Palyno-anatomical studies of monocot taxa and its taxonomic implications using light and scanning electron microscopy.

Palyno-anatomical study of monocots taxa using Light and Scanning Electron Microscopy (SEM) was first time conducted with a view to evaluating their taxonomic significance. Studied plants were collected from different eco-climatic zones of Pakistan ranges from tropical, sub-tropical, and moist habitats. The aim of this study is to use palyno-anatomical features for the correct identification, systematic comparison, and investigation to elucidate the taxonomic significance of these features, which are useful to taxonomists for identifying monocot taxa. A signification variation was observed in quantitative and qualitative characters by using the standard protocol of light microscopy (LM) and SEM. Epidermal cell length varied from maximum in Allium griffthianum (480 ± 35.9) µm at the adaxial surface to minimum in Canna indica (33.6 ± 8.53) µm on abaxial surface. Maximum exine thickness was observed in Canna indica (4.46) µm and minimum in Allium grifthianum (0.8) µm. Variation was observed in shape and exine ornamentation of the pollen, shape of the epidermal cell, number, size, and type of stomata, guard cell shape, and anticlinal wall pattern. Based on these palyno-anatomical features a taxonomic key was developed, which help in the discrimination of studied taxa. In conclusion, LM and SEM pollen and epidermal morphology is explanatory, significant, and can be of special interest for the plant taxonomist in the correct identification of monocots taxa.

Floral diversity and pollination strategies of three rheophytic Schismatoglottideae (Araceae).

Homoplastic evolution of 'unique' morphological characteristics in the Schismatoglottideae - many previously used to define genera - prompted this study to compare morphology and function in connection with pollination biology for Aridarum nicolsonii, Phymatarum borneense and Schottarum sarikeense. Aridarum nicolsonii and P. borneense extrude pollen through a pair of horned thecae while S. sarikeense sheds pollen through a pair of pores on the thecae. Floral traits of spathe constriction, presence and movement of sterile structures on the spadix, the comparable role of horned thecae and thecae pores, the presence of stamen-associated calcium oxalate packages, and the timing of odour emission are discussed in the context of their roles in pollinator management. Pollinators for all investigated species were determined to be species of Colocasiomyia (Diptera: Drosophilidae).

Specific turion yields of different clones of Spirodela polyrhiza depend on external phosphate thresholds.

Turions play an important role in the survival strategy of the duckweed Spirodela polyrhiza. Therefore, factors influencing the formation of these survival organs were studied. Phosphate deficiency is the main natural factor inducing turion formation and the specific turion yield (SY), i.e. the number of turions formed per frond, varied widely for five different clones from different climate zones. The concentrations of phosphate and nitrate in the nutrient media were investigated at the onset of turion formation, with SY ranging from 0.22 to 5.9. Tissue P and N content was also investigated in vegetative fronds at the onset of turion formation and in newly formed turions. The clones were selected to test possible correlations between SY and threshold nutrient concentration for turion formation. Only one correlation, between SY and external phosphate concentration, was significant: clones with high SY started turion formation at higher external phosphate concentrations. Turion formation is thus mainly induced by the external phosphate concentration, below a defined, clone-dependent threshold. We propose the following mechanism: a switch of the developmental programme of frond primordia from vegetative frond to turion formation at a higher phosphate threshold saves more phosphate for turion formation instead of using it for a further vegetative growth. However, the period of growth preceding turion formation does not depend on this threshold value, but rather on the growth rate of the vegetative fronds, which actually produce the phosphate shortage by taking it up from the surrounding medium.

[Comparative identification on Dai medicine "Pokou" and its processing product].

OBJECTIVE: To research identification methods of the Dai Medicine "Pokou" (the rhizome of Homalomena gigantea) and its processing product, and provide basis for identification of the drug in further research and application. METHODS: Macroscopic, microscopic observation and TLC and FTIR techniques were used to authenticate this raw medicine and its processing product. RESULTS: There were certain differences in the macroscopic features. The TLC result and infrared spectra of the samples had also obvious differences. The methods for identification of this raw medicine and its processing product were established, The detailed tissue and powder of this medicine were drawn. CONCLUSION: The results provided the basis for identification of the medicine and establishment of its quality standard.

Floral biology and reproductive isolation by floral scent in three sympatric aroid species in French Guiana.

We studied the reproductive biology of three sympatric Araceae species, Anthurium sagittatum, A. thrinax and Spathiphyllum humboldtii in French Guiana. The plants flowered simultaneously and were visited by scent-collecting male euglossine bees, which were apparently their major pollinators. In total, each species was visited by 3-7 euglossine species, and 2-3 euglossine species accounted for at least 80% of all flower visits, with visits being plant species-specific. Floral scent consisted of 6-10 main compounds, which made up 76-94% of the total amount of volatiles and were specific in these high amounts to each plant species. We suggest that the different floral scents lead to clear separation of the main pollinating euglossine species, providing a directed and efficient intraspecific pollen flow that results in high reproductive success. Since the simple floral (inflorescence) morphology of the studied plants does not support any morphological mechanisms to exclude visitors, as for example in euglossine-pollinated perfume orchids, floral scent might be of major importance for the reproductive isolation and sympatric occurrence of these plants.

Response of Pistia stratiotes to heavy metals (Cr, Ni, and Zn) and phosphorous.

