The role of antioxidant enzymes in photoprotection

Abstract

The enzymatic component of the antioxidant system is discussed as one of the defensive mechanisms providing protection against excessive light absorption in plants. We present an analysis of attempts to improve stress tolerance by means of the creation of transgenic plants with elevated antioxidant enzyme activities and conclude that the effect of such transgenic manipulation strongly depends on the manner in which the stress is imposed. The following factors may diminish the differences in photosynthetic performance between transgenic plants and wild type under field conditions: effective functioning of the thermal dissipation mechanisms providing a primary line of defense against excessive light, long-term adjustments of the antioxidant system and other photoprotective mechanisms, the relatively low level of control over electron transport exerted by the Water-Water cycle, especially under warm conditions, and a decrease in the content of the transgenic product during leaf aging.

Improvement of antioxidant activities and yield of spring maize through seed priming and foliar application of plant growth regulators under heat stress conditions

“…Improvement in yield related traits and grain yield in this study might be due to amelioration of the injurious effects of chilling injury on light harvesting apparatus and CO 2 fixation in maize plants due to exogenous application of these chemicals (LOGAN et al, 2006), which maintained maize growth in stress conditions. Moreover, improved grain yield due to exogenous application of these chemicals may be due to membrane stabilization and improved antioxidant activity which may have helped the maize crop to maintain normal photosynthesis under heat stress thus resulting in more grain number per cob and increased grain weight, which ultimately resulted in higher grain yield.…”

“…We observed that heat stress at anthesis in late sown spring hybrid maize negatively influenced the growth, physiology and grain yield of maize which might be due to over production of reactive oxygen species (ROS) which may have impaired balance between light absorption and its utilization ultimately inhibiting Calvin cycle activity of carbon fixation (LOGAN et al, 2006), over reduction of respiratory electron transport chain (HU et al, 2008) and reduction in the Rubisco activity (ZHOU et al, 2006). However, in this study we observed that exogenous application of AsA, SA or H 2 O 2 either through seed priming or foliar spray improved seedling growth, physiological and biochemical, yield attributes and grain yield which might be due to mitigation of injurious effects of ROS on light harvesting apparatus and fixation of CO 2 in maize due to exogenous application of AsA, SA and H 2 O 2 (LOGAN et al, 2006). In the present study, chlorophyll a and b contents were increased with application of AsA, SA and H 2 O 2 in heat stressed conditions (Table 1), which might be due to enhancement in antioxidants which may have protected chlorophyll from degradation.…”

Morphological and Physiological Responses of <i>Morus alba</i> Seedlings under Different Light Qualities

“…Superoxide dismutase (SOD), POD and CAT are components of the plant reactive oxygen defense system. This system plays an important role in preventing or reducing the damage of reactive oxygen species (ROS) (Logan et al, 2006). Therefore, higher activities of SOD, POD and CAT may effectively scavenge the ROS and alleviate the damage of ROS to the membrane lipid of the cell.…”

An optimality model of photoadaptation in contrasting aquatic light regimes

“…8. The cost of photodamage includes the overhead costs associated with repair of the D1 protein (Vasilikiotis and Melis 1994) and scavenging of reactive oxygen species (Logan et al 2006). It may also include implicitly the influence of damaged photosystems on the ability to acquire chemical energy at low irradiance (Baklouti et al 2006).…”

“…Mechanisms associated with protection and repair of photodamage such as scavenging of reactive oxygen species (Logan et al 2006) and repair of the reaction center protein D1 (Vasilikiotis and Melis 1994) are complex. To explicitly parameterize each of these would go Fig.…”