The present work has explored for the first time acclimation of upper versus lower canopy leaves along an altitudinal gradient. We tested the hypothesis that restrictive climatic conditions associated with high altitudes reduce within-canopy variations of leaf traits. The investigated beech (Fagus sylvatica L.) forest is located on the southern slope of the Hrubý Jeseník Mountains (Czech Republic). All measurements were taken on leaves from upper and lower parts of the canopy of mature trees (>85 years old) growing at low (400 m above sea level, a.s.l.), middle (720 m a.s.l.) and high (1100 m a.s.l.) altitudes. Compared with trees at higher altitudes, those growing at low altitudes had lower stomatal conductance, slightly lower CO(2) assimilation rate (A(max)) and leaf mass per area (LMA), and higher photochemical reflectance index, water-use efficiency and Rubisco content. Given similar stand densities at all altitudes, the different growth conditions result in a more open canopy and higher penetration of light into lower canopy with increasing altitude. Even though strong vertical gradients in light intensity occurred across the canopy at all altitudes, lower canopy leaves at high altitudes tended to acquire the same morphological, biochemical and physiological traits as did upper leaves. While elevation had no significant effect on nitrogen (N) and carbon (C) contents per unit leaf area, LMA, or total content of chlorophylls and epidermal flavonoids in upper leaves, these increased significantly in lower leaves at higher altitudes. The increases in N content of lower leaves were coupled with similar changes in A(max). Moreover, a high N content coincided with high Rubisco concentrations in lower but not in upper canopy leaves. Our results show that the limiting role of light in lower parts of the canopy is reduced at high altitudes. A great capacity of trees to adjust the entire canopy is thus demonstrated.

The main objective of this study was to evaluate the spectral reflectance in the vertical profile of spring barley canopy at the booting growth stage and to determine how the reflectance gradient changes in relation to crop density and nitrogen (N) nutrition. Vertical gradients of spectral reflectance were studied in field trials with three sowing densities (2, 4 and 6 million of germinating seeds/ha) and two levels of N nutrition (0 and 90 kg/ha). It was found that differences in vegetation indices caused by N nutrition are most pronounced in the second and third leaf from the top, and these increase with increasing sowing density. The vertical gradient of reflectance, specifically the ratio between the leaves F-3/F-1 for vegetation indices based on red-edge reflectance, represents a reliable indicator of number of ears per area unit (R = –0.87 for Normalised Red Edge-Red Index (NRERI) and –0.93 for Zarco-Teja-da and Miller Simple Ratio Index (ZM)). A close relationship to ear productivity was found almost for all observed vegetation indices and any leaf in vertical profile (R = 0.79–0.97). In contrast, the prediction of protein content in barley grain was the most reliable when the red-edge reflectance indices (ZM and NRERI) particularly from upper three leaves were used (R = 0.81–0.88). The results show that the knowledge of reflectance heterogeneity in the vertical profile of canopy can significantly contribute to the interpretation of the measured data, to the differentiation of the N nutrition effect from the response to canopy density, and finally to a more accurate estimation of yield parameters and protein content in grain.

Aboveground biomass, allometric relationships and early to late wood proportions were investigated in two even-aged monocultures of Norway spruce (Picea abies [L.] Karst) located at mountain and highland localities of the Czech Republic. However similar stand age and tree size, mountain trees comparing to them from highland showed less/tapering stems, lower aboveground biomass and lower stem wood density along the whole stem vertical profile as a result of different early to late wood proportion. These proportions were 79 % and 54 % for early wood, and 21 % and 46 % for late wood within mean stem annual circle in mountain and highland locality, respectively. These different proportions seem to reflected site specific growing conditions, particularly highly sufficient water availability during spring time in mountain region- support early wood growth, whereas elevated air temperature during summer time in highland region stimulate late wood growth.

The impact of the relative time of emergence on the growth allometry of Galium aparine L. (cleavers) in competition with Triticum aestivum L. (spring wheat) was studied in a greenhouse experiment. The hypothesis that changes in growth allometry, particularly in the leaf area/ height ratio, caused by a shift in the relative time of emergence, could lead to plants overcoming the competition or to competitive suppression was tested. The plant height, dry weight, total leaf area and vertical distribution were analyzed during the first 83 days of growth. The late emergence of G. aparine substantially influenced the growth dynamics for the dry weight and total leaf area. The dynamics of height growth were affected only following a significant delay in G. aparine emergence. The ratio of dry weight to total leaf area was almost unaffected by the competition. By contrast, the allometric relationship between the plant height and total leaf area was highly sensitive to the relative time of emergence. The results suggest that height is the most important growth trait for the plants to resist increasing competition. Even though the plants responded to competition with elongation, the physiological costs linked with "shade avoidance" caused reductions in the dry weight and leaf area growth that resulted in the total suppression of the late-emerging individuals, in particular when their emergence was >10 days after that of the crop.