Seasonal Changes in the Antioxidative Defence System of a Liverwort Dumortiera hirsuta

Liverworts are influenced by several ecological factors, such as photoperiod, temperature, precipitation, and nutrient availability. These factors vary in different seasons of the Indian calendar year, divisible into pre-monsoon (March–May), monsoon (June–August), post-monsoon (September–November), and fruiting (December–February) seasons. Seasonality causes disturbance in cellular homeostasis, which may trigger ROS formation. To restore the threshold level of ROS, liverworts must be equipped with complex antioxidant defence machinery. Thus, in this study, we analysed the effect of seasonal changes on oxidative stress markers [malondialdehyde (MDA) and total peroxide (H2O2 content)], total protein and pigment contents, and enzymatic and non-enzymatic antioxidants activities/contents in a liverwort, Dumortiera hirsuta, during its four distinct growing seasons. During the fruiting season, the results revealed the highest level of MDA and H2O2 with the lowest level during the pre-monsoon/monsoon seasons. The protein and pigment contents were maximal during the monsoon season and minimal during the fruiting season. With the exception of few [ascorbate peroxidase (APX) and ascorbic acid (ASC)], enzymatic [superoxide dismutase (SOD), catalase (CAT), and glutathione reductase (GR)] and non-enzymatic antioxidants (total thiol, proline, and carotenoids) activities/contents were correspondingly high during the fruiting season and low during the pre-monsoon/monsoon seasons, indicating their defensive role in neutralizing/suppressing the increased ROS during the fruiting season when the temperature was very low and the nutrient availability was less. These results therefore suggest that the antioxidative defence machinery plays a potential role in the adaptation of D. hirsuta against oxidative stress, naturally imposed by seasonal climatic changes.