L. Li Y. Yu C. Y. Zheng Y. H. Chen G. Wang 《Biologia Plantarum》2018,62(2):362-368
Brassinosteroids (Brs) have drawn wide attention due to their protective role against toxicity of heavy metals in plants. To better understand the role of Br in arsenic (As) and cadmium (Cd) uptake by rice plants, a hydroponic experiment was conducted to investigate the combined effect of 24-epibrassinolide (Br24) or 28-homobrassinolide (Br28) and iron plaque (IP) on As and Cd uptake and accumulation in rice seedlings. Six-week-old seedlings were sprayed with 0.2 or 0.02 μM Br24 or Br28 and grown in nutrient solution for 3 d, and then 20 or 60 mg Fe2+ dm-3 (Fe20 and Fe60) was used to induce root IP formation for 3 d. These seedlings with or without Br and with or without IP were exposed to solution containing 0.5 mg dm-3 AsIII or Cd for 9 d. The results showed that rice growth decreased when Br24 were applied, but it increased when combination of Br24 and IP was applied. Fe concentrations in dithionite-citratebicarbonate (DCB) extracts were increased after 0.2 or 0.02 μM Br24 application in the absence of IP, but decreased by Br24 in the presence of IP. In the absence of IP, As and Cd content in leaves was significantly reduced by 0.02 μM Br24 and 0.2 μM Br28, respectively. The As content in leaves was also reduced by the combination of 0.02 and 0.2 μM Br28 and IP, and the Cd content in leaves was reduced by the combined effect of 0.2 μM Br24 and IP. These results indicate that Br24 and Br28 could impede As and Cd accumulation, and the interactions between Br and IP may have a potential in restricting the transport of As and Cd into rice shoots. 相似文献
7.
Changes in abscisic acid (ABA) contents in Cd-treated rice (Oryza sativa L.) seedlings of two cultivars were investigated. On treatment with CdCl2, the ABA content rapidly increased in the leaves and roots of Cd-tolerant cultivar (cv. Tainung 67, TNG67) but not in the Cd-sensitive cultivar (cv. Taichung Native 1, TN1). The reduction of transpiration rate of TN1 caused by Cd was less than that of TNG67. Exogenous application of ABA reduced transpiration rate, decreased Cd content, and enhanced Cd tolerance of TN1 seedlings. Exogenous application of the ABA biosynthesis inhibitor, fluridone, reduced ABA accumulation, increased transpiration rate and Cd content, and decreased Cd tolerance of TNG67 seedlings. Fluridone effect on Cd toxicity of TNG67 seedlings was reversed by the application of ABA. The roles of endogenous ABA in Cd tolerance of rice seedlings are discussed and suggested. 相似文献
8.
S. Komatsu H. Karibe T. Hamada R. Rakwal 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1999,98(8):1304-1310
The response of plants to cold stress is not well understood at the biochemical level, although it has been studied extensively
at the ecological level. To investigate whether protein phosphorylation may play an important role in cold stress, we exposed
rice seedlings to low temperatures, prepared protein extracts from the leaves and incubated these in the presence of [γ-32P]ATP. The proteins were then separated by two-dimensional polyacrylamide gel electrophoresis. While several proteins were
found to be phosphorylated upon cold stress one protein, pp35, which has an isoelectric point of 8.0, was more phosphorylated
than the others. The pp35 protein was found to be phosphorylated when rice seedlings were incubated for 6 h at 5°C before
the leaf protein extract was prepared and radioactive labeling was performed. The pp35 was, however, significantly more phosphorylated
in cold-tolerant rice varieties. Antibodies were raised against purified pp35 in adult rabbits. Using this pp35 antibody,
which can recognize the RuBisCO large-chain subunit (LSU), and from amino acid sequencing of pp35, we were able to identify
and confirm the pp35 protein as the fragment of RuBisCO LSU (EC 4.1.1.39). Phosphorylation of the RuBisCO LSU may be important
in cold tolerance.
