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UDC: 634.511
PHOTOSYNTHETICALLY ACTIVE RADIATION AND TRANSPIRATION INDICES
OF TREES AND SHRUBS IN THE WALNUT FORESTS OF THE WESTERN TIEN
SHAN
Muxsimov Nurullo Po‘latovich
,
Doctor of Science (Phys.), Senior Researcher, Research Institute of Forestry
E-mail:
Jo‘rayeva Nargiza Xusan kizi
PhD student at the Forestry Research Institute
E-mail:
Abstract:
This article studies the photosynthetically active radiation (PAR) and transpiration
processes of various tree and shrub species in nut-bearing forests of the Western Tien Shan
mountain range. The study analyzed the influence of climate, soil and microclimate factors on
plant water exchange and photosynthesis processes. The results showed that light intensity and
leaf temperature activate the transpiration process, while relative humidity of the air slows it
down. It was noted that high temperature and low soil moisture negatively affected the
development of seedlings. The results of the study are important as a scientific basis for
ensuring the stability of forest ecosystems in mountainous areas and managing natural
regeneration processes.
INTRODUCTION.
The processes of photosynthesis and transpiration of plants are of great
importance for their growth, development, and adaptation to the environment . Forest
ecosystems, especially in mountainous regions, are exposed to complex climatic conditions,
which affect the ecological stability of plants. The nut-bearing forests of the Western Tien Shan
are characterized by their biodiversity and sensitivity to climate change. Therefore, studying the
photosynthesis and water exchange parameters of plants in this region is necessary to ensure
ecosystem stability and scientifically manage natural regeneration processes. In this study, the
photosynthetically active radiation (PAR) and transpiration indices of tree and shrub species
were studied, and the relationship between them and climatic and soil parameters was analyzed.
MATERIALS AND METHODS
The process of photosynthesis and transpiration are the main mechanisms that ensure water and
energy exchange in plants, and they depend on climatic conditions, soil properties, and
biological characteristics of plant species [11]. Previous studies have shown that changes in
elevation and relief can significantly affect photosynthesis and transpiration rates in
mountainous regions [9]. Under conditions of high temperature and low humidity, stomatal
control of plants can change, reducing photosynthetic efficiency [6]. However, there are limited
studies on the adaptation of tree species to climate change in Uzbekistan, especially in the
Western Tien Shan [3].
The research area was the walnut forests of the Qorankul forest department of the State Forest
Service of the Republic of Uzbekistan, located at an altitude of 1030 m above sea level in the
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Western Tien Shan mountain range. 135 tree and shrub seedlings were identified in the selected
150 m² area, and their biometric and phenological indicators were regularly monitored on the
20th of each month starting from March 2024.
Photosynthetically active radiation (PAR), transpiration rate and transpiration flux were
recorded using a LI-COR 6400XT spectrophotometer and other special instruments.
Microclimate parameters, including air and leaf temperature, relative air and leaf humidity,
were measured using YSI and HOBO measuring devices. Soil samples were analyzed for pH,
moisture and organic matter content using standard laboratory methods. The obtained data were
entered into SPSS and Excel was studied using correlation analysis and statistical methods
using software.
RESULTS
In the nut-bearing forests of the Western Tien Shan, tree and shrub species are
mainly negatively affected by abiotic factors.
Among the problems associated with global
climate change, the lack of soil moisture is of particular importance. The results of the study
showed that the high air temperature (average around 40 °C) and the decrease in soil moisture
to 4–6% observed in the summer months prevent plants from fully satisfying their water needs.
As a result, water shortages slow down the growth process of seedlings, in some cases leading
to heat stroke (heat damage).[10]
Also, unexpectedly warm weather conditions were observed in July 2025. This caused early
fruit drop and extensive leaf scorch of Pontic hawthorn (
Crataegus pontica
C.Koch.) and
Turkestan hawthorn (
Crataegus turkestanica
Pojark.). Low relative humidity and increased
wind speed increased water loss in plants, further increasing the level of damage[2].
