Introduction: Global climate change can affect the sensitivity of tree radial growth to climate factors, but the specific responses of tree radial growth to microclimate along the altitudinal gradient in the long term are still unclear.Methods: In this study, the tree-ring width chronologies of Pinus tabuliformis Carr. in Shanxi Province of China were studied at three altitude gradients (1200-1300 m (low altitude), 1300-1400 m (medium altitude) and 1400-1500 m (high altitude)) during 1958-2017.Results: The results showed that (1) the climate background could be divided into two periods based on the Mann-Kendall test analysis: 1958–1996 was a stable period (mean annual temperature (MAT)=10.25°C, mean annual precipitation (MAP)=614.39 mm), and 1997–2017 was a rapid change period (MAT=10.91°C, MAP=564.70 mm), indicating a warming and drying trend in the study region. (2) The radial growth of P. tabuliformis at different altitudes showed inconsistent variation patterns. The tree radial growth at low and medium altitudes (CV=27.01% for low altitude and CV=24.69% for medium altitude) showed larger variation amplitudes during the rapid change period than that in the stable period (CV=12.40% for low altitude and CV=18.42% for medium altitude). In contrast to the increasing trend, the tree radial growth rates at the high altitude showed a decreasing trend across years. (3) In the stable period, the radial growth of P. tabuliformis at the low altitude showed a significantly negative response to temperature and a positive response to precipitation in May and June. The tree radial growth at the medium altitude was positively related to precipitation in June and minimum temperature in February. The tree growth at the high altitude was mainly positively correlated with the temperature in May and August. In the rapid change period, the radial growth of P. tabuliformis at the low altitude was affected by more meteorological factors than that in the stable period. Medium-altitude trees were positively influenced by precipitation in June and minimum temperature in January, whereas high-altitude trees responded positively to wind speed in February. (4) Along altitudinal gradients, tree radial growth was more related to temperature than precipitation in the stable period. The tree radial growth at the high altitude during the rapid change period was only affected by wind speed in February, whereas the tree radial growth at low and medium altitudes was mainly affected by temperature to a similar extent during the two periods.Discussion: The study indicated that tree growth-climate response models could help deeply understand the impact of climate change on tree growth adaptation and would be beneficial for developing sustainable management policies for forest ecosystems in the transition zone from warm-temperate to subtropical climates.

Dioscorea nipponica Makino is an optimal candidate to develop the diosgenin industry in North China. Due to its increasing demand in the medicine industry, it is urgent to apply new biotechnological tools to foster breeds with desirable traits and enhanced secondary metabolite production. The production of useful metabolites by the in vitro cultured rhizomes can be explored successfully for utilization by various food and drug industries. In this study, we reported callus formation and plantlet regeneration of the medicinal plant D. nipponica. Explants of leaves, stem segments and rhizomes of aseptic seedlings were cultured on Murashige and Skoog (MS) medium containing various combinations of auxin and cytokinin to find the optimal PGRs of each type of explant for callus induction and shoot regeneration of D. nipponica. The paraffin section technique was also used to observe of the morphogenesis of callus and adventitious bud. Explants of seeds and rhizomes formed calli at high frequency in all lines we examined. However, the explant of leaves rarely formed callus. Three kinds of callus were detected during the induction phase. Here, we describe three types of callus (Callus I–III) with different structure characteristics. Greenish in color and a nodule-like protrusion surface (Callus type III) were arranged more closely of cells with less interstitial substance, cell differentiation ability stronger than other callus types. The optimum combination was the maximum shoot differentiation frequency of 90% in callus derived from seeds cultured on MS medium with 2.0 mg L⁻¹6-BA + 0.2 mg L⁻¹NAA. The shoot differentiation frequency (88.57%) of rhizome-induced callus was obtained by the combination of MS medium supplemented with 3.0 mg L⁻¹6-BA + 2.0 mg L⁻¹NAA. 1/2 MS medium plus 0.5 mg L⁻¹NAA resulted in a higher root regeneration frequency of 86.70%. In vitro propagated plantlets with healthy roots were domesticated and transplanted into small plastic pots containing sterile soil rite under greenhouse conditions with 80% survivability. Bud differentiation is mostly of exogenous origin, mostly occurring on the near callus surface. Therefore, it may be surmised that in vitro morphogenesis of D. nipponica is mainly caused by indirect organogenesis (adventitious bud).

