Template-Type: ReDIF-Article 1.0 Author-Name: E. Palátová Author-Workplace-Name: Mendel University of Agriculture and Forestry, Faculty of Forestry and Wood Technology, Brno, Czech Republic Title: Effect of increased nitrogen depositions and drought stress on the development of Scots pine (Pinus sylvestris L.) - II. Root system response Abstract: Effects of drought stress, stress by increased nitrogen depositions and combined effect of the two stress factors on the growth of Scots pine (Pinus sylvestris L.) were studied in two experimental series in 1994-1997. The drought stress was induced by reduction of atmospheric precipitation by 60%, the increased nitrogen depositions were simulated by repeated applications of ammonium sulphate at a dose corresponding to 100 kg N/ha per year. All stress factors under study impacted the biomass, vertical distribution, functionality and mycorrhizal infection of fine roots. The root system responded to simulated stresses as early as from the very first year of their effect exhibiting greater damage than the above-ground part of the plant (see PALÁTOVÁ 2001). Keywords: Pinus sylvestris L., nitrogen, drought, biomass of fine roots, vertical distribution of fine roots, functionality of fine roots, mycorrhiza Journal: Journal of Forest Science Pages: 237-247 Volume: 48 Issue: 6 Year: 2002 DOI: 10.17221/11881-JFS File-URL: http://jfs.agriculturejournals.cz/doi/10.17221/11881-JFS.html File-Format: text/html X-File-Ref: http://agriculturejournals.cz/RePEc/caa/references/jfs-200206-0001.txt Handle: RePEc:caa:jnljfs:v:48:y:2002:i:6:id:11881-JFS Template-Type: ReDIF-Article 1.0 Author-Name: J. Urban Author-Workplace-Name: Mendel University of Agriculture and Forestry, Faculty of Forestry and Wood Technology, Brno, Czech Republic Title: Occurrence, development and natural enemies of Pemphigus spyrothecae (Homoptera, Pemphigidae) Abstract: In 2001, galls were analysed of Pemphigus spyrothecae Pass. taken in one- to three-week intervals from Populus nigra and P. nigra var. italica at 4 localities in Brno. Fundatrices matured in the first half of June and during the first half of summer produced about 50 offsprings. Virgines produced about 10 offsprings which grew up in winged sexuparae. The winged individuals started to occur in galls from the beginning of August. In galls with intact development, on average 500 aphids developed. Galls with intact development on P. nigra var. italica reached larger average dimensions and contained at least by 4% more aphids than galls on P. nigra. About 5% of fundatrices died already in the 1st instar and other 3 to 6% in higher instars by the beginning of reproduction. At localities under investigation, 7.5 to 39.0% of galls on P. nigra and 3.9 to 13.7% of galls on P. nigra var. italica were occupied by the fly Leucopis puncticornis Meig. (Chamaemyiidae). About 24.3 to 32.2% of galls on P. nigra and 23.3 to 49.3% of galls on P. nigra var. italica were occupied by the bug Anthocoris minki Dohrn (Anthocoridae). Hover flies Heringia heringi (Zett.) and Pipiza festiva Meig. (Syrphidae) killing aphids in 3.8 to 30.4% of galls on P. nigra and 6.5 to 6.8% of galls on P. nigra var. italica were an important regulator. In August (i.e. at the beginning of the formation of winged sexuparae), the majority of galls opened through primary slit-shaped or oval emergence holes. A part (7.8 to 19.5%) of galls with so far intact development, however, remained closed and all aphids contained in them died. Diseases (particularly mycoses) often participated in the accelerated dying of aphids. The effect of mortality factors on the gall size differentiation was evaluated in details. The galls do not cause any leaf area reduction. In the case of mass outbreak, they decrease decorativeness of poplars in street alleys. In August and September, liquid excrements fall out from the galls (honeydew) polluting the environment in villages and housing estates. Keywords: Pemphigus spyrothecae, Leucopis puncticornis, Anthocoris minki, Heringia heringi, Pipiza festiva, development, gall size, harmfulness Journal: Journal of Forest Science Pages: 248-270 Volume: 48 Issue: 6 Year: 2002 DOI: 10.17221/11883-JFS File-URL: http://jfs.agriculturejournals.cz/doi/10.17221/11883-JFS.html File-Format: text/html X-File-Ref: http://agriculturejournals.cz/RePEc/caa/references/jfs-200206-0002.txt Handle: RePEc:caa:jnljfs:v:48:y:2002:i:6:id:11883-JFS Template-Type: ReDIF-Article 1.0 Author-Name: B. Slobodník Author-Workplace-Name: Technical University, Faculty of Forestry, Department of Phytology, Zvolen, Slovak Republic Title: Pollination success and full seed percentage in European larch (Larix decidua MILL.) Abstract: A relationship between the success of pollination and the percentage of full seeds of European larch (Larix decidua MILL.) was studied using several models of non-linear correlation analysis. Although the proportion of pollinated ovules was high in most cases (especially in the middle parts of open-pollinated conelets), the mean percentage of full seeds was extraordinarily low (after the controlled self-pollination even close to zero) and most of the calculated correlation coefficients are lower than the corresponding critical value. This fact gives an evidence for the strong effect of additional important factors causing the empty seed formation in Larix even after the successful pollination of ovules. Keywords: European larch, pollen, empty seeds Journal: Journal of Forest Science Pages: 271-280 Volume: 48 Issue: 6 Year: 2002 DOI: 10.17221/11884-JFS File-URL: http://jfs.agriculturejournals.cz/doi/10.17221/11884-JFS.html File-Format: text/html X-File-Ref: http://agriculturejournals.cz/RePEc/caa/references/jfs-200206-0003.txt Handle: RePEc:caa:jnljfs:v:48:y:2002:i:6:id:11884-JFS