Abstract
Drought is an increasingly important limitation on plant productivity worldwide. Understanding the mechanisms of drought tolerance in plants can lead to new strategies for developing drought-tolerant crops. Many moss species are able to survive desiccation—a more severe state of dehydration than drought. Research into the mechanisms and evolution of desiccation tolerance in basal land plants is of particular significance to both biology and agriculture. In this study, we conducted morphological, cytological, and physiological analyses of gametophytes of the highly desiccation-tolerant bryophyte Atrichum undulatum (Hedw.) P. Beauv during dehydration and rehydration. Our results suggested that the mechanisms underlying the dehydration–recovery cycle in A. undulatum gametophytes include maintenance of membrane stability, cellular structure protection, prevention of reactive oxygen species (ROS) generation, elimination of ROS, protection against ROS-induced damage, and repair of ROS-induced damage. Our data also indicate that this dehydration–recovery cycle consists not only of the physical removal and addition of water, but also involves a highly organized series of cytological, physiological, and biochemical changes. These attributes are similar to those reported for other drought- and desiccation-tolerant plant species. Our findings provide major insights into the mechanisms of dehydration-tolerance in the moss A. undulatum.
Highlights
The natural habitats of plants are sometimes unfavorable, which greatly affects plant productivity
Components involved in these processes, such as soluble sugars, glycine betaine, proline, malondialdehyde (MDA), glutathione reductase, superoxide dismutase (SOD), peroxide dismutase (POD) and glutathione (GSH), have been widely reported in organisms ranging from basal land plants to angiosperms (Reddy et al 2004)
Most mosses can survive under −20 to −40 MPa for short periods, which far exceeds the range tolerated by most crop plants (−1.5 to −3 MPa) (Proctor and Pence 2002)
Summary
The natural habitats of plants are sometimes unfavorable, which greatly affects plant productivity. Among the various abiotic stresses limiting plant productivity, drought as a moderate dehydration state is of particular importance to modern agriculture. To survive and sustain growth under unsuitable conditions, various plants have evolved responses to drought (no bulk cytoplasmic water present, with approximately 0.30 g H2O per g dry weight, DW), desiccation (a more severe dehydration state than drought, in which the hydration shells of molecules are lost, with water content as low as 50 mg/g DW), and other stresses at multiple levels (Boyer 1982). The common mechanisms underlying these responses appear to be the accumulation of osmoprotectants, activation of reactive oxygen species (ROS) scavengers, and protection of membrane integrity (Mahajan and Tuteja 2005). Components involved in these processes, such as soluble sugars, glycine betaine, proline, malondialdehyde (MDA), glutathione reductase, superoxide dismutase (SOD), peroxide dismutase (POD) and glutathione (GSH), have been widely reported in organisms ranging from basal land plants to angiosperms (Reddy et al 2004)
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