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  • 1
    Electronic Resource
    Electronic Resource
    Variation in root penetration ability, osmotic adjustment and dehydration tolerance among accessions of rice adapted to rainfed lowland and upland ecosystems (2001)
    Oxford, UK : Blackwell Publishing Ltd
    Plant breeding 120 (2001), S. 0 
    Details
    ISSN: 1439-0523
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Drought is the major constraint limiting rainfed rice production. The ability of rice roots to penetrate compacted soils and therefore to increase water extraction capacity, osmotic adjustment and dehydration tolerance of leaves enables the plant to tolerate drought. Experiments were conducted to determine the extent of genetic variation in root penetration index, osmotic adjustment and dehydration tolerance among indica accessions adapted to rainfed lowlands as well as traditional varieties from rainfed uplands. Root penetration index was evaluated in a system using wax–petrolatum layers to simulate soil compaction. Osmotic adjustment and dehydration tolerance were studied under slow development of water stress. Substantial genetic variation was found for root penetration index, osmotic adjustment and dehydration tolerance among indica ecotypes from lowlands, and the study of several traditional varieties from uplands showed variation in root penetration index and related root traits. An indica accession, IR58821-23-B-1-2-1 had a high root penetration index of 0.38. The accessions, IR61079-33-1-2-2-3, IR62266-42-6-2 and IR63919-38-B-1 had high osmotic adjustment capacities (1.91, 1.90 and 1.78 MPa, respectively); IR61079-33-1-2-2-3 also had high dehydration tolerance. Good osmotic adjustment and dehydration tolerance were associated with poor root system. The traditional varieties ‘Kallurundaikar’ and ‘Norungan’ had higher root penetration indices (0.46 and 0.43, respectively), than even the japonica accessions. The study identified indica accessions and traditional varieties with superior root- and shoot-related drought resistance traits that could be used in breeding for drought resistance in rice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1439-0523.2001.00578.x
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of nitrogen nutrition and root medium water potential on growth, nitrogen uptake and osmotic adjustment of rice (1984)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 60 (1984), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effects of nitrogen (N) nutrition on growth, N uptake and leaf osmotic potential of rice plants (Oryza sativa L. ev. IR 36) during simulated water stress were determined. Twenty-one-day-old seedlings in high (28.6 × 10 −4M) and low (7.14 × 10 4M) N levels were exposed to decreased nutrient solution water potentials by addition of polyethylene glycol 6000. The roots were separated from the solution by a semi-permeable membrane. Nutrient solution water potential was −0.6 × 105 Pa and was lowered stepwise to −1 × 105, −2 × 105, −4 × 105 and −6 × 105 Pa at 2-day intervals. Plant height, leaf area and shoot dry weight of high and low nitrogen plants were reduced by lower osmotic potentials of the root medium. Osmotic stress caused greater shoot growth reduction in high N than in low N plants. Stressed and unstressed plants in 7.14 × 104M N had more root dry matter than the corresponding plants in 28.6 × 104M N. Dawn leaf water potential of stressed plants was 1 × 105 to 5.5 × 105 Pa lower than nutrient solution water potential. Nitrogen-deficient water-stressed plants, however, maintained higher dawn leaf water potential than high nitrogen water-stressed plants. It is suggested that this was due to higher root-to-shoot ratios of N deficient plants. The osmotic potentials of leaves at full turgor for control plants were about 1.3 × 105 Pa higher in 7.14 × 10−4M than in 28.6 × 10−4M N and osmotic adjustment of 2.6 × 105 and 4.3 × 105 Pa was obtained in low and high N plants, respectively. The nitrogen status of plants, therefore, affected the ability of the rice plant to adjust osmotically during water stress.Plant water stress decreased transpiration and total N content in shoots of both N treatments. Reduced shoot growth as a result of water stress caused the decrease in amount of water transpired. Transpiration and N uptake were significantly correlated. Our results show that nitrogen content is reduced in water-stressed plants by the integrated effects of plant water stress per se on accumulation of dry matter and transpiring leaf area as well as the often cited changes in soil physical properties of a drying root medium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1984.tb04919.x
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  • 3
    Electronic Resource
    Electronic Resource
    Epicuticular Wax and Cuticular Resistance in Rice (1979)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 47 (1979), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: High leaf cuticular resistance has been reported as a component adaptation of plants to drought prone regions, Experiments were conducted to evaluate and characterize the role of epicuticular wax as a component of cuticular resistance to water vapor loss from rice (Oryza sativa L.) leaves. This information is necessary to determine the applicability of including higher cuticular resistance in an upland rice breeding program and to evaluate potential selection methods.Diffusion porometry, electron microscopy, and gas liquid chromatography were employed. Measurement of cuticular resistance by leaf diffusive resistance porometry after stomatal closure by exposure of rice leaves to pure CO2 for 15 min was found sufficient to induce complete stomatal closure regardless of light level, and was superior to dark acclimation for this purpose.Removal of epicuticular wax from rice leaves by chloroform dip significantly reduced the cuticular resistance. Stressed plants were observed to increase cuticular resistance, illustrating the responsive nature of this characteristic.Gas liquid chromatography (GLC) of the chloroform leaf dip proved to be an expedient method of characterizing both quantitative and qualitative differences in the epicuticular wax of rice cullivars. The porometry and GLC techniques may be useful in selecting parents, spot checking in a pedigree program, or checking lines reaching the yield testing stage, but ate not well suited lor mass screening early generation progeny.Significant differences were found in the two rice cultivurs, ‘63–83′, an upland adapted rice from West Africa, and “IR20′, bred and selected in submerged paddy culture in ihc Philippines, by tlie above methods of characterizing cuticular resistance and epicuticular wax. These results are of ecological significance to plant breeders.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1979.tb06520.x
