DIGITALNA ARHIVA ŠUMARSKOG LISTA
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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). |