ISSN:0190-4167    

DOI:10.1080/01904169209364349

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:0190-4167    

DOI:10.1080/01904169209364350

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:0190-4167    

DOI:10.1080/01904169209364351

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:0190-4167    

DOI:10.1080/01904169209364352

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Proper growth and function of plant roots are critical for crop production. The study of root systems to elucidate their link to production is expensive and labor intensive. The use of computer simulations, both to summarize existing knowledge of root system growth and to guide research promises to speed our understanding of the complex interdependence of the crop root and shoot systems. Of the many factors restricting root penetration into the profile, soil strength is perhaps the most difficult to describe and measure. We propose to compute with general elastic theory a soil‐imposed resistance to root penetration using an elastic modulus for the soil. The application of the theory to agricultural soils is discussed and the specific application to root expansion in a soil cylinder is developed. Computations of root length density profiles and root depth over time in both uniform and layered profiles with known elastic modulis are provided as examples of predicted root growth based on this theory.

ISSN:0190-4167    

DOI:10.1080/01904169209364353

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Roots have been intensively studied for over one hundred years, and yet little is really known of their morphology and development in vivo. Increasing evidence suggests that there are five or more types of roots, each with distinct genetic, developmental, and physiological characteristics. The presence of these different types and the demonstration that several of the more thoroughly studied types are functionally different suggests that much of the past research on root physiology needs to be re‐examined. The evidence suggests that the roots routinely studied in laboratory experiments are normally either non‐functional in the field, or have different functional characteristics than the majority of the active roots on field grown plants.

ISSN:0190-4167    

DOI:10.1080/01904169209364354

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The light environment of a plant shoot can affect its root size and the shoot/root biomass ratio. Photoperiodic influence on shoot/root ratios of first‐year biennial sweetclover(Melilotus albaDesr.) plants was related to phytochrome measurement of day length and its regulation of photosynthate partitioning to favor successful completion of the life cycle. Short photoperiods alternated with long, uninterrupted nights resulted in low‐growing shoots and rapidly enlarging taproots. The ratio of far‐red (FR) relative to red (R) light and its effect on shoot/root biomass ratios were studied in controlled environments, in different field population densities, and among plants growing in full sunlight but receiving different spectral distributions of upwardly reflected light over different colored soils, plant residues or artificially colored mulches. Altered spectral distribution of reflected light can act through photomorphogenic pigments within a plant and influence photosynthate partitioning and shoot/root biomass ratio. Application of some basic photobiological principles should lead to improved plant‐soil‐water‐light management in crop production systems.

ISSN:0190-4167    

DOI:10.1080/01904169209364355

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Recent development in technologies of irrigation and fertilization enable us to control root size and environment under field conditions. Low volume irrigation and fertilization affects root size and rate of rootlets production and consequently vegetative and reproductive processes of whole plants. The mechanisms involved seem to include growth regulators production at the root apexes and their translocation to the shoots. Field experiments in a few species of deciduous trees and citrus, showed that root systems are very flexible and can adjust to low volume irrigation irrespective of age or size of the trees or stage of development. Root restriction under field conditions was found to cause precocity, increase productivity and reduce the size of the trees. A greater number of trees per unit land can be grown without reducing light penetration which is the most important factor affecting physiological processes controlling fruit bud differentiation, such as assimilate translocation, photosynthetic efficiency fruit composition, size and coloration. Control of root environment in terms of soil matric potential, mineral concentration and aeration can also be achieved by irrigating and fertilizing at the rate of consumptive use. A non uniform distribution of water and minerals was found to exist when a point source irrigation such as drip was used. Nevertheless, a highly efficient uptake of water and minerals were found under conditions of an almost continuous supply of water and minerals by drip irrigation systems. Results of various studies show that this phenomenon may be attributed to transfer of water, minerals and air among individual roots of a root system subjected to gradients of water, minerals, and oxygen concentrations.

ISSN:0190-4167    

DOI:10.1080/01904169209364356

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Scant information is available on the specific effect of root volume on uptake rates of water and N by trees as related to dry matter production and partitioning in the plant. The objectives of this work were to quantify these effects in peach trees and elucidate some of the mechanisms by which roots affect plant development and fruit yield.

ISSN:0190-4167    

DOI:10.1080/01904169209364357

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

This paper reviews 3 recent experiments dealing with root hydraulic resistance of cotton and discusses their implications in modelling the mass flow of ions through the soil‐root interfacial zone. A value of 4.7 x 10‐7cm3/cm•s, which has been assumed in one ion uptake model, is approximately correct for cotton grown in soil that was kept continuously moist, but root uptake rate varies with root age, type of rooting media, soil water content and with frequency and severity of soil drying around the root. Mass flow rate radially through the root material was about 1/2000 of the assumed ion uptake value when the rooting media had been dried severely. These major shifts in root conductivity as the soil dries will have major consequences in the proportionality between mass flow and diffusion of ions through the soil‐root interfacial zone in cotton.

ISSN:0190-4167    

DOI:10.1080/01904169209364358

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor