In vitro sucrose concentration affects growth and acclimatization of <Emphasis Type="Italic">Alocasia amazonica</Emphasis> plantlets

Plantlets of Alocasia amazonica were regenerated on the MS medium supplemented with different concentrations (0–9%) of sucrose. An absence of sucrose in the growth medium induced generation of leaves, however, it decreased multiplication. On contrary, sucrose supply of 6% or 9% enhanced multiplication but hampered photoautotrophic growth (generation of leaves). Increasing sucrose supply also increased sugars and starch content and number of stomata and decreased water potential and size of stomata during in vitro growth period. During ex vitro acclimatization, shoot length, root length, leaf number and root number of Alocasia plantlets grown with 3% sucrose, were found to be better among the other studied sucrose concentrations. Under ex vitro acclimatization, number of stomata, contents of various carbohydrates in the leaves were increased but size of stomata decreased with increasing sucrose supply during in vitro growth period. Moreover, water potential of leaves of plantlets, which have been grown with a sucrose concentration other than 3%, was decreased. During in vitro growth, net CO₂ assimilation rate (P_N), transpiration (E), stomatal conductance (g_s) and variable fluorescence to maximum fluorescence ratio (Fv/Fm) were unaffected, however, during acclimatization these were changed and maximum P_N, E, and g_s were observed in the plantlets micropropagated with 3% sucrose. Fv/Fm was decreased severely in the plantlets micropropagated with 6% sucrose during acclimatization. Thus a sucrose concentration of 3% in the medium is appeared to be better among studied concentrations for both in vitro growth and ex vitro acclimatization of A. amazonica plantlets.     

Immunogold–silver staining-on-a-chip biosensor based on cross-flow chromatography

Immunogold–silver staining (IGSS) was adopted in cross-flow chromatographic analysis in which immunological reactions and silver intensification were sequentially conducted in the vertical and horizontal directions, respectively. Factors controlling the performance, except the silver substrate solution, were optimized to increase the signal-to-background ratio in measurements of cardiac troponin I as a model analyte. In generating the signal, the size of colloidal gold catalyst was critical; the smallest size (5-nm diameter) in the selected range yielded the highest colorimetric signal. To maintain the low background, two processes, blocking the remaining surfaces of membrane after antibody immobilization and washing the residual tracer after immunological reaction, were necessary. Self-nucleation of silver ions also caused a background signal and was controlled to some degree by decreasing the hydrodynamic force that arose when the substrate solution was supplied in the horizontal direction. Finally, a new chip (IGSS-on-a-chip; IOC) that allowed for convenient, efficient IGSS was produced by injection molding of plastic. This method enhanced the detection capability by 51-fold compared to the conventional rapid test kit using 30 nm-sized colloidal gold as the tracer. The IOC biosensor results also showed that silver intensification yield via cross flow after immunological reaction was 19% higher than that by traditional incubation.     

CO2-Enrichment and photosynthetic photon flux affect the growth of in vitro-cultured apple plantlets

Micro-cuttings (shoots with two small leaves) of cultivar M9 apple were cultured in-vitro for 40 d under CO₂-enriched and non-enriched (i.e., ambient air) conditions, and at a PPF of 40 or 100 μmol m^-2 s^-1 Afterward, shoot length, number of leaves, leaf area, chlorophyll content, shoot and root fresh weights, and % survival were recorded. Those plant-lets grown under CO₂- and PPF-enriched treatments were healthy and vigorous, and showed higher values for their growth parameters. In contrast, those grown without supplemental CO₂ or PPF often showed hyperhydricity. We also demonstrated that CO₂ enrichment and a relatively high PPF during in-vitro culture promoted normal photosynthesis and growth after ex-vitro transplantation.