摘要:

In the United States rice (Oryza sativaL.) is entirely flood irrigated. Delaying the application of the floodwater beyond the recommended time is practiced by some Arkansas producers and may (with supplemental rainfall) potentially reduce the water inputs required to produce a crop. Water stress, however, may affect root growth characteristics which could impact fertility management decisions relative to continuous flood culture. Therefore a field study was initiated to identify the responses of root and shoot growth and yield to water management and location. Two water management treatments were imposed on the ‘Tebonnet’ cultivar, i) normal water management where a flood was applied at the four‐ to five‐leaf stage (continuous flood), and ii) flood delayed (but with supplemental irrigation) until 1.25 cm internode elongation. Studies were located on two soils in eastern Arkansas, a Sharkey clay and Crowley silt loam in 1988 and 1989. The floodwater was removed from plots approximately 10 d before harvest. Although there was no treatment effect on total root length, root length densities showed an inconsistent proliferation in response to the delayed flood at the 0–10 cm and 30–40 cm soil depths. This proliferation in root length density differed between locations and years. Delayed flood reduced plant height in 1988 only up to heading and there was a trend for reduced leaf area index in both years. Grain yield was not significantly affected by water management. Yield was greater, however, for rice grown on the Crowley soil than the Sharkey soil by nearly 1100 kg/ha. This yield increase may have been due to higher tiller production on the Crowley soil. Root lengths differed between locations with higher root lengths measured on the Sharkey. Results suggest that delayed flooding does not severely stress the rice plant and yields similar to those achieved with continuous flood can be obtained.

ISSN:0190-4167    

DOI:10.1080/01904169209364359

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

This paper describes the transparent or ‘glass wall’ techniques for observing root growth in plantsin situ. The techniques described include rhizotrons, minirhizotrons, and slant tubes and slant boxes. Brief descriptions of the techniques are presented along with some of the major advantages and disadvantages of each method.

ISSN:0190-4167    

DOI:10.1080/01904169209364360

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Roots represent a considerable carbon cost for plants. Furthermore, plants vary considerably in how carbon is expended for belowground processes. One attribute that varies widely among species is the investment of root biomass in the production of root length. Relatively thin roots have a high specific root length (SRL) or length: dry weight ratio. Since water and nutrient uptake is based more upon root length than mass, one might conclude that species of high SRL invest their root biomass more efficiently than species of low SRL. This, however, ignores many other functional attributes of roots that may permit coarse lateral roots to be more adaptive than fine lateral roots under certain environmental conditions. In leaves, studies on the relationship of structure and function suggest that evergreen plants with greater leaf longevity commonly have thicker leaves, lower photosynthetic capacity, and lower respiration rates than deciduous plants. These kinds of relationships may also be true for thick roots (low SRL). Limited evidence suggests that species of high SRL tend to have greater plasticity in root growth, greater physiological capacity for water and nutrient uptake, but less root longevity and less mycorrhizal dependency than species of low SRL. More study is needed before the physiological traits associated with variation in length‐biomass ratio are understood.

ISSN:0190-4167    

DOI:10.1080/01904169209364361

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Four methods were used to characterize root distribution under drip (trickle) irrigation:root weight, cation exchange capacity (CEC), uptake of86Rb, and the line intersect method. Trickle irrigated tomato(Lycopersicon esculentumMill. var. Naama) and peanut(Arachis hvpogeaeL. var. shulamit) plants were grown on sandy soil (Typic Torripsamment) and their roots were used for the study. The four methods showed that most of the roots are concentrated close to the emitter. A linear correlation was found between root weight and the uptake of86Rb. This indicated that although roots near the emitter seem to be relatively old, the uptake activity is also concentrated there. Furthermore, it is apparent that the effect of the limited root distribution is even more pronounced when using CEC as an indicator for fine roots or surface area, than when using weight as an indicator. It was therefore concluded that all criteria emphasized the restricted distribution of roots as well as their activity in the wetted volume of soil beneath the emitter. When saline water was applied, more roots were found in the leached soil volume than in the saline part of the trickle irrigated hemisphere. In the fresh water irrigated soil, the roots extended also to the periphery of the wettcd volume.

