Abstract
Global warming and associated precipitation changes will negatively impact on many agricultural ecosystems. Major food production areas are expected to experience reduced water availability and increased frequency of drought over the coming decades. In affected areas, this is expected to reduce the production of important food crops including wheat, rice, and maize. The development of crop varieties able to sustain or improve yields with less water input is, therefore, a priority for crop research. Almost all water used for plant growth is lost to the atmosphere by transpiration through stomatal pores on the leaf epidermis. By altering stomatal pore apertures, plants are able to optimize their CO2 uptake for photosynthesis while minimizing water loss. Over longer periods, stomatal development may also be adjusted, with stomatal size and density being adapted to suit the prevailing conditions. Several approaches to improve drought tolerance and water-use efficiency through the modification of stomatal traits have been tested in the model plant Arabidopsis thaliana. However, there is surprisingly little known about the stomata of crop species. Here, we review the current understanding of how stomatal number and morphology are involved in regulating water-use efficiency. Moreover, we discuss the potential and limitations of manipulating stomatal development to increase drought tolerance and to reduce water loss in crops as the climate changes.
Highlights
Changes in climate are already negatively affecting the yields of staple crops in agricultural areas around the world (Lobell et al, 2011; IPCC, 2014)
water-use efficiency (WUE) can be estimated at different scales; at an agronomic level, it is described as the ratio of water used in crop production versus
The knowledge relating to the genetics underpinning stomatal development and physiology in both Arabidopsis and crop species has advanced substantially, with noticeable advancements made in improving WUE
Summary
Changes in climate are already negatively affecting the yields of staple crops in agricultural areas around the world (Lobell et al, 2011; IPCC, 2014). When water becomes limited, signals such as reduced hydraulic conductivity and increased abscisic acid (ABA) arise, causing guard cell turgor pressure decreases, which result in reduced stomatal aperture and gs (Schroeder et al, 2001; Mustilli, 2002; Tombesi et al, 2015; Bartlett et al, 2016; McAdam et al, 2016) These changes lead to an improved water conservation, but often at the expense of A (Flexas and Medrano, 2002). In Arabidopsis, plants grown under water restriction do not show altered SD; reductions in stomatal size (SS, guard cell area, based on guard cell pair length and width) were observed (Doheny-Adams et al, 2012) These plastic modulations of number and size of stomata allow plants to adjust their stomatal pore area in response to the surrounding environment, affecting their maximum and minimum gas exchange. We discuss our current understanding of how alterations in SS, SD, and stomatal morphology contribute to altered WUE and drought tolerance with particular emphasis on the latest advances in crop species
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