In addition, under high temperature conditions, the stomatal control mechanism of plants is
disrupted, reducing the efficiency of photosynthesis and transpiration processes. This, in turn,
worsens the overall physiological state of plants, weakens their ecological stability, and
significantly complicates natural recovery processes[1].
These factors are among the main causes of damage to tree and shrub species in nut forests of
the Western Tien Shan and require special attention in forestry management.
“Photosynthetically active radiation and transpiration indices by tree species”
N
o
.
Tree and
shrub
names
ARH
Relative
humidit
y
%
LRH
Leaf
Moistu
re
%
AirT Air
tempera
ture
(
0
C)
LeafT
Leaf
temper
ature
(
0
C)
PAR
Photosynthe
tically Active
Radiation
(µmol/m²/s)
Transpi
ration
and
water
flow rate
m³/s
Transpira
tion
(µmol/m²/
s)
1 Condo
pistachio
28.2
36.1
33.4
33.2
153
0.66
510
2 Turkestan
hawthorn
30.4
32.3
34.9
36.8
2005
0.67
6683.3
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3 Pontica
hawthorn
29.6
34.9
35.4
35.2
1090
0.69
3633.3
Transferred
field dimensions
as a result different tree - bush types
photosynthesis active radiation ( PAR ) and transpiration indicators noticeable difference
to do was determined . In the case of
Pistacia vera L.
, the average air temperature was 33.4 °C,
leaf temperature was 33.2 °C, relative air humidity was 28.2%, and leaf moisture was 36.1%.
Under these conditions, the PAR value was 153 µmol/m²/s, the transpiration rate was 0.66 m³/s,
and the transpiration flux was 510 µmol/m²/s. This indicates that both photosynthesis and water
exchange are relatively slow at low light intensities ( Table 1 ) [4].
In Turkestan hawthorn (
Crataegus turkestanica
Pojark.) the air temperature was
34.9 °C, the leaf temperature was 36.8 °C, the relative humidity of the air was 30.4%, and the
leaf moisture content was 32.3%, and the PAR value reached 2005 µmol/m²/s. Such a high
intensity of the light flux sharply activated the transpiration process in the leaf, increasing the
transpiration rate to 0.67 m³/s and the transpiration flux to 6683.3 µmol/m²/s. This situation
indicated that under high PAR conditions, the leaf stomata opened wider, and the processes of
gas exchange and water evaporation were activated [8].
Pontic hawthorn (Crataegus pontica C.Koch) had an average air temperature of 35.4 °C,
leaf temperature of 35.2 °C, and a PAR value of 1090 µmol/m²/s. The transpiration rate was
0.69 m³/s, and the transpiration flux was 3633.3 µmol/m²/s. Although this indicator is lower
than that of Turkestan hawthorn, it shows much higher values than that of Khandon pistachio.
STATISTICAL ANALYSIS
Based on the data obtained during the study, the correlation analysis method was used to
determine the relationship between PAR, leaf temperature, relative humidity, and transpiration
flux, and it was found that there was a significant relationship between them.
First, a strong positive correlation was observed between PAR and transpiration flux
(correlation coefficient r = 0.98; p < 0.05). This result suggests that as light intensity increases,
the process of water evaporation (transpiration) in plant leaves also increases. As the amount of
light required for photosynthesis increases, the stomata of the leaves open and water
evaporation increases, which helps plants to actively carry out water exchange and gas
exchange.
Secondly, a significant positive correlation was also found between leaf temperature and
transpiration flux, with a correlation coefficient of r = 0.91 (p < 0.05). This means that as leaf
temperature increases, water evaporation from the leaf surface becomes more active. At higher
temperatures, the rate of evaporation of water molecules from the leaf surface increases, and
transpiration increases. This process helps to maintain the plant's thermal balance.
