The shrub, leaf, and fruit traits of natural blue honeysuckle populations at different elevations were measured to explore the key factors influencing phenotypic variation as well as the intra- and interpopulation differences in phenotype. Thirteen phenotypic traits were measured at seven elevations (600-1800 m) on Changbai Mountain, China. Analysis of variance indicated that the inter-population variance accounted for 16.2261% of the total variation, whereas the intra-population variance accounted for 14.1178%. Our findings indicated that the leaf and fruit characters varied between and within populations, with the diversity between populations being greater than that within populations. The range in the coefficient of variation (11.9419%-21.7084%) suggested that the phenotypic traits varied to some extent at the species and population level and that these traits demonstrated adaptive potential. The Shannon-Wiener index indicated that the phenotypic diversity of the populations at the individual level was high. The inter-population correlation between phenotypic traits and environmental factors showed that tree height, crown length diameter, crown length diameter/crown short diameter, leaf thickness, leaf shape index, and fruit longitudinal diameter were plastic in response to environmental change. We found that inter-population variation was the main source of phenotypic variation, and the temperature changes associated with altitude primarily influenced the phenotypic changes.

To better understand the influence of altitude on fruit characteristics of bog bilberry (Vaccinium uliginosum L.), here we investigated the adaptation of its fruit morphological and chemical traits to the environment at six growing positions along an altitudinal gradient (706, 957, 1 226, 1 315, 2 000 and 2 190 m) on the northern slope of Changbai Mountain, China. Fruit longitudinal diameter, fruit transverse diameter and fruit weight decreased significantly with increasing altitude. Vitamin B 1 content reached its highest at 2 190 m, while both vitamin B 2 and vitamin C contents reached their highest and lowest at 1 226 and 706 m, respectively. Anthocyanin content and DPPH (1,1-diphenyl-2-picrylhydrazyl) free radical scavenging ability initially decreased and then improved with increasing altitude. We observed a highly significant (P < 0.001) negative correlation between external fruit quality traits (fruit length, diameter and weight) and internal fruit quality traits (vitamins B 1 , B 2 , C and anthocyanin), and found that environmental factors significantly influenced fruit characteristics. Taken together, we concluded that on the northern slope of Changbai Mountain, bog bilberry fruits were larger at low altitudes, fruits at mid altitudes contained higher vitamins B 2 and C, while high altitude (especially at 2 190 m) was beneficial for vitamin B 1 , anthocyanin, and DPPH free radical scavenging ability.

Changes in the activity levels of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) in the leaves of Lonicera caerulea, a perennial deciduous shrub, were measured along an altitude gradient (800-1800 m) on the northern slope of Changbai Mountain, China. Enzyme activity levels were statistically analyzed with respect to various environmental factors‘including soil and climate parameters’ to explore the physiological and biochemical mechanisms underlying the adaptation of this shrub to mountainous habitats. From 800 m to 1000 m, POD activity decreased significantly (to 712 U/g·min), then increased significantly to peak at 1600 m (4190 U/g·min), followed by a decrease at 1800 m. The CAT activity increased significantly from 800 m to peak at 1600 m (274 U/g·min), followed by a decrease at 1800 m. SOD activity increased steadily from 800 m to 1800 m. From 800 m to 1000 m, APX activity decreased significantly (to 5201 U/g·min), then increased significantly to peak at 1600 m (14771 U/g·min), followed by a decrease at 1800 m. Multiple regression analysis showed that CAT activity was mainly affected by the number of days with snow cover, soil available P, and soil total P. SOD activity was mainly affected by precipitation from June to September and soil total P. APX activity was mainly affected by soil available P. Correlations between leaf traits and environment indicated that all four enzymes were sensitive to environmental changes, and that enzyme activity levels adjusted to the environment as the elevation changed. The results here showed, antioxidant enzyme activity levels in the leaves of L. caerulea on the northern slope of Changbai Mountain were lower at low altitudes (800-1200 m) and higher at moderate altitudes (1200-1600 m), suggesting that these altitudes are the most conducive to the stable growth of. L. caerulea has high edible and medicinal value, and this plant grows well throughout its wide distribution in the Changbai Mountain area. Therefore, the results of this study suggested that the planting area of L. caerulea can be extended to these altitudes. In addition, these findings provide a basis for improvements of L. caerulea fruit yield and quality.

Background: Lonicera caerulea is a perennial deciduous shrub of medical and edible value that is widely distributed on the northern slope of Changbai Mountain. Soil properties and climate parameters at different elevations affect plant growth, but thus far no studies have been conducted on Lonicera caerulea in different elevation gradients on the northern slope of Changbai Mountain. Here, the leaves of Lonicera caerulea, collected from different elevations (800–1800 m) on the northern slope of Changbai Mountain in China, were used as test materials. The aim was to determine the changes in the leaves’ soluble protein content, soluble sugar content, malondialdehyde (MDA) content, superoxide anion content, and plasma membrane permeability along the altitudinal gradient. The leaf-level data were statistically analyzed with respect to various environmental factors (soil properties and climate parameters) to explore the physiological and biochemical mechanisms of their adaptation to mountainous habitats. Results: The soluble protein and soluble sugar contents initially increased and then decreased with greater altitude. The soluble protein content reached its maximum value of 1.84 mg/g at 1400 m while soluble sugar content peaked at 37.40 mg/g at 1600 m. The soluble protein content of the leaves was mainly affected by the total K content of the soil, while the total K content of the soil, total P content of the soil, and organic matter were the main factors explaining their soluble sugar content. The MDA content increased at first, then decreased, and then increased with altitude, for which the lowest values of 5.76 mol/g and 6.29 mol/g occurred at 1000 m and 1600 m, respectively; the MDA content was mainly influenced by hydrolysis N in soil. The superoxide anion content initially decreased and then increased with greater elevation, for which the minimum value of 26 μg/g occurred at 1200 m. The superoxide anion content was mainly driven by the total K and total P contents. The leaves’ plasma membrane permeability initially decreased and then increased with greater elevation; values were lowest at the intermediate elevations, and the minimum value of 0.30% occurred at 1000 m. Plasma membrane permeability was mainly affected by the total K content. Based on their relationships with the environmental factors (soil properties and climate parameters), the soluble protein, soluble sugar, malondialdehyde (MDA), and superoxide anion contents as well as the plasma membrane permeability of Lonicera caerulea leaves are very sensitive to environmental changes. For plants established at differing elevations, the leaf traits appear able to correspondingly adapt to the local habitat. Conclusions: In general, the growth of Lonicera caerulea at low and high altitude areas on the northern slope of Changbai Mountain is easily restricted by various environmental factors, resulting in its poor growth condition there. By contrast, this shrub grows well at mid-elevations; thus, the planting area of Lonicera caerulea should be expanded to those areas to increase this shrub’s fruit yield and quality.