A comparative study of achene morphology in Korean Polygonaceae

A comparative macro- and micromorphological study was conducted on achenes of Korean Polygonaceae comprising 45 taxa under 10 genera using a Stereo-microscope (SM) and Scanning Electron Microscope (SEM) to evaluate the taxonomical relevance of achene morphological characteristics. The achene shape is lenticular, biconvex, trigonous, or spheroidal. The largest achenes are found in Fagopyrum esculentum Moench (5.80–6.70 × 3.90–4.40 mm) and Rheum rhabarbarum L. (5.00–6.50 × 4.00–5.20 mm), and the smallest is found in Rumex maritimus L. (1.17–1.41 × 0.60–0.84 mm). Three types of embryo shape (curved, straight, and folded) and two types of embryo position (plane and parietal) can be distinguished. Most taxa have a curved embryo shape with plane position. Four types of surface patterns (smooth, papillae, tuberculate, or small pits) are observed. The surface sculpture or embryo type is rather consistent at the generic or tribal level, and the comprehensive consideration of achene characteristics is also useful at the species level. The achene morphology is described in detail, compared, and illustrated. The taxonomic significance of the achene morphology is discussed.

Seasonal Dynamics Of Aquatic Plants And Physicochemical Factors In An Urban Pond Of Jatrabari, Dhaka

Samad Nagar pond situated in Jatrabari, Dhaka showed mean air temperature 20 - 30 °C and water temperature 19 - 28°C. Secchi depth (Zs) varied from 28.67 - 44.5 cm and pH 6.6 - 8.8. The mean DO and alkalinity ranged 5.34 - 10.00 mg/1 and 0.58 - 1.08 meq/1, respectively. Free C02, SRP and SRS ranged 1.31 - 4.21 mg/1, 158.39 - 635.70 pg/1 and 13.32 - 28.65 mg/I, respectively. During the study period, seasonal mean values of transparency was higher in monsoon and lower in winter. pH, alkalinity remained higher in winter but lower in monsoon. From aquatic plant communities of the pond, phytoplankton represented by 33 species of which 54.55% belonged to Chlorophyceae (54.55%) followed by Bacillariophyceae (13.64%), Cyanophyceae (13.64%), Euglenophyceae (13.64%) and Dinophyceae (4.55%). The population density of phytoplankton community ranged 6.16 - 25.96><1 06 ind/1. Benthic diatom density varied from 2.64- 11 .00 x 1 06 ind/1. Benthic diatom population was the highest (I lxlO6 ind/1) in late October and lowest in early September (2.64 xio6 ind/1). Chi a and phaeophytin concentration varied 5.10 - 228.51 pg/1 and 2.05 - 1513.36 pg/1, respectively. Aquatic macrophyte communities were represented by 23 species where Eichhornia crassipes (Mart.) Solms. , Ipomoea aquatica Forsk, Ipomoea fistulosa Mart., Telanthera philoxeroides Moq., Rumex maritimus L., Eclipta prostata (L.) L. and Salvinia natans L. were observed all over the study period. Asiat. Soc. Bangladesh, Sci. 41(2): 253-262, December 2015

Phenology and seed production in Chenopodium rubrum, Rumex maritimus, and Rumex palustris as related to photoperiod in river forelands

Reproductive development in three species from irregularly flooded areas of river forelands was studied in relation to time of emergence. In Chenopodium rubrum, flowering was induced earlier in plants germinated in April–May than in later cohorts. However, the period of vegetative growth diminished and the life cycle was completed in a shorter time in later germinated plants. Seed number was reduced, but seed size as well as reproductive effort per plant increased in later cohorts. Plants of both Rumex species flowered after a certain number of leaves had developed and before a critical photoperiod had passed. In earlier cohorts, the main shoot and several axillary shoots elongated and flowered. Fewer axillary shoots flowered closer to the critical photoperiod, and this resulted in a reduced seed output in later cohorts. The critical photoperiod as well as the time needed for completion of the life cycle was longer in Rumex palustris than in Rumex maritimus. It is argued that in the riparian habitat, plants of both Rumex species are only occasionally able to complete their life cycle in one growing season. Survival of these species on the population level will rely more upon adaptations towards flooding during the established phase than is the case for C. rubrum. Key words: flowering phenology, photoperiod, seed production, Chenopodium rubrum, Rumex maritimus, Rumex palustris.