Elevated CO 2 concentration was adjusted to p. Further comprehensive quantification revealed that, on average, about This surplus resulted despite the fact that the biomass of the well-watered plants was significantly greater than that of the stressed plants Secondary plant products possess remarkable relevance for interaction of plants with their environment Harborne For example, many repel herbivores, protect against pathogens or attract pollinators Hartmann , Wink Some of these substances are also related to abiotic stress, for example protection against UV light or high light intensities or reduction of transpiration, or have relevance as compatible solutes or radical scavengers Edreva1 et al.
The syntheses of secondary metabolites are considered to be frequently induced and modulated by numerous environmental factors, e. Thus, the actual synthesis and accumulation of a particular natural product is influenced and determined by numerous elements. In this context, it is important to consider that a particular stress situation usually influences several factors. For example, high irradiation is frequently accompanied by elevated temperatures; high irradiation by high UV radiation, and elevated temperatures by a higher evaporation, and drought stress may be associated with a greater herbivore pressure but a reduced number of pathogens.
Patterns of complex interferences involving numerous factors should be considered due to these contemporary occurrences. The actual influence of a certain component remains to be elucidated by more comprehensive studies using suitable and reliable markers or indicators for certain stresses. Unfortunately, the actual in situ concentration of either of these components cannot be quantified without major effort and expenditure. Alternatively, the levels of certain so-called stress metabolites that are synthesized and accumulated more or less specifically in a particular stress situation have to be analyzed instead.
In this context, proline is especially useful as it is accumulated as a compatible solute in plants suffering drought stress for review see Rhodes et al. Unfortunately, GABA is not only produced in great quantities in response to drought stress, but it is also accumulated under various other stress conditions Satya Narayan and Nair , Bown and Shelp Therefore, other markers are required. In this context, the abundance of dehydrins is notable.
Dehydrins, first discovered in seeds during late embryogenesis in the course of maturation drying, are also frequently synthesized in plant cells suffering drought stress for reviews, see Close , Allagulova et al. These small hydrophilic proteins are thought to be involved in various protective functions in desiccating cells Hara However, the expression of dehydrins and the accumulation of the stress metabolite GABA may follow different time patterns in the same stressed organism; this has been demonstrated for coffee seeds during drying Kramer et al.
As in leaves of plants exposed to drought stress, apart from over-reduction due to stomatal closure see above , the water availability is also reduced, and various metabolic responses should occur concomitantly or subsequently.
As a consequence, the elucidation of all the metabolic changes induced in drought-stressed plants requires a combination of several markers, e. Concentrations of natural products are generally enhanced in plants suffering drought stress. This increase could either be due to a stress-related decline in biomass production associated with an unchanged biosynthesis rate of natural products or to an authentic enhancement of the total secondary metabolite content.
The latter option is obviously related to drought stress-induced over-reduction, which favors biosynthesis of highly reduced compounds.
This observation is contradictory to the findings of Arakawa et al. E Corresponding author. Analysis of phenolic acids in hyssop Hyssopus officinalis L. Find articles by Giovanni Colella. Christie P. Review on rosmarinic acid extraction, fractionation and its anti-diabetic potential.
However, this simplified model becomes much more complex as these reactions are frequently overlaid by and interact with numerous other factors that also impact on the biosynthesis of secondary plant products. Yet, these considerations suggest that an enhanced synthesis of secondary plant products may also contribute to prevent damage caused by radicals evolved due to the drought-related over-reduced states. The authors thank Dr.
Dave Seigler, University of Illinois for critical reading of the manuscript and helpful suggestions. Project Oxford University Press is a department of the University of Oxford. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide. Sign In or Create an Account.
Sign In. Advanced Search. Article Navigation. Close mobile search navigation Article Navigation. Volume Article Contents. Synthesis and accumulation of secondary plant products in drought-stressed plants. Efficient energy dissipation is essential for plant viability. Putative biochemical mechanism of stress-related enhancement of secondary metabolite synthesis.
Interference with other factors. Oxford Academic. Google Scholar. This review is dedicated to Eric E. Conn on the occasion of his 90th birthday, an outstanding plant biochemist who has contributed exceptionally to our understanding of plant secondary metabolism. Cite Citation. Permissions Icon Permissions.
Abstract Spice and medicinal plants grown under water deficiency conditions reveal much higher concentrations of relevant natural products compared with identical plants of the same species cultivated with an ample water supply. Table 1.
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