Received: 7 July 1998 / Accepted: 19 December 1998 相似文献
9.
Hai-Hong Gu Shu-Shun Zhan Shi-Zhong Wang Ye-Tao Tang Rufus L. Chaney Xiao-Hang Fang Xin-De Cai Rong-Liang Qiu 《Plant and Soil》2012,350(1-2):193-204
Background and aims
Silicon (Si) was suggested to enhance plant resistance to toxic elements, and its beneficial role was mainly based on external and internal plant mechanisms. This work aimed at investigating the internal effect of Si on zinc (Zn) detoxification to rice (Oryza sativa L., cv. Tian You 116) seedlings.Methods
In a hydroponic experiment, we examined the uptake, xylem loading and localization of Zn in rice seedlings under the condition of 200?μM Zn contamination with the additional silicate supply at three levels ( 0, 0.5 and 1.8?mM).Results
The silicate addition significantly increased the seedling biomass, and decreased Zn concentration in both root and shoot of seedlings and in xylem sap flow. Zinpyr-1 fluorescence test and Energy-dispersive X-ray spectroscopy analysis showed the concentration of biologically active Zn2+ decreased, and Zn and Si co-localized in the cell wall of metabolically less active tissues, especially in sclerenchyma of root. The fractionation analysis further supported silicate supply increased about 10% the cell wall bound fraction of Zn.Conclusions
This study suggests the Si-assisted Zn tolerance of rice is mainly due to the reduction of uptake and translocation of excess Zn, and a stronger binding of Zn in the cell wall of less bioactive tissues might also contribute to some degree. 相似文献10.
Background and Aims
Anoxic conditions are seldom considered in root iron plaque induction of wetland plants in hydroponic experiments, but such conditions are essential for root iron plaque formation in the field. Although ferrous ion availability and root radial oxygen loss capacity are generally taken into account, neglect of anoxic conditions in root iron plaque formation might lead to an under- or over-estimate of their functional effects, such as blocking toxic metal uptake. This study hypothesized that anoxic conditions would influence root iron plaque formation characteristics and translocation of Zn and Cd by rice seedlings.Methods
A hydroponic culture was used to grow rice seedlings and a non-disruptive approach for blocking air exchange between the atmosphere and the induction solution matrix was applied for root iron plaque formation, namely flushing the headspace of the induction solution with N2 during root iron plaque induction. Zn and Cd were spiked into the solution after root iron plaque formation, and translocation of both metals was determined.Key Results
Blocking air exchange between the atmosphere and the nutrient solution by N2 flushing increased root plaque Fe content by between 11 and 77 % (average 31 %). The N2 flushing treatment generated root iron plaques with a smoother surface than the non-N2 flushing treatment, as observed by scanning electron microscopy, but Fe oxyhydroxides coating the rice seedling roots were amorphous. The root iron plaques sequestrated Zn and Cd and the N2 flushing enhanced this effect by approx. 17 % for Zn and 71 % for Cd, calculated by both single and combined additions of Zn and Cd.Conclusions
Blocking of oxygen intrusion into the nutrient solution via N2 flushing enhanced root iron plaque formation and increased Cd and Zn sequestration in the iron plaques of rice seedlings. This study suggests that hydroponic studies that do not consider redox potential in the induction matrices might lead to an under-estimate of metal sequestration by root iron plaques of wetland plants. 相似文献11.
