Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5217_Библиотеки_им_академика_М_И_Перельмана.pdf
Chapter 8 Metabolic and hormonal responses of medicinal and aromatic plants 303
8.3.2 Waterlogging stress
In excessive waterlogging, soil pores are filled with water, and oxygen levels decrease.
As a result, it becomes difficult for the roots to absorb oxygen. Some plants develop
resistance to waterlogging through aerenchyma (air tissue) and adventitious roots.
Aerenchyma tissue enables the diffusion of oxygen from the plant’s aerial parts to the
submerged areas, allowing the roots to maintain aerobic respiration [36]. Insufficient
oxygen intake prevents plants from performing aerobic respiration in the mitochondria, and the inhibition of photosynthesis leads to energy deficiency, which results in
ATP production limited to glycolysis. While the end products of aerobic respiration
are CO
result, energy efficiency decreases, and metabolism is disrupted. The lactic acid and
ethanol produced from anaerobic respiration damage the roots, hindering growth.
Roots submerged in water are unable to absorb nutrients properly, slowing down
growth. Due to reduced water uptake by the roots in waterlogging, anaerobic respiration leads to decreased energy production, preventing the ion pumps necessary for
stomatal opening from functioning, causing stomata to close. Additionally, stressed
roots produce high amounts of ABA and ethylene, and the hormones reaching the
leaves play a role in stomatal closure [42, 43]. Stomata can also close for different reasons, such as high CO
to maintain gas balance. Stomata typically facilitate water vaporization from the
plant through transpiration. However, during waterlogging, due to excessive air humidity and water in plant tissues, transpiration is not necessary. As a result, stomata
close. Additionally, during waterlogging, stomata close to prevent pathogens, such as
fungi and bacteria, from entering the plant when they find reproductive opportunities. Stomata tend to remain closed to reduce photosynthesis rate as well. When roots
cannot absorb sufficient nutrients, the raw materials required for photosynthesis cannot be transported to the leaves, and the plant reduces its photosynthesis rate to
lessen metabolic load. As a result, ROS production increases, damaging the cell membrane. Following root decay, the transport of water and nutrients is hindered, leading
the plant to death [44–47].
and H2O, anaerobic respiration produces lactic acid and ethanol [37–41]. As a
2
levels in the soil, which may cause the plant to close its stomata
2
8.4 Temperature stress
8.4.1 High temperature (heat shock)
As a result of high temperature, the physical structure of lipids in cell membranes is
disrupted, and membrane permeability increases [48]. This leads to an imbalance of
ions inside and outside the cell. Cellular functions are impaired, and cell death occurs
due to damage to the cell membrane. Additionally, high temperature causes protein
304 Esra Uçar et al.
denaturation, resulting in the loss of protein function. The disruption of protein structure affects enzymes involved in photosynthesis and respiration. There is an increase
in the number of HSPs, which work to prevent improper protein aggregation and support the normal folding of cellular proteins under stress situations [49–54]. High temperature also affects chloroplasts, which are sensitive to heat. Chlorophylls degrade,
stomata close, and carbon dioxide uptake decreases [55]. As a result of increased respiration due to high temperature, carbon dioxide reserves are depleted, and photosynthesis decreases. Consequently, energy production drops, and metabolism slows
down. The rise in temperature also increases transpiration. Stomata close to counteract this, and photosynthesis slows down. Otherwise, it leads to wilting in the plant,
and in extreme cases, desiccation [56–58]. Decreased water content within the cell
leads to an increase in ROS, resulting in lipid peroxidation, protein, and DNA damage
[59]. As a result of these effects, even if the plant does not die, pollen viability decreases, and fertilization does not occur [60]. An increase in temperature causes variations in plant hormone levels. The production of ABA, which induces stomatal closure, increases, leading to slower growth, while ethylene production induces leaf
abscission [18]. If the stress level is mild, metabolic adaptation and recovery are observed in the plant. If it is moderate, growth and reproduction are hindered, and if
severe stress occurs, it leads to cellular death and desiccation of the plant.
8.4.2 Low-temperature stress
Plants’ physiological and biochemical processes are significantly impacted by low
temperatures, which hinders their growth and development. Cold stress occurs when
temperatures are between around 0 °C and 15 °C, while freezing happens when temperatures are below 0 °C. Lipids that melt at high temperatures become solid at low
temperatures, which makes them less fluid. The membrane gets stiffer and less permeable. The reduction in membrane permeability affects the movement of water and
ions, which decreases cellular functioning [61, 62]. Ions like Na, K, and Ca are essential
for plants to deal with biotic and abiotic stress situations. If there are not enough of
these ions, it may cause harm to the plants [58, 60, 63]. Stomatal closure and inadequate gas exchange occur when energy-dependent systems, such as ion pumps (e.g.,
ATPase), are unable to operate [64, 65]. High protoplasmic viscosity is present [66].