ISSN:0190-4167    

DOI:10.1080/01904169209364362

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The underlying mechanisms by which excessive salinity reduces plant growth are not well understood. A few reports indicate that salinity reduces the hydraulic conductivity of the roots in salt sensitive legumes such as bean and lupin: However salinity had little effect on root conductivity in barley, a cereal plant which is relatively salt tolerant. In order to determine whether roots of other cereal plants respond like those of barley, we investigated the effects of salinity on root growth and root hydraulic conductivity in maize seedlings. The length of the primary roots was reduced by 54% after 4d exposure to 0.1 strength Hoagland's solution salinized with 100 mM NaCl. Root length was only reduced by 20% when 10 mM calcium was also added to the salinized root medium. Salinization with 100 mM NaCl reduced hydraulic conductivity in the apical 4 cm of the primary roots by 80% (from 4.7±1.5x108m/s/MPa to 1.0±0.3xl0‐8m/s/MPa) and by 51% when 10 mM calcium was also added.

ISSN:0190-4167    

DOI:10.1080/01904169209364363

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Root growth was monitored in hydroponic systems under greenhouse conditions. Inoculation withAzospirillum brasilenseincreased the total number and length of adventitious roots ofSorghum bicolorby 33–40% over non‐inoculated controls. This resulted from a higher rate of growth, earlier root appearance and a greater elongation rate of individual sorghum roots. Inoculation also led to a 25–40% increase in hydraulic conductivity of the inoculated root system as compared to controls. In plants subjected to an osmotic stress by the addition of polyethylene glycol (PEG 6000) to the growth medium to produce an osmotic potential of ‐2.0 bar, inoculation significantly diminished most of the drastic adverse effects on root growth. It was concluded that beneficial effects ofAzospirillumon the growth and yield of sorghum can be attributed largely to improved growth and function of the root system.

ISSN:0190-4167    

DOI:10.1080/01904169209364364

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Greenhouse experiments were conducted to determine the effect of different physical structures of the rooting matrix on root development, rhizobial growth, nodulation and nitrogenase activity in the rhisosphere ofMedicago sativaL. andMacroptilium atropurpureum.

ISSN:0190-4167    

DOI:10.1080/01904169209364365

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:0190-4167    

DOI:10.1080/01904169209364366

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Soft red winter wheat(Triticum aestivumL. cv Hart) was used as a test crop in a bioassay technique to assess acid soil chemical constraints in major hill land soils of the Appalachian Region. Seedling root growth was related to amounts and forms of Al in soil solution and Al extracted by 0.01M CaCl2, 1M KC1, 0.5M CuCl2, and 0.33M LaCl3. Aluminum determined in the various extractants, total soil solution Al and soil solution Al reacting with 8‐hydroxy‐quinoline, pyrocatechol violet, and aluminon showed large differences in root growth prediction ability. In general, Al extracted by 0.01M CaCl2was a good predictor of root growth. Root elongation was more inhibited in subsurface horizons than in surface horizons. Although surface horizons had the lowest mean pH, the presence of high levels of exchangeable cations tended to ameliorate the Al toxicity. The root bioassay technique adapted here should be useful in assessing the potential Al toxicity of diverse soil types.

ISSN:0190-4167    

DOI:10.1080/01904169209364367

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

This study addresses the need to determine accurately mineral element concentrations in roots grown in soil so that valid measurements of element uptake and translocation can be made. Wheat(Triticum aestivumL., cv ‘Nugains') was planted in seven soils. Two seeds were planted in each soil and two seeds were planted in a Versapor bag that had been buried in the soil in the same 1.3‐L ceramic pot. The bag separated the roots from soil. The plants were harvested four weeks after planting. Tops and roots were analyzed separately for 12 elements. Estimates were made for the contribution of each element from soil particles contained in the sampled portion, by using the titanium (Ti) concentration in root sample as a measure of contamination by soil. Concentration corrections ranged from an increase of 14% for Na to a decrease of 131% for Al. Corrected estimates of Al and Fe concentrations in the sample portion were usually unreasonably high or low. In most cases, corrected concentration estimates appeared to be reasonable for most elements. Roots grown within Versapor bags do not appear to be particularly good models of roots growing freely in soil, with respect to root tissue element concentration.

ISSN:0190-4167    

DOI:10.1080/01904169209364368

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor