狭叶坡垒传粉生物学初探

狭叶坡垒(Hopea chinensis)为常绿乔木,是我国热带季雨林的代表树种之一。它树型优美,具一定的耐寒性,是我国珍稀濒危保护植物。为阐明其传粉生物学特征和迁地保护的繁殖潜力,该文在引种地桂林植物园对狭叶坡垒的开花物候、花尺寸和花气味进行了观察和测量,运用杂交指数(OCI)、花粉胚珠比(P/O)、花粉活力、柱头活性检测和人工自交等方法对其繁育系统进行了检测,观察了访花昆虫并检验了其传粉效率,通过人工异交检验了繁殖潜力和可能的传粉限制。结果表明:(1)桂林植物园内狭叶坡垒的花期为7月底到9月底,持续60 d左右,一个花序花期约12 d,单花期约3 d,花朵开放时间为17:00—18:45。(2)雌雄同熟,雌蕊空间位置高于雄蕊,高花粉活力和高柱头可授性出现时间基本一致。(3) OCI等于4,P/O为10 788±984。(4)无自动自花授粉能力且自交不亲和,自然条件下和异交授粉能坐果且坐果率无显著差异。(5)蕈蚊是狭叶坡垒唯一的传粉者。(6)主要花香成分为β-榄香烯、(E)-7,11-二甲基-3-亚甲基-1,6,10-十二碳三烯和1-石竹烯。综上所述,狭叶坡垒繁育系统为异交,在迁地保...     

Directional control by male gypsy moths of upwind flight along a pheromone plume in three wind speeds

By attaching a reflective strip to the thorax, we documented with video recordings in a wind tunnel the spatial orientation of male gypsy moths, Lymantria dispar, as they flew along a plume of sex pheromone. In wind speeds of 61, 122, and 183 cm s⁻¹, moths flew very similar tracks along a pheromone plume. Moths aimed their thrust closer to upwind in increasing wind speeds using a roll maneuver. As a result, the orientation of their visual flow field, represented by the slip angle (the angular distance between the direction of flight and the longitudinal body axis), remained relatively constant. We propose that directional control during self-steered zigzagging is achieved by rolling, thereby maintaining a set slip angle. Following a roll at the apex of a turn that aligns the moth with its preferred slip angle, a moth banks toward a cross wind leg. By banking moths may maintain a stable image flow at oblique angles to their longitudinal body axis. Accepted: 16 July 1998     

Pollination ecology in sympatric winter flowering Helleborus (Ranunculaceae)

We studied biotic and abiotic factors that influence pollination in two sympatric winter flowering species. Helleborus foetidus and Helleborus bocconei flower simultaneously in winter. Although climatic conditions are not favorable for biotic pollination both species rely mainly on large bees of the genus Bombus. At the beginning of flowering, harsh climatic conditions are restrictive for insect visits. As flowering continues and temperatures rise, pollinator activity increases. The two plant species share pollinators that visit them indiscriminately. The flowers of the two species differ in form and insects visit H. foetidus by inserting their heads and H. bocconei ventrally: pollen load on insects is highly specialized. With the arrival of spring, many other species start to bloom and in spite of the large number of flowers still on the plants insects abandon Helleborus species. At the end of spring increasing biotic interactions take away pollinators from the Helleborus species.     

Monitoring of Gene Expression Profiles and Isolation of Candidate Genes Involved in Pollination and Fertilization in Rice (Oryza Sativa L.) with a 10K cDNA Microarray

To monitor gene expression profiles during pollination and fertilization in rice at a genome scale, we generated 73,424 high-quality expressed sequence tags (ESTs) derived from the green/etiolated shoot and pistil (0-5 h after pollination, 5hP) of rice, which were subsequently used to construct a cDNA microarray containing ca. 10 000 unique rice genes. This microarray was used to analyze gene expression in pistil unpollinated (UP), 5hP and 5DAP(5 days after pollination), anther, shoot, root, 10-day-old embryo (10EM) and 10-day-old endosperm (10EN). Clustering analysis revealed that the anther has a gene-expression profile more similar to root than to pistil and most pistil-preferentially expressed genes respond to pollination and/or fertilization. There are 253 ESTs exhibiting differential expression (e +/- 2-fold changes) during pollination and fertilization, and about 70% of them can be assigned a putative function. We also recovered 20 genes similar to pollination-related and/or fertility-related genes previously identified as well as genes that were not implicated previously. Microarray and real-time PCR analyses showed that the array sensitivity was estimated at 1-5 copies of mRNA per cell, and the differentially expressed genes showed a high correlation between the two methods. Our results indicated that this cDNA microarray constructed here is reliable and can be used for monitoring gene expression profiles in rice. In addition, the genes that differentially expressed during pollination represent candidate genes for dissecting molecular mechanism of this important biological process in rice.     

