Nagy, Attila

Nyéki, József

Riczu, Péter

Soltész, Miklós

Szabó, Zoltán

Tamás, János

International Journal of Horticultural Science

English

University of Debrecen Electronic Archive

 International Journal of Horticultural Science 2012, 18 (2): 53–56. 
Agroinform Publishing House, Budapest, Printed in Hungary
ISSN 1585-0404
Introduction
In Hungary about 100 000 hectares of orchards can be 
found, from which apple is cultivated on one of the largest 
areas. The total area of apple and pear orchards is more 
than 45 000 ha. Apple orchards cover about 60% of the 
total pomiculture in Hungary, although in the last period 
the production was reduced (Gonda and Apáti, 2011). The 
production of marketable horticulture products is diffi cult 
without quality horticulture practice, which in many cases 
is the primary condition of appropriate management and 
irrigation systems. The data of the Central Statistics Offi ce 
show that 28% of the apple and pear orchards can be irrigated, 
but only 21% is irrigated. Since horticulture is a water 
demanding sector, high quality fruit-production is diffi cult 
without proper irrigation. Furthermore in some horticultural 
farms there is no irrigation applied, or its techniques is 
improper. There are several experiments going on around 
the world to develop methods of irrigation, which draw 
different technology combination for the water and energy 
saving micro-irrigation. One of the biggest professional 
challenges of the following years is to develop the water 
resource management for apple and pear trees. For this the 
water norm of the trees has to be identifi ed in the different 
phenological stages, the irrigation turns, and technology and 
the transpiration surface.
In orchard plant’s leaf area must determine not only in 
absolute terms, but compared with the growing area (T) also. 
The rate of two values called leaf area index (LAI), which 
is leaf area (m2) per 1m2 soil surface. The LAI is the most 
suitable index in the cultivation practice for the plant mass 
(Szász, 1988). 
LAI – as biophysical status – is in a close relationship 
with the amount of biomass, with the photosynthesis and 
transpiration scale (Nemani and Running, 1989). The 
size and number of leaf determine the leaf area (LA). The 
number of leaf produced is reduced by water stress, nutrient 
defi ciencies and is under hormonal control. The leaf area 
index change species, stage of development, methods of 
cultivation, density of crop. Wagenmakers (1989) found that 
leaf area per tree of apples and pears decreased linearly with 
planting density. Verheij (1972) showed that with apple the 
leaf area per tree declined with increasing planting density 
even with unpruned trees, and was accompanied by a relative 
suppression of lateral growth in the lower parts of the trees.
The leaf area determines the area of transpiration. 
Transpiration is taking place through the stomas of the lower 
epidermis (Boyer, 1985). The stoma is a pore, found in the 
leaf and stem epidermis that is used for gas exchange. The 
Evaluation of fruit tree waterstress condition and 
transpiration with heat fl ux sensors
Nagy, A.1, Riczu, P.1, Tamás, J.1, Szabó, Z.2, Soltész, M.2 & Nyéki, J.2
1University of Debrecen, Centre of Agricultural Sciences and Engineering, Faculty of Agricultural and Food 
Sciences and Environmental Management, Institute of Water and Environmental Management, 
H-4032 Debrecen, Böszörményi 138, Hungary, attilanagy@agr.unideb.hu
2University of Debrecen, Centre for Agricultural and Applied Economic Sciences, Faculty of Agricultural and 
Food Sciences and Environmental Management, Institute for Horticulture, 
H-4032 Debrecen, Böszörményi str. 138, Hungary
Summary: In this study the transpiration properties and response to heat stress of Granny Smith and Jonagold apple species were measured. 
The examinations were set at an orchard near to Debrecen. The chosen trees were two years old, without fruits, in 20l container, placed in 
the mixture of mulch matrix, wood chips and sawdust and grown at the same climatic conditions. One of the most important goals was to 
determine the leaf area of the trees which is a basic data for transpiration modeling. Leaf area was larger (signifi cance level p<0.05) in the 
upper part of the canopy to achieve larger photosynthetic surface. Jonagold species with less leaf number (–18% compared to Granny Smith) 
reached almost the same canopy area, than Granny Smith, due to larger leaf area of Jonagold. Another aim was to measure the transpiration 
rate of the apple trees. The transpiration measurements were carried out by sap fl ow meter. Only a small transpiration difference can be found 
between species. During the investigation time there were wet and cool as well as dry and extremely hot periods. In the case of dry and 
extreme hot periods the transpiration is decreased, which causes decrease in transpiration and enhanced the water stress of trees.
Key words: leaf area index, evapotranspiration, water stress
Nagy, A., Riczu, P., Tamás, J., Szabó, Z., Soltész, M. & Nyéki, J.54
pore is bordered by a pair of specialized parenchyma cells 
known as guard cells which are responsible for regulating 
