Pollen viability in Quercus robur L.

The variability of viability (germination rate and the length of pollen tubes) of fresh pedunculate oak (Quercus robur L.) pollen grains was studied in vitro on a medium containing 15% sucrose. Spatial variability was studied by sampling fresh pollen grains from a total of thirteen trees at four different sites in the area of Belgrade (Košutnjak, Banovo Brdo, Ada Ciganlija and Bojcin Forest) in a single year (2011). In order to assess temporal variability and determine the effects of climate change on a small time scale, we studied the viability of the pollen grains collected from one tree at the Banovo Brdo site in six different years (2004, 2005, 2006, 2007, 2011 and 2012). Interindividual variability was tested on the pollen grains sampled from eight trees at Ada Ciganlija in 2004. The percentage values of the pollen grain germination rate and the pollen tube length showed no statistically significant differences between the sites. However, the studied characteristics of the pollen grain viability (germination rate and pollen tube length) showed statistically significant differences in both temporal (between the pollen collection years) and interindividual variability. This type of research makes a valuable contribution to pedunculate oak breeding programs through the identification of trees with stable production and a good quality of pollen. Furthermore, it can be important in defining the patterns of spatial, temporal and individual variability of pollen grain viability under the influence of climate factors, which are showing compelling changing trends from year to year.Archives of Biological Sciences (2017), 69(1): 111-11

PROSTORNA I VREMENSKA VARIJABILNOST CVJETANJA HRASTA LUŽNJAKA (Quercus robur L.)

Climate change, as well as biotic and abiotic stress environmental factors and the exploitation of oak forests have the greatest impact in reducing the pedunculate oak areas. These factors on one side reduce the pedunculate oak living area, while on the other side they create unfavorable conditions for its renewal. In the last decades, there has been an attempt to change this situation, primarily by planting appropriate provenances and more resistant varieties. Knowledge of the phenological variability is one of the essential elements useful in separation of genotypes better adapted to changing environmental conditions.One of the phenological studies of the pedunculate oak implied the analysis of the pollination time as one of the intermediate phase of the flowering phenophase. Observations were carried out in two populations at two locations in the area of Belgrade (Serbia), "Ada Ciganlija" and "Bojčinska šuma", a total of 58 trees (29 trees per location) in three consecutive years (2004, 2005, 2006). According to the ANOVA results differences between locations and years were statistically significantly (all p <0.0001). Time of pollination in the location of "Bojčinska šuma" was earlier compared to location "Ada Ciganlija" in all three years of observation. The obtained time difference gives rise to the assumption that there are different varieties of the pedunculate oak: the "early" and the "late" one. According to the phenological pattern of population, the majority of trees maintain the same trend from year to year, i.e. remain in the same phenological group (labeled as "early", "average" and "late"), or change it for one phenological level, suggesting the genetic influence on the expression of this trait. Since those populations are located in similar environmental conditions, obtained differences between them can be regarded as a consequence of intraspecific variability of the pedunculate oak and of the genetic structure of population.U radu je analizirana individualna i populacijska varijabilnost polinacije kao međufaze fenofaze cvjetanja lužnjaka. Istraživanja su obavljena na 58 stabala u dvije populacije lužnjaka na dva lokaliteta na području Beograda (Srbija) tijekom tri uzastopne godine (2004, 2005, 2006). Populacije se nalaze u oblasti umjereno-kontinentalne klime, na staništima koja odgovaraju lužnjaku, mješovite su strukture, raznodobne, vegetativnog i sjemenog porjekla, starosti 60–120 g. Promatranje je vršeno jedanput tjedno u travnju/svibnju. Lužnjak na analiziranim lokalitetima, uzimajući u obzir sva stabla i godine promatranja, počinje cvjetati najranije 7. travnja a najkasnije 2. svibnja. Cvjetanje na lokalitetu "Bojčinska šuma" događa se oko tjedan dana ranije u odnosu na lokalitet "Ada Ciganlija". Statističkom obradom potvrđen je značajan učinak lokaliteta, godine i individue. Prema fenološkom obrascu populacija i podeli u odnosu na vrijeme cvjetanja, većina stabala na lokalitetu "Bojčinska šuma" pripada fenološkoj grupi "rani" lužnjak, a na lokalitetu "Ada Ciganlija" grupi "kasni" lužnjak. Tijekom godina promatranja, najveći broj stabala ostajao je u istoj fenološkoj grupi ili se mijenjao samo za jednu razinu. S obzirom da se populacije nalaze u sličnim sredinama i stanišnim uvjetima, dobivene razlike mogu se smatrati posljedicom unutarvrsne varijabilnosti lužnjaka i genetičke strukture populacije. Genetička stabilnost fenofaze cvjetanja korisna je u odabiru "ranih" i "kasnih" formi lužnjaka u procesu individualne selekcije pod utjecajem promjene klimatskih čimbenika

