• Korean Journal of Weed Science
• /
• v.31 no.4
• /
• pp.323-329
• /
• 2011

We investigated photodynamic stress-induced antioxidant responses in transgenic rice overexpressing Bradyrhizobium japonicum 5-aminolevulinic acid synthase (ALA-S) coding sequence lacking plastidal transit sequence. High light of $350{\mu}mol\;m^{-2}\;s^{-1}$ decreased the quantum yield in the transgenic lines, C4 and C5, compared to that of wild-type line. By contrast, non-photochemical quenching (NPQ) levels of C4 and C5 under high light were higher than those of the transgenic lines under low light of $150{\mu}mol\;m^{-2}\;s^{-1}$ as well as wild-type line under low and high light. Greater levels of NPQ in the transgenic lines exposed to high light were in a close correlation with increases in the xanthophyll pigment, zeaxanthin. Under high light, levels of neoxanthin, violaxanthin, lutein, and ${\beta}$-carotene in the transgenic lines were lower than those in wild-type line. Taken together, nonphotochemical energy dissipation and photoprotectant xanthophyll pigments play a critical role to deal with the severe photodynamic damage in the transgenic rice plants, although they could not overcome the photodynamic stress, leading to severe photobleaching symptoms.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.11 no.4
• /
• pp.143-150
• /
• 2009

Deicing salt is used to melt snow and ice on the road for traffic safety during the winter season, which accumulates in the roadside vegetation and induces visible injuries. The damage may accelerate particularly when it coincides with early spring leaf out. In order to better understand the response mechanisms, C. kousa (3-year-old) was irrigated twice prior to leaf bud in a rhizosphere with solutions of 0.5, 1.0, and 3.0% calcium chloride ($CaCl_2$) concentration, that were made by using an industrial $CaCl_2$ reagent practical deicing material in Seoul. Physiological traits of the mature leaves were progressively reduced by $CaCl_2$ treatment, resulting in reductions of total chlorophyll contents, chlorophyll a:b, photosynthetic rate, quantum yield, stomatal conductance, $F_V/F_M$, and NPQ. On the contrary, light compensation point and dark respiration were increased at high $CaCl_2$ concentration. A decrease in intercellular $CO_2$ concentration by stomatal closure first resulted in a reduced photosynthetic rate and then was accompanied by low substance metabolic rates and photochemical damage. Based on the reduction of physiological activities at all treatments ($CaCl_2$ 0.5%, 1.0%, and 3.0%), C. kousa was determined as one of the sensitive species to $CaCl_2$.