Third, a strong negative correlation was observed between relative humidity and transpiration (r
= –0.88). This means that the drier the air, the higher the rate of water loss by plants. When
relative humidity is low, the rate of water vapor absorption from the atmosphere is high, and the
process of water evaporation from plant leaves is accelerated. As a result, plants lose more
water and the risk of water shortage in drought conditions increases.
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These correlations are important in understanding the adaptation of plants to environmental
conditions and water exchange processes. They serve as a scientific basis for analyzing the
interrelationship between photosynthesis and transpiration processes, especially in the context
of climate change in mountainous regions, and for developing effective measures to maintain
the ecological stability of forests and manage water resources.
CONCLUSION:
The results of the study showed that the photosynthesis and
transpiration processes of plants in the nut forests of the Western Tien Shan mountain
range are highly sensitive to climate and soil parameters. In the Pistacia vera L.
species, the transpiration process was slow under low light conditions, which
indicated their adaptation to semi-desert and arid climates. In the Turkestan hawthorn
(Crataegus turkestanica Pojark.) and Pontic hawthorn (Crataegus pontica C.Koch.),
high light and temperature conditions significantly activated the transpiration process,
which indicates their ecological adaptability.
Statistical analysis revealed a strong positive correlation between light intensity (PAR) and
transpiration flux (r = 0.98; p < 0.05), as well as a significant positive correlation between leaf
temperature and transpiration flux (r = 0.91; p < 0.05). A strong negative correlation was
observed between relative humidity and transpiration (r = –0.88). These results indicate that
plant water exchange processes are directly dependent on light and temperature conditions.
At the same time, the sharply continental nature of the climate in the region and the decrease in
soil moisture slow down the growth and development processes of plants, negatively affecting
their natural regeneration. The results of this scientific research serve as an important scientific
basis for developing strategies for forest management, water resource conservation, and
environmental sustainability in the Western Tien Shan mountain range.
REFERENCES:
1. Ambs D. Regeneration dynamics in mixed mountain forests at their natural distribution
range in the Western Rhodopes // Forest Ecology and Management. - 2020.
2. Berdiyev ET, Mukhamedjanov A. Scenic tree-bush plants : classification , reproduction ,
care , form to give . – Tashkent: ToshDAU, 2018. – 86 p.
3. Butkov YA Biological characteristics Greek orexa and bogarnix Kulturax and Svyazi s
uluchsheniyem ego mineral pitania - Tashkent, 1974.
4. Chernova GM, Khamzayev AX, Eshankulov BI Foothills of the Western Tien Shan lazy
in their lands trench pistachio industry on plantations cultivation Technology . – Tashkent, 2019.
– P. 51–59.
5. Chazdon RL Beyond deforestation: restoring forests and ecosystem services on
degraded lands // Science. - 2008. - Vol. 320, No. 5882. – P. 1458–1460.
6. Flexas J., Medrano H. Drought-inhibition of photosynthesis in C3 plants: stomatal and
non-stomatal limitations revisited // Annals of Botany. - 2002. - Vol. 89, No. 2. – P. 183–189.
7. Islamov A. Trees and shrubs Biology . – Samarkand: Samarkand University publishing
house , 2015. – 180 p.
8. Jones HG Stomatal control of photosynthesis and transpiration // Journal of
Experimental Botany. - 1998. - Vol. 49, No. 1. – P. 387–398.
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ISSN: 2692-5206, Impact Factor: 12,23
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Journal:
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9. Körner C. The use of altitude in ecological research // Trends in Ecology & Evolution. -
2007. - Vol. 22, No. 11. – P. 569–574.
10.
Mukhsimov NP, Jurayeva NX Forests of the Western Tien Shan status and
monitoring // Uzbekistan agrarian science Bulletin . – 2024. – No. 2(14). – P. 145–147.
11.
Zhang X., Friedl MA, Schaaf CB Monitoring vegetation phenology using
MODIS // Remote Sensing of Environment. - 2003. - Vol. 84, No. 3. – P. 471–475.