The phenotypic plasticity of of Picea omorika /Panc./Purkyne morphological pollen traits

The variability of morphological traits of Picea omorika /Panč./Purkyne pollen was analyzed in two successive years on the pollen sampled from 24 trees in a seed stand at the site of Bela Zemlja in the area of Mt. Zlatibor (Serbia). The aim of the research was to obtain the index of phenotypic plasticity of the equatorial and polar axes and the coefficient of shape of pollen. According to the obtained results, Serbian spruce pollen grains are 93.3 μm/53.2 μm in size with their shape being oblate 57.5%. The climate characteristics of the study years initiated different responses of the pollen traits for each tree. Reaction norms were slightly steep and they crossed as confirmed by the significant interaction between the variability factors of the year and the tree. In the year with lower temperatures and less precipitation, the mean values of the equatorial axis were higher and the polar axis smaller, giving the pollen grain a more oblate form. According to the results of the applied model of analysis of variance where the year and the tree, as well as the interaction between them, were taken as factors of variability, the values of the pollen equatorial axis (length) and the coefficient of shape showed statistically significant differences between the years. Genetic variability (interindividual differences) for the values of both axes of pollen grains was confirmed by statistically significant differences between the trees in a single year. Interindividual differences in the observed morphological pollen traits were affected by environmental conditions specific to the year of sampling (statistically significant year x tree interaction). All the analyzed traits showed interindividual differences in the values of the plasticity index. The lowest values of plasticity were obtained for the equatorial axis (length) of the pollen grain, and they were significantly different from the plasticity indexes of the other traits analyzed herein. The plasticity of pollen traits has an important role in the controlled selection and breeding of species with the aim of obtaining more resistant genotypes with a greater ability to adapt to the fluctuations of environmental factors caused by global climate change

Length of vegetation period as parameter of common oak (Quercus robur L.) phenological variability

Paper presents results for length of vegetation period as factor in common oak’s (Quercus robur L.) phenological variability. Trees in two common oaks populations on two locations in area of Belgrade were researched. Average length of vegetation period on site Ada Ciganlija is 166 days, while in location Bojčinska šuma is 179 days. Regarding that populations are in similar environmental and habitual conditions, differences in results should be treated as consequence of common oaks intra-specific variability and genetic structure of population. Significant differences in three consecutive years of observation are confirmed.U radu su predstavljeni rezultati analize dužine trajanja vegetacije kao faktora fenološke varijabilnosti lužnjaka (Quercus robur L.). Istraživanja su obavljena na stablima u dve populacije lužnjaka na dva lokaliteta na području Beograda. Prosečno dužina trajanja vegetacije na lokalitetu Ada Ciganlija iznosi 166 dana a na lokalitetu Bojčinska šuma 179 dana. Obzirom da se populacije nalaze u sličnim sredinskim i stanišnim uslovima, dobijene razlike se mogu smatrati posledicom unutarvrsne varijabilnosti lužnjaka i genetičke strukture populacije. Potvrđene su značajne razlike između tri uzastopne godine osmatranja.Projekat ministarstva br. 4300

Inter and intra-population variation of leaf stomatal traits of Quercus robur L. in Northern Serbia

