Occurrence Of Seedlings Research Articles

Grab to fill the gap: key factors influencing Reynoutria japonica germination and seedling establishment in the secondary distribution range

Reynoutria japonica (Japanese knotweed) is a highly invasive female plant that primarily reproduces through vegetative regeneration during secondary distribution. Despite producing a substantial number of viable hybrid seeds, the occurrence of seedlings and young plants in the wild remains rare; the reasons for this rarity are unclear. Environmental intolerance and chromosomal anomalies during hybridisation can impede seedling development. This study evaluates the combined impact of these factors by examining substrate, temperature, and light effects on germination, as well as assessing seedling genome sizes and viability. Seeds were cultivated in both natural and controlled environments to manage external influences. Flow cytometry was employed to evaluate chromosomal arrangements. The final germination was notably high at 99%, and 68% of seedlings thrived under controlled conditions, emphasising hybrid seedling viability regardless of highly polyploid levels ranging from pentaploid to aneuploid (2C DNA genome size from 5.17 to 11.95 pg). Thus, it is evident that seeds can germinate and produce vital seedlings despite various chromosomal sets. Even fluctuating temperatures and type of substrate do not limit seed germination. However, these results were obtained under laboratory conditions, with seeds and seedlings receiving regular irrigation. A significant seedling mortality rate (99%) was observed in the field experiment, and the final germination was also low there (15%). Observations suggest that water stress might be the cause of this mortality. Further research on water stress is necessary because it could be the primary factor limiting the successful generative spread of the knotweeds.

Polyembryonic twin seedlings in Madhuca diplostemon (Sapotaceae) - a critically endangered and endemic species of the Western Ghats

Madhuca diplostemon is a critically endangered and endemic species of the southern Western Ghats, represented by a single mature individual. The occurrence of twin seedlings in this species is being reported here for the first time will be useful future genetic improvement and conservation programs for this species.

Effects of Forest Fire on the Regeneration Potentials of Tree Species in Olokemeji Forest Reserve, Ogun State, Nigeria

Effects of forest fire on the regeneration potential of trees at Olokemeji Forest Reserve was established in this study. The Olokemeji fire experimental plot was selected at the reserve. The site was divided into three plots; late fire treatment was applied to Plot A, Early fire treatment was also applied to Plot B and no fire treatment at plot C (Control plot). The diameter at breast height (dbh) and tree height (m) of the tree species in the plots were assessed prior and post fire treatment. The regeneration potential of the selected plots after burning were assessed through the occurrence of saplings and seedlings obtained. The highest basal area (m2) were found in plot C followed by plot B and Plot C with mean value of 0.64, 0.55 and 0.30 m2 respectively. The number of stems per plot ranged from 25 to 67. The regeneration potentials of the three plots were found to be noteworthy. Early and late year fire regime adopted had both positive and negative effect on the regeneration potentials of tree species. This study has established the effect and relevance of fire on forest and wildlife management. It’s therefore recommended in this study that Prescribed or controlled burning should be encouraged as appropriate sivilcultural management tool for stimulating basal area growth, natural regeneration, production of tree species seedlings and saplings.

Microsite requirements for successful regeneration in lowland northern white-cedar (Thuja occidentalis L.) forests

Throughout much of its range, northern white-cedar (Thuja occidentalis L., hereafter cedar) has experienced a bottleneck in recruitment: cedar seedlings are often abundant in these stands, particularly in lowland settings, yet cedar sapling densities are quite low, leading to concerns that cedar canopy trees are not being replaced. Several barriers to cedar recruitment have been suggested; however, findings from previous studies have been inconsistent with regard to limiting factors. Our objective was to characterize the microsite conditions associated with the establishment of cedar seedlings and saplings. We achieved this objective by mapping the location of seedlings, saplings, and overstory trees in 15 lowland cedar stands at five sites in Maine, USA, and examining the fine-scale site conditions (microtopographic features, canopy openness) in which cedar seedlings and saplings occurred. In particular, we recorded the occurrence of seedlings and saplings on microtopographic mounds, pits (small depressions), and flats (transitional features between mounds and pits). Substrate moisture content in these features decreased in the order pits > flats > mounds. Contingency-table results demonstrated that live cedar seedlings, and to a slightly lesser extent saplings, were found more often than expected by chance on mounds, and less often on flats and pits. Logistic regressions using status (live vs. dead) as the response variable generally supported these findings: dead seedlings were strongly associated with pits; however, the occurrence of live seedlings and saplings did not differ between flats and mounds. A companion planted-seedling experiment strongly supported these results, showing that after two growing seasons, survival was significantly lower in pits (12%) when compared to flats and mounds, which had similarly high levels of survival (62 and 80% respectively). Logistic regressions also showed live seedlings and saplings to be prevalent under more open canopy conditions (mean 19%, range 6 to 42% openness); though results from a planted-seedling experiment suggested that greater canopy openness (mean 32%, range 13 to 57%) was detrimental to survival. Regressions also showed that browsed seedlings were more likely to be found dead. These findings point to management prescriptions that maintain microtopographic diversity, create moderately open canopy conditions, and protect stands from browsing to promote viable cedar populations in these ecologically and economically important forests.