Early developmental stages of plants are expected to be a major bottleneck to recruitment. Information on the response of seedling to anticipated water availability is urgently needed in regions where tree seedlings may experience more frequent water deficits. In this paper, we focused on the influence of water deficit on different species (larch vs. birch) and origins (xeric vs. mesic). Prince Rupprecht’s larch (Larix gmelinii var. principis-rupprechtii (Mayr) Pilg.) and white birch (Betula platyphylla Sukaczev) from northern China were selected to represent the xeric origin. Eastern larch (Larix laricina (Du Roi) K. Koch) and paper birch (Betula papyrifera Marshall) from eastern Canada were selected to represent the mesic origin. For each species, half of seedlings were assigned to a well-watered treatment (WW, 75% water holding capacity (WHC) and the other half to a low-watered treatment (LW, 35% WHC). After 20 weeks of treatment, we collected data on morphological indexes of shoot height, root collar diameter, total leaf area and total root area; measured photosynthetic rate (A sat), transpiration rate (E), photosynthetic water-use efficiency (WUE) and apparent chlorophyll concentration (Chl); harvested seedlings and measured biomass allocation of leaf, stem and root. We found that reduced photosynthetic rate, transpiration rate and increased water-use efficiency were physiological responses of the four species to drought, and the responses varied among the species. All larch seedlings appeared no leaf shedding, survived through the drought treatment and showed a longer duration and high tolerance to drought. In low-watered conditions, survival rate, biomass, shoot height, root collar diameter, total leaf area, total root area and chlorophyll concentration of birch seedlings were significantly decreased. The response of seedlings to water deficits also differed according to the seed origins. Xeric origin of Prince Rupprecht’s larch was more affected than mesic origin of eastern larch, mainly because Prince Rupprecht’s larch originated in a narrower range of mountainous regions, resulting in lower adaptation of this species to water deficits, whereas eastern larch was distributed widely along coastal regions, contributing to higher phenotypic plasticity to variable soil conditions. Similarly, higher plasticity of paper birch may be responsible for its better performance in the low-watered treatment than white birch. Larch seedlings were less sensitive to water deficit than birch seedlings. Larch seedlings were characteristics of a conservative water-use strategy, whereas birch seedlings responded with a profligate water-use strategy. Plasticity or adaptation of seedlings outweighs the seed origins in determining their drought responses.

Understanding whether long-term vascular cambium vitality in ancient trees reflects progressive decline or adaptive reprogramming is central to grasping woody plant longevity. We performed an integrative analysis of functional traits, transcriptome profiles, and metabolomic landscapes of cambial zone enriched from 80-, 500-, and 1000-year-old Styphnolobium japonicum trees. With increasing tree age, the vascular cambium showed fewer cell layers, reduced thickness, and lower auxin, gibberellin, and IAA/ABA ratios, whereas bark thickness, malondialdehyde, abscisic acid, jasmonic acid, and salicylic acid contents increased. Transcriptomic and metabolomic analyses revealed that differentially expressed genes and metabolites were primarily enriched in the cell cycle, phytohormone signaling, and phenylpropanoid biosynthesis pathways. Specifically, genes associated with cell division were down-regulated in millennial trees, whereas phenolic acids, flavonoids, and lignin-related metabolites significantly accumulated. Piecewise structural equation modeling suggested associations among tree age, transcription factors, structural genes, metabolites, and cambial functional traits. These results indicate that cambial senescence is not a simple linear decay but a highly coordinated remodeling process, providing crucial evidence for delayed senescence in long-lived woody species.