Mechanism Of Light Action Research Articles

Hypothetical mechanism of light action on nitric oxide physiological effects.

Nitric oxide is a universal cellular mediator. It is involved in many physiological processes, including those induced by light. The disability for complete analysis of the nitric oxide metabolites in tissues prevents the exact understanding of the role of NO in a particular process. The sensitivity and selectivity of an enzymatic sensor developed in our lab is based on the detection of all NO groups that carry a positive charge or acquire it in the chemical processes. Using this sensor, we have shown that dinitrosyl iron complexes (DNIC), being principal nitric oxide donors in most of living tissues, undergo transformations under light irradiation in the wavelength range of 400-700nm. These changes are not associated with nitric oxide release to the environment. But a nitrosyl iron complex without thiol ligands (Fe(NO)n) is produced. Moreover, in the moment of the complex reorganization, the chemical bond between the NO group and other components apparently weakens and, in the presence of a substance possessing chemical affinity to the NO group, the latter acquires the ability of transition from the complex to this substance. Therefore, the efficiency of NO donors first of all depends on the existence of the NO target and its status including that under the action of light. The activation of a donor compound by light can facilitate the transfer of NO to the target. Transfer of NO from the donor to the target occurs without releasing NO, or with a minimum time of its stay in the unbound state.

Fruit-localized photoreceptors increase phenolic compounds in berry skins of field-grown Vitis vinifera L. cv. Malbec

Sunlight exposure has multiple effect on fruits, as it affects the light climate perceived by fruit photoreceptors and fruit tissue temperature. In grapes (Vitis vinifera L.), light exposure can have a strong effect on fruit quality and commercial value; however, the mechanisms of light action are not well understood. The role of fruit-localized photoreceptors in the control of berry quality traits was evaluated under field conditions in a commercial vineyard in Mendoza (Argentina). Characterization of the diurnal dynamics of the fruit light environment in a vertical trellis system indicated that clusters were shaded by leaves during most of the photoperiod. Supplementation of the fruit light environment from 20days before veraison until technological harvest showed that red (R, 660nm) and blue (B, 470nm) light strongly increased total phenolic compound levels at harvest in the berry skins without affecting sugar content, acidity or berry size. Far-red (FR, 730nm) and green (G, 560nm) light supplementation had relatively small effects. The stimulation of berry phytochromes and cryptochromes favored accumulation of flavonoid and non-flavonoid compounds, including anthocyanins, flavonols, flavanols, phenolic acids and stilbenes. These results demonstrate that the chemical composition of grape berries is modulated by the light quality received by the clusters under field conditions, and that fruit photoreceptors are not saturated even in areas of high insolation and under management systems that are considered to result in a relatively high exposure of fruits to solar radiation. Therefore, manipulation of the light environment or the light sensitivity of fruits could have significant effects on critical grape quality traits.

Some Problems Concerning the Mechanism of Light Action in Poultry

Some Problems Concerning the Mechanism of Light Action in Poultry