DIGITALNA ARHIVA ŠUMARSKOG LISTA
prilagođeno pretraživanje po punom tekstu



ŠUMARSKI LIST 11-12/2009 str. 9     <-- 9 -->        PDF

M. Čater, P. Simončič: PHOTOSYNTHETIC RESPONSE OF YOUNG BEECH (Fagus Sylvatica L.) ... Šumarski list br. 11–12, CXXXIII (2009), 569-576


Light saturation curves were established to define
comparable ecophysiological response of net assimilation
(A) in beech leaves to different light intensities in
different plots and in comparable potential light conditions,
as described byPotočić etal. (2009).All photosynthesis
measurements were performed at a
constant temperature of the measurement block (20oC),
a CO concentration of 350 µmol/l, flow 500 µmol/s


2


and different light intensities: 0, 50, 250, 600 and


2


1200µmol/ms. Measurements started at ambient light
conditions that were reduced to reach zero, then followed
by a gradual increase toward maximum values, so
that stomata could adapt.


A-Ci curves were established to compare and define
assimilation response of trees (A) to different intercellular
CO concentrations (Ci): measurements were per


2
2


formed at constant light 600 µmol/ms, humidity,
constant block temperature 20 oC and flow 500µmol/s,
while ambient CO was varied as 0, 50, 100, 350, 700


2


and 1000 µmol/l. Maximal assimilation (A ) rates


max


and calculated compensation points (CP) for the light
saturation andA-Ci curves were used in comparisons
of trees between different plots. Both types of response
were measured with an LI-6400 portable system on at
least three sun leaves per plant, located in the upper
third of the tree-crown height on every plot. Twelve
trees were measured on each plot, four per same canopy
light conditions.


Water use efficiency of photosynthesis (WUE), a
quantitative measure of the instantaneous gas exchange
in leaves was expressed as the ratio of carbon gain per
water lost [mol HO/µmol CO] (Larcher 1995,


22


Lambersetal., 1998), while photosynthetic-use efficiency
(PNUE) as the carbon gain per unit leaf nitrogen
[µmol CO/gN] (Larcher 1995, Lambers et al.,


2


1998) for each light category, respectively.Atotal of 20
leaves were sampled per seedling in the upper crown
position, then cool-stored in airtight conditions. Fresh
leaves were weighed and scanned for the leaf area.
Leaves were dried at 105ofor 24 hours until constant
weight and weighed for the dry mass.


Analyses of variance (ANOVA) and post hoc LSD
analysis were used after testing data to meet conditions
of normality. Probability values of P<0.05 (*), P<0.01
(**) and P<0.001 (***) were considered significant.
Statistical data analysis was done with the programme
R(http://www.r-project.org/).


RESULTS – Rezultati istraživanja


2


The nitrogen content defined per leaf unit (mg/cm)
was different between Pohorje and Kočevje plots in canopy
(df ; F=105.13***), edge (df ; F=6.19*) and


1,30
1,30


gap conditions (df ; F=40.99***). On every plot, the


1,30


amount was highest in forest gap and lowest under
shelter conditions, except in virgin forest, with maximum
values at the forest edge (Table 2). Differences
between edge and open area conditions were not significantly
different on both plots from Kočevje (Table 3).


Table 2
Average leaf nitrogen content per leaf area, water use efficiency (WUE) and photosynthetic nitrogen use efficiency
(PNUE) on plots (means ± SE, n=8)


Tablica 2.Prosječni sadržaj dušika po jedinici površine lista, efikasnost uporabe vode (WUE) i fotosintetska efikasnost uporabe
dušika (PNUE) na plohama (sredine± SE, n=8)


Nitrogen (N) [mg/cm
2
] WUE [mol H
2
O/µmol CO
2
] PNUE [µmol CO
2
/gN]
Plot
Ploha
Canopy
Zastor
Edge
Rub
Gap
Otvoreno
Canopy
Zastor
Edge
Rub
Gap
Otvoreno
Canopy
Zastor
Edge
Rub
Gap
Otvoreno
Brička 7.5±1.2 9.7±1.3 12.7±1.4 20.0±2.1 18.7±2.3 16.6±2.8 0.04±0.002 0.03±0.002 0.04±0.004
Kladje 8.8±1.0 12.4±1.7 18.2±1.9 22.9±2.4 20.4±1.5 15.8±2.2 0.04±0.005 0.03±0.003 0.02±0.003
Vrhovo 4.5±0.9 8.6±1.5 10.9±2.1 17.9±1.8 12.2±2.7 8.9±1.8 0.06±0.008 0.06±0.003 0.04±0.005
Sn. jama 4.7±0.8 10.4±0.7 10.7±1.6 19.9±3.3 18.8±3.2 15.2±1.9 0.10±0.006 0.08±0.002 0.08±0.003
Rajhenav 3.4±0.8 9.0±0.6 8.9± 1.3 20.3±2.6 20.9±3.1 19.9±3.3 0.08±0.006 0.06±0.002 0.04±0.006


The values for water use-efficiency (WUE) were
highest under shelter on all plots, ranging from 17.9


22.9mol HO/µmol CO, with the exception Rajhenav,


22


where maximum values were measured at the forest
edge (20.9 mol HO/µmol CO) (Table 2). Although the


22


value measured at the forest edge in Rajhenav was
greater from that measured in gap it was statistically
not significant (20.9 mol HO/µmol CO compared to


22


20.3mol HO/µmol CO, respectively).Asimilar rela


22


tion was determined for photosynthetic nitrogen use efficiency
(PNUE), highest under shelter at Snežna jama


(0.10µmol CO/gN).The highest values for the maxi


2


mum assimilation rate (A ) was measured in the open


max


(gap) atVrhovo, followed by the plots from the Pohorje
complex (Brička and Kladje), while the lowest values
were measured on plots in Kočevski Rog (Snežna
jama, Rajhenav) (Table 4).