Revival of a resurrection plant correlates with its antioxidant status

Abstract

SummaryMyrothamnus¯abellifolia, a short woody shrub from southern Africa, can survive severe desiccation of its vegetative organs. We studied mechanisms protecting this plant from oxidative damage during desiccation for 2 weeks, 4 and 8 months, and also during subsequent rehydration. This plant retains high concentrations of chlorophyll during desiccation, and these chlorophyll molecules are probably a source for potentially harmful singlet oxygen production. Desiccation triggered substantial increases in zeaxanthin and redox shifts of the antioxidants glutathione and ascorbate towards their oxidised forms. Simultaneously, the concentrations of violaxanthin, b-carotene, ascorbate, a-tocopherol, and glutathione reductase activity progressively decreased. Antheraxanthin, g-tocopherol, lutein, neoxanthin and glucose-6-phosphate dehydrogenase displayed less pronounced changes in response to desiccation. Even after 4 months of desiccation, Myrothamnus¯abellifolia recovered rapidly upon rehydration. Re-watering induced formation of ascorbate and glutathione, simultaneous reduction of their oxidised forms, and rapid production of a-tocopherol and of various carotenoids. Only after 8 months of desiccation did the antioxidant system of M.¯abellifolia break down; 3 weeks after the onset of rehydration, these plants abscised their leaves, but even then they were still able to recover and develop new ones. Ascorbate, b-carotene and a-tocopherol were totally depleted after 8 months of desiccation and did not recover upon rehydration; glutathione was partly maintained, but only in the oxidised form. We present a model demonstrating which parts of antioxidant pathways break down as oxidative stress becomes detrimental and we discuss some potential implications of our results for the genetic modi®cation of crop plants to improve their drought tolerance.

Phenolic compounds and properties of antioxidants in grapevine roots (Vitis vinifera L.) under low-temperature stress followed by recovery

“…However, the gravest obstacle to growing grapevine in this part of Europe is the cool climate. Many researchers suggest that tolerance of plants to abiotic stresses is correlated with an increase in the antioxidant potential (Seel et al 1991;Smirnoff 1993;Kranner et al 2002). Many phenolic compounds in plants poses antioxidant activity and may help to protect cells against the oxidative damage caused by free radicals.…”

Responses of two field-grown coffee species to drought and re-hydration

“…However, Chl contents declined significantly during the severe drought period, which may be related to membrane disintegration due to oxidative stress (Moran et al 1994, Alonso et al 2001. Although it is a negative consequence of stress that photosynthetic apparatus must be re-synthesized de novo upon re-watering, Chl loss has also been considered an adaptive feature, which reduces the possibility of further damage to the photosynthetic machinery by the formation of ROS under an excess of excitation energy (Munné-Bosch and Alegre 2000, Kranner et al 2002). At the same time, relatively higher Car/Chl ratio in droughted C. arabica indicated that water-stressed plants were protected from damage by a relatively higher amount of Car than in C. liberica (Logan et al 1997).…”

Level of protoporphyrinogen oxidase activity tightly correlates with photodynamic and defense responses in oxyfluorfen-treated transgenic rice

“…Chlorophyll loss is not only a negative consequence of stress in which photosynthetic apparatus must be re-synthesized de novo upon photodynamic stress but is also considered an adaptive feature which reduces the possibility of further damage to the photosynthetic machinery under excess excitation energy. 37) Protection of cells against AOS is generally believed to be mediated by carotenoids, especially the xanthophyll-cycle pigments as non-enzymatic scavengers of AOS. 38) Although the transgenic lines, AP1 and TTS4, did not show any significant change in carotenoid levels at 2 days after oxyfluorfen treatment, levels of neoxanthin, violaxanthin and lutein were significantly decreased in the wild-type line, with greater declines in violaxanthin and lutein (Table 2).…”