Silicon deposition in the root reduces sodium uptake in rice (Oryza sativa L.) seedlings by reducing bypass flow 总被引:2,自引:0,他引:2
Sodium chloride reduces the growth of rice seedlings, which accumulate excessive concentrations of sodium and chloride ions in their leaves. In this paper, we describe how silicon decreases transpirational bypass flow and ion concentrations in the xylem sap in rice (Oryza sativa L.) seedlings growing under NaCl stress. Salt (50 mM NaCl) reduced the growth of shoots and roots: adding silicate (3 mM) to the saline culture solution improved the growth of the shoots, but not roots. The improvement of shoot growth in the presence of silicate was correlated with reduced sodium concentration in the shoot. The net transport rate of Na from the root to shoot (expressed per unit of root mass) was also decreased by added silicate. There was, however, no effect of silicate on the net transport of potassium. Furthermore, in salt-stressed plants, silicate did not decrease the transpiration, and even increased it in seedlings pre-treated with silicate for 7 d prior to salt treatment, indicating that the reduction of sodium uptake by silicate was not simply through a reduction in volume flow from root to shoot. Experiments using trisodium-8-hydroxy-1,3,6-pyrenetrisulphonic acid (PTS), an apoplastic tracer, showed that silicate dramatically decreased transpirational bypass flow in rice (from about 4.2 to 0.8%), while the apparent sodium concentration in the xylem, which was estimated indirectly from the flux data, decreased from 6.2 to 2.8 mM. Direct measurements of the concentration of sodium in xylem sap sampled using Philaenus spumarius confirmed that the apparent reduction was not a consequence of sodium recycling. X-ray microanalysis showed that silicon was deposited in the outer part of the root and in the endodermis, being more obvious in the latter than in the former. The results suggest that silicon deposition in the exodermis and endodermis reduced sodium uptake in rice (Oryza sativa L.) seedlings under NaCl stress through a reduction in apoplastic transport across the root. 相似文献
12.
13.
Anthers of two rice (Oryza sativa L.) varieties, Lunhui 422 (P1) and Jinzao 5 (P2), their F1, F2 and first backcross generation-F1 x Lunhui 422 (B1), and F1 x Jinzao 5 (B2)-were cultured in L8 medium to study the inheritance of rice anther culturability using generation mean analysis. Significant effects of generation were observed for the four traits measured: anther response (%), frequency of callus induction (%), frequency of callus differentiation (%) and culture efficiency (%). Variation among the generations was similar for all traits: significant differences were found among six generations and the means of the P2 and B2 were significantly lower than those of the other generations. The frequency of callus differentiation showed a nonsignificant difference among the P1, F1, F2 and B1 generations which had slightly high values than the P2 and B2. Additive genetic variance (VA) was higher than non-additive genetic variance (VD) for anther response and frequency of callus induction. However, AV was lower than VD for frequence of callus differentiation and culture efficiency, VA was significant for all traits except for the culture efficiency, and VD was nonsignificant for all traits except for the frequency of callus differentiation. On the other hand, environmental variation (VE) was significant for the 4 traits. Narrow-sense heritability estimates were 95.52%, 82.19% and 13.54% for anther response, frequency of callus induction and culture efficiency, respectively.Abbreviations 2,4-d
2,4-dichlorophenoxyacetic acid
- IAA
indole-3-acetic acid 相似文献
14.
The results of anther culture of F2 pollen issued from 23 single crosses are presented. A relation between the morphology of the panicle and the microspore stage was established. After cold-pretreatment (8 days at 4°C), the anthers were cultured on the callus-induction medium N6 supplemented with 1 mg l–1 naphthaleneacetic acid. The calli were transferred to MS plant regeneration medium supplemented with 3 mg l–1 kinetin + 0.5 mg l–1 naphthaleneacetic acid. The induction frequency varied from 0.22% to 29% and the regeneration frequency from 0% to 144.4%, dependent upon the crosses used. On average, 27% of the plants obtained were albinos and 59% of the green plants underwent spontaneous chromosome doubling. Thirtynine doubled haploid lines were evaluated and multiplied in the field. Lines with an excellent behaviour in upland culture conditions were selected from two crosses. 相似文献
15.
