Short photoperiod induces dormancy in Lotus (Nelumbo nucifera)

BACKGROUND AND AIMS: Lotus (Nelumbo nucifera) has been cultivated as an ornamental and food plant in Japan for more than 1000 years. As large areas are required for its cultivation (approximately 2 m2 per plant), physiological research, such as into the effect of environmental factors on dormancy, has not been well studied until recently. In this paper, seedlings were used to examine environmental factors affecting dormancy induction. METHODS: In a first experiment, seeds were sown from 6 April to 6 October at 2-month intervals, and cultivated for 2 months in an unheated greenhouse. In a second experiment, seeds were prepared for germination on 16 November and 16 May and the seedlings were grown at 25 or 30 degrees C under natural daylength in phytotron growth rooms. After 1 month, the seedlings were cultivated at 20, 25 or 30 degrees C for a further month. The number of leaves and rhizome branches on the main stem were counted, and growth of rhizomes on the main stem was calculated using a rhizome enlargement index (= maximum internode diameter/internode length) after 2 months of culture in both experiments. KEY RESULTS: Rhizomes elongated without enlargement when the seeds were sown in April and June. Sowing the seeds in August and October resulted in rhizome enlargement from the tenth and fifth internodes, respectively. Rhizomes enlarged in the November-sowing but elongated in the May-sowing irrespective of temperature treatments under natural daylength in the phytotron rooms. The seedlings cultivated from May at 25-30 degrees C for 2 months had more leaves, and more rhizome branches and nodes than those cultivated from November. CONCLUSIONS: Short days led to induced dormancy in lotus.     

甘草根和根状茎的发育解剖学研究

甘草（ＧｌｙｃｙｒｒｈｉｚａｕｒａｌｅｎｓｉｓＦｉｓｃｈ）实生苗具直根系。其根端原分生组织具三层原始细胞,外层产生表皮和根冠,中层和内层分别产生皮层和中柱。根的初生木质部四原型,由中柱鞘细胞产生第一次周皮。成长根中央的初生木质部由于导管周围薄壁细胞的增殖而被分割成几部分,使导管分子星散分布于薄壁细胞间。实生苗生长到第三年春由于叶节处的更新芽萌发形成最初的根状茎,根状茎顶端的原分生组织由两层原套细胞和一团原体细胞组成。初生结构的分化开始于皮层和髓两部分基本分生组织,而原形成层早期在根状茎横切面上呈连续的分生组织环。以后在环内逐渐分化出原形成层束,由它分化出初生锥管束,根状茎第一次周皮产生于初生韧皮部外方的第五或第六层皮层细胞。     

Adaptive architecture in rhizomatous plants

The architecture of few rhizomatous plants has been studied in any morphological detail: a great many of those which have been studied show highly organized and repetitive branching patterns. These branching patterns are largely confined to three basic types: those based on a ± 60° branching angle, those based on a ± 45° branching angle, and those with a predominately linear component. These various configurations must confer certain advantages in terms of substrate exploration and exploitation. The consistent architecture of many rhizomatous plants permits predictive graphic simulation of the branching patterns, and also permits estimates to be made of productivity in terms of meristem/shoot accumulation. As a background to this structural consideration of rhizomatous plants, an extensive bibliography is presented in an appendix, covering all aspects ot rhizomatous and stoloniferous growth.     

乌拉尔甘草根与根状茎发育解剖学研究

应用常规石蜡切片方法,对乌拉尔甘草根和根状茎的结构及其发育进程进行研究.结果显示:(1)乌拉尔甘草根的发育包括原分生组织、初生分生组织、初生生长和次生生长4个发育阶段.原分生组织由3层原始细胞组成,具有典型分生组织细胞的特征;初生分生组织由根冠原、表皮原、皮层原和中柱原组成;初生结构包括表皮、皮层和中柱,初生木质部为4原型,偶见3原型,内皮层细胞具凯氏带;次生生长依靠维管形成层和木栓形成层活动完成,维管形成层源于初生木质部和初生韧皮部之间的薄壁细胞,而木栓形成层由中柱鞘细胞脱分化产生;次生结构由次生维管组织和周皮共同组成,根中央不具髓.(2)根状茎发育过程与地上茎类似,包括原分生组织、初生分生组织、初生生长和次生生长4个发育阶段.原生分生组织由原套和原体组成,其衍生细胞分化成由原表皮、基本分生组织和原形成层组成的初生分生组织;初生结构包括表皮、皮层、外韧维管束、髓和髓射线,维管束呈环形排列;位于维管束中的原形成层细胞恢复活动产生次生木质部和次生韧皮部,束间形成层产生射线细胞;靠近维管束内侧的皮层薄壁组织细胞脱分化产生木栓形成层,以后形成周皮.周皮、次生维管束、射线和髓共同构成根状茎的次生结构.     

