For Corylus avellana, pericarp permeability, seed desiccation tolerance, and the effect of warm and cold moist stratification combinations on germination and of outdoor sowing date on dormancy breaking and seedling emergence were investigated. Seeds with (intact fruit nut) and without the pericarp were subjected to an imbibition test, and water uptake was measured. After nuts had been stored for 5 months at 3–5 °C, seeds and desiccated seeds were cold-stratified at 3–5 °C (for 0, 1, 2 or 3 months), then tested for germination. Nuts were warm-stratified at 20–25 °C (for 0, 1 or 2 months), then cold-stratified (for 0, 1, 2 or 3 months) and tested for seed germination. The nuts were sown outdoors on three dates in the same year of their collection: 15 September (immediately after collection), 2 November, and 17 December, and emerged seedlings were counted the following spring. The pericarp was not a barrier to water uptake by the seed; however, the seeds imbibed water faster and had more mass when the pericarp was removed. Seeds tolerated desiccation; germination percentage was not reduced when seed moisture content was reduced to 8.71%. Germination of seeds without the pericarp (regardless of the moisture content) was the highest when the seeds were cold-stratified for 2 months. When seeds with the pericarp were tested for germination, 2 months of warm stratification before a 2-month cold stratification maximized seed germination. For outdoor sowing of nuts, sowing date affected percentage of seedling emergence the following spring; early autumn sowing (immediately after collection) resulted in the best emergence.

Ginkgo biloba L. is a precious relic tree species with important economic value. Seeds, as a vital reproductive organ of plants, can be used to distinguish cultivars of the species. We chose 400 seeds from two cultivars of ginkgo (“Fozhi” and “Maling”; 200 seeds for each cultivar) as the study material and used the Gielis equation to fit the projected shape of these seeds. The coefficients of variation (CV) in root mean squared errors (RMSE) obtained from the fitted data were used to compare the level of inter-cultivar variations in seed shape. We also used the covariance analysis to compare the allometric relationships between seed weights and projected areas of these two cultivars. The Gielis equation fitted well the seed shapes of two ginkgo cultivars. The lower CV in RMSE of cultivar “Fozhi” than “Maling” indicated a less symmetrical seed shape in the latter than the former. The bootstrap percentile method showed that the seed shape differences between the two cultivars were significant. However, there was no significant difference in the exponents between the seed weights and the projected areas of these two cultivars. Overall, the significant differences in shapes between the seeds of two ginkgo cultivars were well explained by the Gielis equation; this model can be further extended to compare morphological differences in other ginkgo cultivars, and even for plant seeds or animal eggs that have similar oval shapes.

Metasequoia glyptostroboides is an endangered relict plant native to China that has been widely introduced into many countries and areas around the world. However, its seeds germinate at a very low percentage. Consequently, population regeneration by seed is low under natural conditions, which probably contributes to the endangered status of this plant species. The present study aimed to describe the aging mechanism of M. glyptostroboides seeds. Our objective was to elucidate causes of the low germination rate in an effort to enhance potential for conservation of the species. We used germination tests, relative electrical conductivity and malondialdehyde content determination, ultrastructural observation of embryo cells, and analysis of superoxide dismutase, catalase, ascorbate peroxidase, and dehydroascorbate reductase activities during accelerated aging treatment. We found that M. glyptostroboides seeds have a low level of vigor and poor ability to maintain vigor, which is probably associated with the inefficiency of its enzymatic antioxidative system.

Tissue browning is a major problem in tissue culturing of woody plants, especially for Ficus religiosa which occurs by the accumulation and oxidation of phenolic compounds. This study aimed to determine the effect of different concentrations of sodium nitroprusside on the appearance of callus browning from leaf explants. The results indicate that callus browning was significantly reduced by supplementation of sodium nitroprusside to the MS medium and supplemented with 2.26 μM of 2,4-dichlorophenoxyacetic acid and 0.22 μM of 6-benzyl amino purine. The accumulation of hydrogen peroxide and phenolic compounds in the callus tissues decreased at the 50 μM concentration of sodium nitroprusside. Although catalase and peroxidase activities decreased at the 50 μM concentration, the activity of superoxide dismutase and polyphenol oxidases, as well as proline content, increased exponentially. Sodium nitroprusside could be useful for the formation of non-embryogenic callus with high levels of metabolic activity for the production and isolation of secondary metabolites.

