https://pubs.rsc.org/en/content/articlepdf/2019/NP/C8NP00092A

Marine natural products.

The rhizosphere encompasses the millimeters of soil surrounding a plant root where complex biological and ecological processes occur. This review describes recent advances in elucidating the role of root exudates in interactions between plant roots and other plants, microbes, and nematodes present in the rhizosphere. Evidence indicating that root exudates may take part in the signaling events that initiate the execution of these interactions is also presented. Various positive and negative plant-plant and plant-microbe interactions are highlighted and described from the molecular to the ecosystem scale. Furthermore, methodologies to address these interactions under laboratory conditions are presented.

The Role of Root Exudates in Rhizosphere Interactions with Plants and Other Organisms

Interpretation of X-ray Powder Diffraction Patterns . By H. Lipson and H. Steeple. Pp. viii + 335 + 3 plates. (Mac-millan: London; St Martins Press: New York, May 1970.) £4.

X-Ray Diffraction

Biological activities and distribution of plant saponins.

Pigments are present in all living matter and provide attractive colors and play basic roles in the development of organisms. Human beings, like most animals, come in contact with their surroundings through color, and things can or cannot be acceptable based on their color characteristics. This review presents the basic information about pigments focusing attention on the natural ones; it emphasizes the principal plant pigments: carotenoids, anthocyanins, and betalains. Special considerations are given to their salient characteristics; to their biosynthesis, taking into account the biochemical and molecular biology information generated in their elucidation; and to the processing and stability properties of these compounds as food colorants.

Natural Pigments: Carotenoids, Anthocyanins, and Betalains — Characteristics, Biosynthesis, Processing, and Stability

Allelopathy studies the interactions among plants, fungi, algae and bacteria with the organisms living in a certain ecosystem, interactions that are mediated by the secondary metabolites produced and exuded into the environment. Consequently, allelopathy is a multidisciplinary science where ecologists, chemists, soil scientists, agronomists, biologists, plant physiologists and molecular biologists offer their skills to give an overall view of the complex interactions occurring in a certain ecosystem. As a result of these studies, applications in weed and pest management are expected in such different fields as development of new agrochemicals, cultural methods, developing of allelopathic crops with increased weed resistance, etc. The present paper will focus on the chemical aspects of allelopathy, pointing out the most recent advances in the chemicals disclosed, their mode of action and their fate in the ecosystem. Also, attention will be paid to achievements in genomics and proteomics, two emerging fields in allelopathy. Rather than being exhaustive, this paper is intended to reflect a critical vision of the current state of allelopathy and to point to future lines of research where in the authors' opinion the main advances and applications could and should be expected.

Allelopathy--a natural alternative for weed control.

In the search for a standard bioassay of phytotoxicity for allelochemicals, 22 commercial varieties of eight plant species [four dicotyledons: lettuce (Compositae), carrot (Umbelliferae), cress (Cruciferae), tomato (Solanaceae); and four monocotyledons: onion (Liliaceae), barley, wheat, and corn (Gramineae)] proposed as models for the most common weed families have been tested at different pH and solution volumes per set conditions. Nine commercial varieties selected as standard target species (STS) were tested with standard commercial herbicides to ensure their sensitivity to phytotoxic compounds. Results are discussed to establish the proper growth requirements, and sensitivity of commercial seeds of STS and to find the most suitable commercial herbicides that allow comparison with an internal standard to validate the response of potential allelochemicals.

Search for a Standard Phytotoxic Bioassay for Allelochemicals. Selection of Standard Target Species

Prior generalizations about the ecological roles of monoterpenes may be misleading if based on the presumed insolubility of monoterpenes in water. We determined the aqueous solubility of 31 biologically active monoterpenes by gas chromatography. While hydrocarbons were of low solubility (< 35 ppm), oxygenated monoterpenes exhibited solubilities one or two orders of magnitude higher, with ranges of 155-6990 ppm for ketones and of 183-1360 ppm for alcohols. Many monoterpenes are phytotoxic in concentrations under 100 ppm, well below the saturated aqueous concentrations of oxygenated monoterpenes. Therefore, even dilute, unsaturated solutions of monoterpenes, occurring naturally in plant tissues and soil solutions, may act as potent biological inhibitors.

Just how insoluble are monoterpenes

Fungicidal activity of natural and synthetic sesquiterpene lactone analogs

Introduction Reality and Future of Allelopathy, G.R. Waller Chemistry Studies Ecophysiology and Potential Modes of Action for Selected Lichen Secondary Metabolites, J. Romagni, R.C. Rosell, N.P.D. Nanayakkara, and F.E. Dayan Bioactive Compounds from Potomagetonaceae on Aquatic Organisms, M. della Greca, A. Fiorentino, and M. Isidori Fate of Phenolic Allelochemicals in Soils: the Role of Soil and Rhizosphere Microorganisms, U. Blum Benzoxazolin-2(3H)-ones: Generation, Effects, and Detoxification in the Competition Among Plants, D. Sicker, H. Hao, and M. Schulz Heliannanes: A Structure-Activity Relationship (SAR) Study, F.A. Macias, J. C. G. Galindo, and J.M.G. Molinillo Chemistry of the Host-Parasite Interactions, J.C.G. Galindo, F.A. Macias, M.D. Diaz, and J. Jorrin Application of Analytical Techniques to the Determination of Allelopathic Agents in Wheat Root Exudates: A Practical Case Study, T. Haig The Importance of Alkaloidal Functions, M.S. Blum Allelochemical Properties of Quinolizidine Alkaloids, M. Wink Mode of Action Studies Mode of Action of Phytotoxic Terpenoids, S.O. Duke and A. Oliva Mode of Allelochemical Actions of Phenolic Compounds, F. Einhellig Mode of Action of Hydroxamic Acid BOA and Other Related Compounds, A.M. Sanchez-Moreiras, T. Coba de la Pena, A. Martinez, L. Gonzalez, F. Pellisier, and M.J. Reigosa Mode of Action of Phytotoxic Fungal Metabolites, H.G. Cutler, S.J. Cutler, and D. Matesic Proteomic Techniques for the Study of Allelopathic Stress Produced by Some Mexican Plants on Protein Patterns of Bean and Tomato, R. Cruz-Ortega, T. Romero-Romero, G. Ayala-Cordero, and A.L. Anaya Application of Microscopic Techniques of the Study of Seeds and Microalgae Under Olive Oil Wastewater Stress, G. Alliota, R. Ligrone, C. Ciniglia, A. Pollio, M. Stanzione, and G. Pinto Bioassays: Valuable Tools for the Study of Allelopathy, R. Hoagland and R.D. Williams

Francisco A. Macías

Papers

Allelopathy--a natural alternative for weed control.

Search for a Standard Phytotoxic Bioassay for Allelochemicals. Selection of Standard Target Species

Just how insoluble are monoterpenes

Fungicidal activity of natural and synthetic sesquiterpene lactone analogs

Allelopathy: Chemistry and Mode of Action of Allelochemicals