Development of the intercalary meristem in Chorda filum (Laminariales, Phaeophyceae) and other primitive Laminariales

Development of the intercalary meristem in the terete laminarialean species Chorda filum (L.) Stackhouse was studied in culture using light and transmission electron microscopy as well as by tracing elongation and cell divisions in various parts of the sporophyte. Growth of C. filum sporophytes could be classified into three developmental stages: (i) diffuse growth; (ii) basal meristematic growth; and (iii) intercalary meristematic growth. In the diffuse growth stage, elongation and cell division frequency were almost the same in each cell. In the basal meristematic growth stage, elongation and division of cells became localized in the tissues derived from the meristematic initial cell. Cells of the basal meristematic region contained smaller chloroplasts and many small opaque vesicles. In the intercalary meristematic growth stage, there was further elongation and differentiation of cells originating from the meristematic region, and this became more active in adjacent regions below the meristem than in regions above the meristem, causing the relative position of the intercalary meristem to shift towards the tip of the sporophyte. Meristematic cells of C. filum contained well-developed Golgi vesicles around the nucleus (perinuclear Golgi), many secretion vesicles and many small disk-shaped chloroplasts whose thylakoids were not well developed. Sporophytes of three other terete members of Laminariales, Chorda tomentosa Lyngbye, Pseudochorda nagaii (Tokida) Kawai et Kurogi, and Pseudochorda gracilis Kawai et Nabata, show diffuse growth and basal meristematic growth, but no intercalary meristematic growth. This suggests that the common ancestor of the Pseudochordaceae and Chordaceae had basal meristematic growth, and intercalary meristematic growth evolved more recently in C. filum.     

Functional morphology and biomechanics of branch–stem junctions in columnar cacti

Branching in columnar cacti features morphological and anatomical characteristics specific to the subfamily Cactoideae. The most conspicuous features are the pronounced constrictions at the branch–stem junctions, which are also present in the lignified vascular structures within the succulent cortex. Based on finite-element analyses of ramification models, we demonstrate that these indentations in the region of high flexural and torsional stresses are not regions of structural weakness (e.g. allowing vegetative propagation). On the contrary, they can be regarded as anatomical adaptations to increase the stability by fine-tuning the stress state and stress directions in the junction along prevalent fibre directions. Biomimetic adaptations improving the functionality of ramifications in technical components, inspired, in particular, by the fine-tuned geometrical shape and arrangement of lignified strengthening tissues of biological role models, might contribute to the development of alternative concepts for branched fibre-reinforced composite structures within a limited design space.     

Ramet Demography of a Clonal Invader, <Emphasis Type="Italic">Arundo donax</Emphasis> (Poaceae), in Southern California

Arundo donax L. is a rhizomatous perennial, asexually reproducing species that has invaded riparian habitats throughout Mediterranean climate zones. This research evaluated ramet demography of A. donax in two California riparian communities that differed in nitrogen availability. Quadrats were established along 100 m transects at each site and oriented across the advancing fronts of established populations. Morphology and phenology were assessed monthly over 1 year for calculation of demographic parameters and rhizomes were excavated and mapped at the end of the experiment. A. donax exhibited seasonal patterns of recruitment but no dormancy at the high nitrogen site, while at the low nitrogen site no recruitment occurred in the winter and maximum recruitment was delayed by a month relative to the high nitrogen site. Spread of A. donax was delayed until spring and lower overall in the low nitrogen site compared to the high nitrogen site, where lower initial density, greater production of shoots, and higher linear and areal addition indicated that this population was spreading more rapidly. Temperature and precipitation influenced seasonality and amount of recruitment of A. donax in this study. Several recently established, immature clumps were found in gaps at the low nitrogen site, likely due to flood-mediated dispersal of propagules. Recruitment in these clumps occurred from shoot buds, in contrast to the mature populations that reproduced from rhizome buds. Ecologically based management strategies for A. donax and other exotic species should account for differences such as those described here and be tailored to local conditions where the species occurs.     

