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ŠUMARSKI LIST 1-2/2012 str. 18     <-- 18 -->        PDF

Ž. Škvorc, K. Sever, J. Franjić, D. Krstonošić, M. Poljak: INTENZITET FOTOSINTEZE I VEGETATIVNI ... Šumarski list br. 1–2, CXXXVI (2012), 7-17


ves in the crown of a tree temporarily lose their green color and turn yellow,
which is indicative of plant’s lack of nitrogen nutrition, i.e. the nitrogen deficiency
in the soil. The role of nitrogen as a plant nutriment is connected with
numerous physiological processes responsible for successful growth and development
of plants. For example, nitrogen is an essential element responsible
for an uninterrupted continuation of photosynthetic process and vegetative
plant growth, primarily because of its role in the synthesis of chlorophyll and
certain proteins, such as ribulose-1,5-bisphosphate carboxylase oxygenase
(Rubisco), which is responsible for CO2assimilation. In the previous studies
of forest trees, significant differences were determined in the intensity of photosynthesis
and vegetative development regarding the diverse conditions in
the habitats. These variations are usually due to the lengths of summer
droughts and high temperatures, the intensity of illumination, and the differences
between dry and wet years.


The aim of this study was to, (1) determine the effect of various chemical
characteristics of the soil on the intensity of photosynthesis and the vegetative
growth of pedunculate oak, (2) establish a connection between content index
of the total amount of chlorophyll in the leaf, and the intensity of photosynthesis
and the vegetative growth of pedunculate oak.


The study was conducted during the vegetative period in 2010, on 4-yearold
plants, planted with 2 – 2,5 meters of space between plants. Based on visual
differences in the leaf color, two plots have been set aside – the chlorotic
and the control plots (without chlorosis). Each field contained 8 plants, i.e. 16
in total. The average height of the plants under study before the start amounted
to 1.96 ± 0.44 meters, and the diameter of the trunk 2.5 centimeters, measured
30 centimeters above ground.


In order to determine the differences in the soil’s chemical characteristics
between the two studied plots, the samples were taken on the depth of
0–30 centimeters. The soil reaction was determined with a potentiometer in
the suspension of soil and water, i.e. soil and nKCl. Humus was determined by
the Thorin method, and the total nitrogen level by the Kendahl method. The
content of physiologically active phosphorus and potassium was determined
by the Al-method.


The study determined height and diameter increment for the plants studied,
and also height and diameter increment for primary branches of each plant.
The number of spring and summer shoots with its attending leaves was also
determined. Based on the number and surface area of leaves, as well as the
projection of crown surface on the ground, index of leaf surface was calculated
for each tree.


The measurements of photosynthesis intensity and the index of total chlorophyll
content were performed early in September. The photosynthesis intensity
was measured with the help of the infrared gas analizer portable
device LCpro + (ADC BioScientific). While taking photosynthesis intensity
measurements, each leaf was subjected to illumination intensity of 1500
µmol m-2 s-1, CO2concentration of 380 ± 10 µmol mol-1and the air temperature
of 25 ± 2 °C. The chlorophyll content index was determined by using
chlorophyll content meter CCM-200. By using a portable chamber for measuring
water potential, the measurement of water potential was taken in the
leaves (.) of plants under study.


The chemical characteristics of the soil in the test plots were shown in
Table 1. There was an extremely acidic reaction in the chlorotic plot, and acidic
in the control plot. The chlorotic plot was marked by an extremely low nitrogen
supply, while the control plot had a medium to good nitrogen supply.
The content of physiologically active phosphorus in the chlorotic plot was ex