Productivity of young shaded oaks (Quercus robur L.) as corresponding to shoot morphology and leaf anatomy
During a 2 year field experiment, pedunculate oaks (Quercus robur L.) were grown from acorns under different and changing light intensities. The four light intensities studied were full daylight and 50, 25 and 10% of full light intensity. Half of the oaks, subjected to experimental full shade (10% relative light intensity) in the first year of growth were then grown under 25% relative light intensity in the second year. Results of quantitative growth analysis (Evans, 1972) reveal a high shoot productivity of the 2-year-old oaks down to 25% relative light intensity. Oaks subjected to the permanent full shade treatment survived but suffered from heavy growth depressions. Content of the storage carbohydrate ‘starch’ is extraordinarily high in 1-year-old oaks. Storage capacity of the root (rates of starch partitioning associated with root dry mass) was at its minimum in oaks grown under 10% relative light intensity. Selected parameters of leaf transection showed distinct transition from ‘sun-leaves’ to ‘shade-leaves’ in oaks subjected to 25% relative light intensity. The transposed oaks (first year 10% relative light intensity, second year 25% relative light intensity) ‘re-gained’ a considerably high shoot productivity. The selected anatomical parameters of the transposed oaks were determined by the light conditions prevailing in the previous year, with the exception of striking increases of inner and outer leaf surfaces.