In the last decade, our understanding of the processes underlying plant response to drought, at the molecular and whole-plant levels, has rapidly progressed. Here, we review that progress. We draw attention to the perception and signalling processes (chemical and hydraulic) of water deficits. Knowledge of these processes is essential for a holistic understanding of plant resistance to stress, which is needed to improve crop management and breeding techniques. Hundreds of genes that are induced under drought have been identified. A range of tools, from gene expression patterns to the use of transgenic plants, is being used to study the specific function of these genes and their role in plant acclimation or adaptation to water deficit. However, because plant responses to stress are complex, the functions of many of the genes are still unknown. Many of the traits that explain plant adaptation to drought - such as phenology, root size and depth, hydraulic conductivity and the storage of reserves - are those associated with plant development and structure, and are constitutive rather than stress induced. But a large part of plant resistance to drought is the ability to get rid of excess radiation, a concomitant stress under natural conditions. The nature of the mechanisms responsible for leaf photoprotection, especially those related to thermal dissipation, and oxidative stress are being actively researched. The new tools that operate at molecular, plant and ecosystem levels are revolutionising our understanding of plant response to drought, and our ability to monitor it. Techniques such as genome-wide tools, proteomics, stable isotopes and thermal or fluorescence imaging may allow the genotype-phenotype gap to be bridged, which is essential for faster progress in stress biology research.

Understanding plant responses to drought — from genes to the whole plant

The Environmental Protection Agency (EPA) provides access to information on a variety of topics related to the environment and strives to inform citizens of health risks. The EPA also has an extensive library network that consists of 26 libraries throughout the United States, which provide access to a plethora of information to EPA employees, scientists, and researchers. The EPA implemented a reorganization project to digitize their materials so they would be more accessible to a wider range of users, but this plan was drastically accelerated when the EPA was threatened with a budget cut. It chose to close and reduce the hours and services of some of their libraries. As a result, the agency was accused of denying users the “right to know” by making information unavailable, not providing an adequate strategic plan, and discarding vital materials. This case study explores the background of the digitization project, the practices implemented, and the critiques of the project.

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The Environmental Protection Agency

Nature And Properties Of Soils

http://utsc.utoronto.ca/%7Ebritto/publications/amtox.pdf

NH4+ toxicity in higher plants: a critical review

Plant growth-promoting bacteria confer resistance in tomato plants to salt stress.

Introduction, Allen V. Barker and David J. Pilbeam Essential Elements-Macronutrients Nitrogen, Allen V. Barker and Gretchen M. Bryson Phosphorus, Charles A. Sanchez Potassium, Konrad Mengel Calcium, David J. Pilbeam and Philip S. Morley Magnesium, Donald J. Merhaut Sulfur, Silvia Haneklaus, Elke Bloem, Ewald Schnug, Luit J. de Kok and Ineke Stulen Essential Elements-Micronutrients Boron, Umesh C. Gupta Chlorine, Joseph R. Heckman Copper, David E. Kopsel and Dean A. Kopsell Iron, Volker Roemheld and Miroslav Nikolic Manganese, Julia M. Humphries, James C.R. Stangoulis, and Robin D. Graham Molybdenum, Russell L. Hamlin Nickel, Patrick H. Brown Zinc, J. Benton Storey Beneficial Elements Aluminum, Susan C. Miyasaka, N.V. Hue, and Michael A. Dunn Cobalt, Geeta Talukder and Archana Sharmaz Selenium, Dean A. Kopsell and David E. Kopsell Silicon, George H. Snyder, Vladimir V. Matichenkov and Lawrence E. Datnoff Sodium, John Gorham Vanadium, David J Pilbeam and K Drihem Conclusion, Allen V. Barker and David J Pilbeam

Handbook of plant nutrition

Ammonium and nitrate nutrition of horticultural crops.

Handbook of Plant Nutrition, Second Edition

Ammonium toxicity resulted in morphological modifications of tomato leaf chloroplasts. The chloroplasts, which are normally flattened around the protoplast periphery, became ellipsoidally rounded and dispersed through the protoplasm. The first apparent effect of plastid degradation was development of many vesicles from the fretwork. Later the grana lamellae swelled, and some disappeared. Eventually, distinct grana could not be detected.Ammonium accumulation, chlorophyll loss, and photosynthetic decrease occurred simultaneously. Initial changes in these processes preceded the detection of modifications of fine structure; however, each continued with further breakdown of the chloroplasts.

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Structure and Function of Tomato Leaf Chloroplasts During Ammonium Toxicity

/pdf/mineral-nutrition-and-plant-disease-1mi7konht2.pdf

Allen V. Barker

Papers

Handbook of plant nutrition

Ammonium and nitrate nutrition of horticultural crops.

Handbook of Plant Nutrition, Second Edition

Structure and Function of Tomato Leaf Chloroplasts During Ammonium Toxicity

Mineral Nutrition and Plant Disease