How Plants Protect Themselves from Stress
Secrets of survival in the harsh conditions of the taiga are hidden in spruce needles
Imagine the vast expanses of the northern taiga, where spruce forests stretch to the horizon. These mighty trees appear silent and unshakable. But at the chemical level, they wage a constant, invisible struggle for survival. The key to understanding this struggle lies in secondary metabolites, amazing compounds that help plants adapt to complex environmental conditions1 .
Russian scientists have found that the formation of secondary metabolites in plants is a complex, clearly planned process in space and time, involving many enzymes and regulatory proteins1 . These compounds serve as unique "biochemical tools" with which the plant, deprived of the ability to actively move in space, solves most of its "ecological" problems1 .
Secondary metabolites are organic substances synthesized by an organism but not directly involved in growth, development, or reproduction processes9 . Unlike primary metabolites (amino acids, nucleotides), which are necessary for the life of the cell itself, secondary metabolites are not strictly mandatory for plant survival.
Plants synthesize a huge number of these compounds - about 100,000 secondary metabolites have been discovered in higher plants1 . According to modern concepts, 15 to 25% of the total number of plant genes are involved in secondary metabolism processes1 , emphasizing the importance of these compounds for plant life.
Isoprene derivatives including monoterpenes, sesquiterpenes, diterpenes and others3 .
Substances containing phenolic groups such as flavonoids, tannins, lignin2 .
Nitrogen-containing compounds, often with pronounced biological activity6 .
Include non-protein amino acids, cyanogenic glycosides, betalains and others9 .
Many secondary metabolites are poisonous and help the plant protect itself from being eaten by herbivores or from abiotic stress factors3 .
Some compounds serve to attract pollinators due to their coloring or volatile properties3 .
Certain secondary metabolites can serve as a form of nutrient storage3 .
To understand how the content of secondary metabolites varies in natural conditions, a group of Russian scientists conducted a large-scale study in the northern taiga spruce forests of the Kola Peninsula2 . The research team included N. A. Artemkina, M. A. Danilova, and N. V. Lukina from the Institute of Industrial Ecology of the North and the Center for Ecology and Forest Productivity of the Russian Academy of Sciences2 .
Scientists studied the spatial variation in the content of phenolic compounds and nutrients in the needles of Siberian spruce (Picea abies ssp. obovata) - one of the most common forest-forming species in forests at the northern limit of growth2 .
Study of three profiles of geochemically coupled landscape with different types of vegetation: shrub-green moss spruce forests, green moss-shrub spruce forests, and sphagnum-ledum spruce forests2 .
Collection of needle samples of different ages (current year, one-year-old, 5-7-year-old and 8-11-year-old) at the end of the growing season2 .
Analysis of the content of secondary metabolites (phenolic compounds, tannins, lignin) and nutrients in needles of trees of different ages (30-40 years and over 100 years)2 .
Evaluation of both intra-biogeocenotic (between individual elementary biogeoareals) and inter-biogeocenotic variation in the chemical composition of needles2 .
The study revealed clear patterns in the distribution of secondary metabolites depending on landscape position, tree age, and needle age.
In the perennial needles of young spruce trees (30-40 years), higher content of carbon, lignin, high molecular weight phenolic compounds, bound tannins, and wider ratios of "lignin:cellulose" and "lignin:N" were found compared to trees over 100 years old2 .
In the needles of spruce trees over 100 years old in transit and accumulative landscape positions, significantly more bound tannins and low molecular weight phenols were contained than in automorphic (drier) conditions2 .
The content of lignin and the "lignin:N" indicator in 5-7-year-old needles was significantly higher in spruce trees in automorphic conditions, while in current year needles, the maximum values of these indicators were demonstrated by spruce trees in transit and accumulative landscape positions2 .
| Needle Age | Lignin (%) | High Molecular Weight Phenols | Bound Tannins | Low Molecular Weight Phenols |
|---|---|---|---|---|
| Current Year | High in transit and accumulative conditions | Medium | Medium | High in transit and accumulative conditions |
| 5-7 Years | High in automorphic conditions | High | High | Medium |
| Landscape Position | Bound Tannins | Low Molecular Weight Phenols | Total Phenolic Compounds |
|---|---|---|---|
| Automorphic | Lower | Lower | Medium |
| Transit | Higher | Higher | Higher |
| Accumulative | Higher | Higher | Higher |
| Parameter | Young Spruce (30-40 years) | Mature Spruce Trees (>100 years) |
|---|---|---|
| Carbon | Higher content | Standard content |
| Lignin | Higher content | Standard content |
| Lignin:Cellulose Ratio | Wider | Standard |
| Lignin:N Ratio | Wider | Standard |
Researchers studying plant secondary metabolites use a variety of techniques and reagents. Here are the main ones:
(ethanol, methanol, acetone) - used to extract secondary metabolites from plant material2 .
Allow separation of complex compound mixtures into individual components for subsequent analysis6 .
Used for identification and quantitative determination of isolated compounds6 .
Applied to study the activity of key enzymes of secondary metabolism6 .
Including PCR and sequencing, allow studying the expression of genes involved in the biosynthesis of secondary metabolites8 .
The study of spatial variation of secondary metabolites has fundamental significance for understanding the mechanisms of plant adaptation to environmental conditions. According to the "growth/secondary metabolites" (GDB) and "carbon/nutrients" (CNB) hypotheses, plants allocate a substantial share of assimilated carbon to the production of secondary metabolites when growth is limited by unfavorable conditions2 .
Phenolic compounds, including tannins, play an important role in regulating the rate of litter decomposition, which in turn affects the cycles of carbon and nutrients in terrestrial ecosystems2 . The rate of litter decomposition is also influenced by concentrations of carbon, lignin, nitrogen and other nutrients, as well as the ratios C:N, lignin:N2 .
The obtained data help not only to understand the mechanisms of plant survival in the extreme conditions of the northern taiga but also to predict changes in ecosystems under changing climate conditions. Research on secondary metabolism also has practical significance - more than half of all medicines, nutraceuticals and cosmetic products contain substances of plant origin, most of which are secondary metabolites1 .
Future research in this field may be directed at studying the influence of specific stress factors on the synthesis of individual classes of secondary metabolites, as well as identifying the genetic mechanisms controlling these processes.
The invisible chemical life of the forest continues to reveal its secrets, reminding us of the complexity and interconnectedness of natural systems even in the harshest corners of our planet.