Micromorphology of Pine Needle Primordia and Young Needles after Bud Dormancy Breaking.

Using a scanning electron microscope, the micromorphologies of needle primordia and the young needles of seven pine species (Pinus cembra, P. mugo, P. nigra, P. rigida, P. sylvestris, P. strobus, and P. uncinata) were analyzed at phenological stages B2 and B3 (according to Debazac). In B2, needle tips were rounded or pointed, depending on the species. In P. cembra and P. strobus, teeth were noted on the tips. Teeth were also visible on the margins in P. mugo, P. cembra, and P. strobus. Stomata became visible in the late B2 phase (P. sylvestris, P. mugo, and P. nigra) near the needle tips and were arranged in rows. In the B3 phase, needle tips were pointed. Only in P. strobus was the needle tip slightly rounded. The teeth on the margin in all the species were pointed. In P. strobus, their size and density along the margin decreased basipetally. In B3 for all the species, numerous stomata were visible. In P. sylvestris, P. cembra, and P. strobus, Florin rings were also observed. These observations could be useful in pine systematics but also in palaeobotanical or physiological studies. To the best of our knowledge, this is the first study on the micromorphology of very young needles in representatives of the genus Pinus.

The future of Viscum album L. in Europe will be shaped by temperature and host availability.

Viscum album L. is a plant of great importance due to its influence on the host trees and, by extension, entire ecosystems. The species is also significant to humans-on the one hand, because of its use in medicine, and on the other, because of the growing threat it poses to the stability of conifer stands. Therefore, it is important to recognize the future range of three mistletoe subspecies (Viscum album subsp. album, V. album subsp. austriacum, and V. album subsp. abietis). Modelling of the potential range of these subspecies was performed using MAXENT software. Locations were collected from literature and databases. A total number of 3335 stands were used. Bioclimatic data for the current conditions and three future scenarios (SSP 1.26, SSP 3.70, SSP 5.85) were downloaded from the CHELSA database. The results confirmed that the temperature is the key variable on the potential range of the analysed subspecies. V. album subsp. abietis is withdrawing from its range according to all scenarios. In the case of V. album subsp. austriacum, a slight range shift is visible. Only the V. album subsp. album will expand non-directionally. The reason is most likely a very large number of host species and greater genetic variability compared to the subspecies found on conifers.

Past climatic refugia and landscape resistance explain spatial genetic structure in Oriental beech in the South Caucasus.

Predicting species-level effects of climatic changes requires unraveling the factors affecting the spatial genetic composition. However, disentangling the relative contribution of historical and contemporary drivers is challenging. By applying landscape genetics and species distribution modeling, we investigated processes that shaped the neutral genetic structure of Oriental beech (Fagus orientalis), aiming to assess the potential risks involved due to possible future distribution changes in the species. Using nuclear microsatellites, we analyze 32 natural populations from the Georgia and Azerbaijan (South Caucasus). We found that the species colonization history is the most important driver of the genetic pattern. The detected west-east gradient of genetic differentiation corresponds strictly to the Colchis and Hyrcanian glacial refugia. A significant signal of associations to environmental variables suggests that the distinct genetic composition of the Azerbaijan and Hyrcanian stands might also be structured by the local climate. Oriental beech retains an overall high diversity; however, in the context of projected habitat loss, its genetic resources might be greatly impoverished. The most affected are the Azerbaijan and Hyrcanian populations, for which the detected genetic impoverishment may enhance their vulnerability to environmental change. Given the adaptive potential of range-edge populations, the loss of these populations may ultimately affect the specie's adaptation, and thus the stability and resilience of forest ecosystems in the Caucasus ecoregion. Our study is the first approximation of the potential risks involved, inducing far-reaching conclusions about the need of maintaining the genetic resources of Oriental beech for a species' capacity to cope with environmental change.

Stomatal density in Pinus sylvestris as an indicator of temperature rather than CO2 : Evidence from a pan-European transect.

The commonly observed negative relationship between stomatal density (SD) and atmospheric CO2 has led to SD being proposed as an indicator of atmospheric CO2 concentration. The use of SD as a proxy for CO2 , however, has been hampered by an insufficient understanding of the intraspecific variation of this trait. We hypothesized that SD in Pinus sylvestris, a widely distributed conifer, varies geographically and that this variation is determined by major climatic variables. By sampling needles from naturally growing trees along a latitudinal range of 32.25°, equivalent to 13.7°C gradient of mean annual temperature (MAT) across Europe, we found that SD decreased from the warmest southern sites to the coldest sites in the north at a rate of 4 stomata per mm2 for each 1°C, with MAT explaining 44% of the variation. Additionally, samples from a provenance trial exhibited a positive relationship between SD and the MAT of the original localities, suggesting that high SD is an adaptation to warm temperature. Our study revealed one of the strongest intraspecific relationships between SD and climate in any woody species, supporting the utility of SD as a temperature, rather than direct CO2 , proxy. In addition, our results predict the response of SD to climate warming.