Management After Windstorm Affects the Composition of Ectomycorrhizal Symbionts of Regenerating Trees but Not Their Mycorrhizal Networks.

Due to ongoing climate change, forests are expected to face significant disturbances more frequently than in the past. Appropriate management is intended to facilitate forest regeneration. Because European temperate forests mostly consist of trees associated with ectomycorrhizal (ECM) fungi, understanding their role in these disturbances is important to develop strategies to minimize their consequences and effectively restore forests. Our aim was to determine how traditional (EXT) and nonintervention (NEX) management in originally Norway spruce (Picea abies) forests with an admixture of European larch (Larix decidua) affect ECM fungal communities and the potential to interconnect different tree species via ECM networks 15 years after a windstorm. Ten plots in NEX and 10 plots in EXT with the co-occurrences of Norway spruce, European larch, and silver birch (Betula pendula) were selected, and a total of 57 ECM taxa were identified using ITS sequencing from ECM root tips. In both treatments, five ECM species associated with all the studied tree species dominated, with a total abundance of approximately 50% in the examined root samples. Because there were no significant differences between treatments in the number of ECM species associated with different tree species combinations in individual plots, we concluded that the management type did not have a significant effect on networking. However, management significantly affected the compositions of ECM symbionts of Norway spruce and European larch but not those of silver birch. Although this result is explained by the occurrence of seedlings and ECM propagules that were present in the original forest, the consequences are difficult to assess without knowledge of the ecology of different ECM symbionts.

The Influences of Seed Source on Germination and Production of Abnormal Seedling in Big-Leaf Mahogany (<i>Swietenia macrophylla</i> King)

The big-leaf mahogany is one of the fast growing and highly demanded tropical timber species in the world. It is widely grown as an avenue tree as well as commercial plantations due to narrow crown, straightness, wide adaptability and desirable wood qualities. The morphological evaluation and grading of seedling at the early is one of most important aspects for quality planting stock production. The present study was attempted to document the influence of seed source on germination and occurrence of abnormal seedlings in big-leaf mahogany. A total of 25 seed sources collected from Tamil Nadu, Kerala and Karnataka was used in this study. The 100-seed weight, germination % and number of abnormal seedlings were recorded. The results revealed that the seed source had significant influence on these parameters. The highest germination and branched seedlings were found in Karnataka seed sources. The abnormal seedlings percent was high in Mayampady (Tamil Nadu) where as it was absent in Chaliyarmukku (Kerala).

A Streptomyces sp. NEAU-HV9: Isolation, Identification, and Potential as a Biocontrol Agent against Ralstonia Solanacearum of Tomato Plants.

