The study was to evaluate regeneration, mineral nutrients, and antioxidative activities of adventitious shoot in tuberous root radish (Raphanus sativus L.) grown under light and dark conditions in a controlled growth chamber. Small pieces of top of root radish, including adventitious shoots, were detached from mother radish roots (1 st cut) and grown for 22 days (22 DAC 1), which then re-cut (2 nd cut) and re-grown for 23 days (23 DAC 2). Fresh weight was heavier on plants grown under the dark condition (6.2 g) at 22 DAC 1 compared to the light condition (5.2 g) but was not significantly different between the treatment conditions at 23 DAC 2. Shoot length was significantly extended by the dark condition during the experimental period. Leaf concentrations of Ca, Mg, Na, and Mn were significantly increased by the light condition, with high leaf concentrations of Fe, Zn, and Cu observed on the dark condition. Proline of total amino acids was highly increased by the light condition (126.8 mg g-1) compared to dark condition (16.3 mg g-1), but other total amino acid concentrations were varied between the treatment conditions. Fructose and sucrose were increased by dark and light conditions, respectively. Dark condition reduced scavenging activity (9.7%), total phenolic (12.2 mg g-1) and flavonoid compounds (0.05 mg g-1) compared to the light condition (scavenging activity; 49.3%, total phenolic 43.8 mg g-1 and flavonoid compounds; 0.21 mg g-1) at 22 DAC 1 , which was also observed at 23 DAC 2. Excised adventitious shoot of radish grown under the dark condition could be useful propagation technique for convenient consumption at all times and the physicochemical values to some degree.

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Net CO2 assimilation (A) of four birch genotypes (Betula nigra L. ‘Cully’, B. papyrifera Marsh., B. alleghaniensis Britton, and B. davurica Pall.) was studied under varied photosynthetic photon flux density (PPFD) and CO2 concentrations (CO2) as indicators to study their shade tolerance and potential for growth enhancement using CO2 enrichment. Effect of water-deficit stress on assimilation under varied PPFD and (CO2) was also investigated for B. papyrifera. The light saturation point at 350 ppm (CO2) for the four genotypes varied from 743 to 1576 μmol·m−2·s−1 photon, and the CO2 saturation point at 1300 μmol·m−2·s−1 photon varied from 767 to 1251 ppm. Light-saturated assimilation ranged from 10.4 μmol·m−2·s−1 in B. alleghaniensis to 13.1 μmol·m−2·s−1 in B. davurica. CO2-saturated A ranged from 18.8 μmol·m−2·s−1 in B. nigra ‘Cully’ to 33.3 μmol·m−2·s−1 in B. davurica. Water-deficit stress significantly reduced the light saturation point to 366 μmol photon m−2·s−1 but increased the CO2 saturation point in B. papyrifera. Carboxylation efficiency was reduced 46% and quantum efficiency was reduced 30% by water-deficit stress in B. papyrifera.

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