Rubuskaznowskii (Rosaceae), a new bramble species from south-central Poland.

Based on field research in south-central Poland, supplemented with a review of herbarium materials, we identified a stable bramble biotype with a range large enough (190 km distance between the outermost stands) to be described as a new regional agamic species, Rubuskaznowskii sp.nov. It belongs to the series Subthyrsoidei(sect. Corylifolii). Although R.kaznowskii has a unique combination of features, it can be potentially mistaken for R.gothicus. It differs from the latter species in many aspects, including: pruinose primocanes, denser indumentum of the abaxial leaf surface, and more curved prickles on the petiole. R.kaznowskii has mainly been observed on rusty soils, in habitats of mixed coniferous and mixed broadleaf forests, usually in sunny places, along forest margins and roads, in clearings and roadside thickets.

Regulation of the leaf proteome by inoculation of Populus × canescens with two Paxillus involutus isolates differing in root colonization rates.

During ectomycorrhizal symbioses, up to 30% of the carbon produced in leaves may be translocated to the fungal partner. Given that the leaf response to root colonization is largely unknown, we performed a leaf proteome analysis of Populus × canescens inoculated in vitro with two isolates of Paxillus involutus significantly differing in root colonization rates (65 ± 7% vs 14 ± 7%), together with plant growth and leaf biochemistry analyses to determine the response of plant leaves to ectomycorrhizal root colonization. The isolate that more efficiently colonized roots (isolate H) affected 9.1% of the leaf proteome compared with control plants. Simultaneously, ectomycorrhiza in isolate H-inoculated plants led to improved plant growth and an increased abundance of leaf proteins involved in protein turnover, stress response, carbohydrate metabolism, and photosynthesis. The protein increment was also correlated with increases in chlorophyll, foliar carbon, and carbohydrate contents. Although inoculation of P. × canescens roots with the other P. involutus isolate (isolate L, characterized by a low root colonization ratio) affected 6.8% of the leaf proteome compared with control plants, most proteins were downregulated. The proteomic signals of increased carbohydrate biosynthesis were not detected, and carbohydrate, carbon, and leaf pigment levels and plant biomass did not differ from the noninoculated plants. Our results revealed that the upregulation of the photosynthetic protein abundance and levels of leaf carbohydrate are positively related to rates of root colonization. Upregulation of photosynthetic proteins, chlorophyll, and leaf carbohydrate levels in ectomycorrhizal plants was positively related to root colonization rates and resulted in increased carbon translocation and sequestration underground.

Changes in genomic 5-methylcytosine level mirror the response of orthodox (Acer platanoides L.) and recalcitrant (Acer pseudoplatanus L.) seeds to severe desiccation.

Poor storability of recalcitrant seeds is due to their inability to tolerate low moisture content. Understanding the processes underlying their recalcitrance is a prerequisite to developing a maintenance strategy and prolonging their lifespan. Multiple studies have investigated the differences between orthodox (desiccation-tolerant) and recalcitrant (desiccation-sensitive) seeds. Information on epigenetic regulation, however, is lacking and thus limits our understanding of the processes defining the physiology of seeds. In the present comparative study, changes in the global levels of 5-methylcytosine (m5C) in orthodox and recalcitrant seeds of Acer platanoides L. and Acer pseudoplatanus L. were characterized during progressive stages of severe drying. Concomitant with their differential sensitivity to desiccation stress, we demonstrate variation in the response of embryonic axes and cotyledons to water deficit at the level of DNA methylation. Results indicate that desiccation-induced changes in m5C are both tissue- and seed category-specific and are highly correlated with recalcitrant seed viability. Moreover, we demonstrate that m5C global changes in response to desiccation are not retained in DNA isolated from seedlings, except in seedlings that are derived from strongly desiccated orthodox seeds (moisture content of 3.5%). Finally, the potential utilization of m5C status as a universal seed viability marker is discussed.

Is Shape of a Fresh and Dried Leaf the Same?

Plants kept as dried herbarium specimens share many characteristics with their living counterparts, but there are some substantial differences between them. Due to dehydration, leaves of herbarium specimens change not only their mass and colour, but in many cases change their dimensions, too. The present study aimed to determine whether leaf shape changes during the drying process. A total of 794 pairs of fresh and dried leaves or leaflets of 22 plant taxa were studied. The shape of the blades was quantified using elliptic Fourier analysis combined with principal component analysis. In addition, area and mass of the leaves were measured. Statistical tests were applied for comparing fresh and dried leaves. The results indicate that the preservation process of pressing and drying plants for herbarium purposes causes changes in leaf shape. In general, the shape changes were directional. As the shape of fresh and dried plants is different, it is strongly recommended that shape analyses should be performed on datasets containing either of the leaf types.