Ralstonia solanacearum is an important soil-borne bacterial plant pathogen. In this study, an actinomycete strain named NEAU-HV9 that showed strong antibacterial activity against Ralstonia solanacearum was isolated from soil using an in vitro screening technique. Based on physiological and morphological characteristics and 98.90% of 16S rRNA gene sequence similarity with Streptomyces panaciradicis 1MR-8T, the strain was identified as a member of the genus Streptomyces. Tomato seedling and pot culture experiments showed that after pre-inoculation with the strain NEAU-HV9, the disease occurrence of tomato seedlings was effectively prevented for R. solanacearum. Then, a bioactivity-guided approach was employed to isolate and determine the chemical identity of bioactive constituents with antibacterial activity from strain NEAU-HV9. The structure of the antibacterial metabolite was determined as actinomycin D on the basis of extensive spectroscopic analysis. To our knowledge, this is the first report that actinomycin D has strong antibacterial activity against R. solanacearum with a MIC (minimum inhibitory concentration) of 0.6 mg L−1 (0.48 μmol L−1). The in vivo antibacterial activity experiment showed that actinomycin D possessed significant preventive efficacy against R. solanacearum in tomato seedlings. Thus, strain NEAU-HV9 could be used as BCA (biological control agent) against R. solanacearum, and actinomycin D might be a promising candidate for a new antibacterial agent against R. solanacearum.

Post-fire regeneration of endangered limber pine (Pinus flexilis) at the northern extent of its range

Limber pine (Pinus flexilis), an understudied tree species important to montane and subalpine ecosystems, is listed as endangered in Alberta. Dispersal of seeds to newly disturbed, open areas by Clark’s nutcracker (Nucifraga columbiana) is expected to facilitate post-disturbance establishment of limber pine. Prescribed burning has thus been proposed as a tool to stimulate natural regeneration, but no studies have yet surveyed limber pine’s regenerative response to disturbance at the northernmost extent of its range. We examined post-fire regeneration in one prescribed burn and one wildfire at the northern edge of limber pine’s distribution and compared this to a regeneration baseline of plots in nearby unburned limber pine acting as seed sources to the burns. Using a likelihood-based approach, we then compared hypotheses of ecological processes influencing seedling occurrence and abundance. Overall, we found only six post-fire limber pine seedlings within the burns, as compared to one hundred twenty-four similarly aged seedlings found in unburned plots. Akaike information criterion (AIC) identified distance to a seed source and absence of canopy cover as hurdles for seedling establishment in the burn. Analysis of seedling abundance was performed on only the unburned dataset due to low regeneration in the burned areas surveyed; model selection here showed that when distance to a seed source is small, substrate variables, including less prevalent bare mineral soil, more rocky cover, and finer soil textures, take on an important role in driving abundance. Substrates important for limber pine abundance in unburned stands were found with similar frequency in the burns, indicating limber pine colonization post-disturbance was not substrate limited but instead constrained by other factors. Our findings suggest that extensive prescribed burns and stand-replacing wildfire events at the northern extent of limber pine’s range may have limited seedling regeneration in the immediate post-fire period. Conservation efforts may be well-served by focusing on fire mitigation efforts, such as thinning and other fuel treatments, in areas surrounding established limber pine stands. Finally, post-disturbance stands could benefit from supplementary seedling plantings to achieve recovery plan restoration goals for this endangered species.

In vitro organogenesis and growth of Ocimum basilicum ‘Genovese’ (basil) cultivated with growth regulators

Genovese basil is a medicinal plant broadly used in medicine, perfumery, and cooking. In this study, the in vitro organogenesis and growth of Genovese basil seedlings are evaluated through the effect of growth regulators applied in different doses. Eight treatments were performed combining different concentrations of auxins and cytokinins, plus one control. At the end of the trial, growth characteristics of the seedlings were measured, and anatomical sections of the leaves and stems of the basil were prepared. The results demonstrated the need for cytokinins to increase the number and length of shoots and the length of roots. The treatment with 0.2 mgL-1 benzyl aminopurine (BAP) mgL-1 demonstrated the best result. The combined action of auxins and cytokinins increased fresh and dry masses of roots (0.3 mgL-1 BAP + 0.6 mgL-1naphthaleneacetic acid [NAA]). Partial changes in the leaf architecture as well as a reduction in the thickness of the palisade and lacunar parenchyma were observed, especially in treatment T8 (0.4 mgL-1 BAP+ 0.2 mgL-1NAA). In addition, all treatments with regulators presented adventitious roots in the stem, originating from inner-stem cells or vascular tissues. The formation of callus at the base of the plants and the occurrence of abnormal seedlings indicate that Genovese basil was responsive to the action of the growth regulators, although other factors regarding the medium could influence such responses. The growth regulators also function in the expression of genes linked to the stretching process (auxins) and cell proliferation (cytokinin).