This paper reports experiments performed to investigate the influence of various concentrations of streptomycin sulphate on a few parameters of importance in the metabolism of rice (Oryza sativa L.) seedlings. It was shown that respiration rate was accelerated by streptomycin. The specific activities of catalase and peroxidase decreased whereas IAA oxidase increased with increasing streptomycin concentrations. Increased activities of all these enzymes were apparent on a dry weight basis suggesting increased succulence caused by streptomycin treatment. There was a considerable rise in the water soluble protein content following streptomycin application. It may be suggested that growth inhibition by streptomycin results from reduction in the auxin level owing to enhanced auxin destruction. 相似文献
16.
Iron toxicity frequently affects lowland rice and leads to oxidative stress via the Fenton reaction. Tolerance mechanisms were investigated in contrasting genotypes: the intolerant IR29 and the tolerant recombinant inbred line FL483. Seedlings were exposed to 1000 mg L‐1 ferrous iron, and the regulation of genes involved in three hypothetical tolerance mechanisms was investigated (I) Iron uptake, partitioning and storage. The iron concentration and speciation in different plant tissues did not differ significantly between genotypes. Sub‐cellular iron partitioning genes such as vacuolar iron transporters or ferritin showed no genotypic differences. (II) Antioxidant biosynthesis. Only one gene involved in carotenoid biosynthesis showed genotypic differences, but carotenoids are unlikely to scavenge the reactive oxygen species (ROS) involved in Fe toxicity, i.e. H2O2 and hydroxyl radicals. (III) Enzymatic activities for ROS scavenging and antioxidants turnover. In shoots, glutathione‐S‐transferase and ascorbate oxidase genes showed genotypic differences, and consistently, the tolerant FL483 had lower dehydroascorbate reductase and higher ascorbate oxidase activity, suggesting that high rates ascorbate reduction confer sensitivity. This hypothesis was confirmed by application of exogenous reduced ascorbate or L‐galactono‐1,4‐lactone, which increased lipid peroxidation under iron toxic conditions. Our results demonstrate in planta pro‐oxidant activity of reduced ascorbate in the presence of iron. 相似文献
17.
Thorny Chanu Thounaojam Piyalee Panda Shuvasish Choudhury Hemanta Kumar Patra Sanjib Kumar Panda 《Protoplasma》2014,251(1):61-69
Rice (Oryza sativa L.) seedlings were treated with different concentrations of copper (Cu) either in presence or absence of zinc (Zn), and different events were investigated to evaluate the ameliorative effect of Zn on Cu stress. In presence of high Cu concentration, growth of both root and shoots were considerably reduced. Decline in elongation and fresh mass was observed in root and shoot. Zn alone did not show any considerable difference as compared to control, but when supplemented along with high concentration Cu, it prompted the growth of both root and shoot. After 7 days, root growth was 9.36 and 9.59 cm, respectively, at 200 and 500 μM of Cu alone as compared to 10.59 and 12.26 cm at similar Cu concentrations, respectively, in presence of Zn. Cu accumulation was considerably high after 7 days of treatment. In absence of Zn, significant accumulation of Cu was observed. Zn supplementation ameliorated the toxic impact of Cu and minimized its accumulation. Cu treatment for 1 and 7 days resulted in a dose-dependent increase in hydrogen peroxide (H2O2). When Cu was added in presence of Zn, the H2O2 production in root and shoot was reduced significantly. The increase in H2O2 production under Cu stress was accompanied by augmentation of lipid peroxidation. In absence of Zn, Cu alone enhanced the malondialdehyde (MDA) production in both root and shoot after 1 and 7 days of treatment. The MDA content drastically reduced in root and shoot as when Zn was added during Cu treatment. The activities of antioxidant enzymes like superoxide dismutase (SOD), catalase (CAT), and guaiacol peroxidase (GPX) were elevated under Cu stress both in root and shoot. Addition of Zn further stimulated the activities of these enzymes. Both ascorbate (AsA) and glutathione (GSH) contents were high under Cu stress either in presence or absence of Zn. The results suggests that Zn supplementation improves plant survival capacity under high Cu stress by modulating oxidative stress through stimulation of antioxidant mechanisms and restricts the accumulation of toxic concentrations of Cu. 相似文献
18.
