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81.
Ammer Mohammadi-Nasab Alireza Motallebi-Azar Ali Movafeghi Mohammadreza Dadpour 《Russian Agricultural Sciences》2011,37(4):303-306
This research is performed for evaluating the morphogenesis responses of thin cell layers (TCL) of alfalfa (Medicago sativa cv. Karysary) hypocotyls. TCLs (0.1–0.5 mm) were obtained from sterile hypocotyls that were cultured to SH medium containing
various combinations of 2,4-D and kin (0, 0.5, 1, 1.5 and 2 mg/l). Unexpectedly, the percentage of callus induction (PCI)
and Callus diameter (CD) were not affected by different concentrations of 2,4-D and kin. PCI was 100% without any correlation
to hormonal combinations. Significantly the difference between concentrations of 2,4-D and kin for percentage of somatic embryogenesis
(PSE) was observed (p < 0.01) so that, the maximum PSE occurred with 1.5 mg/l 2,4-D and without kin. The 2,4-D and kin interaction was not significant
for PSE showing that each of these hormones affected by PSE independently. The number of embryoids (NE) was significantly
different on the various concentrations of 2,4-D (p < 0.05) and maximum NEs were observed on 1.5 mg/l 2,4-D and without kin. 相似文献
82.
G. Weber-Blaschke R. Heitz M. Blaschke C. Ammer 《European Journal of Forest Research》2008,127(6):465-479
This study aimed to improve knowledge about the nutritional status, site requirements and site classification for European
ash (Fraxinus excelsior L.) and sycamore maple (Acer pseudoplatanus L.) by reinvestigating young plantations from 1991/1992 on windfall-affected areas in Bavaria/Germany after another decade.
Compared to the first survey in 1995, most stands improved their nutritional status until 2006. With the data set of element
concentrations in leaves of ash and sycamore available, the range of adequate nutrition could be determined for these species
in the pole stage phase. Both species show considerable height growth on a wide range of sites. Mean annual height growth
of dominant sycamore trees increased with rising foliar N or P concentrations but not for Ca, Mg, K, Mn, Fe and Al. For ash,
there was no relationship between the foliar nutrient level of any element and mean annual height growth. However, total height
around age 20 was favourably influenced by high base saturation and a good water supply at well-drained sites. On acid soils,
where nutrients are delivered by subsurface water flow, well-growing stands are found as well. Soil water status according
to the state forest soil classification had no significant impact on mean annual height growth. Ash and sycamore show reduced
productivity on some (moderately) dry soils and fail on poorly drained moist sites. Based on these results, the classification
of forest sites suitable for ash and sycamore within the Bavarian study sites was revised.
Dedicated to Professor Dr. Karl-Eugen Rehfuess on his 75th birthday. 相似文献
83.
Sabine Müller Christian Ammer Stefan Nüsslein 《European Journal of Forest Research》2000,119(1-6):32-42
The study applies structural indices using the example of an oak (Quercus petraea (Matt.) Liebl.) — chequer tree (Sorbus torminalis (L.) Crantz) stand in order to derive recommendations for the silvicultural treatment of Chequer trees. The investigated stand, located in the northern part of Bavaria, comprises eight tree species and four shrub species. Various indices were used to analyse the stand structure and the crown coverage frequency. It was shown that chequer trees, which are presently of high economic interest, are strongly oppressed in the upper layer and almost completely missing in the lower layers of the stand. The possible reasons for this finding and alternatives for the further management of the stand are discussed. Persistent and repeated thinnings in order to ensure sufficient crown development of the chequer trees seem to be essential for their survival. 相似文献
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90.
Nicholas Fisichelli Torsten Vor Christian Ammer 《European Journal of Forest Research》2014,133(4):587-596
Climate change includes not only shifts in mean conditions but also changes in the frequency and timing of extreme weather events. Tree seedlings, as the potential future overstory, are responding to the selective pressures of both mean and extreme conditions. We investigated how increases in mean temperature and the occurrence of late spring frosts affect emergence, development, growth, and survival of 13 native and non-native broadleaf and conifer tree species common in central Europe. Three temperature levels (ambient, +3, and +6 °C) and three spring frost treatments (control, late, and very late) were applied. Development responses of first-year seedlings to warmer temperatures were similar in direction and magnitude for broadleaf and conifer species. Stem size also increased with rising mean temperature for most species, though broadleaf species had maximal height advantage over conifer species in the warmest treatment. Sensitivity to frost differed sharply between the broadleaf and conifer groups. Broadleaf survival and stem length exhibited strong reductions due to frost events while conifer species only showed minor decreases in survival. Importantly, more rapid development and earlier leaf-out in response to warmer temperatures were associated with increased mortality from frost for broadleaf species but decreased mortality for conifer species. This research suggests that compositional shifts in the direction of species favored by increasing mean temperatures may be slowed by extreme events, and thus, the occurrence and impacts of such weather events must be acknowledged and incorporated into research and forest planning. 相似文献