Cloning and Expression Analysis of the ScD53 Gene from Sugarcane

D53 is a crucial gene involved in tillering regulation in crops via the strigolactone signaling pathway. The objective of our research was to clone the homologous sugarcane (Saccharum L. spp. hybrids) gene of D53 (ScD53) by in silico cloning combined with RT-PCR and rapid amplification of cDNA ends techniques, and the physicochemical properties and structure of ScD53 protein were analyzed using bioinformatic software and tools. The relationships between the expression of ScD53 and some plant hormones, bud germination and tillering occurrence of seedlings were also detected using the real-time fluorescence quantitative PCR (FQ-PCR) technique. The homolog was named ScD53 and possessed a 3918-bp cDNA sequence. Bioinformatic analysis showed that ScD53 has a complete open reading frame of 3363 bp that encodes 1120 amino acid residues. The ScD53 protein possesses the conserved domain of the P-loop NTPase and ClpB_D2-small superfamilies, which may be unstable hydrophilic proteins and are likely to be located in the nucleus. The main secondary and tertiary structures of the ScD53 protein are composed of random coil and alpha helix structures and exhibit high similarity in structure and homology with D53 proteins from sorghum [Sorghum bicolor (L.) Moench] and maize (Zea mays L.). The FQ-PCR results showed that the expression of ScD53 is tissue specific and is differently expressed in the different tissues. The expression of ScD53 is associated with bud germination, the high expression of which inhibits bud germination. Plant hormone treatment experiments indicated that the expressions of ScD53 were induced in bud and leaf tissues by strigolactones, 3-indole acetic acid and kinetin (KT, a cytokinin analog). The high expression of ScD53 following strigolactone and auxin treatment obviously delayed occurrence of tillers and reduced the number of tillers for the seedlings. However, this was not observed during KT treatment, which implied that the negative effects of this gene on seedlings tillering phenotype were eliminated by the positive influences of other unknown pathways. Our results above help elucidate the function of ScD53 and provide important information and direction for the use of this gene in improving sugarcane yield through tiller regulation.

Is climate the key factor limiting the natural regeneration of silver fir beyond the northeastern border of its distribution range?

Silver fir (Abies alba Mill.) is one of the most important forest tree species in Europe potentially prone to climate changes. The northern limit of its distribution is in central Poland but fir stands were planted also in northern part of the country. It gives opportunity to investigate the potential for silver fir to expand into northern (cooler) Europe which could be an important issue in the face of changing climate. The aim of this research was to identify factors influencing the establishment and advancement of silver fir regeneration within and outside its natural range. Using data collected on sample plots in 48 stands, we examined influences of climatic and stand factors on establishment and development of silver fir regeneration. The Boruta algorithm was used to identify variables relevant for particular stages of fir regeneration (short and tall seedlings and saplings). The variable location (indicating that the analysed plot was located inside or outside the natural range of silver fir) was not the most important variable for any size classes of silver fir regeneration (Boruta algorithm). We found that the mean values of diameter of breast height (DBH) and height of the dominant firs were larger for northerly plantations than for stands within the natural range. The density of seedlings was similar within and outside the natural range but density of saplings was lower, especially tall saplings. Climatic variables (continentality index and summer heat: moisture ratio) were significant in the models predicting the probability of establishing tall seedlings and short saplings. Stand composition was an important factor for all the regeneration stages. For short seedlings, local (sample plot) stand composition was important. The establishment of short seedlings was negatively influenced by shade-tolerant species (sum of the heights of the shade-tolerant trees per plot). Species composition at the forest stand spatial scale was more important for tall seedlings and saplings. The proportion of Scots pine in forest stand volume positively influenced the establishment of tall seedlings. We found that with the growth of regeneration, the role of free space availability increased. The occurrence of tall seedlings and saplings was negatively influenced by increased space filling. Introducing silver fir outside of its natural range requires adjustment to management practices such as creation of vertically diversified mixed stands, decreasing stand stocking, regulation of stand species composition. A lack of experience with silver fir silviculture in northern Poland is one of important factors limiting the advancement of regeneration to the stage of high saplings outside the natural range.