Studies on the growth and respiration of batch suspension cultures of rice (Oryza sativa L.) in a reference medium containing Murashige-Skoog salts, 2% (w/v) sucrose and yeast extract are reported. It was found that the yeast extract contributed 70% of the phosphate in this medium, and that the cells grew equally well in continued subculture in a defined medium which contained 6 mM phosphate and 3% (w/v) sucrose and the remaining Murashige-Skoog salts. Cell clumps (up to 1.5 mm diameter) were prevalent in the initial cultures in the reference medium. In such cultures the critical O2 pressure of cell respiration was high (125 M), and ethanol accumulated. When cell clumps were routinely removed during several weekly subcultures on the defined medium cultures were obtained in which no clumps were present, the critical O2 pressures was decreased to 40 M and no ethanol accumulated.This work was supported by grant PCM-84-03542 from the U.S. National Science Foundation. 相似文献
19.
To address the issue of water eutrophication and to use water more effectively, we conducted experiments on rice (Oryza sativa L.) grown in floating culture. From 2009 to 2011, we compared the photosynthesis and root characteristics of the rice, hybrid line Zhuliangyou 02, grown under a conventional tillage and in a floating culture in Huaihua, the home of hybrid rice. Rice in the floating culture showed a higher net photosynthetic rate and stomatal conductance than that under the conventional tillage. The activities of phosphoenolpyruvate carboxylase and NADP-malic enzyme were 32 and 28% higher, respectively, in rice in the floating culture than under the conventional tillage. Rice in the floating culture also showed significantly greater number of roots, root activity, and antioxidant enzyme activity than that under the conventional tillage. Compared with rice under the conventional tillage, rice in the floating culture had 18 and 24% higher tiller number and effective panicle number, respectively. These results suggested that the floating culture system can promote rice production through enhancing root absorption, increasing effective panicle number, and improving the photosynthetic rate. In addition, rice cultivated in the floating culture could remove excess nutrients from water, which addresses the problems of a lack of arable land and water pollution. 相似文献
20.
S. S. Virmani R. C. Aquino G. S. Khush 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1982,63(4):373-380
Summary Studies conducted at the International Rice Research Institute (IRRI) during 1980 and 1981 have shown up to 73% heterosis, 59% heterobeltiosis and 34% standard heterosis for yield in rice. The latter was estimated in comparison to commercial varieties: IR36 and IR42 (yield 4–5 t/ha in wet season trials and 7–8 t/ha in dry season trials). Generally speaking, absolute yield was lower and extent of standard heterosis was higher in wet season than in dry season with some exception. Yields up to 5.9 t/ha (22% standard heterosis) in the wet season and 10.4 t/ha (34% standard heterosis) in the dry season were obtained. Most of the hybrids performed better in some season while some performed better in both seasons. Hybrids showed better lodging resistance although they were 5–10 cm taller. F1 hybrids had significant positive correlations with the parental traits viz., yield (r = 0.446), tillering (r = 0.746), height (r = 0.810) and flowering (r = 0.843). Selection of parents among elite breeding lines on the basis of their per se yield performance, diverse origin and resistance to insects and diseases should give heterotic combination. Yield advantage of hybrids was due primarily to increase in number of spikelets per unit area even though tiller number was reduced. Grain weight was either the same or slightly higher. High yielding hybrids also showed significant heterosis and heterobeltiosis for total dry matter and harvest index. For commercial utilization of heterosis in rice, effective male sterility and fertility restoration systems are available and up to 45% natural outcrossing on male sterile lines has been observed. Consequently, F1 rice hybrid have been successfully developed and used in China. Prospects of developing hybrid rice varieties elsewhere appear bright especially in countries that have organized seed production, certification and distribution programs and where hybrid seed can be produced at a reasonable cost. 相似文献