the size of the opening and are the closest thing a plant has 
to a muscle. (Boldizsár, 2007). In the case of different apple 
varieties, the number of stomas can be different: 200–450 
pores/m2 (Cowart, 1935; Slack, 1974). The apple varieties 
growing faster the density of stomas is higher, while 
smaller varieties have less stoma density (Beakbane and 
Majumdar, 1975). Cowart (1935) established that less stoma 
can be found in the leaves of lower position. The extent of 
transpiration depends on several physical factors as well as 
the opening or the closing of the stomas (Jackson, 2003). 
One of the most signifi cant factors infl uencing transpiration 
is the wind (Mansfi eld and McAnish, 1995). Beukes (1984) 
established a negative correlation between transpiration and 
wind velocity. The transpiration rate is also determined by 
the leaf temperature and the available moisture content of 
the soil. Transpiration is increasing if more water is available 
in the soil: in case of optimal water supply apple trees 
transpirated more water and the conductance of the stomas 
increased (Alleyne et al., 1989; Gower et al., 1990; Frenandez 
et al., 1997). During the day the water potential of apple and 
pear trees is decreasing with the increasing transpiration: 
Goode and Higgs (1973) observed the lowest water potential 
in noontime. Landsberg et al. (1975) and Fernandez et al. 
(1997) examined apple and pear trees under droughty and 
control conditions. They concluded that the closing of the 
stomas is an effective physiological control that reduces the 
rate of transpiration.
Materials and methods
In this study the transpiration properties and response 
to heat stress of Granny Smith and Jonagold apple species 
were measured. The examinations were set at an orchard 
near to Debrecen without irrigation. The investigation period 
was from 5th of July to 5th of September 2011, with 5 day 
pause, caused by technical problems. The chosen trees were 
two years old, without fruits, in 20l container, placed in the 
mixture of mulch matrix, wood chips and sawdust and grown 
at the same climatic conditions. Since different rootstocks 
affect differently the watermanagement of apple trees, 
species with the same rootstock (MM106) were chosen. One 
of the most important goals was to determine the leaf area 
of the trees which is a basic data for transpiration modeling. 
Another aim was to measure the transpiration rate of the 
apple trees. The transpiration measurements were carried out 
by sap fl ow meter. After determining the transpiration and 
transpiration surface of the examined trees, it is possible to 
defi ne the transpiration rate for one square meter. 
Leaf area determination
On 30th September 2011 the leaves were collected from 
each tree. During the leaf sampling the canopy was divided 
into two parts. The leaves from the lower branches were 
separately collected from the leaves of the upper branches. 
Scanning of the leaves was carried out in the laboratory of 
the Institute of Water- and Environmental Management of 
the Centre for Agricultural and Applied Economic Sciences 
of the University of Debrecen. The leaf areas were measured 
by Area Meter 100 (AM 100) leaf area scanner developed by 
the Analytical Development Company. After scanning, the 
data were stored in the memory of the AM 100, then they 
were downloaded to a computer. Nevertheless the digital 
display of the device ensures a permanent monitoring of the 
measurement data. By means of the scanner, not only the 
surface area of the leaves with different sizes and colours, 
but also of the leaves damaged by pests could be determined. 
After each scanning the length and width of the leaf, the 
average and total area and the number, the time and the date 
of the scanning were displayed and stored.
Transpiration measurement
The transpiration was measured by Sap fl ow meter based 
on Stem Heat Balance theory. Sensors was set on the trunk 
of the apple trees. The Dynagage sap fl ow sensor consists of 
a fl exible heater, a thermopile to measure radial heat loss, 
and differential thermocouple pairs to measure the axial 
temperature differences q
u
-q
d
. All of these sensors and heater 
are mounted on a cork substrate and housed inside white, 
refl ective foam, thermal insulating collar. Once the sensor is 
installed on the stem surface, both the sensor and the stem 
sections above and below the sensor are completely covered 
by a heat insulator to minimize thermal perturbations caused 
by the ambient environment. Power is supplied continuously 
to the heater from a regulated DC power source. The 
Dynamax loggers have a power down mode so that power 
is saved at night and the stem is preserved from overheating. 
During the power down mode and at the transitions to power 
on, the sap fl ow is not computed to maintain the accumulated 
fl ow accurately during this unbalanced transition. Figure 1 
shows a stem section and the possible components of heat 
fl ux, assuming no heat storage. 
The heater surrounds the stem under test and is powered 
by a DC supply with a fi xed amount of heat, Qh. Qh is the 
Figure 1. Stem gage schematics (Dynamax manual)
