No abstract

Identification of heat-tolerant chrysanthemum [Dendranthema ×grandifolia (Ramat.) Kitamura] genotypes for commercial production in hot areas of the world is desirable. The extent to which electrolyte leakage from chrysanthemum leaf discs, measured using a test for cell membrane thermostability (CMT), could be related to the delay in flowering induced by heat in the field-grown plants was determined. The relationship between the relative injury (RI) occurring in leaf tissue discs of chrysanthemum cultivars and treatment temperature was sigmoidal. A single temperature treatment at 50 °C resulted in injury values near the midpoint of the sigmoidal response curve and showed the greatest sensitivity in detecting genotypic differences in heat tolerance. The cultivars with a low RI value are those with the greater CMT and shorter heat-induced delay to flowering.

Elimination of in vitro contamination and shoot multiplication were studied with Aglaonema Schott ‘White Tip’. Apparently, contamination was reduced, but explants browned when 200 mg·L−1 streptomycin was used as either a pretreatment or incorporated into the medium. Reduced occurrence of contamination and browning was achieved in axillary bud explants excised from the stock plants that had not been watered for 2 months. Six shoots per explant elongated normally in Murashige and Skoog (MS) medium containing 30 μm benzylaminopurine (BA). MS medium containing 20 μm thidiazuron (TDZ) also resulted in six shoots per explant, but these shoots failed to extend beyond a rosette. Only microcuttings from 30 μm BA treatment were used for the ex vitro rooting trial, and indole-3-butytric acid (IBA) at 9.8 or 19.7 mm applied to the base of the microcuttings resulted in 100% ex vitro rooting and the longest roots.

No abstract

In vitro bud clusters of Calathea orbifolia (Linden) Kennedy were obtained and subcultured in semi-solid (agar) medium and temporary immersion system (TIS) for 12 weeks. Uniform young plants were selected and transferred to soilless mix in a growth chamber for ex vitro acclimatization during 35 days, followed by growing in a shaded greenhouse for 65 days. Comparison of in vitro leaf anatomy, ex vitro photosynthetic behaviors and growth was made between two cultural systems. Plants in TIS produced thicker leaf chlorenchyma and aquiferous parenchyma, lower stomatal frequency and more epicuticular wax than did those in semi-solid medium. Plants from semi-solid medium had consistently lower leaf Fv/Fm values than plants from TIS. Leaf Fv/Fm value in plants from TIS decreased to 0.65 at day 7 after transfer and increased soon up to 0.76 thereafter. In contrast, leaf Fv/Fm value in plants from semi-solid medium reduced to 0.27 at day 7 after transfer and increased slowly up to 0.68 at day 35. During ex vitro acclimatization, plants in TIS had substantial higher photosynthetic rates than plants in semi-solid medium. Plants from TIS had subsequent higher leaf area, fresh and dry weights than plants from semi-solid medium.