This study was conducted to evaluate the tolerance of 1-year-old seedlings of ten subtropical ornamental tree species against a range of salinity levels of NaCl from May 2015 to October 2015. The levels were further enhanced from November to April 2017 as 100% survival was observed in the initial concentrations for all species. The seedlings were grown during the first week of April 2015 in 10″ earthen pots containing soil: farmyard manure (2:1), irrigated with tap water for 1 month followed by saline irrigation in May by maintaining electrical conductivity at 0.75, 1.00, 1.25, 1.50, 2.25, and 3.00 dS/m for 30, 40, 50, 60, 90, and 120 mM NaCl. Every 3 months, heights, relative leaf water content, and percent survival were determined; total soluble sugars of the upper leaves of each tree were quantified. All species exhibited consistent early growth and survival when supplied with 30, 40, 50 and 60 mM of NaCl. Koelreutaria paniculata, Ficus benjamina, Putranjiva roxburghii, Bauhinia purpurea and Millettia ovalifolia were sensitive to elevated salinity levels and did not survive at the highest salt concentrations of 90 and 120 mM.

Leaf area index (LAI) is one of the most important characteristics of forest stands that affects the fundamentals of tree physiological processes, biomass production, and mechanical stability. The LAI results obtained by the semi-direct and indirect methods (the needle technique and an LAI-2000 PCA) in three European beech (Fagus sylvatica L.) stands and one sycamore maple (Acer pseudoplatanus L.) stand were compared with LAI estimated by litter traps during the 2013 growing season. Seasonal LAI was estimated using an LAI-2000 PCA which showed similar trends among the stands and strongly corresponded to phenological phases of deciduous stands in Europe, with the fastest rate of leaf area increment occurring during the first month following bud break. During the growing season, maximum stand LAI value was on June 19th and reached 4.5–5.1, and 4.0 in the beech and maple stands, respectively. The needle technique significantly underestimated (p < 0.05) direct LAI on average by 22.0% and 40.0% in the beech and maple stands, respectively. The LAI-2000 PCA insignificantly underestimated (p > .05) LAI on average by 15.1% and 5.8% in the beech and maple stands, respectively. All methods for LAI estimation at the stand level could be applicable in deciduous forest stands (beech, maple) with similar site and stand characteristics. However, calibration by direct method is necessary to obtain the required precision.

Eucalyptus adult material requires more successive subcultures in the in vitro multiplication phase for increased vigor and cellular activity. This study evaluated the endophytic manifestation and shoot multiplication of one 13-year-old Eucalyptus benthamii clone under different culture conditions and used canopy branches (CB) and trunk base material as explant sources. The culture media were wood plant medium (WPM), Murashige and Skoog medium (MS) and JADS (Correia and co-authors medium). Based on the results of the initial multiplication experiment, further tests examined sucrose concentrations and pH. Morphophysiology, dry mass production, endophytic manifestation and histochemical were determined. Explant sources responded differently to MS and JADS media, but the WPM medium promoted homogeneous development. The responses were similar for both explant sources when sucrose concentrations varied. Shoots died in the absence of sucrose, showed high oxidation at 60 g L⁻¹ and optimal development at 30 g L⁻¹. Endophytes were more evident for shoots from the CB origin. Explant sources responded distinctively to treatment due to physiological and intrinsic genetic factors. Therefore, explant sources, different culture media, sucrose concentration and pH may determine micropropagation success and influence the presence and/or intensity of endophytic manifestation.