The effects of Cr, Ni, Zn, and P exposure on the root anatomic structure, growth, and chlorophyll a concentration of Pistia stratiotes L. were studied. Plastic aquaria containing 50 g of wet plants and 5 L of pond water added with the contaminant(s) were disposed. The treatments were: (1) Cr, (2) Ni, (3) Zn, (4) P, (5) Cr + Ni + Zn, (6) Cr + Ni + Zn + P, and (7) control. Contaminant additions were done seven times. In each addition, concentrations of 1 mg of metals or 5 mg of P per liter of water were added. Chlorophyll a was an indicator more sensitive to Zn and Cr toxicity than the relative growth rate. Ni and Cr + Ni + Zn treatments were the most toxic ones, in which biomass and the root anatomical parameters (root length, cross-sectional areas [CSAs] of root, stele, and metaxylem vessels) decreased significantly. The addition of P to the treatment with combined metals attenuated the decrease in plant growth and root length, and caused a significant increase in CSAs of total metaxylem vessels, suggesting that P increased the tolerance of P. stratiotes to metals. This fact has important implications for the use of this macrophyte in constructed wetlands for industrial wastewater treatment.

Influence of nitrogen and phosphorus concentrations and ratios on Lemna gibba growth responses to triclosan in laboratory and stream mesocosm experiments.

The effects of co-occurring nutrient and contaminant stressors are very likely to interact in aquatic systems, particularly at the level of primary producers. Site-specific nitrogen (N) and phosphorus (P) concentrations are often much lower and differ in relative availability than those used in nutrient-saturated laboratory assays for aquatic plants, which can introduce uncertainty in prospective ecological hazard and risk assessments. Because triclosan, an antimicrobial agent included in personal care products, potentially presents high relative risk among antimicrobial agents to aquatic plants and algae, we performed laboratory experiments with the model aquatic macrophyte Lemna gibba across a gradient of environmentally relevant N:P levels with and without triclosan co-exposure. Frond numbers (7 d) were significantly higher in N:P treatments of 16 and 23 but were lower in N:P of 937 and 2,500 treatments relative to standardized control media (N:P=3). When triclosan co-exposure occurred at high nutrient concentrations, frond number median effective concentration values at N:P 0.75, 3, and 16 were more than twofold lower than triclosan median effective concentration values in low nutrient media N:P ratios. However, a triclosan median effective concentration for frond number was twofold lower at N:P of 2,500 than at other N:P ratios in low concentration media. Influences of P enrichment on triclosan toxicity to L. gibba were further explored during a 14-d outdoor experimental stream mesocosm study. Effects of 2.6 and 20.8 microg L(-1) triclosan on L. gibba growth rates were more pronounced with increasing P treatment levels, which was generally consistent with our laboratory observations. Findings from these laboratory and field studies indicate that site-specific nutrient concentrations and ratios should be considered during assessments of primary producer responses to chemical stressors.

Conventional and novel modes of exine patterning in members of the Araceae--the consequence of ecological paradigm shifts?

In the family Araceae, the members of all subfamilies except Aroideae follow the conventional mode of exine formation pattern, which conforms with the textbook view of sporoderm stratification and chemistry (sporopollenin ektexine formed before the endexine). Only members of the subfamily Aroideae show a quite uncommon mode of exine formation pattern, with an endexine formed prior to the nonsporopollenin, polysaccharidic outer exine layer. The intine is formed simultaneously with this non-sporopollenin layer. From the differing timetable and especially from the different origin it is concluded that this outer exine layer is not homologous to the angiosperm ektexine. The fundamental question, why members of the Aroideae lack an elaborated sporopollenin ektexine, is discussed in terms of functionality of the nonsporopollenin outer exine layer. It seems that a major change in aroid evolution took place at the point when the family phylogenetically and ecologically shifted from bisexual (most subfamilies) to unisexual flowers (Aroideae only). The hypothesis is that ephemeral spathes and the absence of sporopollenin are the consequence of an adaptive syndrome for a short pollination time window in many members of the Aroideae, with short-lived pollen, an energetically not costly pollen wall, rapid germination of pollen tube, and brief receptivity of stigma.

[Numerical taxonomy of medicinal plants from Areae in Zhejiang Province].

Numerical taxonomic studies were done on 13 species from 3 genera of tribe Areae in Zhejiang, used as 13 operational taxonomic units (OTUS). 40 morphological characters were used for analysis. Euclid distance coefficients used to show quantitative index of similarity among OTUS were computed by standardized data. The dendrograms from 8 systematic cluster methods including single linkage method, complete linkage method, median method (beta = 0 WPGMA) and (beta = -0.25 WPGMA), centroid method, group average method, variable group average method (beta = -0.25) and variable method (beta = 0.25) were constructed respectively. WPGMA was slected as the optimal one by computing the comparative coefficients of every cluster result and the boundary of taxa in its dendrogram determined by a method to treated IBM computer with the program by BASIC language. The Results showed that 13 OTUs were classified as 3 clusters by broken line L2, namely, cluster I: Typhonium; cluster II: Arisaema; cluster III: Pinellia, and cluster II further as 4 groups by L1, which belong to Section Pistillata, Arisaema, Sinarisaema and Tortuosa respectively. Being consistent with those from classical taxonomy, the results in this study may be helpful to the classification and identification of the medicinal plants from tribe Areae in Zhejiang Privince.