Chloroplasts are sensitive to both high and low temperatures. In most plants, the temperature needed for photosynthesis is typically lower than the temperature necessary
for respiration [54]. When temperatures are low, photosynthetic enzymes become less
active, which causes stomata to close and reduces the amount of carbon dioxide that
is absorbed. At the same time, when the amount of water in the soil drops [66] and
the water in the roots gets immobilized under freezing temperatures, the stomata
shut to reduce water loss via restricted transpiration. The formation of ROS is increasing. If freezing happens, the water outside the cell turn into ice crystals. These sharp-
Figure 8.2: Cold stress in plants.
Chapter 8 Metabolic and hormonal responses of medicinal and aromatic plants 305
edged crystals rip the membrane, which cause the cell to die. Because of the presence
of dissolved chemicals, the freezing point of intracellular water is lower than that of
pure water. As a result, the freezing process starts mostly in the areas outside of the
cells. When ice crystals develop outside of the cell, the concentration of dissolved
chemicals in the surrounding medium rises, which reduces the osmotic potential. As a
consequence, the water within the cell flows outward in order to balance the difference in pressure, and an increase in osmotic pressure may be seen. When freezing
occurs, it disrupts the action of enzymes, which has a detrimental impact on activities,
including photosynthesis, respiration, and protein synthesis [61]. Leaf and root development halt, and growth slows down. Low temperatures cause changes in hormone
levels, increasing the ABA level, which leads to stomatal closure, while the increase in
ethylene promotes leaf abscission. A plant’s resistance to low temperatures varies, depending on its developmental stage, meaning the metabolic changes occurring within
it. If this occurs during a period of increased sugar and protein concentrations in the
cells, it reduces ice formation within the cells, thus enhancing frost tolerance [66]. In
response to low temperatures, plants typically increase the amount of soluble proteins in their tissues to cope with stress. Some of these accumulating proteins exhibit
antifreeze properties and are referred to as antifreeze proteins (AFPs); they can alter
the shape of ice crystals [67, 68]. Figure 8.2 shows cold stress schematically.
8.5 Light stress
Light is an important component for the germination of seeds, the growth of leaves, the
elongation of plant height, the timing of blooming, and other activities that occur
306 Esra Uçar et al.
throughout the development and life cycle of plants [69]. Plants have photoreceptors
that are able to detect and react to the intensity, direction, and quality of light. Chromophores, which are photopigments, are found in these light-sensitive proteins. They help
the body perceive and respond to light [70]. Plants may get stressed if they are exposed
to too much or too little light intensity. Photosynthetic activity is greatly affected by the
quality and intensity of light. At first, a rise in light intensity causes the rate of photosynthesis to increase and the plant’s need for CO
to grow, but only up to a certain
2
point. In order to satisfy this demand, plants expand their stomata to take in more carbon dioxide (CO
). However, as the stomata open, transpiration increases, which causes
2
the plant to lose water. Plants maintain water balance by transporting the ABA hormone to the leaves when the water loss in the leaves reaches a threshold level. This is
done by signals sent from the roots to the leaves, which causes the stomata to shut. This
system protects against drought stress. Certain plants are more vulnerable to strong
light stress when their cytokinin levels drop [71]. When plants are stressed, it might
alter the allocation of energy, which can lead to the creation of singlet oxygen from triplet chlorophyll molecules. This may expose the plant to oxidative stress [72, 73]. The
plant type and ambient circumstances might cause this impact to be different. Plants
can carry out photosynthesis most effectively at lower light levels when the temperature and nutritional conditions are right. On the other hand, plants may experience
stress as a result of changes in environmental circumstances. Plants may experience
light stress as a consequence of fluctuations in light intensity caused by climate change,
which may expose them to either low or high light intensity. This has a deleterious effect on the plant’s metabolism of antioxidants and photosynthesis. As a result, the plant
undergoes changes at the biochemical and molecular levels [70, 74].
8.6 Salt stress
Excessive salinity in the soil occurs when there is a higher concentration of salts in the
soil solution. It is one of the abiotic stress factors that causes stress in plants. Improper
fertilization, pesticide applications, waste disposal, and excessive irrigation are all factors
that can lead to the accumulation of ions in the soil, including chloride and sulfate, as
well as cations like Na⁺, K⁺, Ca
NO₃⁻, all of which can be found in high concentrations. When plant cells take in too
many of these ions, it leads to ionic imbalances [75, 76]. Because of the excessive salinity,
sodium and chloride ions start to build up in the tissues of the plant. This disrupts the
ionic equilibrium and negatively impacts the plant’s metabolic processes. As a result, the
enzymes are not able to work properly. The roots of the plant have a harder time taking
in water, which causes the turgor pressure to drop and the plant to start withering.
