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Root Activity (root + activity)
Selected AbstractsThe representation of root processes in models addressing the responses of vegetation to global changeNEW PHYTOLOGIST, Issue 1 2000F. I. WOODWARD The representation of root activity in models is here confined to considerations of applications assessing the impacts of changes in climate or atmospheric [CO2]. Approaches to modelling roots can be classified into four major types: models in which roots are not considered, models in which there is an interplay between only selected above-ground and below-ground processes, models in which growth allocation to all parts of the plants depends on the availability and matching of the capture of external resources, and models with explicit treatments of root growth, architecture and resource capture. All models seem effective in describing the major root activities of water and nutrient uptake, because these processes are highly correlated, particularly at large scales and with slow or equilibrium dynamics. Allocation models can be effective in providing a deeper, perhaps contrary, understanding of the dynamic underpinning to observations made only above ground. The complex and explicit treatment of roots can be achieved only in small-scale highly studied systems because of the requirements for many initialized variables to run the models. [source] Roots, rhizosphere and soil: the route to a better understanding of soil science?EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2006P.J. Gregory Summary The centenary of Hiltner's recognition of a rhizosphere effect is a convenient point to assess the impact of such thinking on the direction of soil science. A review of the major soil journals suggests that for much of the last century, Hiltner's insight had little effect on mainstream thinking outside of soil microbiology, but this situation is changing rapidly as the consequences of spatial and temporal heterogeneity on soil functioning assumes greater importance. Studies of root growth, root distributions and of rhizosphere processes over the last 25 years demonstrate both the size and distribution of root systems and the associated inputs from roots to soils. These inputs result in a plethora of dynamic reactions at the root,soil interface whose consequences are felt at a range of temporal and spatial scales. Root growth and respiration, rhizodeposition, and uptake of water and nutrients result in biological, chemical and physical changes in soils over variable distances from the root surface so that the rhizosphere has different dimensions depending on the process considered. At the root length densities common for many crop species, much of the upper 0.1 m of soil might be influenced by root activity for mobile nutrients, water and root-emitted volatile compounds for a substantial proportion of the growing season. This brief review concludes that roots are an essential component of soil biology and of soil science. [source] Defoliation alters water uptake by deep and shallow roots of Prosopis velutina (Velvet Mesquite)FUNCTIONAL ECOLOGY, Issue 3 2003K. A. Snyder Summary 1Prosopis velutina Woot. (Velvet Mesquite) at a site with limited groundwater availability derived a greater percentage of water from shallow soil at the onset of the summer rainy season than did trees at a site with greater availability of groundwater. Predawn leaf water potentials (,pd) were not a strong indicator of shallow water use for this species with roots in multiple soil layers. 2We experimentally defoliated P. velutina plants to determine if reduced-canopy photosynthesis would alter vertical patterns of root activity. After natural rain events, hydrogen isotope ratios of xylem sap indicated that defoliated P. velutina took up a greater percentage of its water from shallow soils than did undefoliated plants. 3Irrigation with deuterium-labelled water further demonstrated that undefoliated plants were able to use shallow soil water. Defoliation appeared to affect the ability of trees to use deep-water sources. 4Reduced carbon assimilation limited water uptake from deep soil layers. These data highlight that there are internal physiological controls on carbon allocation that may limit water uptake from different soil layers. During periods of high vapour pressure deficit or soil drought, when leaf gas exchange and carbon assimilation decline, this may create positive feedbacks where plants are unable to forage for deep water due to carbon limitations. [source] Preparation and application of a novel environmentally friendly organic seed coating for riceJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 13 2009Defang Zeng Abstract BACKGROUND: Traditional rice seed coating techniques involve the use of chemical pesticides, which can damage the seed in the process and cause possible physical and environmental damage. Increasing knowledge and concern about the traditional applications have brought new attention to the industry and the search for a novel coating agent that is effective, safe and environmentally friendly. A new type of organic rice seed coating agent was developed using liquid-based polymeric adhesives. By using chitosan as the main raw material, modified with sodium hydroxide and polymerised with plant growth regulators and other additives, the novel seed coating agent is a safer, cheaper and more environmentally friendly alternative. RESULTS: The novel seed coating agent significantly enhanced sprout growth over traditional agents. We found it has obvious biological advantages: it stimulates the seedling growth of rice, advances the growth of root, improves root activity and increases the crop yield in the germination test and field trial. Compared with the traditional rice seed coating agent, the crop yield of seeds coated by the novel seed coating agent was increased by 5%, and at 25% less cost. The fungal inhibition test of the novel seed coating agent and acute toxicity test on fish showed that it has an obvious fungal inhibitory effect and a higher safety index during usage and disposal. CONCLUSION: This result suggests that treating seeds with the novel seed coating agent has significant agricultural implications through the enhanced seed vigour as reflected in growth. It is efficient and effective, resulting in better seed and crop protection. The novel seed coating agent demonstrates unique characteristics with great economic and environmental benefits. Copyright © 2009 Society of Chemical Industry [source] The representation of root processes in models addressing the responses of vegetation to global changeNEW PHYTOLOGIST, Issue 1 2000F. I. WOODWARD The representation of root activity in models is here confined to considerations of applications assessing the impacts of changes in climate or atmospheric [CO2]. Approaches to modelling roots can be classified into four major types: models in which roots are not considered, models in which there is an interplay between only selected above-ground and below-ground processes, models in which growth allocation to all parts of the plants depends on the availability and matching of the capture of external resources, and models with explicit treatments of root growth, architecture and resource capture. All models seem effective in describing the major root activities of water and nutrient uptake, because these processes are highly correlated, particularly at large scales and with slow or equilibrium dynamics. Allocation models can be effective in providing a deeper, perhaps contrary, understanding of the dynamic underpinning to observations made only above ground. The complex and explicit treatment of roots can be achieved only in small-scale highly studied systems because of the requirements for many initialized variables to run the models. [source] Compensative Effects of Chemical Regulation with Uniconazole on Physiological Damages Caused by Water Deficiency during the Grain Filling Stage of WheatJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 1 2008L. Duan Abstract Chemical regulation using plant growth regulators has proved to be potentially beneficial in water-saving agriculture. This experiment was conducted with winter wheat (Triticum aestivum L. cv. ,Jingdong 6') to study the effect of chemical regulation on alleviation of water deficit stress during the grain filling stage. Uniconazole, a plant growth regulator, was foliar sprayed at 85 % (adequate irrigation) and 60 % (deficit irrigation) field capacity. Results showed that the distribution of 3H-H2O in roots and flag leaf, characteristics of vascular bundle in primary roots and internode below spike, roots activity, transpiration rate and stomatal conductance of flag leaf were negatively affected by deficit irrigation after flowering. Foliar spraying at the early jointing stage with 13.5 gha,1 uniconazole was able to relieve and compensate for the harmful effects of deficit irrigation. Both the area of vascular bundle in primary roots and internode below the ear were increased by uniconazole, while root viability and their ability to absorb and transport water were increased. In the flag leaf, stomatal conductance was reduced to maintain the transpiration rate and water use efficiency (WUE) measured for a single wheat plant was higher. Uniconazole increased WUE by 25.0 % under adequate and 22 % under deficit irrigations. Under adequate irrigations, the 14C-assimilates export rate from flag leaf in 12 h (E12h) was increased by 65 % and 36 % in early and late filling stages, while under deficit irrigations, the E12h of uniconazole-treated plants exceeded that of control plants by 5 % and 34 % respectively. Physiological damages caused by water deficiency during the grain filling stage of wheat was alleviated by foliar spraying with uniconazole. [source] | |||||||||||||