Rarity of shortleaf, slash, and longleaf pine seedlings in oak-pine forest types: An assessment of associated environmental, stand, site, and disturbance factors

Determining the factors that influence the regeneration of pine in oak-pine forests is crucial for understanding natural regeneration dynamics and for planning forest management strategies. We investigated the vegetation structure and seedling dynamics of shortleaf, slash, and longleaf pine in oak-pine forest types of the southeastern United States. We used logistic regression with penalized maximum likelihood estimation because of the rarity of the regeneration from these pines. We performed canonical correlation, analysis of variance, and community structure analysis to produce multivariate relationships and statistical inferences. The classification accuracy of the logistic regression models for shortleaf, slash, and shortleaf pine were 96.0%, 96.7%, and 97.7%, respectively. The models indicated that environmental, climatic, stand, site productivity, and disturbance factors, or their combinations, had a significant influence on seedling occurrence. The probability of occurrence of seedlings of the three pine species increased with the increase in the overstory basal area from these species: one unit increase in overstory purity ratio of shortleaf, slash, and longleaf pine increased the odds of occurrence of their seedlings by approximately 51, 24, and 7 times, respectively.The probability of occurrence of shortleaf pine seedlings increased with increasing canopy openness in stands with a substantial proportion of shortleaf pine in the overstory. The increase in mean annual temperature and overstory basal area of slash pine increased the probability of occurrence of slash pine seedlings on wetter sites that had disturbance through harvesting and silvicultural treatments. The chances of occurrence of longleaf pine seedlings increased with increasing overstory basal area of longleaf pine, species diversity, and mean annual temperature in low density stands on low productive sites. The findings can help forest managers in designing and implementing silvicultural treatments to promote the natural regeneration of the three pines in oak-pine forests.

Hierarchical Environmental Factors Affecting the Distribution of Abies koreana on the Korean Peninsula

A regional decline in the Korean fir (Abies koreana) has been observed since the 1980s in the subalpine region. To explain this decline, it is important to investigate the degree to which environmental factors have contributed to plant distributions on diverse spatial scales. We applied a hierarchical regression model to determine quantitatively the relationship between the abundance of Korean fir (seedlings) and diverse environmental factors across two different ecological scales. We measured Korean fir density and the occurrence of its seedlings in 102 (84) plots nested at five sites and collected a range of environmental factors at the same plots. Our model included hierarchical explanatory variables at both site-level (weather conditions) and plot-level (micro-topographic factors, soil properties, and competing species). The occurrence of Korean fir seedlings was positively associated with moss cover and rock cover but negatively related to dwarf bamboo cover. At the site level, winter precipitation was significantly and positively related to the occurrence of seedlings. A hierarchical Poisson regression model revealed that Korean fir density was negatively associated with slope aspect, topographic position index, Quercus mongolica cover, and mean summer temperature. Our results suggest that rising temperature, drought, and competition with other species are factors that impede the survival of the Korean fir. We can predict that the population of Korean fir will continue to decline in the subalpine, and only a few Korean fir will survive on northern slopes or valleys due to climate change.

Natural regeneration of Pinus brutia Ten. in a recreational public forest in Zawita-Kurdistan region, Iraq

Zawita natural forest has recently has been subject to mass recreational activities during spring that have denuded large areas of the forest. It was thus essential to assess regeneration before designing optimizing strategies. To this end, we studied the overstory canopy and microhabitat conditions for recruitment of Pinus brutia Ten in 10 plots (20 × 25 m) on the southern aspects where the Zawita natural forest is still present. In total, 1540 regenerating P. brutia were recorded, 854 seedlings, 597 saplings, and 89 trees. Seedlings and saplings were more frequent beyond the canopy than under the canopy of the parent trees. Regeneration requirements differed between seedlings and saplings. The probability of the occurrence of seedlings was negatively correlated with increasing litter depth and increasing soil compaction. The density of saplings only showed a positive significant correlation with increasing slope. The nearest neighbor index showed a trend toward a positive spatial association between understory shrubs with their neighboring seedlings at a mean distance of 1.6 m. Overall, the study highlighted the requirements for seedling regeneration as a relatively open canopy cover, a light understory litter layer, and non-compacted soils. These results are a step towards designing effective management and restoration programs.