Growth stops as turgor pressure decreases. When a plant wilts, its stomata shut, which
restricts the amount of carbon dioxide that can be absorbed, and leads to a decrease in
2
⁺, and Mg2⁺, and anions like Cl⁻, HCO₃⁻, CO₃2⁻, SO₄2⁻, and
Chapter 8 Metabolic and hormonal responses of medicinal and aromatic plants 307
photosynthesis [77–79]. When salt builds up, it causes oxidative stress on cellular components, which may lead to lipid peroxidation, protein degradation, and even DNA damage
[80]. Plants produce enzymes like superoxide dismutase and catalase in order to reduce
the stress that ROS cause [81]. Salt stress causes cells to lose water and destabilizes the
plasma membrane, which leads to damage to the cell membrane and the subsequent release of ions. Calcium ions (Ca
the signaling pathway for salt tolerance. Plants often create ABA when they are exposed
to high saline levels in order to cover their stomata and prevent water loss [82–84]. Plants
try to survive by increasing the amount of water that is retained in their cells. They do
this by accumulating osmolytes, which include proline, sugars, and betaines [85]. Proline
is important for avoiding protein dehydration because it binds its hydrophobic ends to
proteins and its hydrophilic ends to water molecules [86].
2
⁺), protein kinases, and phospholipids are all involved in
8.7 Nutrient stress
Hydrogen, carbon, and oxygen, which together make up around 95% of plant biomass
and are mostly derived from air and water, are among the minimum of 17 basic elements that plants need to maintain normal growth. The other 14 elements, which are
nitrogen, potassium, calcium, magnesium, phosphorus, sulfur, chlorine, boron, iron,
manganese, zinc, copper, nickel, and molybdenum, are taken in directly from the
earth. While sodium, cobalt, and silicon are not regarded essential for plant growth,
some experts suggest that a total of 20 elements are required for optimum plant development [87–90]. When plants do not get nutrients like nitrogen, phosphorus, and potassium, they become stressed, which causes them to respond with changes in their
metabolism and hormones. Nitrogen is not present in the parent rock and mostly
comes from the environment and organic matter. It is essential for physiological and
biochemical activities, such as the synthesis of proteins and chlorophyll, root respiration, and fruit production [88, 91, 92]. Plants may experience a variety of challenges
when they have too much or too little of certain nutritional components. When plants
do not have enough nutrients, their main reaction is to try to adapt. At first, they encourage the main root to grow longer and for more lateral roots to develop so that
they may take up more nutrients. Additionally, the number of root hairs increases.
Excess nitrogen, responsible for the formation of green tissue, leads to delayed flowering and fruit formation. As the plant height increases significantly, lodging or breakage may occur. Excess nitrogen also contributes to the development of fungal diseases
[89, 92, 93]. In nitrogen deficiency, vegetative growth is retarded. Since nitrogen is an
element in the chlorophyll structure, its deficiency leads to chlorophyll degradation,
resulting in a decline in photosynthesis.
Figure 8.3: Nutrient stress in plants.
Figure 8.4: Nutrient stress in plants.
308 Esra Uçar et al.
The plant’s color shifts from dark green to light green, and in severe stages of insufficiency, chlorosis develops. The rates of flowering and fruit set decrease [90, 94]. Chlorophyll generation is dependent on potassium; therefore, a lack of potassium may result in chlorosis. It affects the opening and shutting of stomata in leaves, which causes
water to be lost via transpiration. Additionally, it has an effect on how much water
root cells absorb. As a result of these factors, a deficit causes a drop in turgor pressure, which leads to water stress in the plant [89, 92, 94, 95]. Phosphorus is another
essential element for plant life. Since phosphorus plays a role in flower and fruit formation, its deficiency damages generative organs. As phosphorus increases plants’ resistance to diseases and pests, its deficiency reduces the plant’s resistance to diseases
[90, 92, 94, 95]. Figures 8.3 and 8.4 show nutrient stress schematically.
Chapter 8 Metabolic and hormonal responses of medicinal and aromatic plants 309
8.8 Heavy metal stress
Environmental pollution has become a problem due to the development of technology,
industrialization, high traffic, and other things. Heavy metals are one of the contaminants that are of great concern since they pose a hazard to the health of living beings.
