Fructan and antioxidant metabolisms in plants of Lolium perenne under drought are modulated by exogenous nitric oxide

Drought is a major environmental factor that can trigger oxidative stress and affect plant growth and productivity. Previous studies have shown that exogenous nitric oxide (NO) can minimize oxidative stress-related damage through the modulation of antioxidant enzyme activity. Fructan accumulation also has an important role in drought tolerance, since these carbohydrates participate in osmoregulation, membrane protection and oxidant scavenging. Currently, there are few studies investigating NO-regulated fructan metabolism in response to abiotic stresses. In the present study, we sought to determine if treating plants of Lolium perenne with S-nitrosoglutathione (GSNO), a NO donor, improved drought tolerance. Two-month-old plants received water (control), GSNO and reduced glutathione (GSH) as foliar spray treatments and were then maintained under drought or well-watered conditions for 23 days. At the end of drought period, we evaluated growth, pigment content and antioxidant and fructan metabolisms. None of these conditions influenced dry mass accumulation, but the leaves of plants treated with GSNO exhibited a slight increase in pigment content under drought. GSNO treatment also induced 1-SST activity, which was associated with a 3-fold increase in fructan content. GSNO-treated plants presented higher GR activity and, consequently, increased GSH levels. L. perenne cv. AberAvon was relatively tolerant to the water stress condition employed herein, maintaining ROS homeostasis and mitigating oxidative stress, possibly due to fructan, ascorbate and glutathione pools.