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  • 4
    Electronic Resource
    Electronic Resource
    Photosynthetic Response to Water Stress in Phaseolus vulgaris (1977)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 40 (1977), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Water stressed Phaseolus vulgaris L. plants were monitored to detect the relationships between net photosynthesis, transpiration, boundary layer plus stomatal resistance, mesophyll resistance, CO2 compensation point, ribulose, 1,5-diphosphate carboxylase activity and leaf water potential.At full expansion, the first trifoliate leaves of greenhouse grown bean plants were subjected to water stress by withholding irrigation. Gas exchange and enzyme activity of the central trifoliolate leaflets were monitored as leaf water potential decreased.Although increased stomatal resistance appeared to be the primary causal factor of reduced net photosynthesis, increased mesophyll resistance and decreased ribulose 1,5-diphosphate carboxylase activity further documented the role of non-stomatal factors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1977.tb01505.x
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  • 5
    Electronic Resource
    Electronic Resource
    Locating genes associated with root morphology and drought avoidance in rice via linkage to molecular markers (1995)
    Springer
    Theoretical and applied genetics 90 (1995), S. 969-981 
    Details
    ISSN: 1432-2242
    Keywords: Drought, Rice ; QTL analysis ; Root morphology ; Molecular markers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This research was undertaken to identify and map quantitative trait loci (QTLs) associated with five parameters of rice root morphology and to determine if these QTLs are located in the same chromosomal regions as QTLs associated with drought avoidance/tolerance. Root thickness, root:shoot ratio, root dry weight per tiller, deep root dry weight per tiller, and maximum root length were measured in three replicated experiments (runs) of 203 recombinant inbred lines grown in a greenhouse. The lines were from a cross between indica cultivar Co39 andjaponica cultivar Moroberekan. The 203 RI lines were also grown in three replicated field experiments where they were drought-stressed at the seedling, early vegetative, and late-vegetative growth stage and assigned a visual rating based on leaf rolling as to their degree of drought avoidance/tolerance. The QTL analysis of greenhouse and field data was done using single-marker analysis (ANOVA) and interval analysis (Mapmaker QTL). Most QTLs that were identified were associated with root thickness, root/shoot ratio, and root dry weight per tiller, and only a few with deep root weight. None were reliably associated with maximum root depth due to genotype-by-experiment interaction. Root thickness and root dry weight per tiller were the characters found to be the least influenced by environmental differences between greenhouse runs. Correlations of root parameters measured in greenhouse experiments with field drought avoidance/tolerance were significant but not highly predictive. Twelve of the fourteen chromosomal regions containing putative QTLs associated with field drought avoidance/tolerance also contained QTLs associated with root morphology. Thus, selecting for Moroberekan alleles at marker loci associated with the putative root QTLs identified in this study may be an effective strategy for altering the root phenotype of rice towards that commonly associated with drought-resistant cultivars.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00222910
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  • 6
    Electronic Resource
    Electronic Resource
    Comparison of pressure chamber and psychrometer estimates of leaf water potential in rice (1981)
    Springer
    Plant and soil 62 (1981), S. 313-317 
    Details
    ISSN: 1573-5036
    Keywords: Dew point hygrometer ; Oryza sativa L. ; Pressure chamber
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The need to compare pressure-chamber estimates of leaf water potential with a psychrometric method has been established for several crop species. We investigated this relationship for rice (Oryza sativa L.) as well as the need to protect leaves from water loss during sampling and measuring period in the pressure chamber. Two rice cultivars grown in containers on a clay-loam soil were stressed to varying degrees by withholding water. Fully expanded leaves were sampled for estimation of leaf water potential by the dew point hygrometer and pressure-chamber techniques. The same leaf was used in both methods allowing direct comparison. Additionally, two alternative methods of leaf handling for measurement by the pressure chamber technique were compared. Protection of leaf samples against water loss during excision, transport and handling was found to be more important at higher leaf water potentials (〉−1.0 MPa). The two cultivars used appeared to differ in their response to protection of the leaf sample. These results serve to further caution pressure chamber users on extrapolating comparisons between the two measurement methods and between tissue handling techniques even within a crop species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02374096
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  • 7
    Electronic Resource
    Electronic Resource
    Water stress effects on leaf elongation, leaf water potential, transpiration, and nutrient uptake of rice, maize, and soybean (1987)
    Springer
    Plant and soil 103 (1987), S. 155-168 
    Details
    ISSN: 1573-5036
