University of Peradeniya

About: University of Peradeniya is a education organization based out in Kandy, Sri Lanka. It is known for research contribution in the topics: Population & Poison control. The organization has 5970 authors who have published 7388 publications receiving 197002 citations.

Effect of growth regulators on microspore embryogenesis in coconut anthers

Abstract: The effect of growth regulators on induction of androgenesis in coconut was investigated using seven different growth regulators at various concentrations and combinations. Three auxins (1-naphthalene acetic acid—NAA, indoleacetic acid—IAA, picloram) and three cytokinins (2-isopentyl adenine-2-iP, kinetin, zeatin) were tested either alone or in combination with 2,4-dichlorophenoxyacetic acid (2,4-D), using modified Eeuwens Y3 liquid medium as the basal medium. Among the tested auxins, 100 μM NAA in combination with 100 μM 2,4-D enhanced the production of calli/embryos (123) whereas IAA and picloram showed negative and detrimental effects, respectively, for androgenesis induction over 100 μM 2,4-D alone. Kinetin and 2-iP enhanced the production of calli/embryos when 100 μM 2,4-D was present in the culture medium. Both cytokinins at 10 μM yielded the highest frequencies of embryos (113 and 93, respectively) whereas zeatin (1 or 2.5 μM) had no impact on microspore embryogenesis. When calli/embryos (produced from different treatments in different experiments) were sub-cultured in somatic embryo induction medium (Y3 medium containing 66 μM 2,4-D), followed by maturation medium (Y3 medium without growth regulators) and germination medium (Y3 medium containing 5 μM-6-benzyladenine—BA and 0.35 μM gibberellic acid—GA3), plantlets were regenerated at low frequencies (in most treatments ranging from 0% to 7%).

Assessment of masticatory efficiency: new methods appropriate for clinical research in dental practice

Abstract: A new chewing test has been assessed in which the test food was contained in a chewable rubber bag. Six subjects chewed ten single 'unbagged' almonds and ten single 'bagged' almonds. The bagged experiments gave generally similar results to unbagged ones in terms of the particle size distribution; they also proved more acceptable to the subjects and eliminated the serious, undefinable loss of chewed particles that occurs intraorally in conventional (unbagged) tests. In this study an optical scanning method was used which provided a simple, fast measurement of individual particles.

The feeding behaviour of the rice leaf folder, cnaphalocrocis medinalis

Abstract: During feeding, the larva sits longitudinally on the leaf, bends the head sideways, and scrapes out the soft tissue between bundles longitudinally up and down, leaving only the bundle unit + bundle sheath, sclerenchyma, and the abaxial epidermis + cuticle between the bundles intact, when feeding on the upper side. Feeding on the underside also includes most of the bulliform cells, sparing again the bundle unit plus the remaining adaxial epidermis cells + cuticle between the bundles. Feeding is essentially restricted to green mesophyll tissue and may occur practically over the whole leaf surface. Of the eaten portion of a leaf, about two-thirds is consumed (by dry weight). Regular longitudinal feeding was observed in many other species of Gramineae, and in several Cyperaceae. In a few cases of thick or tough leaves feeding ocurred also in irregular non-linear fashion. Extensive irregular feeding was also observed in one specimen of a soy plant. Young larvae up to the early second instar are gregarious, but subsequently become solitary, with only one larva per leaf roll. ZUSAMMENFASSUNG DAS FRASSVERHALTEN DES REISBLATTROLLERS, CNAPHALOCROCIS MEDINALIS (LEPIDOPTERA, PYRALIDAE, PYRAUSTINAE) Wahrend die Raupen fressen, sitzen ***sie in Langsrichtung auf dem Blatt, neigen den Kopf seitlich und scharren das weiche Gewebe zwischen den Leitbundeln aus. Unberuhrt bleibt beim Fressen von der Oberseite her nur das Leitbundel mit der Bundelscheide, das Sklerenchym, die abaxiale Epidermis mit der Kutikula. Beim Fressen auf den Unterseite wird auch der grosste Teil der ***Bulhformzellen erfasst. Dabei wird das Gefassbundel mit der nun adaxialen Epidermiszellen und der Kutikula zwischen den Bundeln ausgeschlossen. Das Fressen ist hauptsachlich auf das grune Mesophyllgewebe beschrankt und kann praktisch uber die ganze Blattoberflache stattfinden. Ungefahr zwei Drittel des Trockengewichtes eines befressenen Blattabschnittes wird verzehrt. Regelmassiges Fressen in Langsrichtung wurde auch an vielen andern Gramineen- und Cyperaceenarten beobachtet. An einigen dicken und harten Blattern, z.B. Bambus, wurde manchmal in einer ganz unregelmassigen Weise gefressen. Solch unregelmassiges Fressen wurde auch einmal auf einer Soyapflanze beobachtet. Junge Raupen, sind bis zum fruhen zweiten Stadium gregar, werden aber spater solitar mit einer einzigen Raupe in einer Blattrolle.

Review of spectrum sensing in cognitive radio

Abstract: The frequency spectrum bandwidth used in modern wireless systems is limited while the number of wireless systems is rapidly increasing. In order to alleviate the spectrum scarcity, secondary systems can opportunistically access the temporarily unused licensed bands of primary systems which are known as spectrum holes or white spaces, by altering their transmitting parameters so that the interference is minimal to primary user while coordinating access to this channel with other cognitive radio (CR) users in the vicinity. Spectrum sensing is necessary to enable dynamic spectrum access without interfering with primary users. This optimizes the use of available radio frequency spectrum while minimizing interference to other licensed or unlicensed users by detecting and utilizing only the white spaces. This paper explores various sensing methods, their performance, applicability and effectiveness under different transmission conditions and advantages and disadvantages incorporated with each sensing method.

Above- and below-ground interactions of grass and pasture legume species when grown together under drought and low phosphorus availability

Abstract: Interactions between annual grass and perennial legume species when they are grown together under drought and limited phosphorus (P) availability are likely to be very important for pasture productivity, but are not well understood. Therefore, the objective of this study was to compare the interactions of drought and species combination on growth, nutrition, hydraulic lift and photosynthesis of the Australian native legume Cullen australasicum and the exotic legume Medicago sativa when grown with the exotic annual ryegrass (Lolium rigidum) with poorly soluble FePO4 as the source of P. Plants were grown for 22 weeks in monoculture and in legume-grass mixtures in 1-m tall pots filled with river sand. Two moisture treatments were applied, drought (top 70 cm of soil allowed to dry after 16 weeks of establishment) and control (field capacity). In monoculture, shoot dry weight (DW) pot-1 of L. rigidum was higher than that of C. australasicum and M. sativa. In the mixtures, compared with the monocultures, an increase in shoot DW pot-1 for L. rigidum and a decrease for both C. australasicum and M. sativa resulted in a relative yield total >1. Citrate was the main carboxylate in the rhizosphere of all species, except for the drought-treated L. rigidum in monoculture and mixtures, for which malate was the main constituent. Both C. australasicum and M. sativa had higher concentrations of Ca, Mg, S, Cu, Zn, Mn and Mo in their leaves than did L. rigidum. Hydraulic lift was not detected in M. sativa and C. australasicum; likely reasons are discussed. Photosynthetic rate was similar for all species, but L. rigidum had tighter stomatal control. C. australasicum survived longer under drought than did M. sativa. In conclusion, L. rigidum out-competed the legumes. The legumes provided benefits to the growth of L. rigidum through solubilising P, but not through hydraulic lift. In addition, L. rigidum conserved moisture through tight stomatal control and produced an extensive root system to take up water and nutrients efficiently.