长鞭红景天主轴生长特性与年龄判定

长鞭红景天是国家第二批确定的二级保护植物,处于近危状态。在西藏色季拉山区不同海拔带设置样地,观测长鞭红景天花茎环的形成过程,用游标卡尺(IP54型)测量长鞭红景天植株不同年的轴向生长量和径生长量;分析其主轴生长特性,进行年龄判定,结果表明:长鞭红景天每年在主轴上形成一个花茎环结构,并且轴向生长量和径生长量在年际间均无显著差异,但随海拔升高,轴向生长量和径生长量均呈下降趋势。根据长鞭红景天主轴的生长特性,结合主轴的长度则可以判定其年龄,为进一步研究长鞭红景天种群结构及动态奠定基础。     

珠子参根茎结构特征与皂苷积累的动态变化关系

皂苷类物质是珠子参根茎内贮存的重要次生代谢物质。根据皂苷类物质的化学性质,采用组织化学定位、显微制片技术和皂苷定量分析方法对不同生长年限珠子参的根茎节部进行了解剖学与皂苷动态积累的关系研究。结果表明:珠子参根茎节部横切面结构复杂,具有2至多个维管柱,属异常结构。珠子参根茎节部的加粗生长依赖于次生结构与三生结构的发生和分化。根茎节部分泌腔周围的分泌细胞、次生韧皮和三生韧皮部是珠子参皂苷类物质主要积累场所。随着珠子参生长年限的延长,根茎节部分泌腔、异常维管柱的数目及皂苷的含量增加。分泌腔、异常维管柱的数量和相对密集的节部可作为珠子参优良品种选育的结构和形态指标。     

The serine protease inhibitor neuroserpin regulates the growth and maturation of hippocampal neurons through a non-inhibitory mechanism

Neuroserpin is a brain-specific serine protease inhibitor that is expressed in the developing and adult nervous system. Its expression profile led to suggestions that it played roles in neuronal growth and connectivity. In this study, we provide direct evidence to support a role for neuroserpin in axon and dendritic growth. We report that axon growth is enhanced while axon and dendrite diameter are reduced following neuroserpin treatment of hippocampal neurons. More complex effects are seen on dendritic growth and branching with neuroserpin-stimulating dendritic growth and branching in young neurons but switching to an inhibitory response in older neurons. The protease inhibitory activity of neuroserpin is not required to activate changes in neuronal morphology and a proportion of responses are modulated by an antagonist to the LRP1 receptor. Collectively, these findings support a key role for neuroserpin as a regulator of neuronal development through a non-inhibitory mechanism and suggest a basis for neuroserpin's effects on complex emotional behaviours and recent link to schizophrenia.     

松嫩平原赖草无性系构件的形成与空间扩展实验

在松嫩平原栽培条件下, 赖草无性系生长的可塑性较大.在移植当年,赖草经过153 d的生长,4个无性系中最大的为215个分蘖株,是最小（40个）分蘖株的5.4倍,均遵循着相同的指数生长规律.在2个年度8个赖草无性系样本中,其分蘖株、根茎和芽3种构件之间数量与生物量以及3种构件的数量特征与无性系空间大小的变化均有较好的规律性. 赖草分蘖株数量与直径之间为幂函数异速生长;分蘖株和根茎生物量及芽数与直径之间均为指数异速生长;分蘖株及根茎的数量和生物量与所占面积之间均为线性同速生长.在具有充分生长空间且没有种间竞争条件下,赖草无性系采用先生存后发展的构件生长策略,并充分发挥无性系的持续更新潜力.