Floral biology of Philippine morphospecies of the grape relative Leea (Leeaceae)

I observed the floral biology of three Leea morphospecies in a Philippine natural forest habitat. The red-flowered morphospecies Leea guineensis limits selfing through synchronized dichogamy, with male and female flowers temporally separated in the same inflorescence, whereas the two morphospecies of the white-flowered Leea indica might be prone to geitonogamous selfing. Light and soil pH are correlated with phenology. In addition to bees and flies, Leea is visited by wasps, butterflies, beetles, bugs and spiders.     

Natural sway frequencies and damping ratios of trees: concepts,review and synthesis of previous studies

Previous studies that measured the natural frequencies and damping ratios of conifer trees were reviewed and results synthesized. Analysis of natural frequency measurements from 602 trees, belonging to eight different species, showed that natural frequency was strongly and linearly related to the ratio of diameter at breast height to total tree height squared (i.e., DBH/H ²). After accounting for their size, pines (Pinus spp.) were found to have a significantly lower natural frequency than both spruce (Picea spp.) and Douglas-fir (Pseudotsuga spp.). Natural sway frequencies of de-branched trees were significantly higher than those of the same trees with the branches intact, and the difference increased with an increasing ratio of DBH/H ². Damping mechanisms were discussed and methods for measuring damping ratio were presented. Analysis of available data suggested that internal damping ratios were typically less than 0.05 and were not related to tree diameter. External damping was mainly due to aerodynamic drag on the foliage and contact between the crowns of adjacent trees. Analysis of data from previous wind-tunnel studies indicated that damping due to aerodynamic drag is a nonlinear function of velocity. Damping due to crown contact has been suggested by a previous author to be a function of both the distance to and the size of adjacent trees. Therefore, in uniformly spaced stands it may be possible to model crown contact damping as a function of stand density index (SDI), a common forestry measure which incorporates both of these variables.     

Intensified wind pollination mediated by pollen dimorphism after range expansion in an ambophilous biennial Aconitum gymnandrum

Pollination systems and associated floral traits generally differ between core and marginal populations of a species. However, such differences are rarely examined in plants with a mixed wind‐ and bumblebee‐pollination system, and the role of wind pollination during range expansion in ambophilous plants remains unclear. We compared floral traits and the contributions of bumblebee and wind pollination in refugium and marginal populations of the ambophilous plant Aconitum gymnandrum. We found that most floral traits differed between the two populations, and those traits associated with the shift to wind pollination were pronounced in the marginal population. Bumblebee visitation rates varied significantly, but were generally low in the marginal population. Wind pollination occurred in both populations, and the efficiency was lower than that of bumblebee pollination. Two types of pollen grains, namely round and fusiform pollen, were transported to a stigma by bumblebees and wind, but fusiform pollen contributed to wind pollination to a larger degree, especially in the marginal population. Our results suggest that wind pollination was enhanced by pollen dimorphism in the marginal population of A. gymnandrum, and wind pollination may provide reproductive assurance when bumblebee activity is unpredictable during range expansion, indicating that ambophily is stable in this species and shift in pollination system could be common when plants colonize new habitats.     

Pollination of Pteroglossaspis ruwenzoriensis (Rendle) Rolfe (Orchidaceae) by Beetles in Argentina

Beetle pollination by Euphoria lurida (Scarabaeidae: Cetoninae) is documented for Pteroglossaspis ruwenzoriensis (Orchidaceae: Epidendroideae: Cymbideae: Eulophiinae) in its natural habitat in Central Argentina (South America). Flower features with special emphasis on those related to beetle pollination are given. These include: long rigid and well exposed inflorescences, sturdy inconspicuous and deep flowers with small entrance, emission of a yeast-like fragrance, jelly-like nectar, short column, and a head-attaching pollinarium with a broad saddle-like viscidium. Pollinator behaviour and pattern of flower opening favour cross pollination and probably long distance pollen dispersal. Flowering, which lasts about 3 weeks, peaks in summer past mid-January. In natural conditions about 68 flowers are pollinated for every 100 pollinaria removals.