    Keywords: leaf elongation rate ; leaf water potential ; maize ; nitrogen ; nutrient uptake ; phosphorus ; potassium ; rice ; soybean ; transpiration rate ; water stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A pot experiment was conducted in the greenhouse to determine and compare the responses of rice (Oryza sativa L. var, IR 36), maize (Zea mays L. var. DMR-2), and soybean (Glycine max [L.] Merr. var. Clark 63) to soil water stress. Leaf elongation, dawn leaf water potential, transpiration rate, and nutrient uptake in stressed rice declined earlier than in maize and soybean. Maize and soybean, compared with rice, maintained high dawn leaf water potential for a longer period of water stress before leaf water potential. Nutrient uptake under water stress conditions was influenced more by the capacity of the roots to absorb nutrients than by transpiration. Transport of nutrients to the shoots may occur even at reduced transpiration rate It is concluded that the ability of maize and soybean to grow better than rice under water stress conditions may be due to their ability to maintain turgor as a result of the slow decline in leaf water potential brought about by low, transpiration rate and continued uptake of nutrient, especially K, which must have allowed osmotic adjustment to occur.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02370385
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  • 8
    Electronic Resource
    Electronic Resource
    Root pulling resistance in rice: Inheritance and association with drought tolerance (1985)
    Springer
    Euphytica 34 (1985), S. 905-913 
    Details
    ISSN: 1573-5060
    Keywords: Orvza sativa L. ; rice ; drought tolerance ; genetics ; leaf water potential ; root pulling resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Avoidance of drought stress is commonly associated with root system characteristics and root development. The inheritance of root pulling resistance in rice (Oryza sativa L.) was investigated and its relationship with visual field scores for drought tolerance was studied. Transgressive segregation for high root pulling resistance was observed in 3 crosses (high x high, low x high, and intermediate x intermediate). Both dominant and additive genes control the variation. F1 superiority for high root pulling resistance was observed and could be exploited in an F1 hybrid breeding program. F2 distribution curves indicated that plants highly resistant to root pulling can be obtained not only from low x high and high x high crosses, but also from intermediate x intermediate crosses. Root pulling resistance in rice has a low heritability (39 to 47%). Thus, breeding for a high root pulling resistance may best be accomplished by selection based on line means rather than individual plant selection. Field screening showed significant differences in leaf water potential among random F3 lines. F3 lines with higher leaf water potential had better visual scores for drought tolerance. Visual drought tolerance scores were correlated with root pulling resistance. Plants with high root pulling resistance had the ability to maintain higher leaf water potentials under severe drought stress. The usefulness of the root pulling technique in selecting drought tolerant genotypes was confirmed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00035430
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  • 9
    Electronic Resource
    Electronic Resource
    Evaluation of a simple technique for characterizing rice root systems in relation to drought resistance (1981)
    Springer
    Euphytica 30 (1981), S. 283-290 
    Details
    ISSN: 1573-5060
    Keywords: Oryza sativa ; rice ; root pulling force ; drought resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Drought is a constraint to rice yields in much of Asia's rainfed rice crop. Although genotypic variation for root system characteristics is well documented in this semiaquatic species, little improvement of rice for drought resistance has been attempted. No simple method to evaluate root systems exists. In this paper we report the development and testing of a simple device to measure the pulling force required to uproot rice seedlings. The force required to pull rice seedlings from the paddy soil was correlated with root weight, root branching and thick root number. The capability to separate rice cultivars by this technique and relationship of the root pulling force to other drought screening methods are illustrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00033989
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  • 10
    Electronic Resource
    Electronic Resource
    Water deficits and nitrogen uptake as affected by water table depth in rice (Oryza sativa L.) (1984)
    Springer
    Plant and soil 80 (1984), S. 127-132 
    Details
    ISSN: 1573-5036
    Keywords: Entic pellusterts ; Guadalupe clay ; Isothermic clayey mixed aquic tropudalf ; Maahas clay ; Oryza sativa L ; Nitrogen rates ; Water stress ; Water table depth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Nitrogen responsiveness of modern rice cultivars was a key factor in their success in irrigated fields. However, these cultivars and the associated high level of nitrogen fertilization have generally not been adopted in poorly irrigated and rainfed rice sectors. Rice crops grown with inadequate water show less nitrogen uptake although contradictory results are to be found in the literature. In the current study, varying degrees of inadequate irrigation decreased both nitrogen uptake and grain yield in the modern semidwarf rice cultivar IR36. Although there was a linear relationship between nitrogen uptake and grain yield across the two experimental locations, the response functions of nitrogen uptake and grain yield regressed on nitrogen rate and irrigation treatment varied greatly between the two sites. The most significant difference in the locations was the depth to the water table during the crop season. Although the soil surface dried and cracked in both locations because of inadequate surface irrigation, the lower profile must have been affected by water table depth. These findings illustrate the importance of understanding the role of subsurface water depth in soil nitrogen management of partially irrigated and rainfed rice. In addition they provide an explanation for past contradictory reports on the interaction of nitrogen fertilization and irrigation inadequacy on rice crop yield.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02232946
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