Pine wood nematode (PWN), Bursaphelenchus xylophilus, is a serious pathogen of pines throughout the world. Previous work indicated that different concentrations of α-pinene could affect nematode reproduction, however the mechanism of that influence is not clear. In order to examine the reproductive strategies of PWN in response to the stress of the volatile material α-pinene, we investigated different aspects of population changes of B. xylophilus under two concentrations of α-pinene. The results show that a high concentration (214.5 mg ml⁻¹) promoted population growth while a low concentration (56.33 mg ml⁻¹) decreased the population. Population structure was analyzed and it was found that a high concentration of α-pinene decreased the percentage of adults but increased the percentages of larvae and eggs. Furthermore, from the results of an evaluation of sex ratios (female/male), it was determined that a high concentration could elevate sex ratios but a low concentration decreased ratios sharply. These results suggest that the PWN could regulate its population by changing sex ratios under stress of α-pinene. This study has provided a theoretical basis for the prevention and control of pine wilt disease caused by the pine wood nematode.

Global warming-induced changes in tree-growth resilience to climate variations have been widely reported for mid- and high-latitude regions around the world. Most studies have focused on the spatial variability of trees in radial growth–climate relationships on Changbai Mountain in Northeast China, but little is known about temporal changes in tree growth in response to climate. We explored the stability of effect of climate variables on radial growth of Yezo spruce [Picea jezoensis Carr. var. komarovii (V.Vassil.) Cheng et L.K.Fu] at 1200, 1400, and 1600 m above sea level, representing low, middle, and upper ranges of the spruce–fir mixed forest on Changbai Mountain. The results showed that the relation between tree growth and climate did not vary with altitude, but the stability of the tree-growth–climate relationship did vary with altitude as the climate changed. Radial growth of Yezo spruce at all three elevations was influenced primarily by maximum temperature during May (Tmax5) and mean minimum temperature from January to March (Tmin1–3). More specifically, the relationship strengthened significantly at lower elevations, but weakened significantly at higher elevation, and fluctuated at mid elevations since 1980. Increase in Tmin1–3 and decrease in Tmax5 were the main reasons for the decrease in the radial growth at three altitudes. The findings of this study clarified that the decrease in radial growth on Changbai Mountain is not a “divergence problem” of an unexpected decrease in tree growth in response to an increase in mean temperature and provides a reference for using tree-ring data to reconstruct climate patterns and/or predict the growth of trees under various climate change scenarios.

The total biomass of a stand is an indicator of stand productivity and is closely related to the density of plants. According to the self-thinning law, mean individual biomass follows a negative power law with plant density. If the variance of individual biomass is constant, we can expect increased stand productivity with increasing plant density. However, Taylor’s power law (TPL) that relates the variance and the mean of many biological measures (e.g. bilateral areal differences of a leaf, plant biomass at different times, developmental rates at different temperatures, population densities on different spatial or temporal scales), affects the estimate of stand productivity when it is defined as the total biomass of large plants in a stand. Because the variance of individual biomass decreases faster than mean individual biomass, differences in individual biomass decline with increasing density, leading to more homogeneous timbers of greater economic value. We tested whether TPL in plant biomass holds for different species and whether the variance of individual biomass changes faster than the mean with increasing stand density. The height, ground diameter and fresh weight of 50 bamboo species were measured in 50 stands ranging from 1 m by 1 m to 30 m by 30 m to ensure more than 150 bamboos in every stand. We separately examined TPL in height, ground diameter, and weight, and found that TPL holds for all three biological measures, with the relationship strongest for weight. Using analysis of covariance to compare the regression slopes of logarithmic mean and variance against the logarithm of density, we found that the variance in individual biomass declined faster than the mean with increasing density. This suggests that dense planting reduced mean individual biomass but homogenized individual biomass. Thus, there exists a trade-off between effective stand productivity and stand density for optimal forest management. Sparse planting leads to large variation in individual biomass, whereas dense planting reduces mean individual biomass. Consequently, stand density for a plantation should be set based on this trade-off with reference to market demands.

