Plant Stress Tolerance Methods and Protocols
A number of abiotic factors such as drought, salinity, extreme temperatures, low or high light intensity, and deficiency or toxic levels of nutrients have huge impacts on crop productivity, and a furthering of our understanding of the molecular, biochemic
- PDF / 613,305 Bytes
- 22 Pages / 504 x 720 pts Page_size
- 86 Downloads / 180 Views
ntroduction All plants have to cope with the constant tendency of their tissues to equilibrate to the water potential ( w ) of their surrounding environment, whether it is the substrate upon or within which they grow, the soil within which they are rooted, or the air that surrounds them. The gradient in water potential between the tissues of the plant and the surrounding environment determines
R. Sunkar (ed.), Plant Stress Tolerance, Methods in Molecular Biology 639, DOI 10.1007/978-1-60761-702-0_1, © Springer Science+Business Media, LLC 2010
3
4
Oliver, Cushman, and Koster
the direction of water flow and the steepness of the gradient that determines, in part, the speed of that flow. Poikilohydric plants whose water content is governed directly by the water status of the surrounding environment, such as bryophytes, have few morphological safeguards for preventing water loss when free liquid water is not present. Once water is lost from the surface of the leaves they rapidly equilibrate (because the gradient is steep) to the water potential of the air, which is normally dry. If the plant can survive this event then it is considered dehydration tolerant. Many poikilohydric plants can survive moderate dehydration, to equilibrium with air between −20 and −40 MPa, representing a loss of water to approximately 10% of full turgor (relative water content (RWC)) (1). There are, however, a considerable number of poikilohydric plants that can survive dehydration to much lower water potentials and are deemed to be desiccation tolerant. All desiccation-tolerant poikilohydric plants can survive equilibration with air that has a relative humidity of 50%, which translates to a w of approximately −100 MPa. Many of these plants can survive much lower tissue water potentials, even to a w of −600 MPa in the case of the desiccationtolerant moss Tortula ruralis (2). The vast majority of plants species are not poikilohydric, however, and have evolved life forms, from the simple (e.g., the Selaginellas) to the complex (angiosperms), that can maintain a chronic disequilibrium between hydrated tissues and dry air (3). The evolution of this ability undoubtedly led to the radiation of plants into the vast number of ecological niches that the terrestrial habitat offers (4). With the ability to maintain hydration in a drying atmosphere, tracheophytes lost the ability to tolerate desiccation of their vegetative tissues (4). Most present-day angiosperms cannot survive the dehydration of their vegetative tissues to 20– 30% of full turgor (RWC), which translates to between −5 and −10 MPa (1). The lowest reported water potential reached for an angiosperm that is not desiccation tolerant is −12.1 MPa for Larrea divaricata, a desert shrub (5). Most crop species are relatively sensitive to dehydration and rarely survive leaf water potentials of −4 MPa. There are plant species that are desiccation tolerant, i.e., can equilibrate to water potentials at or greater than −100 MPa, but they are relatively few in number: ∼300 species or 0.1% of all a
Data Loading...
