一株特殊生境荒漠药用植物沙蓬内生真菌Rhinocladiella similis中苯甲酸大环内酯化合物

从一株特殊生境荒漠药用植物沙蓬的内生真菌Rhinocladiella similis中分离得到4个苯甲酸大环内酯化合物,包括2个新化合物rhinoclactones E（2）和F（1）、2个已知化合物8,9-dihyrogreensporone D（3）和8,9-dihydrogreensporone A（4）。基于高分辨质谱与核磁共振谱数据以及相关文献比对,确定了新化合物与已知化合物的结构。化合物1和2是一对立体异构体,在大环内酯环中并有一个呋喃环,这种环系统在自然界比较稀少。化合物1-4对3株肿瘤细胞株和植物病原真菌没有抑制活性。本结果进一步丰富了该真菌的化学成分研究,暗示特殊生境荒漠植物内生真菌具有产生结构新颖的次级代谢产物的潜力,是发现新活性天然产物的一个新的重要宝库;此外,根据化合物的结构特征与生物活性结果,本文还探讨了这些化合物潜在的生态学功能。     

Identification,biochemical composition and phycobiliproteins production of Chroococcidiopsis sp. from arid environment

Molecular and microscopic studies were performed to identify Chroococcidiopsis sp., an endolithic cyanobacterium, isolated from gypsum rocks of Atacama Desert (Chile). It was adapted to grow in mineral liquid medium, with 9 mM nitrate, bubbled with CO₂-enriched air (2.5 % v/v), and continuously illuminated with a white light of 70 μmol photons m^–2 s^–1. The obtained biomass (productivity of 0.21 g L^–1 d^–1) had a C/N ratio of 6.67, and it contained carbohydrates (45.40 % of dry weight), proteins (36.72 %), lipids (5.60 %) nucleic acids (3.90 %) and ashes (8.28 %). The lipid fraction was particularly rich in palmitic (29.86 % of total fatty acids), linoleic (18.20 %), palmitoleic (12.75 %), linolenic (10.92 %), stearic (9.64 %) and capric acid (6.29 %). Chroococcidiopsis sp. accumulated phycobiliproteins in a light-dependent process and produced 204 mg g^–1, under incident light of 10 μmol photons·m^–2·s^–1, with a relative abundance of 40.9 % for phycocyanin, 23.3 % for phycoerythrin, and 35.8 % for allophycocyanin. The biomass from this cyanobacterium can be a good source of these pigments, especially APC (maximum of 95 mg g dw⁻¹), which are of interest for pharmacological, cosmetic, and food industries.     

Plant community composition steers grassland vegetation via soil legacy effects

Soil legacy effects are commonly highlighted as drivers of plant community dynamics and species co‐existence. However, experimental evidence for soil legacy effects of conditioning plant communities on responding plant communities under natural conditions is lacking. We conditioned 192 grassland plots using six different plant communities with different ratios of grasses and forbs and for different durations. Soil microbial legacies were evident for soil fungi, but not for soil bacteria, while soil abiotic parameters did not significantly change in response to conditioning. The soil legacies affected the composition of the succeeding vegetation. Plant communities with different ratios of grasses and forbs left soil legacies that negatively affected succeeding plants of the same functional type. We conclude that fungal‐mediated soil legacy effects play a significant role in vegetation assembly of natural plant communities.     

Alpine grassland plants grow earlier and faster but biomass remains unchanged over 35 years of climate change

Satellite data indicate significant advancement in alpine spring phenology over decades of climate warming, but corresponding field evidence is scarce. It is also unknown whether this advancement results from an earlier shift of phenological events, or enhancement of plant growth under unchanged phenological pattern. By analyzing a 35‐year dataset of seasonal biomass dynamics of a Tibetan alpine grassland, we show that climate change promoted both earlier phenology and faster growth, without changing annual biomass production. Biomass production increased in spring due to a warming‐induced earlier onset of plant growth, but decreased in autumn due mainly to increased water stress. Plants grew faster but the fast‐growing period shortened during the mid‐growing season. These findings provide the first in situ evidence of long‐term changes in growth patterns in alpine grassland plant communities, and suggest that earlier phenology and faster growth will jointly contribute to plant growth in a warming climate.