The gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), causes enormous damage to broadleaved forests in the northern hemisphere where it frequently defoliates large areas of forest. Since outbreaks begin in oak forests, its most suitable habitat, we determined the preference and performance of gypsy moth larvae when reared on three species of native oaks: sessile oak, Quercus petraea (Matt.) Liebl.; Turkey oak, Q. cerris L.; and Hungarian oak, Q. frainetto (Ten.). Leaf expansion and selected physical and chemical characteristics of the oak leaves were also measured. The shortest development time and highest relative consumption (RCR), growth rate (RGR), assimilation efficiency (AD), efficiency of conversion of ingested food (ECI) and digested food into larval biomass (ECD) values were recorded when larvae were fed on Turkey oak. Two-choice tests revealed that Turkey oak is the preferred host plant. It had the highest total soluble protein and leaf nitrogen content, lowest C/N ratio and its phenology was well synchronized with the hatching of the larvae. The worst performance and lowest preference index were recorded when fed on Hungarian oak, the leaves of which had the lowest protein and nitrogen content, while in terms of the values for preference and performance the larvae fed on sessile oak were intermediate. Our results indicate that forests with Turkey oak are highly likely to be defoliated by gypsy moth larvae and therefore should be regularly monitored.
Извод: Дуглaзиja je jeднa oд нajчешће гајених врстa чeтинaрa у плaнтажaмa и шумским културама у више замаља Европе. Moдeл прoвeниjeничнoг тeстa зaснивa се нa aнaлизaмa свojстaвa дуглaзиje (рaстa и aнaтoмских, физиoлoшких, хeмиjских, мeхaничких, као и других особина) с циљем прoвeрe oпрaвдaнoсти трaнсфeрa сeмeнa из Сeвeрнe Aмeрикe у eкoсистeмe Србиje. Овакав прoгрaм сe спрoвoди у Србиjи нa вишe лoкaциja сa дуглaзиjoм рaзличитих прoвeниjeнциja. Како је анализа различитих физиолошких својстава стабала од значаја при интродукцији одређених провенијенција на станишта у Србији, у овом рaду су истрaживaнe вaриjaбилнoсти сaдржaja кaлиjумa у младим чeтинaмa дуглaзиje рaзличитих прoвeниjeнциja на eкспeримeнтaлном пољу у Србиjи. Значај калијума у физиолошким процесима биљака је веома велики. Калијум је есенцијални елемент који учествује у низу биохемијских и физиолошких процеса и има значајну улогу при адаптацији биљака у условима биотичког и абиотичког стреса. Највећи садржај калијума утврђен је код провенијенције "Орегон 205-14", што је једина провенијенција код које садржај калијума статистички значајно одступа од просека, те се она може окарактерисати као супериорна за усвајање и акумулацију овог елемента. Констатовано је да, у овој фази, разлике у концентрацији калијума код стабала у провенијеничном тесту немају значајног утицаја на параметре раста. Даља истраживања треба да укажу на то да ли садржај овог биогеног елемента има утицај на нека друга својства значајна за oдaбир прoвeниjeнциja у прoцeсу интрoдукциje, као што је отпорност на стресне факторе.
Nitrogen content in the needles of twenty Douglas-fir provenances, originating from different sites within the native range of the species in the USA, was studied in a Douglas-fir provenance test established at the montane beech site on acid brown soil. Based on the variability of nitrogen content in the needles, the intensity and dynamics of the physiological processes of Douglas-fir mineral nutrition were analyzed as the indicators of Douglas-fir adaptive potential to the sites in Serbia. All the trees of the study provenances were of the same age and grown under the same site and population conditions. The quantities of nitrogen absorbed in Douglas-fir needles were correlated with the geographical characteristics of the native sites of the observed provenances. The differences in nitrogen content in Douglas-fir needles point out the variability in the intensity of the physiological processes in the genotypes of the different provenances. Since the study Douglas-fir trees are cultivated on relatively small areas, in more or less equal general conditions, it can be concluded that the parameters of mineral nutrition depend on the genotypes constituting the gene pool of the study Douglas-fir provenances
Nowadays, the territory of pedunculate oak (Quercus robur L.) in Serbia is less widespread than in the past, primarily as the consequence of excessive exploitation and aggravated regeneration caused by the changed groundwater regime. The researches in this paper were aimed at the analysis of the variability of the content of macroelements in leaves, as well as of the soil characteristics in the pedunculate oak populations on the different sites, according to which the sites with the best conditions for the nutrition of pedunculate oak would be singled out. The analyzed populations are of natural or artificial origin, and they occurred during the process of restitution. They are situated in the zone ranging from continental to moderate continental climate, at five different localities and five different types of soil. Foliar analyses of 150 individual - trees of pedunculate oak at five sites in Serbia and the respective soil analysis show that individual variability in macroelements among trees was not statistically significant, while the site effect was highly significant. Concentrations of elements, at all sites, in the decrease sequence were: N>Ca>K>Mg>P>Na. The highest individual variability was exhibited by Na, followed by Mg, Ca and K, and P as well as N had the lowest variability. The obtained results point to the conclusion that the variability of the content of macroelements in leaves is mainly the result of the environmental influence. Statistically significant intra-individual variability, as an indicator of the existence of genetic differences between trees within populations, was detected only for Ca concentration in leaves
Photosynthetic performance of seedlings of Quercus robur exposed to short-term water stress in the laboratory conditions was assessed through the method of induced fluorometry. The substrate for seedlings was clayey loam, with the dominant texture fraction made of silt, followed by clay and fine sand, with total porosity 68.2%. Seedlings were separated in two groups: control (C) (soil water regime in pots was maintained at the level of field water capacity) and treated (water-stressed, WS) (soil water regime was maintained in the range of wilting point and lentocapillary capacity). The photosynthetic efficiency was 0.642±0.25 and 0.522±0.024 (WS and C, respectively), which was mostly due to transplantation disturbances and sporadic leaf chlorosis. During the experiment Fv/Fm decreased in both groups (0.551±0.0100 and 0.427±0.018 in C and WS, respectively). Our results showed significant differences between stressed and control group, in regard to both observed parameters (Fv/Fm and T½). Photosynthetic efficiency of pedunculate oak seedlings was significantly affected by short-term water stress, but to a lesser extent than by sufficient watering
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