Heavy metals have a specific gravity greater than 5 g/cm
greater than 20, including more than 60 metals such as Fe, Mn, Cu, Zn, Hg, Ni, Cr, Cd,
Co, Mo, Pb, Hg, and Al. Plants need small quantities of certain of these heavy metals (Fe,
Mn, Co, Zn, Cu, Ni, and Mo) in order to flourish. They are involved in a number of physiological and biochemical activities, including photosynthesis, respiration, carbon and
nitrogen metabolism, cell division, and nitrogen fixation [96]. On the other hand, when
plants absorb a large amount of heavy metals, it interferes with their physiological
functioning, which may lead to harmful consequences and slow their growth [97, 98].
The level of toxicity of these metals is different for each plant species and depends on
the chemical structure of the metal. The increase in heavy metals in the soil primarily
disrupts root respiration, mineral absorption, and enzyme activities, leading to damage
in the root structure. As root development is negatively affected, the uptake of essential
nutrients and water for the plant is also impaired, resulting in disruptions in the plant’s
growth [98, 99]. Metals have the ability to replace each other, and some metals can bind
to the magnesium (Mg) element, which is essential for the chlorophyll molecule. As a
result, this causes the chlorophyll molecules to break down [96, 100, 101] and the breakdown of photosynthesis enzymes and chlorophyll structure due to stress negatively affects photosynthesis. The disruption of enzyme activity slows down metabolic processes. Heavy metals impair the function of stomata, reducing transpiration. This
affects the cell’s water balance, leading to osmotic stress. Protein synthesis and hormonal balance are disrupted. Eventually, membrane stability begins to deteriorate,
leading to cellular damage [102, 103]. The intensity and duration of stress in plants play
a critical role in their resilience. As the stress level increases, the plant’s capacity for
adaptation decreases. In stress conditions that exceed the threshold of resilience, initially unnoticed damages gradually become visible, and irreversible structural or functional damage may occur. Additionally, these stresses can pass to humans through
plant-based food sources, leading to chronic and harmful health issues [104, 105]. Some
plant species are capable of accumulating heavy metals in their tissues without causing
any harm (hyperaccumulators), and it has been reported that they can contribute to
the reduction of pollution (phytoremediation). Hyperaccumulators can accumulate
50–500 times more heavy metals compared to the soil [98, 106, 107]. Some plants avoid
heavy metal damage by trapping metals within the cell walls of root hairs, effectively
blocking their movement to aerial parts [108].
3
and an atomic number
310 Esra Uçar et al.
8.9 Molecular docking calculation for stress
For the purpose of comparing the biological activities of molecules to those of biological materials, molecular docking calculations are carried out. Molecular docking calculations were performed using the Maestro Molecular Modeling Platform (version
13.4) created by Schrödinger [109]. Calculations are comprised of a number of different processes. There is a distinct approach to each phase. The first stage is the usage
of the protein preparation module [110] to prepare the proteins. This module is responsible for determining the active sites that are present in the proteins. In the next
stage, the molecules that have been investigated are prepared. The molecules are first
optimized using the Gaussian software tool. After that, the LigPrep module [111] is prepared for calculations using the optimized structures. After preparation, the Glide ligand docking module [112, 113] is utilized to study the interactions that occur between
the compounds and the cancer protein. Throughout all of the computations, the
OPLS4 technique is used to do the calculations. In conclusion, an ADME/T study,
which stands for absorption, distribution, metabolism, excretion, and toxicity, is carried out in order to investigate the possible pharmacological effects of the compounds
that are investigated. The Qik-prop module [114] of the Schrödinger program is used
to forecast the effects and responses of chemicals in human metabolism.
Molecular docking calculations are a powerful computational approach to understand plant responses to environmental stress factors and to identify biomolecular interactions. When plants are exposed to various stress conditions such as drought, salinity, heavy metals, and pathogens, enzymes, proteins, and phytochemicals that
regulate resistance mechanisms against these stresses come into play [115]. The molecular docking method analyzes the interactions of these biomolecules at the atomic
level and allows the identification of effective compounds against plant stress.
These calculations are usually performed to evaluate the binding affinity of natural or synthetic ligands with proteins that play a critical role in the plant defense system (e.g., superoxide dismutase, catalase, and HSPs). Thus, by determining which compounds interact more strongly with target proteins under a certain stress condition,
potential compounds that can increase plant stress tolerance can be identified [116].
In addition, molecular docking studies enable the screening of plant bioactive
compounds and the elucidation of the roles these compounds play in plant metabolism. For example, by examining the interactions of compounds such as proline and
ABA with plant target proteins against drought stress, mechanisms that reduce water
loss and maintain cellular homeostasis can be revealed [117].
