Seasonal plasticity of stem embolism resistance and its potential driving factors in six temperate woody species.

The seasonal plasticity of resistance to xylem embolism has been demonstrated in leaves of some tree species, but is controversial in stems. In this study, we investigated the seasonality of stem xylem resistance to embolism in six temperate woody species (four deciduous and two evergreen tree species) that were grown at the same site. The xylem conduit anatomy, the concentrations, and ratios of the main cation in the xylem sap, as well as the content of nonstructural carbohydrates (including soluble sugars and starch) were measured in each species under each season to reveal the potential mechanisms of seasonal change in embolism resistance. The stem of all species showed increasing resistance to embolism as seasons progressed, with more vulnerable xylem in spring, but no significant adjustment in the other three seasons. The seasonal plasticity of stem embolism resistance was greater in deciduous species than in evergreen. On a seasonal scale, conduit diameter and conduit implosion resistance, the ratios of K+/Ca2+ and K+/Na+, and starch content were generally not correlated with embolism resistance, suggesting that these are probably not the main drivers of seasonal plasticity of stem embolism resistance. The seasonality of embolism resistance provides critical information for better understanding plant hydraulics in response to seasonal environments, especially under climate change.

Characteristic and phylogenetic analyses of chloroplast genome for Syringa komarowii C.K.Schneid. (Oleaceae) from Huoditang, China, an important horticultural plant.

The genus Syringa (Oleaceae) comprises some of the most important cultivated horticultural trees worldwide. Syringa komarowii, is one of these important horticultural plants. We sequenced the complete chloroplast (cp) genomes of S. komarowii (previously identified as var. reflexa) using Illumina Hiseq X Ten platform. The cp genome exhibits a typical quadripartite structure with 158,020 bp in length, which consists of two copies of inverted repeat (IR) regions (25,676 bp) separated by a large single copy (LSC) region (87,628 bp) and a small single copy (SSC) region (19,040 bp). The cp genome of S. komarowii encodes a total of 132 genes, including 88 protein-coding genes, 36 tRNA genes and 8 rRNA genes. A maximum likelihood (ML) phylogenetic analysis resolved that S. komarowii in a clade with S. wolfii and S. yunnanensis. The ML tree also showed Syringa appeared more closely related to Ligustrum than to the other genera in the Oleaceae.

Hyperelatosides A-E, biphenyl ether glycosides from Hypericum elatoides, with neurotrophic activity.

Five new biphenyl ether glycosides, hyperelatosides A-E (1-5), one new benzoate glycoside, hyperelatoside F (6), along with nine known phenolic compounds (7-15), were isolated from the aerial parts of Hypericum elatoides. Their structures were elucidated by 1D and 2D NMR spectroscopy and HRESIMS, as well as chemical derivatization. This is the first report of the identification of biphenyl ether glycosides as plant metabolites and their possible biosynthetic pathway is proposed. Except for 3, the new phenolic metabolites exhibited significant neurotrophic activities to enhance nerve growth factor-induced neurite outgrowth in PC12 cells. In addition, the anti-neuroinflammatory and antioxidant activities of compounds 1-15 were preliminarily evaluated in vitro.

[Light competition and productivity of agroforestry system in loess area of Weibei in Shaanxi].

Agroforestry is the most effective way for the restoration of disturbed land on Loess Plateau and the development of poorly local economy. Taking the tree-based intercropping systems of walnut or plum with soybean or pepper in the loess area of Weibei as test objects, the photosynthesis, growth, and yield of soybean (Qindou 8) and pepper (Shanjiao 981) in the systems were studied. The results showed that the photosynthetic active radiation (PAR), net photosynthetic rate (Pn), growth, and yield of individual soybean or pepper plants were significantly decreased, with the effects increased with decreasing distance from tree rows. Leaf water potential was not significantly or poorly correlated with the Pn, growth, and yield of the two crops. However, there were significant positive correlations between the soil moisture content in 10-20 cm layer and the biomass and yield of soybean, and the above-ground biomass of pepper. PAR was highly correlated with the yield of both crops, which indicated that light competition was one of the key factors leading to the decrease of crop yield.