Study on the Carbon Cycle of Leymus chinensis Steppe in the Xilin River Basin

Based on the past researches, an initial study on the carbon cycle of Leymus chinensis (Trin.) Tzvel. steppe in the Xilin river basin of Neimenggu (Inner Mongolia) was conducted by combining field surveys and the CENTURY model simulation. The major results were summarized as follows: 1) Observed annual amount of carbon fixation via primary production for a L. chinensis community on a fenced site in the basin averaged (231.25 + 74.41 ) g C·m-2·a-1, average annual carbon input into soil was about 220.75 g C· m- 2· a- 1, while carbon output from the community via soil respiration was estimated to be (181.03 + 46.32) g C· m-2· a-1 by CENTURY model simulation; 2) The community had a simulated net carbon gain of about 19.88 g C·m-2·a-1 and an observed carbon gain of 39.72 g C·m-2·a-1; 3) About 12.4% of carbon originally stored in soil had been lost due to over-grazing over the recent 40-year period in Leymus chinensis steppe in the Xilin river basin.     

Designing biomaterials for in situ periodontal tissue regeneration

The regeneration of periodontal tissue poses a significant challenge to biomaterial scientists, tissue engineers and periodontal clinicians. Recent advances in this field have shifted the focus from the attempt to recreate tissue replacements/constructs ex vivo to the development of biofunctionalized biomaterials that incorporate and release regulatory signals in a precise and near-physiological fashion to achieve in situ regeneration. The molecular and physical information coded within the biomaterials define a local biochemical and mechanical niche with complex and dynamic regulation that establishes key interactions with host endogenous cells and, hence, may help to unlock latent regenerative pathways in the body by instructing cell homing and regulating cell proliferation/differentiation. In the future, these innovative principles and biomaterial devices promise to have a profound impact on periodontal reconstructive therapy and are also likely to reconcile the clinical and commercial pressures on other tissue engineering endeavors.     

Morphogenesis of Pistillate Flowers of Cercidiphyllum japonicum （Cercidiphyllaceae）

Floral morphogenesis and the development of Cercidiphyllumjaponicum Sieb. et Zucc. were observed by scanning electron microscopy （SEM）. The results showed that the pistillate inflorescences were congested spikes with the flowers arranged opposite. Great differences between the so-called ＂bract＂ and the vegetative leaf were observed both in morphogenesis and morphology. In morphogenesis, the ＂bract＂ primordium is crescent-shaped, truncated at the apex and not conduplicate, has no stipule primordium at the base but does have some inconspicuous teeth in the margin that are not glandular. The leaf primordium is triangular, cycloidal at the apex, conduplicate, has two stipule primordia at the base, has one gland-tooth at the apex occurring at first and some gland-teeth in the margin that occur later. In morphology, the ＂bract＂ is also different to the vegetative leaf in some characteristics that were also illustrated in the present paper. Based on the hypothesis that the bract is more similar to the vegetative leaf than the tepal, we considered that the so-called ＂bract＂ of C.japonicum might be the tepal of the pistillate flower in morphological nature. Therefore, each pistillate flower contains a tepal and a carpel. We did not find any trace of other floral organs in the morphogenesis of the pistillate flower. Therefore we considered that the unicarpellate status of extant Cercidiphyllum might be to highly reduce and advance characteristics that make the extant Cercidiphyllum isolated from both fossil Cercidiphyllum-like plants and its extant affinities.     

磷高效利用杉木对低磷胁迫的适应性与内源激素的相关性

激素是植物适应逆境的重要信号物质, 从激素调控角度研究植物对养分匮乏环境的适应机制对磷高效营养基因型的选育具有重要意义。该研究通过分析被动忍受型(M1)与主动活化型(M4)两个磷高效利用杉木(Cunninghamia lanceolata)基因型在低磷胁迫下不同处理阶段的激素含量变化规律, 结合根系形态变化、干物质及养分分配规律, 研究磷高效利用杉木对低磷胁迫的适应性与内源激素的相关性。结果表明: 低磷处理下, 磷高效利用杉木M1与M4叶的激素含量与其适应特性之间无相关性, 而根系的激素含量与根系生长显著相关。低磷处理条件下, M1与M4根系中的IAA含量自27 h起表现为大于高磷对照, 且随时间延长呈增加趋势。根系中的IAA含量与根表面积、体积及根长等显著正相关, IAA的增加诱导了根系的增长, M1与M4均表现出一定的根系增长量。其中, M4存在明显的IAA由地上向基部积累的现象, M4的根系增生能力比M1更强。同时, 根系增长促使更多的干物质分配到根系, M4的根冠比在整个处理过程中均高于高磷对照。与IAA相同, M1与M4根系的ABA与GA₃含量总体也表现为低磷处理>高磷对照, 但随时间延长, 低磷条件下ABA与GA₃的含量呈下降趋势, 二者与根系增长量呈负相关关系。M1与M4根系内的ZT含量在低磷条件下也呈下降趋势, 且逐渐低于高磷对照, 而其与低磷适应特性间并无显著相关性。可见, 低磷胁迫下, 磷高效利用杉木M1与M4根系中的IAA、ABA与GA₃含量与其根系形态变化密切相关, 各器官的物质、能量、信息的综合调控是植物适应低磷逆境的重要生存策略。