As a result, molecular docking calculations are an important tool in understanding plant stress biology and developing new biotechnological strategies to increase
plant resistance. This approach contributes to the design of plant stress-resistant genotypes or biotechnological interventions, providing innovative solutions in the fields
of sustainable agriculture and plant biotechnology [118].
Chapter 8 Metabolic and hormonal responses of medicinal and aromatic plants 311
1HJO protein is a protein that plays an important role in cellular processes and is
often associated with antioxidant defense mechanisms [119]. In studies on protein
structures, 1HJO has been associated with enzymes that play a role especially in oxidative stress conditions. This is of critical importance in terms of providing protection
against biotic and abiotic stress factors in plants.
Throughout their life cycle, plants are exposed to a variety of stressors. These
pressures are often classified into two primary categories: abiotic stress and biotic
stress. Environmental conditions such as drought, salt, excessive heat, extreme cold,
and ultraviolet radiation may all produce abiotic stress [120]. These kinds of stressors
disturb the cellular equilibrium of plants and lead to an increase in the creation of
free radicals. Living elements such as harmful organisms (pathogens and insects) and
competitive plants are responsible for biotic stress.
When plants are under stress, they produce more molecules known as ROS. ROS
may cause damage to cellular membranes, mutations in DNA, and damage to protein
structures [121]. The 1HJO protein is important for detoxifying ROS since it has antioxidant action. These characteristics improve the capacity of plants to adapt and endure
under challenging environmental circumstances.
The functions of the 1HJO protein include antioxidant protection, protecting the
structure of proteins that are denatured during stress, and increasing the adaptive capacity of plants by regulating genetic expression during the stress response [122] (Table 8.1).
In the field of agriculture, increasing the stress tolerance of plants is a critical
strategy for maintaining productivity [123]. Promoting the production of proteins such
as 1HJO through biotechnological methods or ensuring that they are expressed more
genetically can increase the resistance of plants to stress conditions such as drought
and salinity. For example, the increase in 1HJO protein in plants exposed to drought
stress can help plants limit water loss and protect cell membranes. In salinity stress,
this protein, which regulates ion balance and plays a role in ROS detoxification, can
maintain plant health and growth [124] (Figures 8.5–8.7).
Molecular docking calculations have been evaluated to understand plant responses to environmental stress factors such as drought, salinity, and pathogens, and
to analyze their biomolecular interactions. By examining the binding affinities of natural or synthetic compounds with defense proteins (e.g., 1HJO), stress mechanisms
have been elucidated, biologically active compounds have been identified, and innovative strategies have been developed to increase plant stress tolerance [125].
The 1YET protein is a molecule that is involved in the defensive systems that
plants generate in response to environmental and biological challenges [126]. This
protein has a regulatory impact, particularly in plant metabolism, and is essential for
maintaining cellular homeostasis and guaranteeing survival under stressful situations.
Throughout their life cycle, plants are subjected to abiotic challenges, including
drought, salt, temperature variations, and ultraviolet radiation, as well as biotic stresses,
such as diseases and insects [127]. These stressors generate abnormalities in the meta-
312 Esra Uçar et al.
Glide
posenum
Glide
einternal
Glide
energy
Glide
emodel
Glide
ecoul
Glide
evdw
Table 8.1: Numerical values of the docking parameters of the molecule against protein.
Glide
hbond
Glide ligand
efficiency
score
HJO Docking
Abscisic acid −. −. . −. −. −. −. −. .
Aminocyclopropane carboxylic acid −. −. −. −. −. −. −. −. .
Ascorbic acid −. −. −. −. −. −. −. −. .
Benzyladenine −. −. −. −. −. . −. −. .
Citric acid −. −. −. −. −. −. −. −. .
EDTA −. −. −. −. −. −. −. −. .
Epigallocatechin gallate −. −. −. −. −. −. −. −. .
Geldanamycin −. −. −. −. −. . −. −. .
Glutathione −. −. −. −. −. −. −. −. .
Jasmonic acid −. −. −. −. −. −. −. −. .
Kinetin −. −. −. −. −. −. −. −. .
Phytochelatins −. −. −. −. −. −. −. −. .
Proline −. −. −. −. −. −. −. −. .
Quercetin −. −. . −. −. . −. −. .
Radicicol −. −. −. −. −. −. −. −. .
Rutin −. −. −. −. −. −. −. −. .
Salicylic acid −. −. −. −. −. −. −. −. .
trans-Zeatin −. −. −. −. −. −. −. −. .
Trehalose −. −. . −. −. . −. −. .
Trolox −. −. −. −. −. −. −. −. .