Levels Of UV-absorbing Compounds Research Articles

Effects of acetic acid treatment on growth and pigment contents in barley

Acetic acid (AA) is an organic acid and has been widely used as food preservative and a dietary spice in vinegar form. In addition to its therapeutic uses in its vinegar form, AA attenuates inhibitory effects of stress in plants. However, in some plant species toxic effects of AA have been found. Therefore, in this study, 0, 2.5 and 5 mM concentrations of AA were applied to 2-day-old barley (Hordeum vulgare L. cv. Bornova-92) seedlings for 2 days in order to investigate the possible toxic effects of AA. After treatments, seedlings were grown in AA-free conditions for 2 days to recover. AA inhibited root and shoot growth; decreased water content, fresh weight, chlorophyll, pheophytin, and carotenoid contents. However, anthocyanin and flavonoid contents, as well as the levels of UV-absorbing compounds and UV-B marker increased in the leaves of AA-treated plants. AA increased hydrogen peroxide (H2O2) content in shoots and induced cell death in roots. Soluble carbohydrate content decreased in roots of AA-treated plants while insoluble carbohydrate content increased. Our results demonstrate that AA in young barley seedlings can exhibit its toxic effects through oxidative stress, which induced antioxidative response in the form of molecules with antioxidative activities. These effects persisted for 2 days after the removal of AA.

Shoot Dry Weight, Chlorophyll and UV-B-absorbing Compounds as Indicators of a Plant’s Sensitivity to UV-B Radiation

When studying the effects of ultraviolet-B (UV-B) radiation on plants, a good measure of UV-B sensitivity is a decrease in dry weight, since this reflects the cumulative effect of many small disruptions in plant function. Measurements of chlorophyll concentration and the level of UV-absorbing compounds are also used to gauge plant health during and after UV-B exposure. When a variety of vegetable crop plants were screened for UV-tolerance, it was found that the levels of chlorophyll and UV-absorbing compounds did not correlate with sensitivity. Biomass accumulation was, however, correlated with UV-sensitivity; plants that accumulated more biomass over a 2-week period were more likely to be UV-B sensitive. This suggests that a rapid growth rate renders plants more sensitive to the injurious effects of UV-B radiation.

UVB-induced cyclobutyl pyrimidine dimer and photorepair with progress of growth and leaf age in rice

We have examined the susceptibility to cyclobutyl pyrimidine dimer (CPD) induction by UVB radiation, the ability to photorepair cyclobutyl pyrimidine dimers (CPDs), and the levels of ultraviolet (UV)-absorbing compounds in various developing stages of leaves in UVB-resistant (Sasanishiki) and -sensitive (Norin 1) rices ( Oryza sativa L.). UVB produces more CPDs in the second, third and fourth fully expanded leaves than in the fifth and sixth fully expanded leaves. In leaves in which the levels of UV-absorbing compounds are lower, more CPDs are produced. The ability to photorepair CPDs in fully expanded leaves of different stages of each cultivar remains approximately constant, although the photorepair capacity in the fourth leaf rapidly increases from leaf emergence until full expansion. The photorepair capacity is lower in Norin 1 than that in Sasanishiki in all the leaf stages or different aged leaves. These results therefore suggest that rice plants could be more susceptible to CPD induction at the stage when the second, third or fourth leaves are developing, and UVB sensitivity correlates with low CPD photorepair.