The research involved the examination of inter- and intra-population variation of stomatal traits: stomatal density, stomatal length and width, stomatal pore surface, potential conductance index and stomatal shape coefficient, in Quercus robur L. leaves. The research was conducted in northern Serbia and included five populations ('Ada Ciganlija', 'Bojčinska šuma', 'Subotica', 'Sombor' and 'Vršac'). The stomatal characteristics were examined in fully expanded leaves, from two leaf positions - the sun-exposed and shaded side of the tree. The leaf position in the tree crown, forming a part of the phenotypic variance, was relevant for the stomatal dimension traits. Within populations, the differences between the genotypes (i.e. trees), were relevant for all analyzed traits. On the basis of the analysis of the inter-populational differences, the 'Bojčinska šuma' population had a statistically significantly lower stomatal density in comparison to the other populations.Projekat ministarstva br. 33012 and 17302

Variability of nutritive macroelements in pedunculate oak (Quercus robur L.) leaves in Serbia

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.Lužnjak (Quercus robur L.) je na području Srbije danas mnogo manje rasprostranjen nego nekada što je posledica prvenstveno preterane eksploatacije i otežanog obnavljanja usled promene režima podzemnih voda. Istraživanja u ovom radu su imala za cilj analizu varijabilnosti sadržaja makroelemenata u lišću lužnjaka (Quercus robur L.) i osobina zemljišta u populacijama lužnjaka na različitim staništima, na osnovu čega bi se izdvojila staništa koja imaju najbolje uslove za ishranu lužnjaka. Analizirane populacije su prirodnog ili veštačkog porekla, nastale u procesu restitucije. Nalaze se u zoni kontinentalne do umereno kontinentalne klime, na pet različitih lokaliteta i pet različitih tipova zemljišta. Folijarnom analizom 150 individua-stabala lužnjaka na 5 lokaliteta na području Srbije i analizom zemljišta sa istih lokaliteta ustanovljena individualna varijabilnost makroelemenata između stabala nije bila statistički opravdana dok su razlike između lokaliteta bile visoko značajne. Koncentracija elemenata, na svim lokalitetima, bila je u opadajućem nizu: N>Ca>K>Mg>P>Na. Najveću individualnu varijabilnost imao je Na, zatim Mg, Ca i K a najmanje varijabilni bili su P i N. Dobijeni rezultati upućuju na zaključak da je varijabilnost sadržaja makroelemenata u listu prvenstveno posledica sredinskog uticaja.nul

Polycyclism and phenological variability in the common oak (Quercus robur L.)

Polycyclism is the ability for a plant to produce several flushes in the same growing season. The rare phenomenon of common oak (Quercus robur L.) summer flowering is proof of complex polycyclism. Common oak summer flowering and the unusual transformation of inflorescences were the starting point for this study of the phenological variability of common oak trees in identical site conditions. This paper presents comparative research of leaf flushing, flowering, and leaf fall phenophases in a common oak with summer flowering and a control tree in which this phenomenon was not observed. Both trees displayed frequent polycyclism (polyphase formation of annual shoots during the growing season), but with different intensities depending on the trees and the years. Compared to the control tree, the tree with summer flowering was characterized by a later onset of leaf-flush phenophase and leaf fall phenophase and a longer retention of the leaves in the crown.Projekat ministarstva br. 43007: Studying climate change and its influence on the environment: Impacts, adaptation and mitigatio

Some characters of the pollen of spring and summer flowering common oak (Quercus robur L.)

Summer flowering of the common oak is a natural rarity, considering the large area of the species natural distribution. This phenomenon can be classified as an ancestral (atavistic) property. Pollen morphological and physiological characters from spring flowering male inflorescences collected over the period 2004 - 2007 and summer flowering male inflorescences collected in 1999 were compared. The analysis included the pollen of a tree with frequent summer flowering and a control tree with spring flowering only. The size and form of summer pollen differed from the spring flowering pollen. The germination percentage and germination energy depended on the pollen growing medium (0, 5, 10, 15, 20, 25% sucrose solution), year of collection (2004 - 2007), temperature (+5°C and -20°C) and storage period (1 to 24 months). The study results are significant for the explanation of common oak phylogenetic development, and they contribute to the knowledge of pollen characters under the effects of different factors.Projekat ministarstva br. 17302