Carbon is continuously being removed from the atmosphere by photosynthesis and stored in carbon pools (live, dead, and soil carbon) of forest ecosystems. However, carbon stock in dead wood and of trees with diameters at breast height (dbh) between 5 and 10 cm is often not considered in many studies carried out in the Congo Basin Forest. The relationship between tree diversity, life-forms and carbon stocks has received little attention. This study was carried out on the outskirts of Deng Deng National Park (DDNP) to determine tree diversity (dominant families, species richness and Shannon index), assess carbon stocks in the five carbon compartments (living tree, understory, fine roots, dead wood and litter) as well as to analyze the relationship between (1) carbon stocks and tree diversity; and, (2) between carbon stock and life-forms. The Shannon index of trees ≥ 10 cm dbh ranged from 2.6 in riparian forest to 4.3 in secondary forest; and for the tree between 5 and 10 cm, it ranged to 1.56 in riparian forest to 3.68 in the secondary forest. The study site housed 16 species, 7 genera and 3 families which are only found in trees of dbh between 5 and 10 cm. The average total carbon stock of the five compartments varied from 200.1 t ha⁻¹ in forest residues to 439.1 t ha⁻¹ in secondary forest. Dead wood carbon stock varied from 1.2 t ha⁻¹ in riparian forests to 12.51t ha⁻¹ in agroforests. The above ground carbon stocks for trees with diameter between 5 and 10 cm varied from 0.7 t ha⁻¹ in young fallow fields to 5.02 t ha⁻¹ in old secondary forests. This study reveals a low but positive correlation between species richness and total carbon stocks, as well as a significant positive relationship between life-forms and total carbon stocks. The findings highlight the need for more data concerning carbon content of dead wood, carbon of trees ≥ 5 cm < 10 cm dbh and the relationship between carbon stocks and tree diversity from other areas of the Congo Basin for a good understanding of the contribution of tropical forests to climate change mitigation.

Bacillus cereus NJSZ-13, an endophytic bacterium with nematicidal activity, was isolated from stems of healthy Pinus elliottii Engelm. Colonization of P. massoniana Lamb. by endophytic B. cereus was studied using scanning electron microscopy and confocal laser scanning microscopy. After the plasmid pGFP78 containing the green fluorescent protein (GFP) gene was transformed into the NJSZ-13 strain, the NJSZ-13:gfp showed the same nematicidal activity and growth curve as the wild-type strain, and the plasmid pGFP78 was stably maintained in strain NJSZ-13 for at least 96 h of bacterial cultivation on medium without antibiotics. After inoculation into Masson pine roots, colonization of the NJSZ-13:gfp strain in plant roots and stems was visualized using confocal laser scanning and the strain was enumerated in inoculated roots and stems. These results suggest that NJSZ-13:gfp is an efficient colonizer of Masson pine and can transfer vertically from roots to stems.

This study investigates the biocontrol potential of Trichoderma asperellum mutants against Rhizoctonia solani, Alternaria alternata, and Fusarium oxysporum and growth promotion of Populus davidiana ×  P. alba var. pyramidalis (PdPap poplar) seedlings. A T-DNA insertion mutant library of T. asperellum was constructed using Agrobacterium tumefaciens-mediated transformation. Sixty-five positive transformants (T1–T65) were obtained. Growth rates of the mutants T39 and T45 were the same, 39.68% faster than the WT. In toxin tolerance tests, only T39 had greater tolerance to A. alternata fermentation broth than the WT, but mutant T45 had the same tolerance as the WT to all fermentation broths. Furthermore, T39 and T45 had a greater antagonistic ability than the WT strain against R. solani and A. alternata. The inhibition rate of the mutants T39 and T45 against A. alternata are 73.92% and 80.76%, respectively, and 63.51% and 63.74%, respectively. Furthermore, the three strains increased the activities of superoxide dismutases, peroxidase, catalase (CAT) and phenylalanine ammonia lyase (PAL) in PdPap seedling leaves. CAT and PAL activity in the PdPap seedling leaves was 11.25 and 5.50 times higher, respectively, in the presence of T39 than in the control group and 12 and 6.35 times higher, respectively, in the presence of T45 than in the control group. All three strains promoted seedling growth and the root and stem development, especially mutant T45. Mutants T39 and T45 reduced the incidence of pathogenic fungi in poplar and stimulated poplar seedling growth.