Regeneration dynamics of mixed stands of Pinus pinaster Ait. and Pinus pinea L. in Central Spain

The dynamics of mixed stands are more complex and less studied than those of monospecific stands. The objective of this work was to analyze the variables involved in seedling occurrence and seedling survival in mixed stands of Pinus pinaster and P. pinea in Mediterranean areas. From 2011 to 2016, regeneration of both species was monitored at two sites located in Central Spain. We installed 72 regeneration plots where seedling dynamics were monitored. All the trees in the study areas were measured and mapped. Additionally, we took hemispherical photographs in each regeneration plot. The average density of P. pinea seedlings over the study period was almost 20 times larger than that of P. pinaster. Our results indicate that the seedlings of both species grow under moderate light conditions. In addition, we found that the occurrence of seedlings of both species was related to the structure of the stand. P. pinea seedlings grew where the density and size of P. pinaster trees were low and where P. pinea trees provided moderately sheltered conditions, whereas the number of P. pinaster seedlings was related to under intermediate densities of P. pinaster trees. Furthermore, seedling survival was positively associated with age of the seedlings and negatively with the August average maximum temperature. The temporal continuity of mixed stands of P. pinea and P. pinaster in the study area is compromised by the observed lack of regeneration of P. pinaster.

Moderate shade environment facilitates establishment of desert phreatophytic species Alhagi sparsifolia seedlings by enlarge fine root biomass

Phreatophytic species (Alhagi sparsifolia Shap.) is commonly found to distribute in open area with full sun light environment without shading, and spontaneous occurrence of seedlings in mixed species communities is rare in arid and semi-arid regions. Seedlings and field-grown perennial plants at the southern rim of the Taklamakan Desert were grown under three light availability, i.e., full sun light, 80 and 20% of full sun light treated as high-light (HL), moderately high-light (MHL), and low-light (LL) groups. Plastic acclimation of leaf morphological and photosynthetic traits induced by low light was evident. Low-light-grown plants exhibited higher maximum photochemical efficiency (F v/F m) and relatively low assimilation rate (P n ), while difference in daily P n between the HL and MHL was not significant. Photosynthetic efficiency at the HL on summer midday was constrained partially due to lower quantum yield of electron transport at the primary quinone acceptors between photosystem II and I. Compared with the HL and LL, seedlings at the MHL group had larger relatively growth rate, net primary production per plant, and longer assimilative branch. Allocation proportions of biomass into root, assimilative branches, leaves, and stem, root/shoot ratio, and specific root length between the HL and MHL were, respectively, similar. However, very fine root biomass (<1 mm) was significantly enlarged by the MHL, which directly contributed to biomass production. Collectively, plant growth of A. sparsifolia favored by the MHL was mainly ascribed to rapid growth rate, photosynthetic efficiency without suffering midday stresses, and importantly to strong root system featured by enlarged fine root biomass.

Sensitivity of salad greens (Lactuca sativa L. and Eruca sativa Mill.) exposed to crude extracts of toxic and non-toxic cyanobacteria.

We evaluated the effect of crude extracts of the microcystin-producing (MC+) cyanobacteria Microcystis aeruginosa on seed germination and initial development of lettuce and arugula, at concentrations between 0.5 μg.L(-1) and 100 μg.L(-1) of MC-LR equivalent, and compared it to crude extracts of the same species without the toxin (MC-). Crude extracts of the cyanobacteria with MC (+) and without MC (-) caused different effects on seed germination and initial development of the salad green seedlings, lettuce being more sensitive to both extracts when compared to arugula. Crude extracts of M. aeruginosa (MC+) caused more evident effects on seed germination and initial development of both species of salad greens than MC-. Concentrations of 75 μg.L(-1) and 100 μg.L(-1) of MC-LR equivalent induced a greater occurrence of abnormal seedlings in lettuce, due to necrosis of the radicle and shortening of this organ in normal seedlings, as well as the reduction in total chlorophyll content and increase in the activity of the antioxidant enzyme peroxidase (POD). The MC- extract caused no harmful effects to seed germination and initial development of seedlings of arugula. However, in lettuce, it caused elevation of POD enzyme activity, decrease in seed germination at concentrations of 75 μg.L(-1) (MC-75) and 100 μg.L(-1) (MC-100), and shortening of the radicle length, suggesting that other compounds present in the cyanobacteria extracts contributed to this result. Crude extracts of M. aeruginosa (MC-) may contain other compounds, besides the cyanotoxins, capable of causing inhibitory or stimulatory effects on seed germination and initial development of salad green seedlings. Arugula was more sensitive to the crude extracts of M. aeruginosa (MC+) and (MC-) and to other possible compounds produced by the cyanobacteria.