Population and individual variability of the leafing phenophase of pedunculate oak in three successive years

The leafing phenophase of pedunculate oak (Quercus robur L.) was analyzed at two locations in Belgrade (Ada Ciganlija - 'AC', Bojčinska šuma - 'BS'). The observations were made on 29 trees per site for three consecutive years (2004, 2005, 2006). In the 'BS' site the phenophase of leafing starts and ends earlier than in the 'AC' site. The largest number of trees in the 'AC' site are classified in the late phenological group and in the 'BS' site they belong to the 'average' group. Population variability of the analyzed parameters of the phenophase of leafing was confirmed by the results of a Mann - Witney U - test for each year of observation, except for the end of the second year of observation and start of leafing in the first year of observation. According to the results of an F - test significant differences between sites were confirmed for all analyzed parameters except for the duration of leafing (2005) and the start of leafing (2006). Differences among the years of observation in the 'AC' site were significant only in the end and in the 'BS' site for they were significant for all three growth stages of scrolling. Despite the different environmental conditions in the three years of monitoring the stability of the phenology of analyzed populations was maintained (the percentage of trees that were always over the years of observation in the same phenological group relative to the start of leafing 'AC' - 41.3%, 'BS' - 55.2%), which is primarily the result of the genetic structure of populations and intraspecies variability.Fenofaza listanja lužnjaka (Quercus robur L.) je analizirana u dve populacije na području Beograda (Ada Ciganlija - 'AC', Bojčinska šuma - 'BŠ'). Osmatranja su vršena na 29 stabala po populaciji tokom tri uzastopne godine (2004, 2005, 2006). U populaciji 'BŠ' fenofaza listanja počinje i završava ranije u odnosu na populaciju 'AC'. Najveći broj stabala u populaciji 'AC' pripada 'kasnoj' fenološkoj grupi, a u populaciji 'BŠ' grupi 'prosek'. Populaciona varijabilnost analiziranih parametara fenofaze listanja je potvrđena rezultatima Mann-Witney U - testa za svaku godinu osmatranja (2004, 2005, 2006), osim za kraj u drugoj i početak listanja u prvoj godini osmatranja. Prema rezultatima F - testa između populacija su potvrđene značajne razlike za sve analizirane parametre osim za trajanje (2005) i početak listanja (2006). Između godina osmatranja u populaciji 'AC' razlike su bile značajne samo za kraj, a u populaciji 'BŠ' za početak i kraj listanja. I pored različitih ekoloških uslova u tri godine osmatranja stabilnost fenologije analiziranih populacija (procenat stabala koja su tokom godina osmatranja bila uvek u istoj fenološkoj grupi u odnosu na početak listanja: 'AC' 41.3%, 'BŠ' 55.2%) se održala, što je pre svega rezultat genetičke strukture populacija i unutar vrsne varijabilnosti.Projekat ministarstva br. 4300

Length of vegetation period as parameter of common oak (Quercus robur L.) phenological variability

Paper presents results for length of vegetation period as factor in common oak’s (Quercus robur L.) phenological variability. Trees in two common oaks populations on two locations in area of Belgrade were researched. Average length of vegetation period on site Ada Ciganlija is 166 days, while in location Bojčinska šuma is 179 days. Regarding that populations are in similar environmental and habitual conditions, differences in results should be treated as consequence of common oaks intra-specific variability and genetic structure of population. Significant differences in three consecutive years of observation are confirmed.U radu su predstavljeni rezultati analize dužine trajanja vegetacije kao faktora fenološke varijabilnosti lužnjaka (Quercus robur L.). Istraživanja su obavljena na stablima u dve populacije lužnjaka na dva lokaliteta na području Beograda. Prosečno dužina trajanja vegetacije na lokalitetu Ada Ciganlija iznosi 166 dana a na lokalitetu Bojčinska šuma 179 dana. Obzirom da se populacije nalaze u sličnim sredinskim i stanišnim uslovima, dobijene razlike se mogu smatrati posledicom unutarvrsne varijabilnosti lužnjaka i genetičke strukture populacije. Potvrđene su značajne razlike između tri uzastopne godine osmatranja.Projekat ministarstva br. 4300