Evaluation of fruit tree waterstress condition and transpiration with heat fl ux sensors 55
equivalent to the power input to the stem from the heater, 
Pin. Qr is the radial heat conducted through the gage to the 
ambient. Qv, the vertical, or axial heat conduction through 
the stem has two components, Qu and Qd. By measuring Pin, 
Qu, Qd, and Qr, the remainder, Qf can be calculated. Qf is 
the heat convection carried by the sap. After dividing by the 
specifi c heat of water and the sap temperature increase, the 
heat fl ux is converted directly to mass fl ow rate. Flow rate is 
expressed as g moisture/hour.
Results and discussion
Transpiration surface
The apple tree leaves collected at the end of the fi nal 
phenological state were scanned and the total transpiration 
and the average leaf areas were determined (Table 1.). 
Concerning Granny Smith species 144 leaves from lower 
part of canopy and 244 from upper part were collected. In the 
case of Jonagold 136 leaves from lower part of canopy and 
183 from upper part were collected. Comparing the leaf size 
within and transpiration surfaces, it can be stated, that in the 
case of both species the photosyntetically active canopy area 
was larger in the upper part of the canopy. This was simply 
caused by the structure of tree for better utilization of the 
light. Leaf area was also larger (signifi cance l evel p<0.05) in 
the upper part of the canopy to achieve larger photosynthetic 
surface. Naturally the transpiration is also higher in this 
region. 
Table 4. Canopy and leaf area of Jonagold and Granny Smith apple species
Leaf area (cm2)
Granny Smith Jonagold
Upper part of canopy
∑ 5413.5 4723.7
1 leaf (mean)       22.19       25.81
Lower part of canopy
∑ 2187.9 2542.3
1 leaf (mean)      15.19       18.69
Whole canopy
∑ 7601.4 7265.9
1 leaf (mean)       19.59       22.77
Comparing the measured area parameters between 
species, there were some differences is found. Though 
only a slight total canopy differences was found (4.44% 
differences between species) the average leaf area was 
signifi cantly (signifi cance level p<0.05) larger in the case of 
Jonagold species. That means Jonagold species with less leaf 
number reached almost the same canopy area, than Granny 
Smith, since there is 18% differences between the species 
concerning number of the leaves, which probably due to 
species properties.
Transpiration of apple trees
For the characterization of the water use and stress of 
the fruit trees, the transpiration of them was investigated, 
concerning the climatic parameters, such as temperature 
and rainfall. In order to compare the transpiration properties 
of apple trees, the measured sap fl ow (g/day) was adjusted 
to one square meter of canopy. On the base of values of 
transpiration only a small difference can be found between 
species. Concerning the whole transpiration period, there was 
an only 4874 g difference in transpiration, which is less than 
5 l. Therefore it can be declared, that signifi cant difference in 
transpiration can not be found between the examined species.
During the investigation time there were wet and cool as 
well as dry and extremely hot periods. In the case of dry and 
extreme hot periods (9th – 13th of July and 24th – 29th August) 
the transpiration is decreased, due to the lack of water in the 
soil and the huge water potential. The decreased transpiration 
means that stomatal closure occurred thus, according to 
several studies (Pethô, 1996) the photosynthesis is also 
blocked and reach its minimum. Not only the transpiration is 
blocked but also the CO
2
 uptake, therefore reactive hidroxil 
radicals are produced which are harmful for the chloroplasts 
and cell membranes, which eventually causes the water stress 
symptoms in plants.
Concerning the wet periods there was suffi cient water 
supply for the apple trees. While the temperature increased 
the transpiration increased as well, furthermore, positive 
correlation (r=0.77) was found between the maximum 
temperature and transpiration.
Conclusions
In the case of both species the photosyntetically active 
canopy area and leaf area was larger in the upper part of the 
canopy for better utilization of the light. Leaves of Jonagold 
tree are signifi cantly larger than Granny Smith which probably 
due to species properties. In the case of dry and extreme hot 
periods the transpiration is decreased, water stress occurred. 
Since there is a positive correlation was found between the 
Figure 2. Transpiration of 1 m2 canopy and the climatic conditions
Nagy, A., Riczu, P., Tamás, J., Szabó, Z., Soltész, M. & Nyéki, J.56
maximum temperature and transpiration properties Sap Flow 
meter can be suitable for not only transpiration monitoring, 
but also for irrigation scheduling and water stress assessment.
Acknowledgements
This study is funded by TECH_08-A3/2-2008-0373 and 
TECH_08-A4/2-2008-0138 projects.
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Evaluation of fruit tree water stress condition and transpiration with heat flux sensors

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Evaluation of fruit tree water stress condition and transpiration with heat flux sensors

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