Spontaneous establishment of late successional tree species English oak (Quercus robur) and European beech (Fagus sylvatica) at reclaimed alder plantation and unreclaimed post mining sites

Nitrogen-fixing trees are often used in disturbed areas to promote soil development and to prepare the ground for more demanding tree species. However, their effect on the establishment of climax tree species has seldom been tested. We mapped the occurrence of volunteer seedlings of European beech (Fagus sylvatica) and English oak (Quercus robur) in patches reclaimed by planting alder (Alnus glutinosa and Alnus incana) and in unreclaimed forest patches (dominated by Salix caprea, Betula pendula and Populus tremula). Both communities were about 30 years old and occurred on one large spoil heap from coal mining near the town of Sokolov (Czech Republic). At the same time, we mapped mature beech and oak trees in the surrounding area. We planted oak and beеch seedling in an alder plantation, an unreclaimed forest stand and a grass-covered area without trees, and recorded their growth for two consecutive years. The closest mature beech grew 1km from the heap whereas seed-producing oaks occurred in its close vicinity and on the heap itself in a 30 to 40-year-old oak plantation. In both species, seedling density decreased with increasing distance from mature trees. Unreclaimed sites supported significantly higher seedling densities than reclaimed ones. Seedlings in the unreclaimed forest stand grew significantly better than in the other two habitats. Oak seedlings exhibited significantly higher mycorrhizal colonization in unreclaimed forest stands than in the other habitats. Unreclaimed forest stands are better habitat for the establishment of climax trees, than the reclaimed alder plantation. Using of spontaneous woody vegetation as nursing cover for climax trees can be recommended in restoration practice. Risk and benefits of nitrogen-fixing trees should be carefully considered.

Production of interspecific Campanula hybrids by ovule culture: exploring the effect of ovule isolation time

The Campanula genus comprises several economically important ornamental plants species. Wide hybridisation is a method to increase phenotypic variability, but is limited due to interspecies hybridisation barriers. In this study we investigated whether ovule culture could be used to increase the success rate of interspecific hybridisation between C. portenschlagiana × C. poscharskyana and C. medium × C. formanekiana. The effect of different ovule isolation times on ovule germination in vitro was examined. In general, the number of collectible ovules and ovule germination was low. Interspecific hybrids between C. medium and C. formanekiana exhibited an increased number of viable ovules with later isolation time, but with different ovule germination rates. A parent-of-origin effect on both the number of collectible ovules and ovule germination was observed for C. medium × C. formanekiana. Histological analysis of embryo and endosperm development in collectible ovules isolated at different time points from interspecific crosses showed that the vast majority of ovules did not contain an embryo. When present, embryo development only progressed with ovule collection time in the C. medium and C. formanekiana crosses. The occurrence of miscoloured seedlings in interspecific crosses indicated incompatibilities between the parental lines that could not be prevented by reciprocal crossing. The low number of collectible ovules and germination rates might be inhibited due to fertilisation barriers. With this study, a protocol for ovule culture was established and the usefulness of ovule culture to obtain interspecific hybrids of selected Campanula species was demonstrated.

Occurrence of Polyembryony in Juniperus Polycarpos C. Koch.

The natural regeneration in Juniperus polycarpos is quite low due to seed dormancy. While studying the seed germination behaviour of Juniperus polycarpos, a twin seedling was found germinated from a single seed which has been reported. This is the first instance of occurrence of polyembryonic seedlings in Juniperus polycarpos which have been reported in this paper. The twin seedlings have been resulted due to the phenomenon of polyembryony which is of rare occurrence in this species, however, the production of twin seedlings has been reported earlier also in other forest tree species. The twin seedlings were found to be independent having separate taproots and cotyledons. The seedlings were later transplanted in a polybags filled with Soil: Sand: FYM (2:1:1 :) to observe the further growth of twin seedlings. After three months, it was noticed that both the twin seedlings shriveled and died where as normal seedlings continued to grow normally and produced all the essential features of a plant.