Quantitative characters variability and diseases / pests’ tolerance of some of Salix SP. Accessions

The oil crisis of the last decades of the twentieth century has led researchers to turn their attention to alternative sources of energy, the so-called green energy. One of the genres intensively studied for bi-omass production was the genus Salix. In Europe, in Sweden, were made the first Salix hybrids for short-rotation crops (SRC). Willows are used for wood plantation, cellulose and paper production, in pharma-ceutical industry, for soil phytoremediation, like pioneer species by their role in ecosystem restoration, increasing biodiversity and for biomass production (Berg, 2002). In Romania, willow SRC for biomass production started after 2005. There are about 1500 ha of willow SRC, 400 ha of them are in Banat area. All of these cultures were established with Swedish clones, especially clone Inger. Swedish clones and hybrids registered good results in Sweden and North-West Europe countries with cool, wet climate, but in Romania they have not achieved spectacular results in some areas, such as North-Est Timis county and Oltenia area, the crops being compromised in the first years. In the view of the extension of cultivated areas unsuitable for agriculture, with forestry and energy crops, there are necessary comprehensive studies to find optimal solutions - selection of genotypes to their potential production, but also to be adapted at temperatures over 35ºC and severe drought. A willow breeding program for the biomass production has to be started and a potential genitors collection (local germplasm) sets the stage for the beginning of a science-based breeding program. The collection of potential genitors (39 genotypes, 12 species) was established in the spring of 2015 on the territory of the Experimental Didactical Station belonging to Banat’s University of Agricul-tural Sciences and Veterinary Medicine from Timisoara. The biological material (46 cuttings for each genotype) was planted in double rows 75 cm apart with double rows spaced at 150 cm and an 80 cm in-row spacing. During the growing season was made chemical and mechanical weed control. There were not applied phytosanitary treatments, in order to test the natural resistance of the genotypes. The sprouting capacity and biometric observations were made in an experimental trial with uncut and cutback shoots and biomass was estimated. Following the biometric observations performed biannually and the evaluation of tolerance / re-sistance to diseases and pests, a wide variability was noticed, both interspecific and intraspecific. The quantitative traits varied significantly with genotype and management practice. Large variability was ob-served in terms of survival rate but also in sprouting capacity, maximum height, and diameter. The field trial recommends some genotypes with particularly high production, clone 30 Salix pentandra L. and clone 31 S. triandra L. for crops with short rotation cycle, both in normal soil and climatic conditions and on degraded lands. The most tolerant genotypes both to pests and diseases were belonging to S. rosmarinifolia and S. pentandra. The most sensitive species include genitors from S. fragilis, S.alba and S.purpurea. Tolerance to pests and diseases was dependent on species and origin.

Modeling the Emergence and Growth of Alligatorweed at Different Field Capacity Levels

ABSTRACT: A study focusing on different field capacity levels was planned in the Weed Science Lab, Department of Agronomy, University of Agriculture Faisalabad. Fresh alligatorweed was harvested from the Agronomy fields and cuttings (2 cm length) were made from it. These cuttings were placed at 25%, 50%, 75% and 100% field capacity levels in pots for 25 days. The results of the experiments revealed that at all field capacity levels, fragments of alligatorweed were able to sprout and grow. Increased moisture levels significantly increased the emergence ability and survival of the alligatorweed plants upto a certain level. Compared with the control (25% FC), emergence time of the sprouts in the maximum moisture regime (100% of FC) decreased by 40% (12.94 days vs.7.17 days). By contrast, the survival rate of the fragments decreased by 60% (5 vs. 1.75) although survival and growth rate increased at first with 50% FC and 75% FC. Maximum sprouting and growth were found at 50% field capacity. Field capacity does affect the sprouting capacity of alligatorweed fragments but it has only a little influence on growth parameters. The results suggest that alligatorweed can sustain dry conditions to a great extent and also has the ability to sprout and grow in fully submerged soils.

Sprouts of shoot-clipped oak (Quercus alba and Q. robur) germinants show morphological and photosynthetic acclimation to contrasting light environments

Sprouting by woody plants can increase species resilience to disturbance and foster regeneration during periods with little recruitment from seed. Though sprouting often plays a critical role in oak forest regeneration, there is little information available on sprouting capacity and sprout physiology at the seedling stage, particularly for new germinants. This study compared sprouting capacity and sprout photosynthesis of shoot-clipped germinants of two temperate oaks established in contrasting light environments. We studied the North American Quercus alba and the European Q. robur, both are in the section Quercus and appear to share similar biological and ecological requirements. Sprouting capacity for both species was enhanced under high light availability (29% more sprouts per plant), a response not previously noted for oak germinants. Seedling sprouts acclimated to high light with a 34% decrease in leaf area ratio, a 56% increase in leaf mass per area, and a 49% increase in the light-saturated maximum photosynthetic rate. Though both species appeared similarly adapted to shoot loss, a greater sprouting capacity (29% more sprouts per plant) and plant-level net photosynthesis (73% higher) was observed for Q. robur, regardless of light environment. As naturally regenerated oak seedlings in forest understories often experience disturbance or stress resulting in shoot loss or die-back, our results highlight the importance of the light environment during early plant development. Our comparison of temperate oaks from different continents should facilitate exchange of successful stand regeneration practices within the range of temperate oak forests.

Coppice Woods and Pollard Trees in the Visual Arts

The sprouting capacity of some broadleaves has been used for their regeneration since ancient times. Often concurrently with taking advantage of sprouting stools, the trees used to be shaped also by pruning their stems, namely on pasturelands and in grazing forests. The activity of woodcutters and shepherds was obviously rather common in warmer climates with broadleaved stands because coppice and pollard trees appear relatively often in the visual arts from ancient works through the period if the Italian and German Renaissance up to the romantic and realistic landscape painting of the 19thcentury overlapping into the 20thcentury. For centuries, most frequently illustrated in European and Czech paintings have been pollard willows (Salix spp.). Other coppice and pollard tree species identified in paintings are oaks (Quercus spp.), hornbeam (Carpinus betulus), European beech (Fagus sylvatica), European chestnut (Castanea sativa), and rarely other species, too. Artists apparently often used bizarrely shaped woods to increase the dramatic atmosphere of their landscape sceneries as well as figural compositions, and the coppice and pollard trees had certainly also a symbolic meaning in some of their works.